f 


^K*^.*^^ 

), 


MANUAL 


HUMAN  MICEOSCOPICAL  ANATOMY. 


MANUAL 


OF 


HUMAN  MICROSCOPICAL  ANATOMY, 


BY 


A.  KOLLIKER, 

M 

PROFESSOR  OF  ANATOMY  AND  PHYSIOLOGY  IN  WUSZBURG. 

TRANSLATED   BY 

GEORGE  BUSK,  F.R.S.,  AND  THOMAS  HUXLEY,  F.R.S. 

EDITED,   WITH   NOTES   AND   ADDITIONS, 
BY 

J.  DA  COSTA,  M.D. 

ILLUSTRATED  BY  THREE  HUNDRED  AND  THIRTEEN  ENGRAVINGS  ON  WOOD, 


PHILADELPHIA: 
LIPPINCOTT,    GRAMBO    &    CO., 


vs- 


CONTENTS. 


INTRODUCTION. 

SECT.  PAGE. 

1.  Historical  Introduction,          .......        33 

2.  Present  position  of  the  Science,  .....  34 

3.  Aids  to  the  Study  (Literature,  Microscope,  Preparations),  .  .        36 

GENERAL  HISTOLOGY. 
I.— OF  THE  ELEMENTARY  PARTS,  pp.  39,  40. 

4.  Simple  and  compound  elementary  parts,     .  .  .  .  .39 

5.  Plastic  fluid,  fundamental  substance,     .....  40 

A.    SIMPLE    ELEMENTARY   PARTS,  pp.  41-70. 

1.  Elementary  Granules, — vesicles,  nuclei — 

6 41 

2.  Of  the  Cells:— 

7.  Composition,  .  .  .  .  .  .  .  .43 

8.  Form,  chemical  relations,  nucleus,  nucleolus,  ...  44 

9.  Cell-formation,  .  .    -  .  .  .  .  .48 

10.  Free  cell-formation,     •    .            .            .            .            .            .            .  48 

11.  Endogenous  cell-formation,  .            .            .            .            .            .  .49 

12.  Multiplication  of  cells  by  division,         .....  54 

13.  Theory  of  cell-formation,      .......        56 

14.  Vital  phenomena  of  cells,  growth,          .....  59 

15.  Processes  in  the  interior  of  the  cells — Absorption,               .            .  .61 

16.  Excretive  processes,       .......  67 

17.  Contractility  of  the  cells,       .            .            .            .            .            .  .  •      68 

18.  Metamorphoses  of  the  cells,  kinds  of  cells,        ....  69 

B.    HIGHER   ELEMENTARY   PARTS,    pp.  70-72. 

19.  ..........  70 

II._OF  THE  TISSUES,  ORGANS,  AND  SYSTEMS,  pp.  72-119. 

20.  Enumeration  of  them,     .  .  .  .  .  .  72 

21.  Epidermic  tissue,       ....:...        74 


XV111  CONTENTS. 

SECT.                                                                                                                                                                                                           .  PAGE 

22.  Cartilaginous  tissue,       .......  78 

23.  Elastic  tissue,  .  .  .  .  .  .  .  .81 

24.  Connective  tissue,            .            .            .....  89 

25.  Osseous  tissue,           ........  99 

26.  Tissue  of  the  smooth  muscles,                .....  102 

27.  Tissue  of  the  striped  muscles,          ...             ...  106 

28.  Nerve-tissue,       .            .            .            .            .            .            .            .  109 

29.  Tissue  of  the  true  glands,      .        "  .  •          .-           .            .            .            .  113 

30.  Tissue  of  the  blood-vascular  glands,       .            »            .-          .            .  116 


SPECIAL  HISTOLOGY. 

OF  THE  EXTERNAL  INTEGUMENT,  pp.  119-222. 
I.— OF  THE  SKIN  IN  THE  MORE  RESTRICTED  SENSE,  pp.  119-159. 

A.    CUTIS   DERMA,  pp.   119-139. 

31.  Parts  of  the  common  integument,    .            .  ^  .  .            .119 

32.  Subcutaneous  cellular  tissue,      .         .  -;.            .  .  ".  .            119 

33.  Parts  of  the  corium,  tactile  papillae,  .            .  .  .  .      120 

34.  Connective  tissue,  elastic  fibres,  and  muscles  of  the  corium,  .          .  .  ••.         123 

35.  Fat-cells,        .            .            .            .        '    .  .  '.  .125 

36.  Vessels  of  the  Skin,         .            ...       '  .;   '        .  .  .  •.  '          127 

37.  Nerves,          .            .            .            .,       =   OfiSI  .  .  ',        few     129 

38.  Development  of  the  Cutis,          .             .            .  .  .  134 

39.  Physiological  remarks,          .            .          „  :  .  ,  .            :      135 

B.    CUTICLE    OR   EPIDERMIS,  pp.  139-159. 

40.  Parts  of  the  Epidermis,    .            .            .            .            .'  .        .->      ,  ^  .          I39 

41.  Mucous  layer,            ......'.  V     140 

42.  Horny  layer,        .             .            jj£j    -....':          .  142 

43.  Colour  of  the  Epidermis,       .            .            i'            .            .  .143 

44.  Thickness  of  the  Epidermis,       .            .            .            .            .  145 

45.  Physical  and  Chemical  relations,     ......  ..      146 

46.  Growth  and  regeneration,            .....  150 

47.  Development,            .            .            .           vO         .            •            •  .154 

II.— OF  THE  NAILS,  pp.  159-171. 

48.  Parts  of  the  Nail,  .  .    .        -  -  .  159 

49.  Structure  of  the  Nail,  .  .  .  .  .  .161 

50.  Relation  of  the  Nail  to  the  epidermis,    ...  164 

51.  Growth  of  the  Nails,  .......      165 

52.  Development  of  the  Nails,          ......  169 

III.— OF  THE  HAIRS,  pp.  171-199. 

OF   THE    HAIRS    IN   THE    MORE    RESTRICTED    SENSE. 

53.  Parts  of  the  Hair,       .  .  .  .  •  •  •  .171 


CONTENTS.  XIX 

SECT.  PAGE 

54.  Disposition  and  size  of  the  Hairs,           .            .            .            .            .  171 

55.  External  peculiarities,  and  Chemical  composition  of  the  Hairs,     .  .      172 

56.  Structure  of  the  Hairs,  cortical  substance,           ....  173 

57.  Medullary  substance,  .......      177 

58.  Cuticular  covering,          ...             ....  180 

59.  Hair-follicles,              .             .             .             .             .             .             .  .182 

60.  Hair-follicle  in  the  more  restricted  sense,           ....  182 

61.  Root-sheaths,  ........      184 

62.  Development  of  the  Hair,            .             .             .             .                          .  186 

63.  Shedding  of  the  Hair,            .             .             .             .             .             .  .191 

64.  Physiological  remarks,                .            .            .            .            .            .  193 


IV.__OF  THE  CUTANEOUS  GLANDS,  pp.  199,  222. 

A.    OF    THE    SUDORIPAROUS    GLANDS,    pp.   199-209. 

65.  Disposition,          ........  199 

66.  Structure,        .-  .  .  .  .  .  .  .  .199 

67.  More  intimate  structure  of  the  glandular  coil,    ....  200 

68.  Secretion  of  the  sudoriparous  glands,            .....  202 

69.  Sweat-Ducts,        ........  204 

70.  Development  of  the  sudoriparous  glands,     .....  205 

B.    OF   THE    CERUMINOUS    GLANDS,    pp.    209-212. 

71.  Structure,              ........  209 

72.  Secretion  and  development,              ......  210 

C.    OF   THE    SEBACEOUS    GLANDS,    pp.    212-222. 

73.  Structure,  form,  arid  disposition,              .             .             .             .             .  212 

74.  More  intimate  structure,        .......  216 

75.  Development,      .            .            .            .            .            ,            .            .  218 

OF  THE  MUSCULAR  SYSTEM,  pp.  222-266. 

76.  Definition  of  it,          ........  222 

77.  Structure  of  the  muscular  fibres,             .....  223 

78.  The  mode  in  which  they  are  associated,     .....  229 

79.  Connection  with  other  parts,       .            .            .            .            .            .  231 

80.  Structure  of  the  tendons,       .......  232 

81.  Connection  of  the  tendons  with  other  parts,        ....  235 

82.  Accessory  organs  of  the  muscles  and  tendons,        ....  238 

83.  Vessels  of  the  muscles  and  accessory  organs,    ....  243 

84.  Nerves  of  the  muscles,           .            .            .            .            .            .            .  245 

85.  Chemical  and  physical  relations  of  the  muscles,           .            .            .  250 

86.  Development  of  the  muscles  and  tendons,  .....  253 

87.  Physiological  remarks,    .......  259 

OF  THE  OSSEOUS  SYSTEM,  pp.  266-345. 

88.  Definition,  form,  occurrence,            ......  266 

89.  Intimate  structure  of  the  osseous  tissue,             ....  267 


XX  CONTENTS. 

SECT.  PAGE 

90.  Matrix  of  bone,       ........  270 

91.  Lacunse  and  canaliculi,               ......  275 

92.  Periosteum,              .....                                       .  281 

93.  Marrow,              ...                          .  282 

94.  Articulations  of  the  bones  :  ( A.}  Synarthrosis,        ....  284 

95.  (#.)  Movable  articulation,  Diarthrosis,             .             .             .             .  291 

96.  Articular  capsules,  ......                          .  295 

97.  Physical  and  chemical  properties  of  the  bones  and  their  accessory  organs,  299 

98.  Vessels  of  the  bones,  &c.,  .                         .'            .                         .            .  301 

99.  Nerves  of  the  osseous  system,  ..'...         ''•'.'"  303 

100.  Development  of  the  bones,           \v           .'            .             .         :;'-.            .  306 

101.  Primordial  cartilaginous  skeleton,         .             .             .             .             .  306 

102.  Metamorphoses  of  the  primordial  cartilaginous  skeleton,             .            .  310 

103.  Changes  in  the  ossifying  cartilage,       .                                                '  %  314 

104.  Ossification  of  the  cartilage,  .  .  .  .  .316 

105.  Elementary  processes  in  the  layers  formed  from  the  periosteum,       .  324 

106.  Bones,  not  primarily  cartilaginous,              ,f            .             .                          ,  330 

107.  Growth  of  the  secondary  cranial  bones,            .             .    '        .             .  330 

108.  Vital  phenomena  in  the  mature  bones,      .            .            .            .          .,,  336 


OF  THE  NERVOUS  SYSTEM,  pp.  345-436. 

109.  Definition,  division,     ,.    ,     ...         ....            .            .  345 

ELEMENTS    OF    THE    NERVOUS    SYSTEM,    pp.    345-359. 

110.  Nerve-tubes  or  fibres,.          .......  345 

111.  Nerve-cells,        .            ....        ....  v  ,         .            .  356 

CENTRAL   NERVOUS    SYSTEM,    pp.    359-404. 

112.  Spinal  cord,              ........  359 

113.  Conjectural  course  of  the  fibres  in  the  spinal  cord,      .            .            .  369 

114.  Medulla  oblongata  and  Pons  Varolii,          .....  372 

115.  Cerebellum,       .          '  .    :         ......  379 

117.  Ganglia  of  the  cerebrum,    .....  .  '  382 

117.  Hemispheres  of  the  cerebrum,              .....  385 

118.  Membranes  and  vessels  of  the  central  nervous  system,    .            .  392 

PERIPHERAL   NERVOUS    SYSTEM,    pp.    404-436. 

119.  Spinal  nerves,    .........  404 

120.  Structure  of  the  spinal  ganglia,        ......  405 

121.  Further  course  of  the  spinal  nerves,      .            .            .            .            .  411 

122.  Cerebral  nerves,       .  .  .  .  .  .  .  .416 

123.  Ganglionic  nerves,         .             .             .             .             .             .             .  418 

124.  Main  trunk  of  the  ganglionic  nerves,          .....  418 

125.  Peripheral  distribution  of  the  ganglionic  nerves,          .             .            .  423 

126.  Development  of  the  elements  of  the  nervous  system,        .            .            .  426 

127.  Functions  of  the  nervous  system,         .            .            .            .            .  431 


CONTENTS.  XXI 


OF  THE  DIGESTIVE  ORGANS,  pp.  436-568. 
OF  THE  INTESTINAL  CANAL,  pp.  436-528. 

SECT.  PAGE 

128.  General  structure,    ...  ....      436 

OF  THE  ORAL  CAVITY,  pp.  436-499. 

A.  OF  THE  MUCOUS  MEMBRANE  OF  THE  ORAL  CAVITY,  pp.  436-441. 

129.  Mucous  membrane  and  submucous  tissue,  .  .  .      436 

130.  Epithelium  of  the  cavity  of  the  mouth,  .  .  .  438 

B.    OF   THE    TONGUE,    pp.    441-455. 

131.  Muscular  structure  of  the  tongue,  ......      441 

132.  Mucous  membrane  of  the  tongue.        .....  446 

C.     OF    THE    GLANDS    OF    THE    ORAL    CAVITY,    pp.    455-467. 

1.  Mucous  Glands: — 

133.  Different  kinds  of  glands,    .......      455 

134.  Their  more  intimate  structure,  ...  .  456 

2.  Follicular  Glands:— 

135.  Simple  follicles  and  Tonsils,  .  .      459 

3.  Salivary  Glands: — 

136.  :.  .  .  .  .  .  .  .  .  .463 

D.    OF   THE   TEETH,    pp.    467-499. 

137.  Constituent  parts,    ........  467 

138.  Dentine  (substantia  eburned],     ......  468 

139.  Enamel  (substantia  vitrea],  .  .  .  .  .  .476 

140.  Cement  (substantia  osteoidea),    .            .             «             .             .             .  480 

141.  Soft  parts  of  the  teeth,         .                          .             ..            .             .             .  483 

142.  Development  of  the  teeth,         .                                     .            .            .  484 

143.  Physiological  conditions  of  the  teeth,        v            ....  494 

OF  THE  ORGANS  OF  DEGLUTITION,  pp.  499-502. 

1,    THE   PHARYNX. 

144 .499 

1.     THE    (ESOPHAGUS. 

145.  ..........      501 

OF  THE  ALIMENTARY  CANAL,  pp.  502-528. 

146.  General  conformation,               .                         .            .            .            .  502 

147.  Peritoneum,               ........  502 

148.  Muscular  coat  of  the  alimentary  canal,            ....  503 

149.  Mucous  membrane  of  the  stomach,           .....  505 


XX11  CONTENTS. 

SECT.  PAGE 

150.  Gastric  glands,  .....  .506 

151.  Other  particulars  of  the  mucous  membrane,           .             .             .             .  509 

152.  Mucous  membrane  of  the  small  intestine,       .            .             .             .  511 

153.  VHli  of  the  small  intestine,               ......  511 

154.  Glands  of  the  small  intestine,   ......  518 

155.  Closed  follicles  of  the  small  intestine,         .....  520 

156.  Mucous  Membrane  of  the  large  intestine,        .            .    '       .,            .  524 

157.  Development  of  the  intestinal  canal,  ..          .  .  ,;  .  •    526 

OF  THE  LIVER,  pp.  528-549. 

158.  General  structure,    .            .            .            .            .            .        ,;..f, ,,       ,.  528 

159.  More  intimate  structure,             ......  528 

160.  Hepatic  cells  and  cell  networks,     .             .             .            '."           .'           .  532 

161.  Excretory  ducts  of  the  liver,      .            .            .            ...           «•.           .  537 

162.  Vessels  and  nerves  of  the  liver,      .         •-<.•  ^\'--    " .  »..tf         .             .             .  541 

163.  Development  of  the  liver,          .            .  ..        .         -.,,.        ..       •-.,*>„  546 

OF  THE  PANCREAS,  pp.  549-551. 

164.  ..       •' .'  '•'        $9      T-.'v'-J        ^        :i-  jio       -.„:.      ,-?;••.     r,   ^            ^  549 

OF  THE  SPLEEN,  pp.  551-568. 

165.  General  structure,    .           .,            .            ./:•         .         '  .'         :-«  r       ;.  551 

166.  Coats  and  trabecular  structure  of  the  spleen,  .            .            .,         .-.   .  551 

167.  Malpighian  structure  of  the  spleen,             .            .            .            .            .  552 

168.  Red  substance  of  the  spleen,                 .            .            .          "." '  '        .•  556 

169.  Vessels  and  nerves  of  the  spleen.  ....        --  v?       •">. .  562 

170.  Physiological  remarks,             *.           .,            .           ••  <        ••            .  567 

OF  THE  RESPIRATORY  ORGANS,  pp.  568-595. 

171.  Enumeration  of  the  respiratory  organs,            ;  568 

OF  THE  LUNGS,  pp.  568-585. 

172.  General  structure,    .'......          :.  568 

173.  Larynx,               .             ;             .             .             .             .             .             .  569 

174.  Trachea,       ;  \  .  .  .  ...  .  .    .  572 

175.  Lungs,    .             .             .             .             .             .             .                         ;.  •  574 

176.  Air-vessels  and  cells,           .            .            .            .            .            y            .  575 

177.  Minute  structure  of  the  bronchia,           .            .            .        '• •  '»''          .  578 

178.  Vessels  and  nerves  of  the  lungs,     .            .             .            .            .  580 

179.  Development  of  the  lungs,        .            ..        *  .            .            .            .  583 

OF  THE  THYROID  GLAND,  pp.  585-589. 

180.  General  structure  of  the  thyroid  gland,       .            .            .            .  585 

181.  Minute  structure,  -......;  586 

OF  THE  THYMUS,  pp.  589-595. 

182.  General  structure  of  the  thymus,      .  .  .  .  .  .589 

183.  Minute  structure,           .            .            .            .            .            .            .  591 

184.  Development  of  the  thymus,            ......  593 


CONTENTS.  XX111 

OF  THE  URINARY  ORGANS,  pp.  595-613. 


PAGE 


185.  Enumeration  of  the  urinary  organs,            .....  595 

186.  Kidneys — general  structure  of,  .             .             .             .             .             .  595 

187.  Composition  of  the  renal  substance,           .....  596 

188.  Tubuli  uriniferi,              .......  598 

189.  Vessels  and  nerves  of  the  kidneys,             .....  602 

190.  Urinary  passages,          .......  607 

191.  Physiological  remarks,        .  .  .  .  .  .  .608 

OF  THE  SUPRARENAL  GLANDS,  pp.  613-618. 

192.  General  description  of  the  suprarenal  glands,         .  .  .  .613 

193.  Minute  structure,            .             .             .             .             .             .             .  613 

194.  Vessels  and  nerves,  .  .  .  .  .  .  .615 

1,95.  Physiological  remarks,               .             .             .             .             .             .  616 

OF  THE  SEXUAL  ORGANS,  pp.  618-667. 

A.    MALE    SEXUAL   ORGANS,    pp.    618-640. 

196.  Enumeration  of  the  male  sexual  organs,          .            .            .            .    .  618 

197.  Testes,  .  .  .  .  .  .  .  .  .618 

198.  Tubuli  seminiferi,          .             ......  621 

199.  Membranes,  vessels  and  nerves  of  the  testes,         ....  626 

200.  Vasa  deferentia,  vesiculce  seminales,  and  accessory  glands,          .            .  627 

201.  Organ  of  copulation,             .......  630 

202.  Physiological  remarks,              .            .            .            .            .            .  634 

B.  FEMALE  SEXUAL  ORGANS,  pp.  640-660. 

203.  Enumeration  of  the  female  sexual  organs,             .            .            .            .  640 

204.  Ovary,  parovarium,         .            .            .             .             .             .             .  640 

205.  Detachment  and  re-formation  of  the  ova,   .....  643 

206.  Uterus  and  oviducts,      .            .                         .            .            .            .  646 

207.  Changes  in  the  uterus  at  the  menstrual  period  and  in  pregnancy,            .  649 

208.  Vagina  and  external  genitals,   ......  654 

209.  Physiological  remarks,        .......  656 

C.    OF    THE    LACTEAL   GLANDS,    660-667. 

210.  Their  structure,              .......  660 

211.  Physiological  remarks,        .......  663 

OF  THE  VASCULAR  SYSTEM,  pp.  66T-715. 

212.  Its  elements,            ........  667 

I.— OF  THE  HEART,  pp.  667-674. 

213 667 

II.— OF  THE  BLOODVESSELS,  pp.  674-693. 

214.  General  structure  of  the  bloodvessels,        .....  674 

215.  Arteries,             ........  678 

216.  Veins,          .........  684 

217.  Capillaries,        .            .            .            .                         .            .            .  689 


XXIV  CONTENTS. 

III.— OF  THE   LYMPHATIC  SYSTEM,  pp.  693-699. 

SECT.  PAGE 

218.  Lymphatic  vessels,              .            .            .            .            .             .  .693 

219.  Lymphatic  glands,         .......  695 

IV._OF  THE  BLOOD  AND  LYMPH,  pp.  699-725. 

220.  Different  kinds  of  fluids  included  in  those  terms,  and  their  mode  of 

occurrence,        .            .            .            ;            .            .            .  .      699 

221.  General  structure  of  the  morphological  elements,        .            5.  '         '. '  700 

222.  Of  the  blood,            .             .             .             ...             .  .703 

223.  Physiological  remarks,              .        IV.?'        .            .            .        "•?/  715 

OF  THE  HIGHER  ORGANS  OF  SENSE,  pp.  725-785. 

I.— OF  THE  ORGAN  OF  VISION,  pp.  725-767. 

224.  Its  parts,       .            .            .            .            .            .            .            .  .725 

A.    OF    THE    EYEBALL,  pp.   725-757. 

225.  Fibrous  tunic  of  the  eye,       ;  •            •            •        '•'  •'•           •            .  725 

226.  Vascular  tunic,        .            .         .  ..  ,        '•          v   |        •'  -         .  .      733 

227.  Nervous  tunic,  .  .  > '        \  ,.  ..  ..          .„,.-.•        739 

228.  The  lens,      .           ,.           ..           ..            ..           ;.            .         .    .  .      750 

229.  The  vitreous  humor,     .          ...^     •  • ..,-,          .        N  -.;         ..        ,    .;  753 

B.    ACCESSORY   ORGANS,    pp.    757-760. 

230.  Eyelids,  conjunctiva,  lachrymal  apparatus,              .-,      ..-.        .  .      757 

231.  Physiological  remarks,              .            .            .                         .  760 

II.— OF  THE  ORGAN  OF  HEARING,  pp.  767-778. 

232.  -.             .             .            -.                          -.          -.-.         -'y           .  ,      767 

233.  External  and  middle  ear,         >  -,'         .            ;           -.'^      ;;>.            .  767 

234.  The  vestibule  and  semicircular  canals,      .                         .            .  .'     769 

235.  Cochlea,              ..-•'.;         .            .            .            .             .  770 

III.— OF  THE  OLFACTORY  ORGAN,  pp.  778-785. 

236.  Its  parts,       .            ,            .            .            .            .            .            .  .      778 


APPENDIX. 

1.  Corpuscula  tacttis  and  Pacinian  bodies,     .            .            .            .            .  785 

2.  Malpighian  bodies  of  the  spleen,       .            .            .            .            .  .      786 

3.  Corpora  lutea,        .  ....        .......  787 

4.  Development  -of  the  teeth,     .            .            .            .            .            .  .^     789 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1.  Nerve-cells  of  the  Thalamus  Opticus  of  Man,     .  .             .             .             .44 

2.  Contents  of  a  Malpighian  Corpuscle  of  the  Ox,         ....  48 

3.  Cells  from  the  Cephalic  Cartilage  of  a  Tadpole,  .             .             .             .50 

4.  Nuclei  from  the  Ovum  of  an  Ascaris  dentata,  ....             50 

5.  Ova  of  Ascarus  nigrovenosa,        ......  .51 

6.  Cartilage-cells  from  Articular  Cartilage  of  the  Condyle  of  the  Femur  of  Man,        53 

7.  Cells  from  the  Medullary  Cavities  of  the  Flat  Bones  of  the  Skull  in  Man,  53 

8.  Dividing  Blood-corpuscles  of  the  Chick,  .             .             .             .             .54 

9.  Dentine  Cells,  from  the  Dog,  ......             55 

10.  Cartilage  Cells  of  Man,    ........      60 

11.  Bone-cells  from  a  Rachitic  Bone,      ......  60 

12.  Plates  of  the  Horny  Layer  of  the  Epidermis  in  Man,     .  .             .             .75 

13.  Epidermis  of  a  two  months'  Human  Embryo,  ...                          76 

14.  Epithelial  Cells  of  the  Bloodvessels,        .  .             .             .             .             .76 

15.  Epithelium  of  the  Intestinal  Villi  of  the  Rabbit,      ....  76 

16.  Ciliated  cells  from  the  finer  Bronchise,    ....  .76 

17.  A  simple  Papilla  with  manifold  Vessels  and  Epithelium  from  the  Gums  of  a  Child,      77 

18.  Ciliated  Epithelium  from  the  Trachea  of  Man,  .             .             .             .77 

19.  Portion  of  the  Chorda  Dorsalis  of  an  Embryo  Sheep,  ...             80 

20.  Cartilage  Cells  from  the  White  Layer  of  the  Cricoid  Cartilage,  .             .      80 

21.  Portion  of  a  Human  Epiglottis,       .  .  .             .             .             .             .             81 

22.  Elastic  Network  from  the  Tunica  Media  of  the  Pulmonary  Artery  of  a  Horse,       81 

23.  Bundles  of  Connective  Tissue  from  the  Arachnoid  of  Man,  .             .             82 

24.  Network  of  Fine  Elastic  Fibres  from  the  Peritoneum  of  a  Child,  .             .      82 

25.  Elastic  Membrane  from  the  Tunica  Media  of  the  Carotid  of  a  Horse,  .             82 

26.  Formative  Cells  of  Elastic  Fibres,  from  the  Tendo-Achillis,      .  .             .83 

27.  Stellate  Formative  Cells  of  the  Nucleus  Fibres  of  Tendo-Achillis  of  a  new- 

born Infant,  .  .  .  .  .  .  .  .83 

28.  Lax  Connective  Tissue  with  Fat-cells,  from  Man,    ....  89 

29.  Formative  Cells  of  the  Connective  Tissue  from  the  Skin  of  a  Sheep's  Embryo,       90 
80.  Formative  Cells  of  the  Areolated  Connective  Tissue  from  the  Allantois  of  a 

Sheep's  Embryo,      ........      90 

31.  Perpendicular  section  of  a  Parietal  Bone,    .....  99 

32.  Developing  Bone-cells  from  a  Rachitic  Bone,     .  .             .             .             .100 

33.  Muscular  Fibre-cell  from  the  Small  Intestine  of  Man,         .  103 

34.  Muscular  Fibre-cell  from  the  Investment  of  the  Spleen  of  a  Dog,          .  .    103 

35.  Muscular  Fibres  from  Man,  ......          106 

36.  Primitive  Fibrils  from  a  Primitive  Bundle  of  the  Axolotl,         .  .            .106 


XXVI  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

37.  Tubular  Nerve-fibres  of  Man,            ......  110 

38.  Nerve-cell  of  the  Pike,     .            .            .            .            .            .            .  .110 

39.  Nerve-cells  from  the  floor  of  the  Fourth  Ventricle  in  Man,               .             .  Ill 

40.  Network  of  Hepatic  Cells,            .             .             .             .            .             .  .113 

41.  Two  of  the  Smallest  Lobes  of  the  Lung  from  a  new-born  Child,      .             .  113 

42.  Gastric  Gland  from  the  Pylorus  of  the  Dog,        .....    114 

43.  Glandular  Vesicles  from  the  Thyroid  Gland  of  a  Child,         .             .             .  117 

44.  Malpighian  Corpuscle  from  the  Spleen  of  the  Ox,          .             .             .  .117 

45.  Perpendicular  section  of  the  Skin  of  the  Ball  of  the  Thumb,            .             .  119 

46.  Compound  Papillae  of  the  Surface  of  the  Hand,               .             .             .  .121 

47.  Horizontal  Section  of  the  Skin  of  the  Heel,                .             .             .             .  121 

48.  Two  Papillae  of  the  Surface  of  the  Hand,            .             .             .             .  .122 

49.  Elastic  Fibres  from  the  Fascia  Lata  of  Man,             .             .  123 

50.  Normal  Fat-cells  from  the  Breast,           ....             .  •  .    125 

51.  Fat-cells  with  Crystals  of  Margarin,             .             .             .                          .  125 

52.  Vessels  of  the  Fat- cells;  after  Todd  and  Bowman,        .             .             .  .128 

53.  Vessels  of  the  Papillae  of  the  Cutis;   after  Berres,  ....  128 

54.  Two  Papilke  from  the  extremities  of  the  Fingers,  with  Axile-corpuscles,  .     129 

55.  A.  Surface  of  the  Palm  from  within,             ....        •-•-*•  139 

55.  B.  Perpendicular  section  of  the  Skin  of  the  Negro,        .  .  .  .    140 

56.  Horny  Epidermic  Plates  of  Man,      .  .  .  .  .  .  142 

57.  Horny  Plates  boiled  with  Caustic  Potassa,          .  .  .         *  ;.   ..         .    148 

58.  Transverse  section  through  the  Body  and  Bed  of  the  Nail,  .•  .;.    :.       159 

59.  Capillaries  of  the  Bed  of  the  Nail ;  after  Berres,  .  .          :•:./<*         .    160 

60.  Longitudinal  section  through  the  Matrix  of  the  Nail,  .  .  .  .;          161 

61.  Transverse  section  through  the  Body  of  the  Nail,          .  .  .-.  .     162 

62.  Nail  Plates  boiled  with  Caustic  Soda,  .  .  .  .  ..163 

63.  Hair  and  Hair-sacs  of  middling  size,      ...  .  .          -. .;» ..  ..        .    171 

64.  Plates  of  the  Cortical  Substance  of  a  Hair,  .  .  .  ,,  174 

65.  White  Hair  after  treatment  with  Caustic  Soda,  .  .          . :, : ;         .175 

66.  Cells  from  the  Cortex  of  the  Root  of  the  Hair,          ....  176 

67.  Cells  from  deepest  part  of  Hair  Bulb,     .  .  .  .  .  .176 

68.  Root  of  a  dark  Hair  acted  upon  by  Caustic  Soda,    ....  177 

69.  Medullary  Cells  of  Hair,  .  .  .  .  .  .  .178 

70.  Surface  of  the  Shaft  of  a  White  Hair,  .  .  .  .  .180 

71.  Portion  of  the  transverse  fibrous  layer  and  structureless  membrane  of  a  Human 

Hair-sac,      .........    183 

72.  Elements  of  the  inner  Root-sheath,  .  .  .  .185 

73.  Rudiment  of  the  Hair  from  the  Brow  of  a  Human  Embryo,       .  .  .    187 

74.  Rudiment  of  the  Hair  from  the  Eyebrow,     .....  189 

75.  Rudimental  Hair  from  the  Eyebrow,      .  .  .  .  .  .189 

76.  Eyelashes  of  a  Child,  .......  191 

77.  Eyelashes  with  the  Root-sheaths  from  a  Child,  .  .  .  .191 

78.  A  Sudoriparous  Coil  and  its  Vessels,  .....  199 

79.  Sweat-ducts,         .........    201 

80.  Perpendicular    section   through    the    Epidermis  and   outer   surface   of   the 

Corium,        .            .            .            .             .             .            .            .  .    204 

81.  Rudiment  of  a  Sudoriparous  Gland  of  a  Human  Embryo,  .             .             .  206 

82.  Rudiment  of  a  Sudoriparous  Gland  from  a  seven  months'  Foetus,          .  .    206 

83.  Perpendicular  section  through  the  Skin  of  the  External  Auditory  Meatus,  210 

84.  Sebaceous  Glands  from  the  Nose,           .            .            .            .            .  .213 

85.  A  Gland  from  the  Nose,  with  Hair-sac  opening  into  it,                     .             .  213 

86.  Two  Sebaceous  Glands,  ........    215 

87.  A  Glandular  Vesicle  of  a  common  Sebaceous  Gland,            .            •            .  216 


LIST     OF    ILLUSTRATIONS.  XXV11 

FIG.  PAGE 

88.  The  development  of  the  Sebaceous  Glands  in  a  six  months'  Foetus,    .             .  219 

89.  Primitive  Fibrils  from  a  primitive  fasciculus  of  the  Axolotl,          .             .  223 

90.  Transverse  sections  of  Muscular  Fibre,             .....  224 

91.  Human  Muscular  Fibre  treated  with  Acetic  Acid,              .             .             .  224 

92.  A  Primitive  Fasciculus,  separating  transversely  into  discs  ;   after  Bowman,  225 

93.  Primitive  Fibres  from  a  transversely  striated  Muscle  of  a  Bug,     .             .  226 

94.  Transverse  section  of  Rectus  Capitis  Anticus  Major  of  Man,  .             .             .  230 

95.  Transverse  section  of  a  Tendon  of  a  Calf,  ..... 

96.  Tendon  of  the  Tibialis  Posticus,            ....                          .  234 

97.  A  Primitive  Fasciculus  from  Intercostal  Muscle  of  Man,  .             .             .  235 

98.  Disposition  of  Muscular  Fibres  at  their  insertion  into  the  Tendon,      .             .  235 

99.  Insertion  of  the  Tendo-Achillis  into  the  Calcaneum,           .             .  237 

100.  Cartilage- cells  from  the  Vaginal  Ligaments  surrounding  the  Tendons  of  the 

Poplitseus,  .  .  .  .    -  .  .  .241 

101.  Capillary  Vessels  in  Muscle,      .......  243 

102.  Expansion  of  the  Nerves  in  the  Omo-hyoid  muscle  of  Man,            .             .  246 

103.  Divisions  of  the  Primitive  Nerve-fibres  in  Muscle,        ....  246 

104.  Divisions  of  Nerve-fibres  in  Thoracic  Muscle  of  the  Frog,               .             .  250 

105.  Primitive  Fasciculi  of  a  Human  Embryo,          .....  254 

106.  Primitive  Fibres  of  a  Human  Embryo,        .....  254 

107.  From  the  Tendo-Achillis  of  a  New-born  Child,  .  .  .  .256 

108.  Primitive  Fibres  from  the  Alar  Muscles  of  the  Dung-fly,  .             .             .  259 

109.  Primitive  Fasciculae  of  a  Frog's  Muscle  in  different  degrees  of  Extension,       .  264 

110.  Transverse  section  of  Human  Femur,          .....  268 

111.  Haversian  Canals  from  Superficial  Layer  of  Human  Femur,    .             .             .  268 

112.  Transverse  section  of  Human  Metacarpal  Bone,     ....  271 

113.  Transverse  section  of  Shaft  of  Humerus,           .....  271 

114.  Perpendicular  section  of  Parietal  Bone,     .             .             .             .             .  273 

115.  Transverse  section  of  Shaft  of  Humerus,           .....  276 

116.  Section  parallel  with  Surface  of  Human  Femur,    ....  276 

117.  Lacunae  and  Canaliculi  of  Parietal  Bone,          .....  277 

118.  Surface  of  a  Tibia  of  Calf,                ......  279 

119.  Bony  Spicula)  from  Apophysis,               ......  280 

120.  Fat^cells  from  Marrow  of  Human  Femur,                .             .  283 

121.  Transverse  section  of  Ligamentum  Nuchae  of  Ox,         ....  285 

122.  Cells  from  Gelatinous  Nucleus  of  the  Lig.  Intervertebralia,            .             .  286 

123.  Cartilaginous  border  of  Human  Symphysis,      .....  289 

124.  Human  Cartilage  Cells,       .......  290 

125.  Perpendicular  section  of  Articular  Cartilage  of  Human  Metacarpal  Bone,      .  292 

126.  Diagram  of  Transverse  Section  of  Phalangeal  Articulation,           .             .  295 

127.  Synovial  Membrane  of  Phalangeal  Articulation,           ....  297 

128.  Falciform  Ligament  of  Knee,           ......  298 

129.  Cartilage  Cells  from  Humerus  of  Embryo  of  Sheep,     ....  308 
130    Perpendicular  section  of  Ossifying  border  of  Shaft  of  Femur,        .             .  314 

131.  Femur  of  a  Child,  .  .  .  .  .  .  .  .314 

132.  Femur  of  a  Rachitic  Child,              ......  317 

133.  Transverse  section  of  Metatarsus  of  Calf,         .....  324 

134.  Diagram  of  Growth  of  Cylindrical  Bone,     .....  327 

135.  Parietal  Bone  of  Foetus,          .  .             .            .             .             .             .             .  331 

136.  Parietal  Bone  of  new-born  Child,    ......  331 

137.  Nerve  Fibres  of  Man,     .  .  .  .  .  .  .  .346 

138.  Human  Nerve-tubes,            .......  346 

139.  Nerve  Fibres,     .  .  .  .  .  .  .  .348 

140.  Nerve-cells  from  Acoustic  Nerve,    .            .            .            .            .            .  357 


XXV111  LIST    OF    ILLUSTRATIONS. 

Fid.  PAGE 

141.  Transverse  section  of  Spinal  cord,         ......  361 

142.  Cells  from  Gray  Central  Nucleus  of  Cord,                ....  363 

143.  Nerve-cells  from  Anterior  Cornua  of  Cord  in  Man,       ....  364 

144.  Vertical  section  of  Spinal  Cord,       ......  366 

145.  Five  transverse  sections  of  Human  Spinal  Cord,           ....  370 

146.  Transverse  section  through  Human  Medulla  Oblongata,    .             .             .  373 

147.  Nerve-cells  of  the  Substantia  Ferruginea,        .....  376 

148.  Large  Cells  of  Cortical  Substance  of  Human  Cerebellum,               .             .  380 

149.  Internal  portions  of  Gray  Layer  of  Human  Cerebral  Convolutions,     .             .  387 
150    Finest  Nerve-tubes  of  Superficial  White  Substance  of  Human  Cerebrum,  388 

151.  Ependyma  in  Man,         ........  397 

152.  Vessels  of  Cerebral  Substance  of  Sheep,     .             .             .         -v            .  400 

153.  Brain-sand  from  Pineal  Gland,              ....         ...  .,.!;<         .  401 

154.  Lumbar  Ganglion  of  Young  Dog,     .             .             ...             .           f.  405 

155.  Ganglion  Globules  from  Gasserian  Ganglion  of  Cat,     .             .            :r            .  407 

156.  Cells  from  Sheath  of  Nerve-cells  of  Spinal  Ganglia  in  Man,         ,  ,.-       .    .  407 

157.  Coccygeal  Nerve,  with  an  adherent  Nerve-cell,             .         i    ..-           ,             .  408 

158.  Nerve-cell  of  the  Pike,         .             .             .             .                      •   „,  ,      "...  409 

159.  A  Pacinian  Body  in  Man,           .             .             .              .         ......             .  413 

160.  Transverse  section  of  Ischiatic  Nerve,         .             .             .          ;  .            .  414 

161.  Ganglion  of  Sympathetic  Nerve  of  Rabbit,        .             .             .          ,.             .  419 

162.  From  the  Sympathetic  in  Man,        .             .             .             .          ;,,  - .     .    ,  •  419 

163.  Nerve-cells  from  the  Cardiac  Ganglion  of  the  Frog,     .          -.            ......        .  424 

164.  Nerve-cells  from  Spinal  Ganglion  of  Human  Embryo,         .        .-' *  .          •  .  427 

165.  Nerve-fibres  from  Ischiatic  Nerve  of  Human  Embryo,              .         •-,  .<           .  427 

166.  Nerve  from  the  Tail  of  a  Tadpole,                .             .             .             .         ...  428 

167.  Simple  Papilla,  with  Vessels  and  Epithelium,               .             .           .  .-            .  438 

168.  Epithelial  cells  in  Oral  Cavity  of  Man,        .             .             .             .             .  439 

169.  Longitudinal  section  of  Human  Tongue,            .  442 

170.  Transverse  section  of  Human  Tongue,         ....            v  -;  443 

171.  Portion  of  longitudinal  section  of  Human  Tongue,       .             .     :      .  .             .  445 

172.  Branched  Primitive  Muscular  Bundle  from  Tongue  of  Frog,          .             .  446 

173.  Two  Papillse  Filiformes  of  Man;  after  Todd  and  Bowman,      .  .  .448 

174.  Papilla  Fungiformis  ;  after  Todd  and  Bowman,     ....  448 

175.  Papilla  Circuuavallata  of  Man,               ......  450 

176.  Epithelial  Cells  covered  with  Granular  Matrix  of  Fungus,             .             .  451 

177.  Papilla  Filiformis  invested  by  a  Fungus,           .....  452 

178.  Racemose  Mucous  Glands  from  the  Floor  of  the  Oral  Cavity,        .             .  457 

179.  Diagram  of  two  Ducts  of  a  Lobe  of  a  Mucous  Gland,   ....  457 

180.  Two.  Glandular  Vesicles  of  a  racemose  Mucous  Gland  of  Man,      .             .  458 

181.  Follicular  Gland  from  the  root  of  the  Tongue  in  Man,              .             .             .  460 

182.  Vesicles  of  a  few  follicles  from  a  Human  Tonsil,      .             .           .             .  461 

183.  Human  Molar  Tooth,     .  .  .  .  .  .  .  .468 

184.  Transverse  section  of  Dentinal  Canals,       .....  469 

185.  Dentinal  Tubules,  .  .  .  .  .  .  .  .470 

186.  Transverse  section  through  the  Dentinal  Canal  of  a  Human  Tooth,           .  470 

187.  Perpendicular  section  of  the  Apex  of  an  Incisor  Tooth,            .             .             .  473 

188.  Dentine  with  Dentinal  Globular  and  Interglobular  Spaces,            .             .  473 

189.  Surface  of  Enamel  from  the  Calf,  .  .  .  .  .  .478 

190.  Enamel  Prisms  from  Man,  .......  478 

191.  Dentine  and  Enamel  from  Man,             ......  479 

192.  Dentine  and  Cement  from  Fang  of  Incisor  Tooth,  ....  481 

193.  Cement  and  Dentine  of  the  Root  of  an  old  Tooth,         ....  482 

194.  Lower  Jaw  of  a  Human  Foetus,       ......  485 


LIST    OF    ILLUSTRATIONS.  XXIX 

FIG.  PAGE 

195.  Diagram  of  the  Development  of  a  Milk-tooth  ;  after  Goodsir,  .  .    485 

196.  Tooth-sac  of  Incisor  of  a  Foetus,      ......  488 

197.  Surface  of  Dentinal  Pulp  of  an  Infant,  ......    489 

198.  Transverse  section  of  Human  (Esophagus,  ....  501 

199.  Muscular-fibre  Cells  from  (Esophageal  Mucous  Membrane,      .  .  .501 

200.  Stomach  of  Man,      .  .......  503 

201.  Muscular-fibre  Cells  from  Small  Intestine,        .....    504 

202.  Bloodvessels  of  Smooth  Muscles  of  Intestine,          .  .  .  .  505 

203.  Perpendicular  section  through  Tunics  of  Pig's  Stomach,          .  .  .    506 

204.  Mucous  Gastric  Gland  of  a  Dog,     ......  507 

205.  Vessels  of  Large  Intestine  of  a  Dog,      ......    510 

206.  Section  through  the  Walls  of  a  Calf's  Ileum,          .  .  .  .512 

207.  Intestinal  Villus  of  a  Young  Kitten,      .  .  .  .  .  .512 

208.  Vessels  of  Villi  of  the  Mouse;  after  Gerlach,          ....  513 

209.  Villi  without  Epithelium  and  with  a  Lacteal,    .  .  .  .  .513 

210.  Intestinal  Villi  of  the  Cat,   .......  514 

211.  Villi  with  the  Epithelium,  from  the  Rabbit,      .....    515 

212.  Lieberkuhnian  Glands  of  the  Pig,    ......  519 

213.  Peyer's  Patch,  in  Man,  .  .  .  .  .    x  .521 

214.  Portion  of  a  Peyer's  Patch  of  an  Old  Man,  ....  521 

215.  Horizontal  section  from  the  middle  of  Peyer's  Follicle  of  the  Rabbit,  .    522 
210.  Solitary  Follicle  from  the  Small  Intestine;  after  Bohm,    .  523 

217.  Solitary  Follicle  from  the  Colon  of  a  Child,       .  .  .  .  .525 

218.  Segment  of  a  Pig's  Liver,     .  .  .....  530 

219.  Portal  Vessel  of  the  Pig;  after  Kiernan,  .  .•  .  .  .530 

220.  Hepatic  Cells  of  Man,  .......  532 

221.  Hepatic  Cell-network,    ........    533 

222.  Hepatic  Cell-network  and  its  capillaries,    .....  542 

223.  Hepatic  Veins  of  the  Rabbit,     .  .  .  .  .  .  .542 

224.  Arterial  Network  upon  surface  of  a  Child's  Liver,  .  .  .  545 

225.  Vessels  ©f  the  Pancreas  of  a  Rabbit,      ......    550 

226.  Section  through  the  middle  of  the  Spleen  of  an  Ox,  .  .  .  551 

227.  Fibres  from  the  Pulp  of  Human  Spleen,  .  .  .  ...    552 

228.  Artery  covered  with  Malpighian  Corpuscles  from  Spleen  of  Dog,  .  553 

229.  Malpighian  Corpuscles  from  Spleen  of  an  Ox,  .....    554 

230.  Contents  of  a  Malpighian  Corpuscle,  .....  554 

231.  Blood-corpuscle-holding  Cells  and  their  Metamorphoses,          .  .  .    559 

232.  Artery  from  the  Spleen  of  a  Pig,     ......  563 

233.  Ciliated  Epithelium  from  the  Human  Trachea,  .  .  .  .571 

234.  Vertical  Section  through  Anterior  'Wall  of  Human  Trachea,          .  .  573 

235.  Lymphatics  in  the  Tracheal  Mucous  Membrane  of  Man,          .  .  .    574 

236.  Pulmonary  Lobules  from  a  Child,    ......  575 

237.  External  Surface  of  the  Lung  of  a  Cow,  .....    577 

238.  Human  Air-cell,        ........  579 

239.  Capillary  plexus  of  Human  Air-cell,      .......    581 

240.  Gland-vesicles  from  the  Thyroid  Gland  of  a  Child,  .  .  .586 

241.  Gland-vesicles  of  Thyroid  filled  with  Colored  Matter,  .  .  .    587 

242.  Portion  of  Thymus  of  a  Calf,  ......          590 

243.  Half  of  Human  Thymus,  .  .  .  .  .  .  .590 

244.  Section  of  an  injected  Lobule  of  Thymus  of  a  Child,  .  .  .  591 

245.  Vertical  section  of  an  injected  Rabbit's  Kidney,  ....    597 

246.  Tubuli  Uriniferi  of  Man,     .......  599 

247.  A  Malpighian  Corpuscle,  .......    599 

248.  From  the  Human  Kidney ;  after  Bowman,  ....          603 


XXX  LIST    OP    ILLUSTRATIONS. 

FIG.  PAGE 

249.  Malpighian  Corpuscle  from  Kidney  of  a  Horse,      ....  603 

250.  Transverse  section  through  Cortical  Tubules,  .....     606 

251.  Epithelium  of  Pelvis  of  Human  Kidney,      .....  606 

252.  Vertical  section  through  Suprarenal  Capsule  in  Man,  .  .  .    614 

253.  From  the  Suprarenal  Capsule  of  Man,        .....  614 

254.  Section  of  Suprarenal  Body  of  the  Calf,  .  .  .  .  .616 

255.  Section  through  Testis  and  its  Tunics  in  Man,       ....  619 

256.  Diagram  of  the  Course  of  a  Spermatic  Tubule,  .  619 

257.  Human  Testis  and  Epididymis  ;  after  Arnold,        ....  619 

258.  Portion  of  a  Spermatic  Tube  in  Man,   ......    621 

259.  Human  Spermatic  Filaments,  ......  622 

260.  Development  of  the  Spermatic  Filaments  in  a  Rabbit,  .  .  .    622 

261.  Glands  of  a  Littre,  .  .  .  .  .  .  .  .631 

262.  Arteries  from  Corpora  Cavernosa  Penis,  .  .  .  l«-l'        .    633 

263.  Section  through  the  Ovary  of  a  Woman,     .  .  .         •* •  ...      ...- ..-•'•"       640 

264.  Graafian  Follicle  of  the  Sow,     .  .  .  .  :,.         -    .  .    641 

265.  Human  Ovulum,       .  .  .  .  .  ...  642 

266.  Two  Corpora  Lutea,       .'....  .  .  .  .    644 

267.  Muscular  Elements  from  the  Uterus  in  Pregnancy,  .  .  ...          649 

268.  Muscular  Fibre-cell  from  a  Gravid  Uterus,       .  .  •        -    *  •    650 

269.  Uterine  Gland,          ......         .-:  .  .  650 

270.  Muscular  Fibre-cell  of  the  Uterus,         .  .  .  .  .652 

271.  Graafian  Follicles  from  Ovary  of  a  Newly-born  Child,       .  .  <  656 

272.  Lobules  of  the  Lacteal  Gland  of  a  Puerperal  Female,  ..  .  .          .    661 

273.  Development  of  Lacteal  Gland,        .  .  .  .  ....          663 

274.  Elementary  Forms  in  Milk,        .  .  .  .  .  .  .    664 

275.  Anastomosing  Primitive  Fasciculus  from  the  Human  Heart,      ;  ,  .  .  668 

276.  Diagram  showing  the  course  of  the  Muscular  Fibres  of  the  Heart,      .  .    672 

277.  Elastic  Membrane  from  the  Tunica  Media  of  the  Popliteal  Artery  in  Man,         675 

278.  Muscular  Fibre-cells  from  the  Human  Arteries,  ....    675 

279.  Artery  and  Vein  from  Mesentery  of  a  Child,  .  .  .*-  .     .    .  679 

280.  Artery  and  Vein  treated  with  Acetic  Acid,        .  .  .  ••••»  .    680 

281.  Transverse  section  of  Art.  Prof.  Femoris  of  Man,  .  .  .          ..  681 

282.  Transverse  section  of  Aorta,       .  .  .  .  - .  ..  ... .  682 

283.  Muscular  Fibre-cell  from  innermost  layer  of  Axillary  Artery,       .  .  683 

284.  Transverse  section  of  the  Saphena  Vein,  .....    685 

285.  Muscular  Fibre-cell  from  Renal  Vein  of  Man,        ....  686 

286.  Longitudinal  section  of  Inferior  Vena  Cav a,     .....    688 

287.  Finest  Vessels  on  the  arterial  side  of  the  Capillaries,         .  .         •  -•:...'       691 

288.  Capillary  Lymphatic  from  the  tail  of  a  Tadpole,  .  .         .'..-..          .693 

289.  Transverse  section  of  Human  Thoracic  Duct,         .  .          -.    .          '.  695 

290.  Elements  of  the  Chyle,  .  .  .  .  .  .700 

291.  Human  Blood-globules,        .  .  .  •  .703 

292.  Colorless  Blood-globules,  .  .  .  .  .  .  .707 

293.  Blood-cells  of  the  Frog  and  of  the  Pigeon,  .  .  .  .  713 

294.  Capillaries  from  the  Tail  of  a  Tadpole,  .  .  .  .  .717 

295.  Blood-corpuscles  of  a  Foetal  Lamb,  .  .  .  .  .  718 

296.  Transverse  section  of  Eye,         .......    726 

297.  Capillaries  and  Lymphatics  of  Cornea  of  a  Kitten,  .  .  .  731 

298.  Nerves  of  the  Cornea  of  a  Rabbit,          .  .  .  .  .  .732 

299.  Cells  from  the  Stroma  of  the  Choroid,          .  ...  .  .734 

300.  Cells  of  the  Pigmentum  Nigrum  of  Man,  .....     735 

301.  Vessels  of  the  Choroid  and  Iris  of  a  Child  ;  after  Arnold,  .  .  737 

302.  Vertical  Transverse  section  of  Human  Retina,  .  .  .  .739 


LIST     OF    ILLUSTRATIONS.  XXxi 

11 5-  PAGE 

303.  Elements  of  Human  Retina,             .;....  740 

304.  Bacillar  Layer  of  Retina,           .......  742 

305.  Nerve-cells  from  Retina  of  the  Ox,               .....  743 

306.  Fibres  of  the  Lens,  from  the  Ox,           .             .             .              .             .             .  751 

307.  Human  lens ;  after  Arnold,              ......  753 

308.  Transverse  section  of  a  Semicircular  Canal,     .....  769 

309.  Vertical  section  of  the  Lamina  Spiralis  ;  after  Corti,         .             .             .  771 

310.  Vestibular  surface  of  the  Lamina  Spiralis  Membranacea,        .             .             .  771 

311.  Bipolar  Ganglion-globule  from  Lamina  Spiralis  of  a  Pig;  after  Corti,      .  774 

312.  From  Nasal  Mucous  Membrane  of  the  Sheep,               ....  780 

313.  From  the  Olfactory  Nerve  of  Man,              .....  782 


INTRODUCTION. 


§  1.  THE  doctrine  of  the  elementary  structure  of  Plants  and  Animals, 
belongs  to  the  last  two  centuries,  originating  with  Marcellus  Malpighi 
(1628-94),  and  Anton  van  Leeuwenhoek  (1632-1723),  at  the  period 
when  the  assistance  of  magnifying  glasses,  powerful,  though  of  very 
simple  form,  was  first  offered  to  observers.  The  ultimate  constituents 
in  respect  of  form,  of  organisms,  were  unknown  to  antiquity  and  to  the 
middle  ages,  for  although  Aristotle  and  Galen  speak  of  the  homogeneous 
and  heterogeneous  parts  of  the  body  (partes  similares  et  dissimilares), 
and  Fallopius  (1523-62)  defined  still  more  exactly  the  idea  of  "  Tissues," 
and  even  attempted  to  classify  them  ('  Tractatus  quinque  de  partibus 
similaribus,'  opera,  torn.  ii.  Francof.  1600),  yet  the  minuter  structures 
were  completely  hidden  from  these  investigators.  Brilliant  as  were  the 
first  efforts  of  the  young  science  under  the  guidance  of  these  men  and  after- 
wards of  a  Ruysch,  Swammerdam,  and  others,  yet  they  were  not  adequate 
to  acquire  a  safe  footing  for  it,  since,  on  the  one  hand,  the  philosophers 
were  far  too  little  masters  of  microscopic  investigation  to  strive  at  once, 
with  a  clear  insight,  towards  the  true  goal ;  while,  on  the  other,  the  deve- 
lopment of  other  branches  of  study,  as  of  the  grosser  Anatomy,  of  Physio- 
logy, of  Embryology,  and  of  Comparative  Anatomy,  claimed  too  large  a 
share  of  their  attention.  It  thus  happened  that,  with  the  exception 
of  a  few  to  some  extent  important  works  (Fontana,  Muys,  Lieberkuhn, 
Hewson,  Prochaska),  Histology  made  no  considerable  progress  during 
the  whole  of  the  18th  century,  and  acquired  no  importance  greater  than 
that  due  to  a  disjointed  collection  of  isolated  observations.  It  was  in 
the  year  1801  that  it  first  acquired  a  rank  co-equal  with  that  of  its 
sister  anatomical  sciences  by  the  genius  of  a  man  to  whom  indeed,  Histo- 
logy owes  no  great  discoveries,  but  who  understood,  as  no  one  before 
him  had  done,  so  to  arrange  existing  materials  and  so  to  connect 
them  with  Physiology  and  Medicine,  that  for  the  future  its  independence 
was  assured.  In  fact,  Bichat's  '  Anatomic  Generale'  (Paris,  1801), 
was  the  first  attempt  to  treat  Histology  scientifically,  and  on  this  ac- 
count merely,  it  constitutes  an  epoch ;  but  besides  this,  its  importance 

3 


31  INTRODUCTION. 

was  still  greater,  inasmuch  as  the  tissues  were  not  merely  clearly  defined 
and  fully  and  logically  treated  of,  but  full  account  was  taken  of  their 
physiological  functions  and  morbid  alterations.  To  this  great  internal 
progress,  the  present  century  has  added  an  ever-increasing  perfection 
of  the  external  aids  of  the  microscope,  and  a  steadily  increasing  zeal  in 
the  investigation  of  nature,  so  that  it  is  not  to  be  wondered  at,  that  in 
its  five  decades,  it  has  left  far  behind  all  that  was  done  in  the  century 
and  a  half  of  its  earlier  existence.  In  the  last  thirty  years  particularly, 
discoveries  have  so  trodden  upon  one  another's  heels,  that  it  must  be 
considered  truly  fortunate  that  a  bond  of  connection  has  arisen,  and 
that  Microscopical  Anatomy  has  thus  escaped  the  danger  of  becoming, 
as  in  earlier  days,  lost  in  minutiae.  In  the  year  1838,  in  fact,  the 
demonstration  by  Dr.  Th.  Schwann,  of  the  originally  perfectly  identical 
cellular  composition  of  all  animal  organisms,  and  of  the  origin  of  their 
higher  structures  from  these  elements,  afforded  the  appropriate  concep- 
tion which  united  all  previous  observations,  and  afforded  a  clue  for 
further  investigations.  If  Bichat  founded  histology  more  theoretically 
by  constructing  a  system  and  carrying  it  out  logically,  Schwann  has, 
by  his  investigations,  afforded  a  basis  of  fact,  and  has  thus  won  the 
second  laurels  in  this  field.  What  has  been  done  in  this  science  since 
Schwann,  has  been  indeed  of  great  importance  to  physiology  and  medi- 
cine, and  in  part  of  great  value  in  a  purely  scientific  point  of  view, 
inasmuch  as  a  great  deal  which  Schwann  only  indicated,  or  shortly 
adverted  to,  as  the  genesis  of  the  cell,  the  import  of  the  nucleus,  the 
development  of  the  higher  tissues,  their  chemical  relations,  &c.,  has  re- 
ceived a  further  development ;  but  all  this  has  not  amounted  to  a  step 
so  greatly  in  advance  as  to  constitute  a  new  epoch.  If,  without  pre- 
tensions to  prescience,  it  be  permitted  to  speak  of  the  future,  this 
condition  of  Histology  will  last  as  long  as  no  essential  advance  is  made 
towards  penetrating  more  deeply  into  organic  structure,  and  becoming 
acquainted  with  those  elements,  of  which  that  which  we  at  present  hold 
to  be  simple,  is  composed.  If  it  be  possible  that  the  molecules  which 
constitute  cell-membranes,  muscular  fibrils,  axile  fibre  of  nerves,  &c., 
should  be  discovered,  and  the  laws  of  their  apposition,  and  of  the  altera- 
tions which  they  undergo  in  the  course  of  the  origin,  the  growth,  and 
the  activity  of  the  present  so-called  elementary  parts,  should  be  made 
out,  then  a  new  era  will  commence  for  Histology,  and  the  discoverer 
of  the  law  of  cell  genesis,  or  of  a  molecular  theory,  will  be  as  much  or 
more  celebrated  than  the  originator  of  the  doctrine  of  the  composition 
of  all  animal  tissues  out  of  cells. 

§  2.  In  characterizing  the  present  position  of  Histology  and  of  its 
objects,  we  must  by  no  means  forget  that,  properly  speaking,  it  con- 
siders only  one  of  the  three  aspects  which  the  elementary  parts  present 


INTRODUCTION.  35 

to  observation,  namely,  their  form.  Microscopical  anatomy  is  concerned 
with  the  understanding  of  the  microscopic  forms,  and  with  the  laws  of 
their  structure  and  development,  not  with  any  general  doctrine  of  the 
elementary  parts.  Composition  and  function  are  only  involved,  so  far 
as  they  relate  to  the  origin  of  forms  and  to  their  variety.  Whatever 
else  respecting  the  activity  of  the  perfect  elements  and  their  chemical 
relations  is  to  be  found  in  Histology,  is  there  either  on  practical  grounds 
in  order  to  give  some  useful  application  of  the  morphological  conditions, 
or  to  complete  them  ;  or  from  its  intimate  alliance  with  the  subject,  it  is 
added  only  because  physiology  proper  does  not  afford  a  due  place  for 
the  functions  of  the  elementary  parts. 

If  Histology  is  to  attain  the  rank  of  a  science,  its  first  need  is  to 
have  as  broad  and  certain  an  objective  basis  as  possible.  To  this  end 
the  minuter  structural  characters  of  animal  organisms  are  to  be  examined 
on  all  sides,  and  not  only  in  fully  formed  structures,  but  in  all  the 
earlier  periods  from  their  first  development.  When  the  morphological 
elements  have  been  perfectly  made  out,  the  next  object  is  to  discover 
the  laws  according  to  which  they  arise,  wherein  one  must  not  fail  to 
have  regard  also  to  their  relations  of  composition  and  function.  In  dis- 
covering these  laws,  here  as  in  the  experimental  sciences  generally, 
continual  observation  separates  more  and  more,  among  the  collective 
mass  of  scattered  facts  and  observations,  the  occasional  from  the  con- 
stant, the  accidental  from  the  essential,  till  at  last  a  series  of  more  and 
more  general  expressions  of  the  facts  arises, — from  which,  in  the  end, 
mathematical  expressions  or  formulae  proceed,  and  thus  the  laws  are 
enunciated. 

If  we  inquire  how  far  Histology  has  satisfied  these  requirements, 
and  what  are  its  prospects  in  the  immediate  future,  the  answer  must  be 
a  modest  one.  Not  only  does  it  not  possess  a  single  law,  but  the 
materials  at  hand  from  which  such  should  be  deduced,  are  as  yet  re- 
latively so  scanty,  that  not  even  any  considerable  number  of  general 
propositions  appear  well  founded.  Not  to  speak  of  a  complete  know- 
ledge of  the  minuter  structure  of  animals  in  general,  we  are  not  ac- 
quainted with  the  structure  of  a  single  creature  throughout,  not  even 
of  man,  although  he  has  been  so  frequently  the  object  of  investigation, 
— and  therefore  it  has  hitherto  been  impossible  to  bring  the  science 
essentially  any  nearer  its  goal.  It  would,  however,  be  unjust  to  over- 
look and  depreciate  what  we  do  possess ;  and  it  may  at  any  rate  be  said 
that  we  have  acquired  a  rich  store  of  facts  and  a  few  more  trustworthy 
general  propositions.  To  indicate  only  the  more  important  of  the  for- 
mer, it  may  be  mentioned,  that  we  have  a  very  sufficient  acquaintance 
with  the  perfect  elementary  parts  of  the  higher  animals,  and  that  we 
also  understand  their  development,  with  the  exception  of  the  elastic 
tissue,  and  of  the  elements  of  the  teeth  and  bones.  The  mode  in  which 


36  INTRODUCTION. 

these  are  united  into  organs  has  been  less  examined,  yet  on  this  head 
also,  much  has  been  added  of  late,  especially  in  man,  whose  individual 
organs  with  the  exception  of  the  nervous  system,  the  higher  organs  of 
sense,  and  a  few  glands  (the  liver,  blood-vascular  glands),  have  been 
almost  exhaustively  investigated.  If  the  like  progress  continue  to  be 
made,  the  structure  of  the  human  body  will  in  a  few  years  be  so  clearly 
made  out,  that,  except  perhaps  in  the  nervous  system,  nothing  more  of 
importance  will  remain  to  be  done  with  our  present  modes  of  investiga- 
tion. With  comparative  Histology  it  is  otherwise ;  hardly  commenced, 
not  years  but  decades  will  be  needed  to  carry  out  the  necessary  investi- 
gations. Whoever  will  do  good  work  in  this  field  must,  by  monographs  of 
typical  forms  embracing  their  whole  structure  from  the  earliest  periods 
of  development,*  obtain  a  general  view  of  all  the  divisions  of  the  ani- 
mal kingdom,  and  then,  by  the  methods  above  described,  strive  to 
develop  their  laws. 

As  regards  the  general  propositions  of  Histology,  the  science  has 
made  no  important  progress  since  Schwann,  however  much  has  been 
attained  by  the  confirmation  of  the  broad  outlines  of  his  doctrines. 
The  position  that  all  the  higher  animals  at  one  time  consist  wholly  of 
cells  and  develop  from  these  their  higher  elementary  parts,  stands  firm, 
though  it  must  not  be  understood  as  if  cells,  or  their  derivatives,  were 
the  sole  possible  or  existing  elements  of  animals.  In  the  same  way, 
Schwann's  conception  of  the  genesis  of  cells,  though  considerably 
modified  and  extended,  has  not  been  essentially  changed,  since  the  cell 
nucleus  still  remains  as  the  principal  factor  of  cell-development  and  of 
cell-multiplication.  Least  advance  has  been  made  in  the  laws  which 
regulate  the  origin  of  cells  and  of  the  higher  elements,  and  our  acquain- 
tance with  the  elementary  processes  which  take  place  during  the  for- 
mation of  organs  must  be  regarded  as  very  slight.  Yet  the  right  track 
in  clearing  up  these  points  has  been  entered  upon  ;  and  a  logical  inves- 
tigation of  the  chemical  relations  of  the  elementary  parts  and  of  their 
molecular  forces,  after  the  manner  of  Bonders,  Ludwig,  and  others,  com- 
bined with  a  more  profound  microscopical  examination  of  them,  such 
as  has  already  taken  place  with  regard  to  the  muscles  and  nerves, — 
further,  a  histological  treatment  of  embryology,  such  as  has  been  at- 
tempted by  Reichert,  Vogt,  and  myself,  will  assuredly  raise  the  veil,  and 
bring  us,  step  by  step,  nearer  to  the  desired  though  perhaps  never  to 
be  reached,  end. 

§  8.  The  aids  in  studying  Histology  may  here  be  best  shortly  ad- 
verted to.  With  respect  to  the  literature  of  the  subject,  the  more  impor- 

*  [See  a  very  praiseworthy  monograph  of  this  kind  by  Leydig,  Beitrage  zur  Mikrosko- 
pischen  Anatomie  und  Entwickelungs-geschichte  der  Rochen  u.  Haie,  1852.  (Microscopic 
Anatomy  and  Development  of  the  Rays  and  Sharks.) — TRS.] 


IKTRODUCTION.  37 

tant  monographic  works  are  cited  under  their  appropriate  section,  and 
here  only  those  large  independent  works  will  be  noticed,  in  which  further 
instruction  is  to  be  found.  It  is  right  to  head  the  list  with  Schwann's 
1  Mikroskopische  Untersuchungen  liber  die  Uebereinstimmung  in  der 
Struktur  und  dem  Wachsthumder  Thiere  und  Pflanzen'  (Berlin,  1839),* 
abstracted  in  Froriep's  'Neue  Notizen'  (1838),  as  the  most  fitting  intro- 
duction to  Histology.  Beside  this,  we  may  name  X.  Bichat,  'Anatomie 
Ge'ne'rale,'  Tom.  iv.  (Paris,  1801);  E.  H.  Weber,  'Handbuchder  Ana- 
tomie  des  Menschen  von  Hildebrandt,'  Bd.  1,  'Algemeine  Anatomie' 
(Braunschweig,  1830),  a  work  distinguished  in  its  day,  and  even  now 
indispensably  necessary,  as  a  store  of  old  literature  [or  Ed.  4  (Stuttgart, 
1833)];  Brun's  'Lehrbuch  der  Allgemeinen  Anatomie  des  Menschen' 
(Braunschweig,  1841),  very  clear,  concise,  and  good  ;  Henle, '  Allgemeine 
Anatomie'  (Leipzig,  1841),  containing  a  classical  account  of  Histo- 
logy in  the  year  1840,  many  original  statements,  and  physiological, 
pathological,  and  historical  remarks  ;  G.  Valentin,  article  i  Gewebe,' 
in  R.  Wagner's  <  Handworterbuch  d.  Physiologic,'  Bd.  i.  (1842);  R.  B. 
Todd  and  W.  Bowman,  '  The  Physiological  Anatomy  and  Physiology  of 
Man,'  Parts  i.  ii.  (London  1845-47),  mostly  based  upon  original  observa- 
tions, very  comprehensive  and  good  [also  Parts  iii.  iv.  (1847—52)]  ; 
Bendz,  '  Haandbogiden  almindelige  Anatomie'  (Kiobenhavn,  1846-47), 
with  industriously  collected  historical  data  ;  A.  Kb'lliker,  '  Mikrosko- 
pische Anatomie  oder  Gewebelehre  des  Menschen,  Band  II.  Specielle 
Gewebelehre,  1,  Halfte.  u.  2  ;  Halfte.  1  Abtheilung'  (Leipzig,  1850-52), 
containing  an  exposition,  as  complete  as  possible,  of  the  minute  struc- 
ture of  the  organs  and  systems  of  man.  With  these  are  to  be  compared 
the  yearly  Reports  of  Henle,  in  Cannstatt's  *  Jahresbericht,'  and  those 
of  Reichert,  in  Muller's  '  Archiv,'  in  the  latter  of  which,  more  objective 
views  and  an  earlier  appearance  would  be  desirable. 

Useful  figures  are  found  in  all  the  works  above  cited,  with  the  excep- 
tion of  those  of  Bichat,  Weber,  and  Bruns;  furthermore,  the  figures  of 
injections  in  Berres'  i  Anatomie  der  Mikroskopischen  Gebilde  des  men- 
schlichen  Korpers,'  Heft  1-12  (Wien,  1836-42),  are  for  the  most 
part  excellent,  as  are  the  representations  of  tissues  in  R.  Wagner's 
*  Icones  Physiologic^,'  second  edition,  by  A.  Ecker.  Those  of  Langen- 
beck,  4  Mikroskopisch-anatomische  Abbildungen.'  Lief.  1-4  (Gottingen, 
1846-51) ;  of  A.  H.  Hassall,  '  The  Microscopic  Anatomy  of  the  Human 
Body'  (London,  1846-49) ;  and  Mandl,  '  Anatomie  Microscopique'  (Paris 
1838-48),  are  middling ;  while  on  the  other  hand,  those  given  by 
Quekett,  '  Catalogue  of  the  Histological  Series  in  the  Museum  of  the 
Royal  College  of  Surgeons  of  England'  (London,  1850),  are  admirable. 

As  regards  Microscopes,  I  may  express  my  opinion  that  of  the  more 
easily  accessible,  those  of  Plossl,  Oberhauser,  and  Schiek,  take  the  first 

*  Translated  for  the  Sydenham  Society,  1847. 


38  INTRODUCTION. 

rank.  In  Italy,  Amici ;  in  England,  Ross,  Powell,  and  others,  produce 
instruments  quite  equal  to  the  above,  but  out  of  the  question  for  Ger- 
many ;  among  small,  cheap,  but  not  particularly  useful  instruments  for 
students  and  physicians,  for  115  to  150  francs,  George  Oberhauser 
(Rue  Dauphine,  19,  Paris),  furnishes  the  best.  The  much-famed  instru- 
ments of  Nachet  are  good,  but  inferior  to  those  of  Oberhauser ;  on  the 
other  hand,  the  small  ones  of  Schiek  for  40  thalers  [30  dollars],  and  those 
of  Plossl  for  70  to  100  Fl.  [30  to  45  dollars],  would  be  very  serviceable 
if  these  artists  were  as  productive  as  Oberhauser.*  For  the  use  of  the  mi- 
croscope I  refer  to  J.  Vogel,  "Anleitung  zum  Gebrauche  des  Mikroskops" 
(Leipzig,  1841);  H.  von  Mohl,  "Mikrographie"  (Tubingen,  1846);  Hart- 
ing,  "  Het  Mikroskoop  deszelfs  gebruik,  geschiedenis  en  tegenwoordige 
toestand"  (Utrecht,  1848-50),  3  Theile;  Purkinje,  article  "Mikroskop," 
in  Wagner's  "  Handworterbuch  der  Physiologic,"  Bd.  2,  1844;  in  which 
works,  as  well  as  in  that  of  Quekett,  "  A  Practical  Treatise  on  the  Use 
of  the  Microscope"  (London,  1848,  translated,  by  Hartmann,  Weimar, 
1850,  [also  Ed.  2,  London,  1852)] ;  and  Robin,  "  Du  Microscope  et  des 
Injections  dans  leurs  applications  a  1'Anatomie  et  a  la  Pathologic" 
(Paris,  1848),  the  preparation  of  microscopical  objects  is  in  part  very 
elaborately  treated  of. 

A  collection  of  microscopical  preparations  is  indispensably  necessary 
for  a  more  exact  study  of  Histology,  especially  sections  of  bones  and 
teeth  and  injections.  Every  one  may  with  a  little  trouble,  form  a  mode- 
rate collection  for  himself,  hints  towards  which  he  will  find  in  the  para- 
graphs standing  at  the  end  of  each  section  of  the  special  part,  as 
well  as  in  the  works  just  cited.  Microscopical  preparations  may  also 
be  exchanged  with  or  purchased  of  Hyrtl,  in  Vienna ;  Dr.  Oschatz,  in 
Berlin ;  Topping,  Smith,  and  Beck,  Hett  and  others,  in  London ;  and 
also  in  Paris.  The  largest  private  and  public  collections  of  microscopi- 
cal preparations  exist  in  Vienna,  with  Hyrtl  (injections) ;  in  Utrecht, 
with  Harting  and  Schroder  van  der  Kolk  (injections,  sections,  muscles, 
nerves) ;  in  London,  in  the  College  of  Surgeons  (animal  and  vegetable 
tissues  of  all  kinds) ;  with  Tomes  (sections  of  bones  and  teeth) ;  and 
with  Carpenter  (hard  tissues  of  the  lower  animals). 

*  [The  opinion  expressed  in  the  above  lines  with  regard  to  microscopes  seems  entirely 
too  national.  For  clearness  of  definition  of  the  object  glasses  and  neatness  of  the  stand,  the 
instruments  furnished  by  Ross,  and  Powell,  and  Lealand,  are  not  only  "  quite  equal/'  but 
far  superior  to  those  of  PlOssl,  Oberhauser,  or  Schiek,  the  only  objection  to  them  being  their 
high  price.  Of  the  cheaper  microscopes,  those  most  used  at  present  in  this  country  and  in 
England  are  the  small  instruments  of  Nachet  (Rue  Serpente,  Paris),  the  glasses  of  which 
are  superior  to  those  of  PlOssl  and  Schiek,  whilst  the  great  convenience  of  the  present  stand, 
modelled  according  to  the  English  style,  renders  them  preferable  to  those  of  Oberhauser. 
In  this  country  microscopes  have  been  made  by  Mr.  Spencer,  of  New  York,  the  lenses 
of  which  are  not  inferior  to  the  best  glasses  either  of  Ross,  or  of  Powell  and  Lealand,  but 
which  are  as  yet  too  expensive  to  be  introduced  into  general  use. — 


THE 


GENERAL  ANATOMY  OF  THE  TISSUES. 


I.  OF  THE  ELEMENTARY  PARTS. 

§  4.  IF  the  solid  and  fluid  constituents  of  the  human  body  be  examined 
with  the  aid  of  strong  magnifying  powers,  it  appears  at  once  that  the 
smallest  parts  which  they  exhibit  to  the  naked  eye,  as  granules,  fibres, 
tubes,  membranes,  &c.,  are  not  the  ultimate  elements  in  respect  of  form, 
but  on  the  contrary,  that  all,  in  conjunction  with  a  universally  distri- 
buted, fluid,  semi-fluid,  or  even  solid,  homogeneous,  uniting  substance, 
contain  minute  particles  which  differ  in  different  organs  but  in  the 
same  organs  have  always  a  similar  appearance.  There  are  various 
kinds  of  these  so-called  elementary  parts,  simple  and  compound.  The 
simplest  are  quite  homogeneous,  without  any  trace  of  their  being  com- 
posed of  heterogeneous  portions  and  are  nearly  allied  to  the  inorganic 
forms,  the  crystalline  granules  and  crystals,  which  also  occur  in  the 
animal  organism.  Others  already  show  that  they  have  suffered  a  diffe- 
rentiation into  an  investment  and  determinate,  though  homogeneous 
contents :  in  others  again,  the  contents  present  differences.  The  most 
important  among  all  these  forms,  which  may  be  comprehended  under 
the  general  title  of  "simple  elementary  parts,"  are  the  cells,  which  not 
only  form  the  starting-point  of  every  animal  and  vegetable  organism,  but 
also,  either  as  cells  or  after  having  undergone  manifold  metamorphoses, 
make  up  the  body  of  the  perfect  animal,  and  in  the  simplest  animal 
and  vegetable  formations  (unicellular  animals  and  plants),  even  enjoy 
an  independent  existence.  Compared  with  cells,  all  other  simple  ele- 
mentary parts  have  quite  a  subordinate  importance,  so  far  as  their  direct 
participation  in  the  formation  of  the  tissues  and  organs  is  concerned  ; 
while,  from  their  being  almost  all  contained  in  the  interior  of  cells  and 
from  their  being  concerned  in  many  and  most  important  ways  in  the 
vital  processes  of  these  cells,  their  importance  in  other  respects  is  very 
great. 

The  simple  elementary  parts,  which  at  first  wholly  comprise  the  com- 
mencing animal  (or  plant),  often  unite  in  the  course  of  development  in 


40  GENERAL    ANATOMY    OF    THE    TISSUES. 

such  a  manner  that  they  lose  their  independence  and  cease  to  exist  as 
isolated  elements.  In  this  manner  compound  forms  arise,  each  of  which 
answers  genetically  to  a  whole  series  of  simple  ones,  and  which  may 
most  fittingly  be  called  the  "  higher  elementary  parts."  Such  a  coa- 
lescence has  been  observed  with  certainty  only  in  cells,  and  from  these 
most  of  the  tubular  and  fibrous  elements  of  the  body  are  produced. 

§  5.  Formative  and  Nutritive  Fluid — Interstitial  substance  or  matrix. 
— While  in  plants  the  elementary  parts  in  by  far  the  majority  of  cases, 
unite  directly  with  one  another,  in  animals  there  is  a  very  wide  differ- 
ence ;  a  peculiar  interstitial  substance  which  combines  them,  and  is  ulti- 
mately derived  from  the  blood,  is  always  in  a  lower  or  more  distant  rela- 
tion therewith.  If  this  take  a  direct  share  in  the  formation  of  the  elemen- 
tary parts  it  is  called  "  formative  fluid,"  CytoUastema  (Schleiden),  from 
xt/fas,  a  vesicle,  and  /S^O-T^^  germ  substance  ;  if  it  be  present  for  their 
maintenance,  it  is  called  "nutritive  fluid;"  if  it  have  nothing  to  do 
with  either  the  one  or  the  other  of  these  functions,  it  is  called  the  "  ma- 
trix" or  connecting  substance.  The  cytoblastema  is  usually  quite  fluid, 
as  in  the  blood,  in  the  chyle,  in  many  glandular  secretions,  in  the  con- 
tents of  the  glandular  follicles,  and  in  many  embryonic  organs;  more 
rarely,  viscid  and  like  mucus,  as  in  the  gelatinous  cellular  tissue  of 
embryos  (vide  infra),  still  more  rarely  solid,  as  the  blastema  from  which 
the  villi  of  the  chorion  arise  and  grow.  The  "  nutritive  fluid"  takes 
the  place  of  the  formative  fluid  in  all  perfect  organs ;  and  except  when 
it  is  contained  in  special  canals  and  cavities,  as  in  bones,  teeth,  and 
perhaps  in  some  cellular  organs,  is  present  in  so  small  a  quantity,  that 
it  cannot  be  directly  observed.  A  matrix,  lastly,  is  found  in  cartilages 
and  bones  as  a  solid,  homogeneous,  granular,  or  even  fibrous  substance 
connecting  the  cellular  elements  and  for  the  most  part  arising  from  the 
blood,  independently  of  them. 

The  occurrence  of  a  solid  blastema,  growing  independently,  in  the 
villi  of  the  chorion  and  of  a  solid  matrix  deposited  directly  out  of  the 
blood  demonstrates  that  all  parts  of  the  body  are  not,  as  Schwann  was 
disposed  to  believe,  without  exception  developed  from  cells  or  in  depen- 
dence upon  cells.  A  few  more  recent  authors,  as  Reichert,  Donders, 
and  Virchow,  also  consider  that  the  connective  tissue,  excepting  its  elas- 
tic element,  is  to  be  reckoned  among  those  tissues  which  are  not  at  all, 
or  not  wholly,  derived  from  cells  ;  but,  as  we  shall  see  below,  incorrectly. 
On  the  other  hand,  it  is  certain  that  in  pathological  formations  such 
masses  very  frequently  occur,  fibrinous  exudations  becoming  changed  in 
great  measure,  without  previous  organization,  i.  e.  cell  formation  into 
permanent  tissues.* 

[*  The  Enamel  and  the  Dentine  of  the  teeth,  and  the  so-called  Cuticle  of  the  hair  (see  §§ 
'O.i  Hair  and  Teeth,  and  '  Quarterly  Journal  of  Microscopical  Science'  for  April,  1853),  must 


ELEMENTARY    GRANULES.  41 

A.     SIMPLE  ELEMENTAKY  PARTS. 

1.    ELEMENTARY  GRANULES,  ELEMENTARY  VESICLES,  NUCLEI. 

§  6.  In  almost  all  animal  fluids,  whether  contained  in  canals,  or  enclosed 
in  cells,  as  well  as  in  many  more  solid  tissues,  there  are  found  and  often 
in  immense  quantities,  roundish  corpuscles  of  very  small,  hardly  mea- 
urable  dimensions.  Henle  has  called  them  "elementary  granules," 
and  has  expressed  the  opinion  that  they  are  vesicular.  This,  however, 
is  not  always  true,  since  it  is  demonstrable  that  many  of  these  corpus- 
cles possess  no  investment.  Such  is  the  case  with  the  fatty  particles 
which  occur  in  many  cells  and  glandular  secretiohs,  with  the  granules  of 
the  black  pigment  of  the  eye  and  of  other  colored  cells,  the  granular 
precipitates  of  biliary  coloring  matter,  of  different  salts  in  the  kidneys, 
and  in  the  urine ;  lastly,  the  protein  granules  (albuminous  granules) 
which  are  found  free  in  certain  portions  of  the  gray  substance  of  the 
central  nervous  system  and  of  the  retina.  Among  the  pathological  but 
very  common  formations,  we  must  enumerate  here  amorphous  deposits, 
the  colloid  granules  in  the  thyroid  and  elsewhere,  and  the  corpuscula 
amylacea  of  the  central  nervous  system,  although  these  sometimes  attain 
a  very  considerable  size.  All  these  granules  want  the  properties  ob- 
served in  the  higher  elementary  parts,  such  as  endogenous  growth,  mul- 
tiplication, assimilation,  and  excretion,  and  so  far  incline  towards  the 
purely  inorganic  forms — crystals;  which  are  also  found,  though  less 
commonly,  in  the  organism,  as  for  example  in  the  spleen,  in  the  lungs 
(black  columns),  in  the  ear,  in  the  cells  of  the  prseputial  glands  of  the 
rat,  in  the  blood-corpuscles  of  the  dog  and  of  fishes,  in  the  fat-cells  of 
man,  arid  in  the  cells  of  the  chorion  of  the  embryo  of  sheep. 

Elementary  vesicles  also  occur  very  frequently,  and  are  for  the  most 
part  allied,  physiologically,  with  the  elementary  granules,  since,  once 
formed  they  do  not  increase,  and  neither  multiply  by  division  nor  by 
endogenous  development.  The  milk-globules  may  with  tolerable  cer- 
tainty be  arranged  among  these ;  at  first  included  within  the  cells  of 
the  nascent  milk,  they  are  subsequently  found  free,  in  enormous  numbers, 
in  the  perfect  secretion,  and,  as  Henle  first  stated,  consist  of  the  fatty 
matter  of  the  milk,  with  an  investment  of  casein.  The  immeasurably 
small  molecules  of  the  chyle  and  of  the  blood,  are  also,  according  to 
H.  Miiller's  investigation,  fat  globules  with  a  protein  envelop,  and 
similar  vesicles  may  be  found  in  most  other  fluids  containing  fat  and 
albumen  in  abundance.  In  fact,  since  the  discovery  of  Ascherson 
(Muller's  '  Archiv,'  1840,  p.  49),  that  whenever  fluid  fat  and  fluid  albu- 
men are  shaken  together,  the  fat  globules  which  are  formed  always 

certainly  be  regarded  as  structures  which  are  not  derived  directly  from  the  metamorphosis  of 
cells.  We  are  inclined  also  to  believe,  that  the  opinion  of  Reichert,  Bonders,  and  Virchow, 
as  to  the  nature  of  the  connective  tissue  deserves  much  more  attention  than  Professor  Kolli- 
ker  seems  disposed  to  bestow  on  it.  See  §§  on  Connective  and  Elastic  Tissues. — TRS.] 


42         GENERAL  ANATOMY  OF  THE  TISSUES. 

become  surrounded  by  an  albuminous  coat,  it  is  more  than  probable  that 
•whenever,  in  the  body,  fat  and  albumen  in  the  fluid  condition  come  into 
contact,  similar  vesicles  are  produced. 

A  peculiar  class  of  elementary  vesicles  is  formed  by  the  elements 
which  occur  in  the  yelk  of  certain  animals.  We  are  best  acquainted 
with  them  in  the  yelk  of  the  hen's  egg,*  in  whose  proper  yelk-substance 
and  yelk-cavity  the  globules  which  have  been  so  long  known  are  all  vesi- 
cular, but  have  not  the  nature  of  cells.  The  membranes  of  these  yelk- 
vesicles  are  excessively  delicate  and  consist  of  a  protein  compound;  the 
contents  are  fluid  albumen,  and,  in  the  globules  of  the  yelk-cavity,  there 
is  usually  a  large  parietal  fat  globule,  while  in  the  others  there  are  many 
smaller  and  larger  ones.  The  development  of  these  vesicles  proceeds, 
in  all  probability,  from  the  fat  globules  as  in  other  elementary  vesicles, 
from  which,  however,  they  are  distinguished  by  the  fact  that  they  dis- 
tinctly possess  the  power  of  growth,  during  which  their  contents  undergo 
metamorphosis,  since  in  many  the  number  of  fat  globules  increases  with 
age.  Similar  vesicles  exist,  also,  in  the  yelk  of  fishes,  Crustacea,  and 
spiders,  and  here,  as  in  birds,  they  have  only  a  temporary  importance, 
since  they  are  not  directly  applied  to  the  formation  of  the  embryo,  but 
only  serve  to  nourish  it. 

Lastly,  free  nuclei  occur  in  many  localities,  either  temporarily,  where 
cells  are  formed  immediately  round  nuclei,  as  in  the  chyle,  the  blood- 
vascular  glands,  the  Peyerian  patches;  or  permanently,  as  proper  ele- 
ments of  the  tissue,  in  the  wall  of  the  thymus  vesicles,  in  the  rust-colored 
layer  of  the  cerebellum,  and  in  the  granular  layer  of  the  retina. f 

Von  Wittich  (<De  Hymenogonia  albuminis,'  Regimontanii.  1850), 
has  lately  given  some  information  upon  the  formation  of  the  so-called 
Aschersonian  vesicles.  According  to  Wittich,  whenever  oil  and  albumen 
come  in  contact,  a  portion  of  the  oil  is  saponified  by  uniting  with  the 
alkali  of  the  layer  of  albumen  in  contact  with  it,  and  this  layer  being 
thus  rendered  insoluble  by  the  deprivation  of  its  alkali  becomes  precipi- 
tated and  thus  forms  the  Aschersonian  so-called  haptogen  membrane. 
According  to  this  explanation  the  process  would  be  purely  chemical  and 
not  physical,  and  still  less  vital.  In  opposition  to  this  view,  how- 
ever, Harting  ('Ned.  Lane.'  Sept.  1851),  observed,  not  long!  ago,  the 
formation  of  pseudo-cells  by  the  agitation  of  albumen  with  mercury,  in 
which  case  the  albumen  must  be  solidified,  in  the  same  way  as  by  the  mere 
shaking  with  water  or  otherwise  (Melsens,  in  '  Bull,  de  1' Acad.  de  Bel- 
gique,'  1850.  Harting,  &c.).  Again,  if  by  the  bringing  together  of 

*  [It  is,  however,  by  no  means  certain  that  the  yelk-corpuscles  of  the  hen's  egg  are  elemen- 
tary granules.  According  to  Dr.  H.  Meckel  (Die  Bildnng  der  fiir  partielle  Furchungbestirnm- 
ten  Eier  der  Vogel,  £c.,  Siebold  and  Kolliker's  '  Zeitschrift,'  1852,)  they  are  altered  cells. — 

TBS.] 

t  [The  blood  corpuscles  of  man  and  the  mammalia  should  be  added  to  this  list.  See 
Wharton  Jones,  'Phil.  Transactions,'  1846. — TKS.] 


CELLS. 


43 


albumen  and  chloroform,  serum-casein  and  fat,  chondrin  and  chloro- 
form,— albuminous,  casein,  and  chondrin  membranes  are  formed,  as 
Panum  observed  (see  in  part,  '  Archiv  f.  Path.  Anatomic,'  iv.  2),  it  can 
hardly  be  permissible  to  assume  any  chemical  action. 

II.    OF   THE   CELLS. 

7.  The  cells,  cellulce,  called  also  elementary  cells,  or  nucleated  cells, 
are  perfectly  closed  vesicles  of  0-005 0-01  of  a  Paris  line,*  in  mean 

*  [The  measurements  employed  by  Prof.  Kolliker  are,  according  to  the  old  French 
standard,  of  inches  and  lines.  In  the  original  work  a  line  is  expressed  by  '",  an  inch  by  ". 
As  these  signs  are  not  used  in  this  country,  I  have,  in  every  instance,  substituted  the 
words  for  the  signs.  Most  English  and  American  authors  express  the  size  of  objects  in 
fractions  of  an  inch,  but  rarely  in  lines.  The  English  inch  and  line  differ  but  little  from 
the  Paris  inch  and  line.  The  old  Paris  inch  (")  was  divided  into  12  lines  ('")  ;  one  line 
being  equal  to  gsffths,  or  rather  more  than  the  llth  of  an  English  inch  :  hence  the  difference 
between  a  Paris  line  and  an  English  line  is  very  slight;  s^th  of  an  English  line  being 
equal  to  ^^d  of  a  Paris  line;  an  English  inch  is  thus  exactly  11-26  Paris  lines.  All  the 
French  and  many  of  the  continental  microscopists  employ  the  recent  French  measure- 
ments: the  centimetre  and  millimetre.  The  proportion  they  bear  to  the  English  and  French 
inch  is  as  follows:  one  millimetre  (mm)  is  equal  to  0-03937,  or  about  ^jjth  of  an  English 
inch,  or  to  ^d  of  a  Paris  line.  The  subjoined  table  of  the  main  measurements,  noted 
throughout  the  work  in  lines,  reduced  to  fractions  of  an  English  inch,  and  parts  of  millime- 
tres, will  aid  the  student  in  forming  a  comparative  estimate  of  the  size  of  objects,  as 
measured  by  observers  in  different  countries : — 

TABLE    OF   MEASUREMENTS. 


O'l         of  a  Paris  line. 

j  j~  jth  of  an  English  inch. 

022      millimetres. 

0-01               «           " 

TlVs           "             " 

0-022             " 

0-04               " 

J8ff 

0-09               « 

0-001             «           « 

Trriw 

0-0022           « 

0-003             «           " 

nVw 

0-0068           « 

0-004             «            " 

^S'T?        "         " 

0-009             « 

0-005             "            " 

zsW        "         " 

0-011             « 

0-008              «            " 

T  ""'ff  7T                   "                     " 

0-018             « 

0-016             «            « 

T^7             "             " 

0-036             « 

0-028             "           " 

?k 

0063             « 

0-035             «            " 

7?(T              "              " 

0-079             " 

0072             "           " 

T** 

0-17               « 

0-0001            "            « 

TTzVffff          "              " 

0-0002           " 

0-0004            «            " 

yyjyy                       "                            " 

00009           " 

0-0008            «            « 

T?0"5? 

0-0018           " 

0-0012            "           " 

1                             ((                       1C 

0-0027           " 

0-0016           «            « 

TffW              "               " 

0-0036           " 

0-0025            '«            " 

1                  «               «( 

0-0056           " 

0-0033            "           " 

^^V^ 

0-0074           " 

0-0045            «            " 

J^QTTI 

0-0100           " 

0-0055            «            « 

70]4J 

0-012             « 

0  00001          «            « 

TTy|ffUTy           "                 « 

000002         " 

0-00009          "            « 

TF^IFIF          " 

0-0002           " 

DAC.] 


44  GENERAL    ANATOMY    OF    THE    TISSUES. 

diameter,  in  which  we  may  distinguish  a  special  investment,  the  cell  mem- 
brane and  contents.  The  latter  are 
always  composed  of  a  fluid,  containing 
formed  particles  of  various  kinds,  and  a 
peculiar  rounded  body,  the  cell-nucleus, 
which  again  contains  in  its  interior  a 
fluid  and  a  still  smaller  corpuscle,  the 
nucleolus.  These  cells,  which  must  be 
considered  to  be  endowed  with  peculiar 
vital  powers,  and  to  be  capable  of  ab- 
sorption and  assimilation,  of  growth 
and  of  multiplication,  not  only  at  the  earliest  period  entirely  compose 
the  body  of  the  higher  and  that  of  most  of  the  lower  animals,  but  almost 
wholly  generate  the  higher  elementary  parts  of  the  fully  developed  body. 
In  fact,  even  in  adult  animals,  we  find  in  very  many  places  that  the  ele- 
ments are  simply  in  the  condition  of  cells,  and  that  as  such  they  take  a 
more  or  less  marked  share  in  the  performance  of  the  organic  functions. 

It  is  not  yet  quite  decided  what  part  cells  play  in  the  composition  of 
the  simplest  animals.  Siebold  and  I  have  expressed  the  opinion  that 
the  Protozoa,  like  the  simplest  plants,  are  unicellular  organisms,  but 
it  is  granted  that  no  demonstration  of  this  has  been  given  in  many, 
especially  the  Rhizopods.  In  all  creatures  above  the  Protozoa,  it  would 
seem  to  be  certain  that  their  body  proceeds  from  a  mass  of  cells,  although 
in  the  fully  formed  animals,  as  for  example  the  Hydra,  according  to 
Ecker,*  this  is  not  always  clearly  demonstrable. 

§  8.  A  more  exact  consideration  of  the  relations  of  cells  give  us  the 
following  results.  Their  fundamental  form  is  globular  or  lenticular  ;  it 
is  such  in  all  cells  during  their  earliest  state,  and  is  permanent  in  those 
which  occur  in  the  fluids  (blood-corpuscles,  &c.).  Less  common  forms 
are :  1.  Polygonal  (pavement  epithelium).  2.  Conical  or  pyramidal 
(ciliated  epithelium).  3.  Cylindrical  (cylinder  epithelium).  4.  Spindle- 
shaped  (contractile  fibre-cells).  5.  Squamous  (epidermic  scales).  6.  Stel- 
late (nerve-cells).  The  size  of  cells  descends  upon  the  one  hand,  as  in 
many  young  cells,  blood-cells,  &c.,  as  low  as  0-002-0-003  of  a  line, 
and  upon  the  other  attains,  as  in  the  cysts  of  the  semen  and  the  nerve- 

FiG.  1. — Nerve-cells  of  the  Thalamus  opticus  of  man, — three  of  them  having  their  processes 
torn  off.  Magnified  3f)0  diam. 

*  [The  tissue  of  the  Hydra  presents  no  essential  features  of  difference  from  that  of  the  higher 
animals,  and  closely  resembles  the  most  superficial  layer  of  the  dermis  in  the  latter.  In  its 
outer  part  the  so-called  nuclei  are  almost  wholly  converted  into  thread-cells;  but  they  may 
be  very  readily  demonstrated  in  their  ordinary  condition  in  the  deeper  portions.  The  resem- 
blance of  the  gelatinous  tissue  of  the  disk  of  the  Medusae  to  Professor  Koiliker's  "  reticulative 
connective  tissue"  is  still  more  striking. — TKS.] 


CELLS.  45 

cells,  that  of  0'02-0'04  of  a  line.  The  largest  animal  cells  are  the 
yelk-cells  or  ova,  especially  those  of  birds  and  amphibia,  and  a  few  of 
those  animals  which  consist  of  single  cells,  these,  in  certain  Gregarinse, 
attaining  0*7  of  a  line. 

The  membrane  of  the  cells  is  generally  very  delicate,  smooth,  hardly 
separable,  and  marked  by  a  single  contour,  rarely  of  any  considerable 
density  or  measurable  thickness ;  with  our  present  optical  instruments 
it  exhibits  no  structure  of  any  kind.  In  the  interior  of  the  cells  there 
are  invariably  found,  at  a  certain  time,  one  or  many  nuclei,  besides 
fluid  and  granules  of  various  proportions  and  of  different  natures.  Cells 
which  contain  only  fluid  are  rare  (fat-cells,  blood-cells,  cells  of  the  chorda 
dorsalis),  and  it  is  colorless  or  reddish ;  in  general  they  contain,  in 
addition,  corpuscles  in  greater  or  less  number  (elementary  granules, 
elementary  vesicles,  perhaps  crystals),  and  in  fact,  as  a  rule,  young  cells 
possess  few,  while  older  ones  contain  many,  which  are  very  often  more 
densely  grouped  round  the  nucleus,  or  occupy  only  a  single  spot  (colored 
nerve-cells). 

The  chemical  composition  of  the  cells  is  as  yet  very  obscure.  The 
contents  in  most  cells  present  certain  generally  disseminated  substances, 
which  occur  dissolved  in  the  nutritive  fluid  or  cytoblasteina,  as  water, 
albumen,  fat,  extractive  matter,  salts ;  a  nitrogenous  substance,  which 
is  precipitated  by  water  and  by  dilute  acids,  thus  resembling  mucus,  is 
very  extensively  distributed,  and  considerably  impedes  the  microscopical 
analysis  of  the  cells  and  tissues,  inasmuch  as  it  causes  them  to  be  ob- 
scure and  granular,  instead  of  clear  and  transparent.  Many  cells  con- 
tain yet  other  compounds,  as  those  of  the  liver,  of  the  kidneys,  of  the 
blood,  &c.  The  cell-membrane  consists  of  a  nitrogenous  substance, 
which  is  unquestionably  a  protein  compound  in  young  cells,  as  we  may 
conclude  from  its  solubility  in  acetic  acid  (partly  even  in  the  cold)  and 
in  dilute  caustic  alkalies.  Subsequently  the  membrane  in  many  cells, 
yet  by  no  means  in  all  (e.  g.  not  in  the  blood-corpuscles,  in  the  deepest 
cells  of  the  epidermis  and  epithelium,  nor  in  the  cells  of  the  glandular 
follicles),  becomes  less  soluble,  and  here  and  there  more  or  less  approxi- 
mates the  substance  of  the  elastic  tissue. 

The  cell-nucleus  is  a  globular  or  lenticular,  clear,  or  yellowish  body, 
which  in  the  mean  measures  0*002-0*004  of  a  line,  and  rarely,  as  in 
the  ganglion-globules  and  ova,  attains  a  diameter  of  0-01-0-04  of  a 
line.  All  nuclei  are  vesicles,  as  Schwann  supposed  and  as  I  have 
recognized  to  be  their  original  and  universal  structure  in  embryos 
and  adult  animals.  The  membrane  is  very  delicate  in  the  smaller 
ones,  appearing  as  a  simple,  fine,  dark  line ;  in  the  larger  it  is  more 
marked,  even  of  measurable  thickness  and  limited  by  a  double  contour, 
as  in  the  nuclei  of  the  ganglion-globules,  of  ova  and  of  many  embryos. 
The  contents  of  the  nuclear  vesicle  consist,  excepting  the  nucleolus, 


46  GENERAL    ANATOMY    OF    THE    TISSUES. 

almost  invariably  of  a  pellucid  or  slightly  yellowish — never  more  darkly 
tinged — fluid,  in  which  water  and  acetic  acid  precipitate  the  same  dark 
granules,  as  in  the  cells,  for  which  reason,  the  nuclei  never  preserve  their 
natural  homogeneous  clear  appearance,  when  examined  according  to  the 
ordinary  methods.  More  rarely  the  nuclei  have  formed  contents,  as 
the  spermatic  filament  in  the  semen ;  in  ova  peculiar  granules,  the  so- 
called  germinal  spots  ;  also  in  the  fat  of  Piscicola  (Leydig).  In  respect 
of  their  chemical  composition,  only  this  much  can  be  said  of  the  nuclei, 
that  their  membranes  are  nitrogenous,  and  in  general  but  little  different 
from  the  substance  forming  the  younger  cell-membranes;  they  are,  how- 
ever, dissolved  more  slowly  in  alkalies,  and  are  but  slightly  attacked  by 
dilute  acetic  and  mineral  acids.  In  the  latter  circumstance  they  ap- 
proximate the  elastic  tissue,  from  which,  however,  they  are  most  essen- 
tially distinguished  by  their  easy  solubility  in  alkalies. 

The  nuclei  are  found,  so  far  as  I  have  observed,  in  all  cells  of  embryos 
without  exception,  and  in  those  of  adults,  so  long  as  the  cells  are  still 
young.  In  general  only  a  single  nucleus  exists  in  each  cell,  except 
when  it  is  multiplying;  in  the  latter  case,  however,  two  or  more  nuclei 
arise,  according  to  the  number  of  the  developing  cells.  In  certain  cells 
we  meet  with  more  numerous  nuclei ;  thus,  in  those  of  the  semen,  4, 
10,  20,  and  more;  also  in  the  substantia  grisea  centralis  of  the  spinal 
cord,  of  the  supra-renal  capsules,  of  the  pituitary  body,  in  the  hepatic 
cells  of  embryos,  in  the  foetal  medullary  cells  of  bone,  and  elsewhere. 
That  nuclei  also  occur  free,  and  take  part  in  the  formation  of  certain 
tissues,  has  already  been  stated. 

The  nucleoli  are  round,  sharply  defined,  generally  dark,  fat-like  gra- 
nules, which,  on  the  average,  measure  0-001-0-0015  of  a  line,  are  often 
almost  immeasurably  small,  and  in  embryos,  in  the  germinal  vesicles  of 
ova  as  the  germinal  spots,  and  in  the  ganglion-globules,  attain  the  size 
of  O'003-O'Ol  of  a  line.  In  all  probability  they  are  always  vesicular, 
as  may  be  surmised  from  their  sharply  circumscribed  form,  their  simi- 
larity to  elementary  vesicles,  and  also  from  the  circumstance  that  in 
certain  cells,  especially  in  ova  and  ganglion-globules,  a  larger  or  smaller 
cavity  filled  with  fluid  frequently  becomes  developed  in  them.  The 
chemical  composition  of  the  nucleoli  is  unknown :  their  external 
appearance,  their  similarity  to  the  elementary  vesicles,  their  disap- 
pearance in  caustic  alkalies,  and  their  insolubility  in  acetic  acid, 
would  lead  us  to  ^suppose  them  to  be  fat ;  the  membranes  may,  as  in 
the  elementary  vesicles,  be  a  protein  compound,  Nucleoli  are  found 
in  the  great  majority  of  nuclei,  so  long  as  these  are  still  young,  and 
in  many  during  their  whole  existence ;  but  nuclei  also  exist,  in  which 
nucleoli  cannot  be  recognized  with  certainty,  or  at  least  become  ob- 
vious only  at  a  later  period ;  and  therefore,  at  present,  the  nucleolus 
cannot  be  so  unconditionally  recognized  to  be  an  essential  constituent 


CELLS.  47 

of  the  cell,  as  the  nucleus.  Generally,  a  nucleus  contains  only  one 
nucleolus,  frequently  there  are  two,  rarely  three,  and,  in  solitary  cases, 
four  or  five  may  be  present,  which  are  then  either  eccentric  or  lie  free 
in  the  nucleus. 

A  short  time  since,  Bonders,  in  a  very  remarkable  work  (vide  infra), 
expressed  the  opinion  that  all  cell-membranes  consist  of  one  and  the 
same,  or  at  least  of  very  nearly  allied  substances,  which  agree  in  their 
characters  with  the  elastic  tissue.  For  my  own  part  I  believe  that  all 
animal  cell-membranes  consist  originally  of  the  same  substance — of  a 
protein  compound,  in  fact ;  that,  however,  in  consequence  of  its  subse- 
quent metamorphoses,  it  may  acquire  differences  of  composition  and 
of  reaction.  Many  membranes  in  this  manner  become  more  resistant 
with  time  and,  as  Donders  justly  states,  approach  elastic  tissue ;  others 
change  into  collagenous  tissue,  as  those  of  the  formative  cells  of  the 
connective  tissue,*  and  of  the  cartilage  cells  during  ossification  ;  others 
into  syntonin,  as  in  the  smooth  muscles  ;  into  the  so-called  horn,  and 
so  on.  If  we  assume  the  primitive  cell-membrane  to  be  a  protein  com- 
pound, and  from  the  reaction  of  young  cells  and  of  embryonic  paren- 
chyma it  can  hardly  be  otherwise,  we  obtain  a  correspondence  with  the 
vegetable  cell,  since  in  this  case  the  primordial  utricle,  consisting  of  a 
protein  compound,  can  be  considered  as  the  analogue  of  the  animal  cell- 
membrane,  whilst  the  cellulose  membrane  appears  as  a  secondary  pro- 
duct, as  an  excretion.  Such  may  be  the  true  condition  also  in  those 
animal  structures  of  the  Tunicata  which  are  formed  of  cellulose,  in  which 
case  my  assertion  that  here  the  cell-membranes  are  composed  of  woody 
fibre,  and  that  of  Schacht  (Muller's  "Archiv,"  1851),  that  they 
are  nitrogenous,  would  coincide.  If  future  investigation  justify  this 
comparison  of  the  animal  cell  with  the  primordial  utricle  of  plants,  the 
further  question  would  arise  in  animals,  whether  perhaps  all  the  so-called 
metamorphoses  of  the  cell-membrane  are  not  to  be  laid  to  the  account 
of  deposits  which  are  thrown  down  upon  the  outer  side  of  it,  similarly 
to  the  cellulose  in  plants,  so  that,  perhaps,  together  with  the  original 
protein  membrane,  other  secondary  collagenous  or  elastic  membranes, 
&c.,  might  be  distinguished,  and  even  the  most  considerable  thicken- 
ings of  the  animal  cell  be  produced,  in  a  manner  analogous  to  that 
which  occurs  in  the  ligneous  tissues  of  plants  on  the  outer  side  of  the 
protein  membrane ;  so  that,  for  example,  within  ossified  cartilage-cells 
the  original  cell-membrane  might  perhaps  still  exist. 

In  all  normal  cells  of  the  higher  animals,  the  nuclei  can  be  readily 
shown  by  the  vesicles,  and  most  beautifully  so  in  embryos ;  only  in  those 
cells  which  arise  directly  around  nuclei,  are  the  nuclei  at  first  more 

*  [The  term  "connective  tissue"  (Bindegewebe)  has  been  used  by  the  translators  to  de- 
signate the  tissue  more  generally  known  as  "  white  fibrous  tissue.'' — 


48  GENERAL    ANATOMY    OF    THE    TISSUES. 

homogeneous,  and  subsequently  exhibit  a  distinct  membrane.  In 
pathological  formations,  this  character  of  the  nucleus,  which  may  be 
called  an  undeveloped  form,  is  very  frequent,  and  the  nucleus-like 
structures  in  the  Protozoa  are  also  for  the  most  part  homogeneous 
bodies. 

§  9.  Development  of  Cells. — With  regard  to  the  development  of  cells, 
we  have  to  distinguish  between  their  free  origin  and  their  production 
by  the  intermediation  of  other  cells.  In  the  former  case  the  cells  are 
developed,  independently  of  others,  in  a  plastic  fluid,  the  cytoblastema 
of  Schleiden,  containing  chiefly  fat,  protein,  and  salts  in  solution ;  in 
the  other,  or  in  cell-multiplication,  the  existent  cells  either  produce  the 
so-called  daughter  or  secondary  cells  within  themselves,  or  multiply  by 
division  ;  endogenous  cell-formation  and  fissiparous  cell-formation.  Both 
kinds  of  cell-formation  agree  in  this,  that  the  cell  nuclei  play  a  very 
important  part,  and  appear  to  be  the  proper  centres  of  development  of 
the  young  cells. 

§  10.  Free  cell-development  is,  in  man  and  the  higher  animals,  far 
less  common  than  has  been  hitherto  assumed,  and  under  this  category 
we  can  enumerate,  so  far  as  is  at  present  known,  only  the  development 
of  the  chyle  and  lymph  corpuscles,  of  the  cells  of  certain  glandular 
secretions  (spermatic  cells,  ova),  and  gland-like  organs  (closed  follicles 
of  the  intestine,  lymph  glands,  splenic  corpuscles  and  pulp,  thymus)  ; 
lastly,  of  the  cellular  elements  in  the  pregnant  uterus,  in  the  corpus 
luteum,  in  the  medulla  of  foetal  bones,  and  in  the  soft 
ossifying  blastemata.  The  separate  steps  of  the  process 
in  this  mode  of  cell-development  have  as  yet  been  traced 
principally  in  the  first-named  cells,  but  much  is  yet  want- 
ing to  complete  our  knowledge  of  it.  This  much  is  cer- 
tain, that  the  origin  of  the  cells  is  always  preceded  by  the  development 
of  cell-nuclei,  while  it  is  doubtful,  on  the  other  hand,  how  these  are 
formed.  In  the  chyle  and  in  the  spleen  we  see  as  the  first  indication  of 
cell-formation  rounded  homogeneous-looking  corpuscles  of  0-001--002 
of  a  line,  which,  increasing  somewhat  in  size,  soon  clearly  appear 
to  be  vesicles,  and  often,  upon  the  addition  of  water,  exhibit  in  their 
interior,  together  with  small  granules,  a  large  granule,  like  a  nucleolus. 
Whether  this  last,  as  is  certainly  the  case  in  the  dependent  mode  of 
cell-development,  arises  before  the  nucleus  and  is  the  condition  of  the 
development  of  the  latter,  or  whether  it  is  formed  subsequently  therein; 
how,  again,  the  nuclei  themselves  are  developed,  whether  as  originally 
homogeneous  corpuscles,  which  subsequently  exhibit  a  differentiation 

FIG.  2. — Contents  of  a  Malpighian  corpuscle  of  the  ox:  a,  small;  6,  larger  cells;  r,  free 
nuclei ;  magnified  350  diameters. 


CELLS.  49 

into  inner  and  outer  parts, — envelop,  and  contents,  or  whether  they 
are  not,  from  the  first,  vesicular,  cannot  at  present  be  decided. 

The  nuclei  being  once  formed,  the  cell-membranes  are  developed 
around  them,  though  not  always  in  the  same  way.  In  the  first  place 
they  may  be  applied  directly  around  the  nucleus,  so  that  the  nascent 
cell  is  but  little  larger  than  its  nucleus ;  or,  in  the  second  place,  the 
latter  may  become  surrounded  by  a  greater  or  smaller  quantity  of  solidi- 
fying cytoblastema,  and  it  is  only  around  this  enveloping  mass,  which 
I  have  called  an  investing  globule,  that  a  membrane  forms.  This  last 
occurrence  in  the  free  cell-formation  has  hitherto  been  observed  only 
in  the  ovum,  in  which  the  germinal  vesicle,  i.  e.  the  nucleus  of  the  egg- 
cell,  being  first  formed,  surrounds  itself  with  some  yelk  before  the  vitel- 
lary  membrane  appears.  On  the  other  hand,  cell-development  directly 
round  the  nucleus  takes  place  in  all  the  other  localities  which  have  been 
mentioned  above,  and  is  demonstrated  by  the  occurrence,  among  free 
nuclei  and  large  cells,  of  very  small  cells,  which  closely  invest  the  nu- 
cleus or  are  but  little  separated  from  it.  It  may,  however,  be  remarked, 
that  perhaps  in  these  cases  also,  the  cell-membranes  at  their  origin 
are  separated  from  the  nuclei  by  a  very  small  quantity  of  cytoblastema, 
so  small  as  to  be  incapable  of  detection. 

Free  cell-formation  is  exceedingly  frequent  in  pathological  produc- 
tions, and  the  cells  in  pus  and  in  exudations  of  all  kinds  arise  in  this 
manner ;  in  fact,  all  pathological  cell-formation  properly  comes  under 
this  head.  Usually  the  cell-membranes  here  arise  directly  round  the 
nucleus,  less  commonly  as  it  would  seem  round  investing  globules. 
With  regard  to  physiological  processes,  as  has  been  already  shown,  free 
cell-development  has  been  much  too  readily  taken  for  granted;  and 
especially  as  regards  the  epithelial  and  horny  tissues,  as  well  as  in  many 
glandular  secretions,  it  has  been  assumed  without  any  sufficient  grounds. 
Botany  knows  no  free  cell-development.* 

§  11.  The  development  of  cells  within  other  cells,  or  their  endoge- 
nous origin,  is  of  very  frequent  occurrence,  and  easy  to  be  observed 
in  embryos.  The  commonest  form  of  this  cell  genesis  is,  that  a  so-called 
parent  cell  produces  two  secondary  cells,  which  from  the  first  wholly  fill 

*  [There  cannot  be  said  to  be  any  evidence  of  the  occurrence  of  free  cell-development  in 
animals,  so  long  as  in  any  case  cited  it  is  not  shown  that  the  first-formed  particles  which 
make  their  appearance  cannot  have  derived  their  origin  from  pre-existing  formed  particles, 
either  by  the  detachment  or  fission  of  the  latter.  Not  only  does  this  condition  remain  unful- 
filled for  all  the  instances  cited,  but  it  has  not  been  attempted,  and  would  seem  to  be  im- 
possible. In  pathological  exudations,  for  instance,  who  shall  determine  that  the  first  struc- 
tural elements  which  appear,  granules,  free  "  nuclei,"  exudation  corpuscles,  &c.,  are  not 
directly  derived  either  from  the  blood,  or  from  the  tissue  into  which  the  exudation  has  taken 
place?— TBS.] 

4 


50  GENERAL    ANATOMY    OF    THE    TISSUES. 

x 

it.     The  first  thing  to  be  observed  in  this  case,  in  the  parent  cell,  is  a 
metamorphosis  of  its  nucleus,  which  grows,  ac- 
Fig- 3<  quires    two    nucleoli,    becomes    elongated,    and 

divides  into  two.  When  this  has  once  taken 
place,  the  nuclei  become  somewhat  divaricated 
and  then  a  wall  of  separation  arises  between 
the  cells,  which  divides  tha  parent  cell  into 
two  perfectly  distinct  spaces,  each  of  which  con- 
tains a  single  nucleus  and  one  half  of  the  con- 
tents. The  mode  in  which  the  multiplication 
of  the  nucleus  takes  place,  has  not  yet  been 
•'  V  '  '^"-0  "-r S  made  out  with  exactness.  This  much,  however, 
\^—^"L — **/  is  certain,  that  where  clear  observation  is  pos- 

sible, it  is  always  the  nucleoli  which  first  divide  into  two  and  then  diverge 
a  little.  In  the  nuclei,  which  have  at  the  same  time  slightly  elongated, 
there  then  usually  appears,  making  the  first  trace  of  their  division,  a 
median  partition,  which  in  favorable  cases  may  be  recognized  as  com- 
posed of  two  secondary  nuclei  applied  to  one  another  by  their  flat  sides 
and  completely  filling  the  parent  nucleus.  Very  frequently  we  see,  in 
the  course  of  this  process  of  multiplication  of  the  nuclei,  no- 
thing  more  than,  first  an  elongated  nucleus,  with  a  partition  and 
two  nucleoli,  and  then  two  hemispherical  nuclei  applied  by  their 
plane  faces  to  one  another,  without  its  being  possible  to  demon- 
strate with  certainty  any  endogenous  development  of  nuclei  ; 
so  much  the  less,  as  it  is  not  to  be  doubted  that,  together  with  the  latter 
process,  a  multiplication  of  nuclei  by  division  takes  place,  in  which  an 
elongated  parent  nucleus,  with  two  nucleoli,  breaks  up  into  two  by  the 
formation  of  a  constriction  which  gradually  deepens  in  the  middle. 

The  further  destiny  of  the  parent  cells,  with  a  partition  and  two 
nuclei,  is  not  always  the  same.  As  a  rule,  it  appears  that  in  each,  two 
perfect  secondary  cells  afterwards  become  evident,  which  may  serve  as 
a  demonstration  that  the  partition  is  double  from  the  very  first.  At 
other  times,  distinct  secondary  cells  are  not  recognizable,  which  however 
does  not  imply  that  there  exists  a  mode  of  cell-development  by  the  mere 
formation  of  partitions,  but  only  that  in  such  cases  the  secondary  cells 
do  not  become  distinctly  separated  from  the  parent  cells.  Whether  the 
one  process  or  the  other  take  place,  it  rarely  stops  at  one  performance, 
but  is  generally  repeated  a  certain,  often  very  considerable  number  of 
times ;  in  fact,  as  long  as  the  organism  grows.  The  parent  cells  either 
remain,  or  they  cease  earlier  or  later  to  be  histologically  distinct  struc- 

FlG.  3. — From  the  cephalic  cartilage  of  an  advanced  tadpole.  Parent  cells,  with  1  and 
2  nuclei,  or  2-4  secondary  cells,  and  some  interstitial  substance;  magnified  350  diameters. 

FIG.  4. — An  elongated  nucleus,  and  one  containing  two  secondary  nuclei,  from  the  ovum 
of  an  Ascaris  dentata;  magnified  350  diameters. 


CELLS.  51 

tures,  and  coalesce  with  the  substance  which  unites  the  cells  as  a  matrix. 
The  occurrence  of  this  endogenous  cell-development,  which  may  be 
called  cell-development  around  the  collective  contents,  and  which  agrees 
in  all  essential  points  with  free  cell-development  around  investing  masses, 
has  been  made  out  with  certainty  in  the  young  cartilage  of  all  animals, 
and  probably  occurs  in  embryonic  organs  in  general,  in  which,  from  the 
moment  when  they  consist  of  actual  cells,  the  total  growth  essentially 
depends  upon  a  self -multiplication  of  the  cells  without  free-cell  develop- 
ment. Since,  however,  it  is  as  yet  undecided,  whether  perhaps  cell-de- 
velopment by  division,  to  which  attention  has  been  very  lately  drawn, 
does  not  play  a  part  in  the  one  case  or  in  the  other,  our  judgment,  so 
far  as  regards  the  latter,  must  as  yet  be  suspended,  until  more  particu- 
lar investigations  have  been  undertaken ;  and  the  same  holds  good  for 
many  organs  of  the  adult,  as  the  horny  tissues  and  certain  glandular 
secretions.  Only,  when  secondary  cells  are  observed  in  parent  cells,  as 
especially  in  the  pituitary  body  and  in  the  supra-renal  capsules,  there 
can  of  course  be  no  doubt  as  to  the  existence  of  endogenous  cell-develop- 
ment. 

Besides  these  most  usual  forms  of  cell-development,  there  exist  yet  a 
few  others. 

1.  In  the  ova  of  most  animals  a  peculiar  process,  the  so-called 
cleavage  of  the  yelk,  occurs  at  the  earliest  period  of  development, 
which  is  to  be  regarded  as  the  introduction  to  the  formation  of  the  first 
cells  of  the  embryo;  and  since  the  ovum  has  the  nature  of  a  simple  cell, 
it  is  a  case  of  endogenous  cell-development.  This  cleavage  takes  place 
as  follows.  After  the  original  nucleus  of  the  egg-cell,  the  germinal 
vesicle,  has  disappeared  with  the  occurrence  of  fecundation,  the  granules 
of  the  yelk  no  longer  form  a  com- 
pact mass  as  before,  but  become 
dispersed  and  fill  the  whole  egg- 
cell.  Then,  as  the  earliest  sign 
of  commencing  development,  there 
arises  in  the  midst  of  the  yelk, 
around  a  new  nucleolus,  a  new 
nucleus,  the  primary  nucleus  of  the  embryo,  which  operates  as  a  centre 
of  attraction  upon  the  yelk  and  unites  it  again  into  a  globular  mass,  the 
first  "  cleavage  mass"  (Furchungs-kugel).  In  the  further  course  of  de- 
velopment two  new  nuclei  are  formed  by  endogenous  development  from 
the  first  nucleus,  and  these,  as  soon  as  they  have  become  freed  by  the 
solution  of  the  parent  nucleus,  separate  from  one  another  for  a  short 
distance,  act  as  new  centres  upon  the  yelk,  and  thus  break  up  the  first 

FIG.  5. — The  ova  ofdscaris  nigovenosa, —  1  from  the  second,  2  from  the  third,  and  3  from 
the  fifth  stage  of  division,  with  2,  4,  and  1C  division-masses:  a,  chorion;  6,  cleavage  masse?. 
In  1  the  nucleus  of  the  lower  mass  contains  two  riucleoli,  in  2  the  lowest  contains  two  nuclei. 


52  GENERAL    ANATOMY    OF    THE    TISSUES. 

cleavage  mass  into  two.  In  this  way  the  multiplication  of  nuclei  and 
of  cleavage  masses  proceeds, — the  former  always  taking  the  lead,  until 
a  very  great  number  of  small  globules  are  produced  which  fill  the  whole 
cavity  of  the  yelk-cell ;  it  is  only  in  exceptional  cases  that  the  cleavage- 
masses  break  up  after  the  development  of  three  or  four  nuclei  within 
them  ;  so  that  then,  instead  of  two,  three  or  four  cleavage-masses  imme- 
diately proceed  from  one.  This  process  is  called  total  cleavage,  because 
here  the  whole  yelk  is  disposed  around  the  newly-developed  nuclei : 
partial  cleavage  is  essentially  similar,  differing  only  in  the  circumstance 
that  it  is  not  the  whole  yelk,  but  a  greater  or  lesser  portion,  according 
to  the  animal,  which  invests  the  nascent  nuclei. 

When  the  process  has  attained  a  certain  stage,  the  cleavage-masses 
all  together,  or  in  successive  layers,  surround  themselves  with  membranes, 
and  become  actual  cells,  whence  we  are  justified  in  considering  this  to 
be  a  process  of  endogenous  cell-development.  In  fact,  it  is  nothing  else 
than  an  introduction  to  cell-development  in  the  egg-cell,  and  differs 
from  the  ordinary  phenomena  of  that  class  only  in  this,  that  firstly,  the 
nucleus  of  the  parent  cell  or  the  germinal  vesicle,  in  most  cases  (Miiller 
saw  a  division  of  it  occur  in  the  Molluscs  which  are  developed  within 
Synapta  digitata*)  has  nothing  to  do  with  it ;  secondly,  that  the  parent 
cell  itself  persists ;  and  thirdly,  that  the  investing  globules  developed  by 
the  successive  multiplication  of  nuclei  become  cells  only  in  the  latest 
generations.  This  view  is  the  more  justifiable,  as  the  cells  which  have 
arisen  in  consequence  of  the  metamorphosis  of  the  last  cleavage-masses 
long  continue  to  multiply  by  endogenous  development ;  and  the  whole 
process  of  division  may  be  regarded  as  a  kind  of  endogenous  cell-deve- 
lopment, in  which,  on  account  of  the  rapidity  with  which  the  nuclei  mul- 
tiply, no  formation  of  cell-membrane  takes  place  in  the  early  genera- 
tions of  "cleavage-masses." 

2.  Closely  allied,  in  some  respects,  to  the  cleavage  process,  are  those 
forms  of  endogenous  cell-development,  in  which,  a  greater  or  smaller 
number  of  secondary  cells  are  developed  within  persistent  parent  cells, 
as  we  see  here  and  there  in  the  cartilages,  in  the  supra-renal  capsules, 
and  in  the  pituitary  body.  In  this  case  there  either  arise  in  the  ordinary 
manner,  in  a  cell,  two  secondary  cells,  which  wholly  or  partially  fill  it, 
and  from  these  by  continued  multiplication,  other  generations,  which 
sometimes  lie  quite  free,  and  sometimes  are  wholly  or  partially  included 
in  the  parent  cells  of  the  second  generation  ;  or  a  more  free  development 
of  a  secondary  cell  within  a  parent  cell  occurs,  from  which  cell-develop- 
ment then  takes  place  in  one  mode  or  in  the  other. 

In  connection  with  the  process  of  endogenous  cell-development,  we  may 
very  properly  speak  of  the  formation  of  a  great  number  of  nuclei  within 
cells,  a  process  which  is  frequently  the  precursor  of  cell-development, 

*  [Dr.  Nelson  (Phil.  Trans.,  1852,  p.  580),  has  observed  the  same  thing  in  Ascaris  inystax. 
-TBS.] 

V 


CELLS. 


53 


but  which  may  also  continue  alone.     Even  in  the  common  endogenous 
cell-development  (and  also  rig.  e. 

in  the  cleavage  process)  we 
not  unfrequently  observe 
three  and.  four  nuclei  in  a 
parent  cell,  so  that  then, 
instead  of  two  secondary 
cells,  many  arise  at  once, 
e.  g.  in  the  hepatic  cells  of 
embryos.  In  certain  ani- 
mals (Cucullanus,  Ascaris 
dentata,  Distoma^  Cestoi- 
dea),  instead  of  cleavage 
masses,  nuclei  alone  are 
developed  in  the  first  stages 
of  development,  and  it  is 
only  later,  when  by  succes- 
sive endogenous  multiplica- 
tion these  have  increased  to 
a  great  bulk,  that  they  be- 
come surrounded  by  cell 
membranes.  Something 
similar  appears  to  take 
place  in  the  cells  of  the 
germ  in  the  Crustacea,  in  which  10-20  nuclei  are  often  found  (Rathke, 
4  De  Anim.  Crustac.  gen.,'  Regim.  Fig.  7 

1844.)  On  the  other  hand,  the  nu- 
merous nuclei  in  the  spermatic  cells 
of  most  animals  are,  in  general,  in 
no  way  connected  with  cell-develop- 
ment, since  the  spermatic  filaments 
are  developed  in  them ;  and  the  like 
holds  good  of  those  cells  of  the  lower 
animals,  whose  multitudinous  nuclei 
are  changed  into  thread-cells.  The 
import  of  the  number  of  nuclei  in 
certain  nerve-cells,  and  in  the  large 
cells  of  the  bone-medulla,  which  Robin  and  I  have  observed,  is  doubt- 
ful ;  in  the  latter,  I  think  it  is  not  improbable  that  the  multiplication 

FIG.  G. — Cartilage  cells  from  a  fibrous,  velvety,  articular  cartilage  of  the  condyle  of  the 
femur  of  rnan,  magnified  350  diameters;  all  lying  in  a  fibrous  matrix,  and  readily  isolated: 
a,  simple  cells,  with  or  without  a  thickened  wall,  with  1  or  2  nuclei ;  6,  secondary  cells,  or 
cells  of  the  first  generation,  with  1  or  2  nuclei;  1,  2-5  or  more,  in  parent  cells;  6,  c,  cells 
of  the  second  generation,  1-3  in  number,  in  cells  of  the  first ;  rf,  freed  groups  of  secondary  cells. 

FIG.  7. — a.  Peculiar  granulated  cells  with  many  nuclei  from  the  youngest  medullary  cavi- 
ties of  the  flat  bones  of  the  skull  in  man.  Magnified  350  diameters. 


<*•' 


54  GENERAL    ANATOMY    OF    THE    TISSUES. 

of  the  nuclei  is  preliminary  to  their  breaking  up  into  smaller  cells.  In 
all  these  cases,  it  may  be  easily  demonstrated  that  the  nuclei  multiply 
spontaneously,  but  it  is  generally  doubtful  whether  this  happens  by 
division  or  by  endogenous  development. 

Cell-development  round  a  mass  of  blastema  containing  a  nucleus  in 
its  interior,  which  may  take  place  either  freely  or  in  an  endogenous 
manner  (cell-development  round  portions  of  contents),  had  long  ago 
been  seen  by  Von  Siebold  in  the  ova  of  Distoma  globiporum,  and  by 
Bergmann  in  the  cleavage-masses  of  Rana,  but  no  further  importance 
was  attached  to  it.  Vogt  and  Nageli  were  the  first  who  regarded  this 
cell-development  as  a  deviation  from  the  theory  of  Schleiden  and 
Schwann,  whereupon,  supported  by  observations  upon  embryos,  I  (in 
1844,  "  Entwick.  d.  Cephalopoden")  placed  this  as  a  second  kind  of 
cell-development  under  the  name  of  "  cell-development  round  investing 
masses,"  beside  that  which  takes  place  immediately  round  nuclei,  and 
pointed  out  its  very  extensive  occurrence,  especially  in  embryos,  where 
at  first  it  is  the  sole  mode.  Later  observations  upon  normal  and  patho- 
logical products  have  supported  this  view,  and  at  the  present  time  the 
formation  of  a  cell-membrane  immediately  around  the  nucleus  requires 
demonstration,  rather  than  the  opposite  method.  Endogenous  cell- 
development  occurs  in  many  pathological  products, — most  frequently  in 
cancer,  yet  the  steps  of  the  process  have  not  yet  been  exactly  made  out. 
In  plants  this  mode  of  multiplication  of  cells  is  the  most  extensive,  and 
it  occurs  commonly  as  "cell-development  around  portions  of  contents," 
more  rarely  (in  the  embryo  sac)  by  free  development  within  parent  cells.* 

§  12.  A  multiplication  of  cells  by  division  certainly  takes  place  in 
the  red  blood-corpuscles  of  the  embryos  of  Birds  and  Mammalia,  and 
in  the  first  colorless  blood-corpuscles  of  the 
Tadpole  (Remak).  It  takes  place  also,  in  all 
probability,  in  the  colorless  blood-corpuscles  of 
embryos,  and  in  the  chyle-corpuscles  of  adult 
Mammalia  under  certain  circumstances.  In  all 
these  cases,  we  see,  in  elongating  cells,  the  pro- 
duction of  two  nuclei  from  the  originally  simple 

FIG.  8. — Dividing  blood  corpuscles  of  the  chick;  magnified  350  diam. 

*  [The  endogenous  development  of  secondary  "  nuclei"  seems  to  us  to  be  extremely  doubt- 
ful, even  upon  the  evidence  adduced,  and  we  have  been  unable  to  observe  anything  indi- 
cating that  regularity  of  occurrence  and  importance  of  function  attributed  to  the  nucleolus  by 
Professor  Kolliker.  In  cartilage,  in  the  tooth-pulp,  in  the  homogeneous  layers  of  the  cuti?, 
and  in  other  localities,  in  which  unaltered  "  nuclei"  occur,  the  presence  and  number  of  the 
granules  which  might  be  called  nucleoli  is  in  the  highest  degree  variable  and  uncertain. 
The  same  irregularity  as  to  the  presence  of  nucleoli  occurs  in  the  plant  (vide  Von  Mohl,  1.  c., 
and  Schacht,  "  Die  Pflanzenzelle,"  p.  30). 

Upon  this  subject  consult  the  valuable  memoir  of  Remak  (Ueber  extra-cellulare  Knste- 
hung  Thierischen  Zellen,"  &c.,  Mflll.  Archiv,  1852),  which  by  no  means  deserves  the  epi- 
thet of"  no  longer  available  ;"  in  fact,  Remak's  views  seem  to  be  essentially  correct. — TRS.] 


CELLS. 


55 


Fig.  9. 


nucleus,  apparently  by  division  ;  the  cells  then  suffer  constriction  in 
the  middle,  and  contract  more  and  more  around  the  nuclei,  as  they  recede 
from  each  other,  and  at  last  separate  into  two  cells,  each  of  which  con- 
tains a  nucleus.  In  the  chick  we  see  blood-corpuscles  in  all  conceiva- 
ble stages  of  separation,  so  that  at  length  they  are  connected  only  by 
a  delicate  thread,  and  there  can  be  no  doubt  whatever  as  to  the  actual 
occurrence  of  this  process. 

Whether  division  ever  take  place  in  other  cells  than  these  is  not  yet 
determined.  If  it  be  allowable  to  explain,  by  this  process  of  division, 
the  occurrence  of  constricted  cells  with 
two  nuclei,  we  may  suppose  it  to  take 
place  in  the  nerve-cells,  which,  in  young 
mammalia,  are  not  unfrequently  more 
or  less  divided  or  even  united  merely 
by  a  narrow  isthmus,  and  also  in  the 
ciliated  epithelium  cells,  which,  al- 
though rarely,  present  two  or  three 
enlargements  lying  one  behind  the 
other,  each  with  a  nucleus.  A  peculiar 
kind  of  cell-development,  which  is  very 
closely  related  to  division,  occurs  in 
the  formative  cells  of  the  ivory,  which 
as  they  go  on  growing,  multiply  their 
nuclei  and  become  constricted  from 
time  to  time,  so  that  whilst  the  portion 
next  the  ivory  ossifies,  the  other  serves  in  a  manner  as  a  reserve  for  the 
subsequent  formation  of  fresh  ossifying  tissue. 

Schwann  knew  nothing  of  the  occurrence  of  cell-division.  The  first 
who  observed  it  in  the  blood-corpuscles  of  embryos  was  Remak  ("Med. 
Verein."  1841,  No.  27:  Schmidt,  "  Jahrbiicher,"  1841,  p.  145;  Can- 
statt,  "Jahresb.,"  1841),  yet  he  subsequently  retracted  his  opinion 
("  Diagn.  und  Pathol.  Untersuchungen,"  p.  100),  and  only  now,  since  I 
have  confirmed  it  and  declared  it  to  be  true  (Wiegm.  "  Archiv," 
Jahrg.  13,  Bd.  1,  p.  19),  has  he  again  advocated  it  ("Entwick.  d.  Wir- 
belthiere,'  I.)  It  is  extremely  probable  that  this  mode  of  cell-development 
occurs  very  extensively,  and  it  may  perhaps  turn  out  that  in  many  em- 
bryos and  adult  tissues,  in  which  a  self-multiplication  of  the  cell  is  cer- 
tain, and  yet  in  which  no  parent  cells  with  secondary  cells  can  be  demon- 
strated, cell-development  by  division  may  occur  instead  of  endogenous 
cell-development.  It  is  certain  that  the  transverse  and  longitudinal 
division  of  the  Protozoa  is  to  be  placed  here,  since  these  animals  have 


FIG.  9. — Dentine  cells  from  the  dog  ;  magnified  350  diam. 


56  GENERAL    ANATOMY    OF    THE    TISSUES. 

\ 

the  structure  of  simple  cells,  and  the  nucleus-like  body  they  contain 
takes  a  share  in  the  process  of  cell  division,  like  that  of  the  cell-nucleus 
in  common  cells.  In  pathological  formations  cell  division  has  not  yet 
been  observed.  In  the  vegetable  kingdom  it  is  rare,  and  has  been  seen 
only  in  the  lower  organisms ;  unless,  indeed,  we  are  to  reckon  here  the 
constriction  of  the  primordial  utricle  observed  by  Von  Mohl  in  the  course 
of  endogenous  cell-development.* 

§  13.  Theory  of  Cell-development. — Among  the  few  hypotheses  which 
have,  up  to  the  present  time,  been  proposed  in  explanation  of  the  develop- 
ment of  cells,  that  of  Schwann,  who  compares  it  with  the  formation  of  crys- 
tals, is  certainly  the  most  attractive.  Without  overlooking  the  differences 
between  a  crystal  and  a  cell,  which  chiefly  consist  in  the  former  being 
solid  and  homogeneous,  in  its  growing  by  apposition,  and  in  its  being 
bounded  by  plane  surfaces  and  angles,  Schwann  endeavors  to  explain 
cell-development  as  a  crystallization  of  organic  matter,  and  to  deduce 
from  the  permeability  of  the  latter  the  differences  in  the  phenomena 
presented  by  the  two.  In  a  fluid  containing  organic  matters  dissolved 

*  [There  can,  we  think,  be  little  doubt  that  Von  Mohl  is  quite  correct  in  the  view  he  takes 
of  the  multiplication  of  cells  in  plants  by  division,  and  therefore  we  are  by  no  means  inclined 
to  agree  with  Professor  Kolliker,  as  to  the  rarity  of  this  form  of  cell-multiplication  in  the 
vegetable  kingdom,  nor,  consequently,  in  what  he  says  at  the  conclusion  of  the  preceding 
note.  All  botanists  of  any  note  (Nageli,  Von  Mohl,  Holfmeister,  Alex.  Braun,  Schacht,  Hen- 
frey)  maintain  at  the  present  time,  that  the  process  of  cell-division  so  far  from  being  "  rare,'' 
is  that  which  occurs  in  by  far  the  great  majority  of  cases  in  plants.  "That  the  formation 
of  cells,  in  all  organs  of  plants  (except  the  cells  originating  in  the  embryo  sac),  depends 
upon  the  division  of  older  cells,  is  an  opinion,  which  could  not  for  a  long  time  past  be  op- 
posed by  any  careful  observer,  unless  he  were  misled  by  preconceived  notions."  (Von 
Mohl,  "Anatomy  and  Physiology  of  the  Vegetable  Cell,"  1851,  Henfrey's  translation).  Nor 
can  we  agree  with  Professor  KoMliker's  estimate  of  the  relative  frequency  of  occurrence  and 
importance  of  endogenous  cell-development  and  cell-division  in  the  animal  world.  In  young 
cartilage,  which  is  cited  by  our  author  as  a  locality  in  which  endogenous  cell-development 
takes  place,  we  must  affirm,  on  the  contrary,  that  the  process  is  as  much  one  of  cell-division 
as  it  is  in  any  plant.  At  this  period  the  so-called  "  nuclei"  of  the  cartilage  completely  rill 
their  cavities  (e.  g.  nasal  cartilage  of  four  months'  fcetus),  and  may  be  seen  in  all  stages  of 
division.  The  walls  of  the  cavities  grow  in,  pari  passu,  and  eventually  form  a  partition 
between  the  two  nuclei,  or  rather  primordial  utricles,  which  have  been  thus  developed  from 
one. 

Remak,  who,  in  a  very  valuable  paper  (Ueber  die  Entstehung  der  Bindegewebes  und 
Knorpels,  Mull.  Archiv,  1852),  has  advocated  this  view,  so  far  as  cartilage  and  connective- 
tisue  are  concerned,  does  not  appear  to  have  seen  the  necessity  of  extending  it  to  the  other 
tissues.  As  Reichert,  however,  long  since  pointed  out  (see  note,  §  oti  Connective  Tissue) 
whatever  determines  the  nature  of  the  cartilage  corpuscle,  and  of  its  matrix,  determines  that 
of  all  the  other  tissues  whose  anatomical  continuity  with  cartilage  can  be  traced  directly  or 
indirectly.  Thus  a  direct  anatomical  continuity  may  be  shown  to  exist  between  the  matrix 
of  cartilage,  the  apparent  fibrilhe  of  connective  tissue,  the  fibrillaeof  muscle,  the  homogeneous 
matrix  of  the  cutis  and  of  its  papillae,  and  the  so-called  walls  of  the  epithelial  cells;  while 
a  perfect  identity  in  size,  structure,  and  relation,  may  be  traced  between  the  corpuscles  of 
cartilage,  the  "  nuclei"  of  connective  tissue,  those  of  muscle,  of  the  papillae  and  of  the  epithe- 
lial cells.— TES.] 


CELLS.  5T 

in  considerable  proportions,  a  granule,  the  nucleolus,  is  precipitated. 
Once  formed,  this  attracts  nutriment  from  the  cytoblastema,  and  thus 
becomes  the  nucleus,  which  Schwanri  considers  to  be  solid.  This  still 
goes  on  attracting  to  itself  a  substance,  which,  becoming  more  and  more 
condensed,  at  last  forms  a  membrane  ;  which,  allowing  the  passage  of 
fluid  cytoblastema  through  its  pores,  becomes  detached  from  the  nucleus, 
and  we  have  a  cell.  In  this  exposition,  we  must  admire  not  only  the 
skilful,  acute  working  out  of  the  fundamental  idea  which  the  original 
treatise  manifests,  but  also  the  assumption  of  a  molecular  attraction  in 
cell-development,  analogous  to  that  which  occurs  in  the  formation  of 
crystals,  for  the  existence  of  which  there  is,  in  fact,  decisive  evidence 
(only  in  part,  however,  known  to  Schwann),  such  as  the  action  of  the 
nuclei  in  the  cleavage  process,  in  cell-division,  in  cell-development,  round 
portions  of  contents,  in  the  cyclosis,  and  in  the  formation  of  granular 
precipitates  in  cells.*  On  the  other  hand,  it  is  evidently  going  too  far 
to  call  cell-development  simply  a  crystallization  of  permeable  organic 
substances,  since  in  this  case  important  differences  are  overlooked,  and 
non-essentials  are  made  unduly  prominent.  For  it  must  not  be  forgot- 
ten that  organic  permeable  substances  also  crystallize  ;  that,  in  fact,  if 
Reichert  have  observed  correctly  (Miiller's  "  Archiv,"  1849),  and  I  see 
no  reason  for  doubt,  histogenetic  substances  capable  of  forming  tissues,  as 
albumen  for  instance,  assume  a  crystalline  form.  Hence  the  molecular 
attraction  concerned  in  the  formation  of  cells  is  so  far  peculiar,  that — 1,  it 
never  produces  geometrical  solids,  but  even  in  the  nucleus  and  nucleolus 
determines  the  globular  form  ;  2,  that  it  aggregates,  not  homogeneous  but 
chemically  different  substances,  as  those  which  constitute  the  nucleus 
and  the  cell-membrane  ;  3,  lastly,  that  without  exception,  in  the  develop- 
ment of  the  cell-membrane  it  limits  itself,  and  does  not,  like  the  crystal- 
lizing force,  repeatedly  apply  layer  upon  layer.  Of  these  differences, 
the  two  latter  might  perhaps  be  set  aside,  if  with  regard  to  the  second 
point,  it  were  assumed  that  the  nuclei  at  first  consist  of  the  same  sub- 
stance as  the  cell-membranes,  or  are  almost  identical  with  them  in 
chemical  composition ;  or  if  we  referred  to  the  fact  that  in  crystalliza- 
tion also,  different  substances  may  unite  into  one  crystal,  or  that  a 
substance,  5,  may  crystallize  round  a  substance,  a. 

In  order  to  diminish  the  force  of  the  third  fact  adduced  (this  objec- 
tion, indeed,  does  not  hold  with  regard  to  endogenous  development,  and 
therefore  in  almost  all  plants,  since  it  is  impossible  here  that  the  cells 
should  produce  any  more  layers  around  themselves),  it  might  be  urged 
that  the  permeability  of  the  organic  membranes,  the  exchange  of  con- 
stituents which  take  place  between  the  juices  of  the  cell  and  the  cyto- 
blastema, and  the  application  of  the  molecules  attracted  from  the  cyto- 
blastema to  the  growth  of  the  membrane,  and  to  precipitates  within  the 

*  [See  note,  p.  52.— TRS.] 


58  GENERAL    ANATOMY    OF    THE    TISSUES. 

interior,  are  perhaps  the  reasons  why  the  cells  develop  no  new  circum- 
ferential layers.  It  is  not  necessary  to  carry  out  this  last  possibility 
any  further,  nor  to  bring  forward  the  difficulties  which  are  opposed  to 
this  view  also, — among  which  not  the  smallest  is,  that  the  organic  deve- 
lopment of  vesicles  does  not  stop  at  the  formation  of  nuclei,  but  is  only 
finished  with  the  completion  of  the  cell  membrane ;  since  in  any  case 
the  facts  brought  forward  are  more  than  enough  to  demonstrate  the 
insufficiency  of  Schwann's  hypothesis.  I  do  not  see,  however,  any- 
thing better  or  more  positive  to  substitute  in  its  place,  and  I  therefore 
think  it  will  be  most  expedient  simply  to  group  together  the  ascertained 
facts  into  a  few  general  propositions,  which  may,  perhaps,  be  done  as 
follows. 

1.  The  nucleus  of  the  cell  arises  in  the  first  place,  as  a  precipitate  in 
an  organizable  fluid,  and   afterwards  becomes   consolidated   in  such   a 
manner,  that  a  special  investment  and  contents  with  a  nucleolus  appear. 
Its  development  may  in  this  case  be  compared  to  that  of  inorganic  pre- 
cipitates, yet  the   constantly  globular  figure,   and  the  size  of  nuclei 
which  are  just  formed,  indicate  some  essential  though  not  yet  recognized 
condition  peculiar  to  them.     Secondly,  cell-nuclei  are  produced  endo- 
genously  in  nuclei,  or  by  their  division  under  the  influence  of  a  nucleo- 
lus, which  also  divides.     Here  is  one  condition  which  is  never  presented 
by  crystals, — the  division  from  an  internal  cause ;  while  the  other,  the 
influence  of  the  nucleoli  upon  the  nucleus,  can  hardly  be  comprehended 
in  any  but  a  physical  way,  as  a  molecular  attraction  proceeding  from 
the  nucleoli,  of  an  indefinable  nature,  which  at  last  draws  the  entire 
half  of  the  parent  nucleus  within  its  influence. 

2.  In  the  development  of  cells  by  division,  the  cell-nucleus  plays 
exactly  the  same  part  which  was  previously  ascribed   to  the  nucleolus, 
and  the  occurrence  of  the  formation  of  cells  in  this  manner  demonstrates 
that  chemical  conditions  are  not  necessarily  concerned  therein. 

3.  In   cell   development   around  portions  of  contents,   and   in  the 
cleavage  process,  the  nuclei  also  operate  as  simple  centres  of  attraction 
(einfach  attrahirend)  upon  a  certain  mass  of  blastema,  and  then  follows 
the  formation  of  a  membrane  upon  the  surface  of  this  mass,  which  is 
most  simply  understood  as  a  condensation  of  the  blastema. 

4.  In  cell-development  directly  around  the  nucleus,  the  investment  with 
blastema  is  wanting,  and  the  nucleus  develops  the  membrane  imme- 
diately around  itself.    This  process  admits  of  both  a  physical  and  a  chemi- 
cal explanation.      In  the  first  place,  we  may  with   Schwann  assume 
that  the  nucleus  attracts  molecules,  which,  when  they  have  reached  a 
certain  amount,  condense  into  a  membrane,  and,  by  growing,  become 
detached  from  the  nucleus.    Or  secondly,  it  is  conceivable,  that  the  nucleus 
in  some  manner  initiates  chemical  processes,  which  terminate  with  the 
formation  of  a  membrane  around  it.     In  this  way  a  coagulable  sub- 


CELLS.  59 

stance  might  be  produced  within  and  excreted  from  it ;  or,  like  rennet 
upon  casein,  it  might  act  upon  the  protein  combinations  in  the  cyto- 
blastema,  in  such  a  manner  that  they  should  coagulate  where  in  contact 
with  it ;  or  lastly,  by  the  extraction  of  the  alkali  it  might  render  an 
albuminous  substance  insoluble,  as  is  the  case  in  the  development  of 
Ascherson's  vesicles.  Which  of  these  various  possibilities  really  obtains, 
must  at  present  remain  undetermined,  yet,  for  my  own  part,  I  should 
prefer  the  first  view,  in  order  to  retain  one  and  the  same  condition,  a 
physical  one,  for  all  the  different  modes  of  cell-development. 

I  do  not  think  it  necessary  to  enter  at  greater  length,  in  the  present 
place,  into  this  very  obscure  subject,  and  I  will  therefore  only  once 
more  express  my  opinion,  that  I  hold  the  physical  processes  of  cell- 
development,  which  may  pass  under  the  general  name  of  molecular  at- 
traction, to  be  something  quite  different  from  those  which  attend  crystal- 
lization. Although  in  both,  solids  arise  out  of  fluids,  and  grow  by  the 
further  agglomeration  of  molecules,  yet  in  cell-development  different 
substances  are  as  a  rule  superimposed,  plane  geometrical  solids  are  never 
formed,  and  the  process  is  always  limited  in  the  same  way,  after  the 
formation  of  the  cell-membrane.  Since  organic  and  even  histogenetic 
substances  are  crystallizable,  the  reason  of  cell-development  is  not  to  be 
found  in  permeability  nor  in  any  of  the  other  properties  of  organic  com- 
pounds, which  in  fact,  even  if  the  substances  did  not  crystallize,  would 
not  suffice  to  explain  all  the  peculiarities  of  cells  in  question,  nor  their 
power  of  self-division  and  multiplication ;  but  in  those  peculiar,  as  yet 
unknown  combinations  of  the  powers  of  nature  which  are  concerned  in 
organic  development.  To  discover  these  is  the  further  and  difficult 
task  of  Histology,  which  to  this  end  must  be  wholly  directed  to  the  so- 
called  molecular  forces  of  organic  forms,  especially  to  those  electrical 
phenomena  which  must  indubitably  occur  in  the  cells  as  well  as  in  their 
derivative  structures,  the  nerve-tubes  and  muscular  fibres.* 

§  14.  Vital  Phenomena  of  the  Perfect  Cells.  Growth.— The  cells, 
when  once  completed,  perform  a  considerable  number  of  functions,  which 
relate  as  well  to  the  form  of  the  whole  cell  and  of  its  contents,  as  to  their 
chemical  composition,  and  are  called  growth  and  change  of  substance. 

*  [The  essential  distinction  between  living  organized  matter  (the  cell)  and  mere  inorganic 
iormed  matter  (the  crystal)  appears  to  us  to  be  here  overlooked.  If  some  inorganic  substance 
should  be  discovered  crystallizing  in  the  form  of  nucleated  cells,  it  would  not  the  more  ap- 
proximate to  an  animal  or  vegetable  cell ;  for  the  essential  character  of  the  latter,  which 
is  its  passage  through  a  definite  succession  of  states  and  not  its  form  merely,  would  still  be  absent. 
It  is  this  characteristic  peculiarity  of  organized  living  beings,  which  has  been  exhibited 
with  so  much  force  by  Alex.  Braun,  in  the  plant,  under  the  somewhat  fanciful  title  of '  Ver- 
jungung'  (rejuvenescence),  but  which  equally  obtains  in  the  animal.  The  crystal  tends  to 
attain  a  permanent  condition,  the  cell  towards  its  own  disappearance,  either  by  death  or 
division.  The  crystal  tends  towards  an  equilibrium  with  the  forces  around  it,  the  cell 
incessantly  disturbs  that  equilibrium, — life  and  change  being  one. — TBS.] 


60 


GENERAL    ANATOMY     OF    THE    TISSUES. 


Fig.  10. 


Fig.  11. 


As  to  growth,  it  occurs  perhaps  in  all  cells,  though  not  in  all  to  the 
same  extent.  It  is  clearly  manifested  in  all  those  cells  which  are 
formed  directly  round  a  nucleus,  since  in  this  case  the  membranes  which 
at  first  closely  invest  the  nucleus,  in  time  become  more  and  more  sepa- 
rated, whilst  the  cells  which  arise  around  portions  of  contents  or  invest- 
ing masses,  and  are  from  the  first  provided  with  contents,  often 
increase  in  size  but  very  slightly.  Growth  is  either  in  surface  or  in 
thickness.  The  former  appears  very  usually  to  be  general,  when  cells 
increase  without  altering  their  form,  e.  g.  the  ova,  many  nerve-cells, 
&c. ;  frequently  however  it  is  partial,  as  in  all  cells  which  depart  from 
the  primitive  globular  form,  in  such  a  manner  that  the  cell-membranes 
only  add  new  substance  and  extend  at  two  or  more  points.  Growth  in 
thickness  also  occurs,  to  a  certain 
extent,  in  all  cells,  since  all  cell- 
membranes  become  somewhat 
thicker  with  age :  and  it  produces 
in  some  localities  a  very  consider- 
able thickening  of  the  membrane, 
occasionally  with  evident  lamina- 
tion (as  in  the  cartilage  cells),  and 
even  gives  rise  to  certain  structures  (Fig.  11),  which  have  the  greatest 
similarity  to  the  sclerogenous  cells  of  plants  (bone-cells). 

The  nuclei  and  nucleoli  also  take  part,  to  a  certain  extent,  in  the 
gro\vth  of  the  cells.  In  the  former,  a  general  growth  is  easily  demon- 
strable in  all  growing  cells ;  in  many,  as  in  those  of  the  smooth  muscles, 
of  the  epithelium  of  the  vessels,  of  the  formative  cells  of  elastic  tissue, 
and  others,  there  is  also  a  partial  growth,  in  consequence  of  which  they 
often  assume  the  form  of  long  slender  rods.  The  nucleoli  also  not  un- 
frequently  grow  with  their  cells  (nerve-cells,  ova);  but  except  when 
dividing  they  never  assume  any  but  the  globular  form. 

Schwann  has  given  an  explanation  of  the  growth,  as  well  of  the  cell 
as  of  the  nucleus.  He  considers  that  the  molecules  of  the  cell-mem- 
brane exert  an  attractive  influence  upon  the  fluid  which  surrounds  them, 
and  deposits  its  newly-formed  particles  among  themselves ;  if  the  depo- 
sition take  place  between  molecules  already  present  in  the  substance  of 
the  membrane,  the  cell  becomes  distended ;  if  it  take  place  only  in  the 
direction  of  the  radius  of  the  cell,  the  membrane  becomes  thickened. 

FIG.  10. — Cartilage  cells  of  man.  Two  cells  with  thickened  walls,  from  the  cartilage  of 
the  great  cornu  of  the  hyoidbone,  containing  a  clear  drop  of  fat  beside  their  nucleus.  Mag- 
nified 350  diameters. 

FIG.  11. — Six  developing  bone-cells  from  a  rickety  bone  as  yet  sharply  defined  from  the 
interstitial  substance: — a,  simple  bone-cells;  6,  a  compound  one,  answering  to  a  parent  cell 
with  two  secondary  cells;  c,  similar  ones  with  three  cells.  Magnified  350  diameters. 

*  [This  increased  thickness  of  the  cell-wall  with  age  is  well  seen  in  all  epithelial  tissues 
normal  as  well  as  pathological. — 


CELLS.  61 

The  nucleus  grows  less  than  the  cell,  because  as  soon  as  the  latter  is 
formed  it  no  longer  comes  into  direct  contact  with  the  concentrated 
cytoblastema.  General  growth  takes  place  when  the  molecules  of  the 
membranes  all  attract  equally;  partial  growth,  when  this  happens  only 
or  especially  at  particular  spots,  where  the  apposition  of  new  matter 
takes  place  to  a  greater  extent.  With  reference  to  the  mode  of  forma- 
tion of  precipitates  and  of  crystals,  this  theory  appears  to  me  to  ex- 
plain very  well  the  phenomena  of  general  growth,  supposing  that  we 
ascribe  to  the  cell-membrane  the  faculty  of  readily  taking  up  molecules 
and  applying  them  to  its  increase.  Such,  however,  must  be  the  case, 
for  the  relations  of  the  nuclei,  which  even  when  free,  never  grow  very 
considerably,  and  particularly  never  in  one  direction*  show  that  the 
power  of  growth  is  not  simply  innate  in  every  organic  membrane,  mani- 
festing itself  when  sufficient  formative  material  is  offered,  but  requires 
peculiar  conditions  which  are  realized  only  in  the  cell-membrane.  To 
account  for  partial  growth,  Schwann's  view  must  be  somewhat  extended  ; 
for  only  those  modes  of  growth  in  which  the  cells,  during  their  increase 
in  certain  directions,  lose  nothing  of  their  original  dimensions  in  others, 
can  be  interpreted  in  Schwann's  way,  but  not  those  in  which  the  cells 
become  narrower  as  they  elongate ;  here  we  must  assume  that  whilst 
new  substance  is  deposited  in  the  one  direction,  in  the  other  an  absorption 
takes  place,  for  we  can  in  nowise  consider  the  process  to  be  a  mechani- 
cal one.  For  the  rest,  it  may  be  remarked,  that  partial  growth  may 
depend  upon  the  occurrence  of  assimilation,  in  particular  cells,  only  in 
certain  directions,  as  in  the  thickened  vegetable  cells  with  pore-canals, 
which  is  possibly  connected  with  a  one-sided  direction  of  the  currents  in 
the  cell-contents. 

§  15.  Processes  in  the  Interior  of  the  Cells. — In  order  to  obtain  a  clear 
conception  of  the  processes  which  go  on  in  the  interior  of  cells,  it  would 
before  all  things  be  necessary  to  have  a  more  exact  acquaintance  with 
the  chemical  composition  of  the  cell-contents  than  we  at  present  possess. 
Only  two  kinds  of  cells,  the  ovum  and  the  blood-globule,  have  been  in- 
vestigated with  care  (see  Remarks) ;  but  these  have  such  peculiar  rela- 
tions that  they  can  hardly  be  regarded  as  types  of  cells  in  general. 
However,  we  may  from  these  analyses  draw  certain  inferences  with 
regard  to  other  cells,  and  bearing  in  mind  what  micro-chemical  investi- 
gation teaches  us,  it  may  be  permissible  to  regard  the  cell-contents  in 
general,  as  a  moderately  concentrated  solution  of  protein  with  alkaline 
and  earthy  salts,  and  dissolved  or  suspended  fatty  particles.  From 
these  common  characters,  presented  without  doubt  by  all  cells,  at  least 
in  their  young  condition,  many  cells  differ  very  widely,  insomuch  as 
either  some  of  these  constituents  greatly  predominate  or  altogether  new 

*  [This  is  surely  incorrect.     The  "  nuclei"  in  the  hair-pulp,  in  the  tooth  pulp,  in  connec- 
tive tissue,  in  organic  muscle,  grow  in  one  direction  to  a  very  considerable  extent. — TRS]. 


bZ  GENERAL     ANATOMY    OF    THE    TISSUES. 

substances  occur.  Thus,  there  exist  cells  with  much  protein,  as  the 
nerve-cells ;  and  with  much  fat,  as  the  fat-cells,  the  cells  of  the  seba- 
ceous follicles,  of  the  milk-glands,  &c. ; — then  such  as  contain  haematin, 
pigment,  biliary,  and  urinary  constituents,  mucus  (epithelium-cells),  milk, 
sugar,  &c.  &c. 

The  phenomena  manifested  by  these,  so  variously  constituted  cell- 
contents,  during  life,  may  be  best  enumerated  as — absorption,  assimila- 
tion, and  excretion.  These  depend  principally  upon  chemical  and 
physical  conditions,  and  are  to  a  great  extent  capable  of  microscopic 
investigation,  since  very  frequently  the  changes  of  form  in  the  cell  and 
the  changes  of  its  contents  go  hand  in  hand.  Absorption  is  manifested 
in  all  cells,  but  to  far  the  greatest  extent  in  those  which  at  first  have 
little  or  no  contents  save  the  nucleus.  In  these,  the  primary  cause  of 
the  absorption  is  not  to  be  sought  in  endosmose,  but,  as  Schwann  has 
indicated,  in  this — that  while  the  membranes  grow  by  the  attraction  of 
material  from  the  surrounding  fluid,  by  virtue  of  their  porosity  they 
allow  substances  to  penetrate  into  the  interior.  This  filling,  however, 
does  not  take  place  by  the  cells  admitting  every  kind  of  matter  indis- 
criminately, but  they  exhibit  peculiar  relations  to  the  cytoblastema, 
varying  with  the  period  and  with  the  locality ;  so  that  they  take  up  one 
constituent  and  reject  another ;  and  the  like  occurs  with  the  absorptive 
powers  of  those  cells  which  possess  contents  from  their  earliest  exis- 
tence. 

That  this  is  actually  the  case,  is  demonstrated,  for  instance,  by  the 
fact,  that  in  embryos,  notwithstanding  the  identity  of  the  formative 
material  in  all  cells,  i.  e.  the  plasma  of  the  blood,  some  take  up  more  of 
one  substance,  some  more  of  another ;  and  it  is  still  more  clearly  evi- 
denced by  the  fact,  that  the  cell-contents  of  probably  all  cells  are 
chemically  different  from  the  cytoblastema  out  of  which  they  are  formed 
and  by  which  they  are  nourished,  as  has  been  clearly  shown  lately,  in 
the  ova  and  blood-corpuscles,  which  for  example  contain  far  more  po- 
tassa  than  the  blood.  The  reason  of  this  phenomenon  may  be  generally 
stated  to  be,  that  the  cell-membranes  do  not  act  as  mere  filters,  but 
allow  one  substance  or  another  to  permeate  them,  according  to  their 
chemical  composition,  the  constitution  of  the  fluid  which  imbues  them, 
their  condition  of  aggregation,  and  their  thickness. 

Endosmose  must  also  be  taken  into  account  as  a  condition  in  the  ab- 
sorptive actions  of  cells,  though  hitherto  it  has  been  too  freely  appealed 
to,  and  cells  have  been  too  often  considered  as  vesicles  provided  with 
merely  indifferent  porous  membranes.  That  endosmose  operates  is  not 
to  be  denied,  when  it  is  observed  how  the  addition  of  concentrated  or 
diluted  solutions,  causes  cells  to  dilate  or  to  collapse,  yet  it  is  not  easy 
to  determine  what  influence  such  conditions  have  during  life,  nor  what 
results  are  produced  by  the  combined  operation  of  the  cell-membranes 


CELLS.  63 

and  their  contents.  From  a  few  facts  in  vegetable  physiology  (growth 
of  plants  in  arsenical  and  cupreous  solutions,  without  the  admission  of 
these  substances),  it  might  be  believed  that  the  membranes  exercised 
the  more  important  influence  in  determining  absorption. 

It  is  an  important   question  whether  the  substances  received  by  the 
cells  and  composing  them   become   modified  by  their  vital  processes. 
Schwann  has  answered  it  in  the  affirmative,  and  has  denominated  meta- 
bolic processes  of  cells,  all  those  chemical  metamorphoses  which  go  on  in 
them  and  in  their  separate  parts  ;  and  justly  so,  for  the  occurrence  of 
such  chemical  changes  is  not  only  very  probable  a  priori,  since  in  plants 
all  such  metamorphoses  (and  these  of  the  most  various  kinds)  take  place 
in  the  cells,  but  may  very  easily  be  demonstrated  by  observation.  These 
changes  affect,  firstly,  the  cell-membrane,  and  secondly,  the  cell-contents. 
As  regards  the  former,  this  much  is  certain,  that  the  membranes  of  most 
cells  not  only  become  denser  and  more  solid  with  age,  but  also  that 
they  take  on  a  different  chemical  constitution,  though  it  is  impossible  in 
particular  cases  to  say  on  what  the  change  depends.  In  the  horny  tissues, 
the  membranes  of  the  young  cells  are  easily  soluble  in  alkalies  and  acids, 
whilst  subsequently  they  sometimes  offer  extreme  resistance  to  their 
action :  the  same  takes  place  in  a  few  of  the  higher  elementary  parts, 
as  the  nervous  tubules,  the  animal  muscles,  and  the  capillaries,  in  which 
the  sarcolemma,  the  sheath  of  the  nerve  fibre,  the  capillary  membranes, 
which  are  metamorphosed  cell-membranes,   react  in  a  very  different 
manner  from  the  original  formative  cells.     In  the  cartilage  cells  also, 
the  membrane  becomes  more  resistant  with  age,  and  in  the  course  of 
ossification  not  only  thickens,  but  is  for  the  most  part  changed  into  col- 
lagenous  tissue,  which  is  subsequently  impregnated  with  calcareous  salts. 
These  examples,  which  might  be  multiplied,  may  suffice  to  demonstrate 
the  occurrence  of  a  metamorphosis  of  the  cell-membranes  ;  further  inves- 
tigations will  be  needed  to  show  upon  what  it  depends,  whether,  as  it 
would  seem,  the  original  animal  cell-membrane  actually  alters  in  compo- 
sition in  course  of  time,  or  whether  the  change  in  the  reaction  depends 
upon  the  addition  of  foreign  substances,  on  the  incrustation  of  the  mem- 
branes with  salts,  and  so  forth,  such  as  botanists  are  inclined  to  assume 
for  the  vegetable  cell-membranes,  or  whether  it  depends  upon  secondary 
deposits  on  the  exterior  of  the  original  membranes. 

The  changes  of  the  cell-contents  are  of  two  kinds,  formative  and  re- 
solvent. Both  processes  are  easily  followed  in  the  embryos  of  different 
animals,  in  which,  in  the  first  place,  the  primary  formative  cells,  which 
at  the  beginning  are  distended  with  the  elements  of  the  yelk,  especially 
with  oil,  acquire  by  degrees  more  fluid  and  homogeneous  contents,  the 
yelk  granules  dissolving,  sometimes  from  the  cell-membrane  towards  the 
nucleus,  sometimes  from  within  outwards ;  and  secondly,  in  cells  thus 
formed,  the  most  various  new  formations  take  place,  among  which  that 


64  GENERAL    ANATOMY    OF    THE    TISSUES. 

of  haematin,  of  different  kinds  of  pigment,  and  of  fat,  are  the  most 
obvious.  But  metamorphoses  of  the  cell-contents  are  very  common  in 
adult  animals  also,  and  are  at  the  same  time  very  important,  since  in 
many  places,  on  account  of  the  great  number  of  cells  which  are  affected 
in  the  same  way  at  the  same  time,  unexpectedly  great  results  are  pro- 
duced, as  one  of  the  most  important  of  which  we  may  name  the  biliary 
secretion,  which  is  brought  about,  so  to  say,  only  by  the  activity  of  the 
many  millions  of  cells  which  form  the  liver.  A  pretty  series  of  changes 
may  also  be  traced  in  the  fat-cells,  which,  according  to  the  deficiency  or 
superfluity  of  nutritive  fluid,  in  the  one  case  lose  their  proper  contents, 
and  may  even  become  cells  containing  mere  serum,  in  others  are  filled 
to  bursting  with  drops  of  oil ;  again,  in  the  cells  of  the  fat-secreting 
glands,  which  at  first  contain  but  little  fat,  and  finally  become  crammed 
with  it ;  and  also  in  the  lymph-corpuscles,  which  develop  the  coloring 
matter  of  the  blood  within  themselves,  and  thus  become  blood-corpus- 
cles.* The  formation  of  mucus,  again,  must  probably  be  assigned  to 
the  epithelial  cells  of  the  mucous  glands  and  mucous  membranes  ;  that 
of  the  so-called  pepsin  to  the  cells  of  the  gastric  glands ;  and  that  of 
semen  to  the  spermatic  cells.  A  multiplicity  of  confirmatory  evidence 
is  afforded  by  comparative  anatomy,  and  I  will  here  only  advert  to  the 
development  of  the  concretions  of  uric  acid  in  the  renal  cells  of  the  mol- 
lusca,  that  of  sepia  in  the  cells  of  the  ink  bag  of  the  Cephalopod,  of 
crystals  and  concretions  of  different  kinds  in  the  cells  of  the  invertebrata, 
and  of  certain  pigments  in  those  of  the  mollusca.  Pathological  anatomy 
affords  us  the  pigment  formations,  the  metamorphoses  of  cells  containing 
blood-corpuscles,  and  the  fatty  deposits  in  cells  of  all  kinds. 

Manifold  morphological  phenomena  go  hand  in  hand  with  these 
changes,  such  as  the  thickenings  of  the  cell-membrane,  which  have  been 
already  adverted  to,  with  laminated  depositions  upon  their  inner  surface, 
and  even  with  the  formation  of  pore-canals  ;  as  the  precipitation  in  the 
cell-contents  of  granules  of  different  sorts,  as  of  pigment,  albumen, 
casein  (in  the  yelk,  perhaps  in  the  hepatic  cells) ;  and  as  the  formation 
of  fat  drops,  of  elementary  vesicles,  of  concretions,  crystals,  and  nuclei. 
Even  movements  resembling  the  cyclosis  of  plants  appear  to  occur  in 
the  cells  of  the  lower  animals  (seen  by  me  in  the  cells  of  the  arms  of  a 
minute  Medusa,  a  new  JEginopsis  from  the  Mediterranean,  and  of  Poly- 
clinum  stellatum),  and  in  Protozoa  (currents  in  Loxodes  bursaria,  con- 
tracted vesicles  in  different  genera) ;  while  on  the  other  hand,  the  Brownian 
molecular  movements,  i.  e.  a  more  or  less  active  tremulous  motion 
of  granules  without  further  change  of  place,  which  may  be  observed  in 
many  cells  under  the  microscope,  most  beautifully  in  the  pigment  cells 
of  the  eye,  are  also,  perhaps,  hardly  to  be  reckoned  among  vital  pheno- 
mena. 

*  [In  the  oviparous  vertebrata. — TES.] 


CELLS.  65 

The  nuclei  also  occasionally,,  though  upon  the  whole  rarely,  take  part 
in  the  changes  of  the  cells.  The  commonest  of  these  appearances  is 
their  becoming  clear,  as  a  consequence  of  the  liquefaction  of  the  at  first 
more  viscid  contents,  upon  which  circumstance  it  depends  that  in  young 
cells  they  are  homogeneous,  while  in  the  larger  they  evidently  appear  to 
be  vesicles.  A  formation  of  granules  in  the  nuclei  is  very  rare  (see 
above) ;  concretions,  coloring  matters,  and  crystals,  are  also  not  found 
here  in  animals ;  on  the  other  hand,  the  development  of  the  urticating 
threads  in  certain  animals  and  that  of  the  spermatozoa,  takes  place  in 
nuclei. 

In  endeavoring  to  explain  the  metabolic  processes  of  cells,  we  must 
in  all  cases  especially  regard  the  cell-nucleus ;  for  just  as  it  excites  the 
development  of  the  cell,  so  is  it  the  centre  of  the  currents  of  the  contents, 
and  of  the  deposits  and  solutions ;  but  it  is  not  to  be  regarded  as  the 
sole  agent,  for,  firstly,  it  does  not  appear  why  the  cell-contents  should 
not,  like  the  cytoblastema,  become  changed  of  themselves  ;  and,  secondly, 
the  changes  of  the  cell-membrane  are,  at  all  events,  more  independent, 
and  probably  also  have  a  certain  influence  upon  the  cell-contents,  as 
the  depositions  which  take  place  upon  it,  and  the  solution  of  the  solid 
contents  which  often  occurs  in  its  neighborhood,  demonstrate.  To 
assume  with  Schwann  a  special  metabolic  force  is  incorrect,  for,  in  the 
first  place,  the  causes  of  the  metabolic  phenomena  are  certainly  very 
various ;  and,  secondly,  there  is  every  reason  to  reduce  them  to  known 
molecular  forces.  Thus,  for  instance,  even  the  action  of  the  nucleus* 
may  not  unfittingly  be  compared  with  the  so-called  catalytic,  or  contact 
action,  inasmuch  as  it  is  hardly  at  all  altered  during  the  changes  of  the 
cells,  and  consists  of  a  nitrogenous  substance,  which  like  pepsin  (which 
is  also  nothing  but  cell-contents),  very  readily  produces  a  chemical  altera- 
tion in  other  substances.  The  relation  of  the  cell-membrane  to  absorp- 
tion also,  may  even  now  be  referred  to  the  general  laws  of  imbibition 
and  diffusion. 

I  here  give  two  analyses  as  examples  of  the  chemical  composition  of 
the  cell-contents.  The  yelk  of  the  hen's  egg  contains :  water,  48-55  ; 
casein,  13-93;  albumen,  mixed  with  casein,  0-892;  albumen,  2-841; 
membranes  of  the  yelk  vesicles,  0-459;  fats,  31*146  (30-46  according 
to  Gobley),  consisting  of  olein  and  margarin;  21-304;  cholesterine, 
0-438  ;  lecithin  (containing  phosphoric  acid),  8*426  ;  and  cerebrin  ;  salts, 
1-523;  a  hundred  parts  of  the  ash  yielded,  potass,  8-60-8-93  ;  chloride 
of  sodium,  9-12;  phosphatic  salts,  66-7—67*8;  lime,  12-21;  magnesia, 
2-07  ;  oxide  of  iron,  1-45  ;  silica,  0-055.  The  blood-corpuscles  contain  : 

*  [This  "  action  of  nucleus  "  is  a  wholly  hypothetical  though  a  very  general  assumption 
It  is  important  to  bear  in  mind,  on  the  contrary,  that  there  is  every  reason  to  believe  that 
the  molecular  and  chemical  changes  of  the  cell-membrane  and  the  nucleus  are  independent 
of  one  another. — TRS.] 

5 


66          GENERAL  ANATOMY  OF  THE  TISSUES. 

water,  68-88  ;  hsematin,  1-67  ;  globulin  and  membranes,  28-22  ;  fat.  0-23  ; 
extractive  matters,  0-26;  mineral  substances  (without  iron),  0-81;  of 
which  chlorine,  0-16 ;  sulphuric  acid,  0-006 ;  phosphoric  acid,  0-4 ; 
potassium,  0-83;  sodium,  0-10;  oxygen,  0-06;  phosphate  of  lime,  0-01 ; 
phosphate  of  magnesia,  0-007.  To  these  must  also  be  added,  free  oxygen 
and  carbonic  acid,  which  likewise  occur  in  the  yelk. 

We  have  here  instances  of  cells  containing  much  protein,  and  espe- 
cially fat,  and  may  consider  them  to  be  fair  examples  of  this  kind  of  cell. 
The  comparison  of  the  contents  of  these  cells  with  the  plasma  of  the 
blood,  out  of  which  those  of  the  one  kind  are  formed,  while  the  others 
live  in  it,  is  very  interesting.  In  the  blood-globules  there  is  a  consider- 
able preponderance  of  solid  constituents,  since  the  blood-plasma  only 
contains  about  10  per  cent,  of  solids,  which  is  evidence  that  there  are 
cells  whose  contents  do  not  attain  an  equilibrium  with  the  cytoblastema 
by  which  they  are  supported.  With  regard  to  particular  substances, 
the  blood-corpuscles  contain  more  fat ;  hsematin,  which  is  not  found  in 
the  plasma;  more  potassa  and  phosphoric  acid;  less  chlorine,  extractive 
matters,  soda,  and  earths.  The  yelk  of  the  hen's  egg  contains  also  con- 
siderably more  solid  constituents  than  the  blood,  which  however  is  here 
less  surprising  than  in  the  blood-corpuscles  which  swim  in  the  blood- 
plasma.  It  is  interesting,  that  the  relative  proportions  of  the  different 
substances  are  quite  different  in  this  case  from  the  other.  We  have, 
namely,  an  exceedingly  large  quantity  of  fat,  more  protein  and  salts ; 
and  among  the  latter,  again,  more  potassa,  and  also  more  earthy  salts. 

Even  these  facts  indicate  a  considerable  independence  of  action  in 
the  cells ;  but  those  which  have  been  lately  made  known  by  Ludwig, 
tend  still  more  forcibly  in  the  same  direction ;  for  the  influence  of  the 
nerves  upon  the  salivary  glands  discovered  by  this  observer  must,  I 
believe,  be  so  interpreted,  that  it  is  not  only  the  membranes  propriss 
of  the  vesicles  of  the  salivary  glands,  which  are  so  altered  in  their  mole- 
cular relations  by  the  nervous  influence  that  they  directly  exercise  an 
energetic  attraction  upon  the  blood-plasma  which  surrounds  them,  but 
the  epithelial  cells  which  line  them  also.  If  this  really  be  the  case,  we 
have  an  insight  into  an  altogether  new  condition  regulating  the  absorp- 
tive powers  of  cells,  and  at  the  same  time  cell-life  is  brought  into  such 
connection  with  the  activity  of  the  nervous  system,  that  it  no  longer 
appears  out  of  reason  to  speak  of  the  positive  functions  of  the  latter. 
Such  relations  are  in  nowise  opposed  to  analogy,  since  in  the  contrac- 
tile elements  we  have  already  a  connection  between  nervous  activity 
and  the  modification  of  cell-contents,  which  perhaps  upon  further  inves- 
tigation may  come  under  the  same  general  category  as  the  foregoing. 
In  any  case,  these  considerations  lead  anew  to  an  exact  investigation  of 
the  molecular  forces  of  cells,  especially  of  those  electrical  phenomena 
which  will  certainly  be  found  in  them. 


CELLS.  67 

Very  recently  Bonders  (Nederlanclsch.  Lancet.)  has  justly  brought 
forward  a  character  which  until  now  had  received  no  attention,  viz.,  the 
elasticity  of  the  cell-membranes  and  the  pressure  consequently  exercised 
upon  the  cell-contents.  It  is  an  ascertained  fact  that  the  cell-membranes 
are  elastic  ;  and  it  thence  naturally  follows  that,  according  to  the  greater 
or  less  amount  of  the  contents  of  the  cells,  so  will  these  suffer  a  greater 
or  less  pressure.  This,  however,  reacts  again  upon  the  absorptive  and 
excretive  processes,  so  that  under  a  more  considerable  pressure  the 
latter,  under  a  less,  the  former  prevails,  and  in  certain  circumstances 
it  may  conduce  to  the  maintaining  of  a  regular  interchange  of  sub- 
stances. Bonders  believes,  that  the  greater  density  of  the  cell-contents 
may  be  derived  from  their  always  being  under  greater  pressure  than 
the  cytoblastema. 

§  16.  Excretive  processes. — The  vegetative  functions  of  animal  cells 
are  not  limited  to  mere  absorption  and  metamorphosis,  but  substances 
are  excreted  as  a  result  of  their  operation.  This  may  take  place  in  two 
ways. 

1.  The  cells  give  out  unaltered,  the  substances  which  they  have  re- 
ceived from  ivithout. — This  occurs  in  the  epithelium  cells  of  those  glands 
which,  like  the  kidneys,  lachrymal  glands,  lungs,  &c.,  simply  permit  of 
the  discharge  of  substances  from  the  blood,  also  in  those  cells  which 
line  the  serous  membranes,  and  probably  many  others. 

2.  The  cells  excrete  substances  which  they  have  prepared  within  them- 
selves.— Thus  the  blood-cells   give  up  their  hsematin  in   dilute  blood- 
plasma  ;  the  fat-cells  their  fat  in  emaciated  persons  ;  the  hepatic  cells, 
bile  ;    those  of  the  gastric  glands,  gastric  juice ;  those  of  the  mucous 
glands  and  membranes,  mucus. 

The  occurrence  of  these  excretions,  of  which,  in  fact,  there  are  assu- 
redly very  many  with  which  we  are  still  unacquainted,  may  in  some 
cases  be  explained  by  exosmose ;  in  others,  however,  as  in  the  secretions 
of  the  glands,  this  cannot  take  place.  Here  the  exit^of  the  contents  is 
a  consequence  of  the  pressure  to  which  they  are  exposed,  which  pres- 
sure is  to  be  referred  upon  the  one  hand  to  the  force  of  the  blood,  on 
the  other  to  an  attractive  force  exercised  by  the  cells  themselves  in  ab- 
sorbing the  substances,  and  to  the  elasticity  of  the  cell-membranes. 

The  excreted  matters  in  general  no  longer  continue  in  the  organism, 
but  are  completely  removed  as  in  the  glands  ;  in  a  few  localities  they 
remain,  taking  a  solid  form,  as  extra-cellular  substance,  outside  the  cells, 
and  form  the  genuine  membrane  propria?  of  the  glands  (e.  g.  of  the  renal 
canals),  the  proper  envelop  of  the  chorda  dorsalis,  and  probably  also  the 
so-called  vitreous  membranes  (capsule  of  the  lens,  membrana  Demoursii). 
An  intercellular  substance  is  rare  in  animals,  for  the  matrix  of  the 
cartilages  and  bones,  which  for  the  most  part  is  not  excreted  by  the 


68  GENERAL    ANATOMY    OF    THE    TISSUES. 

cells,  but  is  deposited  from  the  blood-plasma  or  is  even  formed  out  of 
cells,  does  not  come  under  this  head.  It  may  be  said  to  be  present  in 
a  smaller  quantity  and  more  fluid,  however,  not  only  in  the  cellular 
tissues,  but  also  in  the  higher  structures,  among  which  there  everywhere 
exists  a  small  quantity  of  connecting  substance.  Intercellular  spaces 
developed  by  the  excretions  of  cells  between  one  another,  have  not 
been  demonstrated  with  certainty  in  animals,  yet  it  is  probable  that 
most  glandular  cavities  and  those  of  the  heart  and  of  the  great  vessels 
are  of  this  nature,  since  they  appear  to  rise  by  the  excretion  of  fluid  in 
the  interior  of  originally  compact  masses  of  cells. 

My  view,  that  the  genuine,  membrance  proprice  and  the  vitreous 
membranes  are  formed  as  excretions,  is  founded  particularly  upon  the 
examination  of  the  chorda  dorsalis  and  of  the  renal  canals,  in  which  it 
may  be  readily  shown  that  the  structureless  membranes  are  secondary 
formations,  arise  in  intimate  union  with  the  cells  of  this  part,  and  from 
the  very  first  appear  perfectly  homogeneous.  The  supposition  of  many 
authors,  especially  of  Reichert,  that  these  membranes  belong  to  the 
homogeneous  connective  tissue,  is  readily  refuted  by  chemical  examina- 
tion, since  they  yield  no  gelatine,  but  consist  of  a  substance  which  most 
closely  approximates  to  the  sarcolemma  and  elastic  tissue  (comp.  Men- 
sonides  in  'Nederl.  Lancet.'  d.  iv.  694,  and  Bonders,  ibid.  August,  1851, 
p.  73).  To  what  extent  homogeneous  membranes  formed  by  excretions 
from  cells,  occur  among  animals  is  not  yet  determined,  but  the  homoge- 
neous chitin-investments  of  the  intestine,  and  of  the  external  surface  in 
the  Artieulata,  appear  to  be  of  this  nature. 

§  17.  Contractility  of  the  Cells. — Among  the  vital  phenomena  of  cells 
must  be  enumerated  those  contractions  which  are  manifested  by  cell- 
membranes  and  also  by  cell-contents.  Contractile  cell-membranes  are 
possessed  by  many  if  not  all  Protozoa  ;  and  among  subordinate  cells,  by 
the  yelk-cells  of  the  Pladarise,  the  heart-cells  of  many  embryos  (Alytes, 
Sepia,  Limax),  the  cells  of  the  tail  of  embryo  Botrylli.  The  cilia  also, 
as  processes  of  the  cell-membrane,  may  be  mentioned  here.  Contractile 
cell-contents  are  found  in  the  fibre-cells  of  the  smooth  muscles,  in  the 
stellate  cells  of  the  skin  of  the  embryo  of  Limax,  and  in  the  animal 
muscular  fibres  ;  which  last,  as  they  consist  of  a  number  of  united  cells, 
may  be  here  enumerated.  Here  also  I  place  the  contractile  phenomena 
exhibited  by  the  contents  of  the  Protozoa  (contractile  vesicles)  and  by 
the  Rhizopoda.* 

*  [To  this  list  of  contractile  cells  must  be  added  the  colorless  corpuscle  of  the  blood  of 
man,  the  Frog,  and  the  Skate,  and  probably  that  of  other  Vertebrata  (Wharton  Jones,  I.  c.), 
the  cells  which  lie  in  the  meshes  of  the  areolar  tissue  of  the  disc  of  the  Medusae  (Cyanced) 
and  the  young  epithelium  cells  (mucus-corpuscles)  of  the  mucous  membranes,  in  which 
most  distinct  protean  movements,  like  those  of  the  colorless  corpuscle,  may  be  observed. 


CELLS.  69 

Donders  has  recently  promulgated  the  view  that  it  is  only  the  cell- 
contents  which  are  contractile,  not  the  cell-membranes.  Although  it 
must  be  granted,  that  it  is  difficult,  in  the  cases  in  question,  to  decide 
what  part  of  the  cell  contracts,  yet  it  seems  very  hazardous  to  endeavor 
to  refer  the  movements  of  the  cilia  in  plants  and  animals,  in  free  and 
combined  cells,  to  indemonstrable  contents  in  these  cilia  communicating 
with  the  cell.  In  the  cells  of  the  Planariae  and  in  the  Protozoa,  any 
one  who  has  actually  seen  the  movements  will  hardly  refer  them  to 
anything  but  the  cell-membranes.  In  the  transversely  striated  muscular 
fibres  on  the  other  hand,  it  is  evidently  the  fibrillae  or  the  contents 
which  are  contractile,  and  the  sarcolemma,  as  an  elastic  yielding  body, 
only  moves  with  them  :  the  same  appears  to  hold  good  with  the  muscular 
fibre-cells,  in  which  a  special  membrane  cannot  be  demonstrated. 

§  18.  Metamorphoses  of  Cells — Kinds  of  Cells. — The  destination  of 
the  cells  which  are  found  at  an  early  period  in  the  organism  is  very 
various.  A  very  considerable  portion  of  them  remain  but  for  a  short 
time  in  their  primitive  condition,  and  subsequently  coalesce  with  others 
to  form  the  higher  elementary  parts.  Another  portion,  while  they  enter 
into  no  such  combinations,  change  more  or  less  their  previous  nature  ; 
as  the  horny  plates  of  the  epidermis  and  nails.  Many  cells,  lastly, 
never  become  metamorphosed  at  all,  but  remain  as  cells,  until  sooner 
or  later,  often  not  before  the  decay  of  the  organism,  they  disappear 
accidentally  or  typically,  as  the  epithelia,  glandular  parenchymata,  &c. 

The  permanent  cells  may  be  most  conveniently  arranged  under  the 
following  heads : — 

1.  True  cells,  which  have  in  no  essential  respect  altered  their  cellular 
nature.  These  occur  in  the  epidermis  (stratum  MalpigJtii)  and  the 
epithelia;  in  the  blood,  chyle,  lymph;  in  the  glandular  secretions,  in 
the  fatty  tissue,  in  the  gray  nervous  substance,  the  red  bone-medulla  ;  in 
the  glands  (liver,  spleen,  suprarenal  capsules,  closed  glandular  follicles), 
and  the  cartilages.  According  to  their  form,  these  cells  may  be  divided 
into  round,  discoid,  cylindrical,  conical  with  cilia,  and  stellate;  accord- 
ing to  their  contents,  they  may  be  distinguished  as  containing  fat,  protein 
or  serum,  hgematin,  bilin,  pepsin,  mucus,  or  pigment  ;  and  as  to  their 
modes  of  occurrence,  some  are  either  isolated  in  fluids  or  in  solid  tis- 
sues, others  are  united  into  a  simple  cellular  parenchyma,  while  others 
are  conjoined  by  an  intercellular  substance  of  one  kind  or  another. 

It  is  certainly  the  membrane  which  contracts  in  these  cases,  for  it  pushes  out  processes 
which  are  only  subsequently  filled  by  the  granular  contents. 

In  the  lower  plants  (Jllgce)  the  occurrence  of  contractile  processes  in  the  shape  of  cilia  is 
universal,  and  the  contractility  of  the  cell  substance  in  the  zoospores  of  Volvox  is  evinced 
by  the  occurrence  of  a  rhythmically  contracting  space  in  them.  (See  Busk  on  Volvox  globator, 
<(  Quarterly  Journ.  of  Micr.  Sc.,;'  No.  2,  1853.) — TRS.] 


70  GENERAL    ANATOMY     OF    THE    TISSUES. 

2.  Metamorphosed  cells,  which  have  more  or  less  altered  their  original 
structure.  To  these  belong  : — 

a.  The  horny  scales :  flattened,  polygonal,  or  fusiform :  their  membrane 
being  fused  into  one  mass  with  the  contents.     In  the  epidermis,  the 
laminated  pavement  epithelium,  the  hairs  and  nails. 

b.  The  contractile  fibre  cells:  fusiform,  slightly  flattened,  considerably 
elongated  cells,  whose  membrane,  together  with  its  soft  solid  contents  is 
changed  into  a  contractile  substance.     In  the  smooth  muscles. 

c.  The  tubules  of  the  lens :  very  much  elongated  cells,  with  viscid, 
albuminous  contents. 

d.  The  prisms  of  the  enamel:  greatly  elongated,  prismatic,  and  strongly 
calcified  cells. 

e.  The  lone  cells :  thickened  cells  with  pore  canals  which  have  coa- 
lesced with  the  homogeneous  matrix  of  the  bones  and  anastomose  by 
means  of  excavations  in  it. 

/.  The  transversely  striated  muscular  cells:  large  polygonal  cells, 
whose  contents  have  become  metamorphosed  into  a  transversely  striated 
tissue,  such  as  is  found  in  the  transversely  striated  muscular  fibre.  In 
the  endocardium  of  ruminants. 

B.  HIGHER  ELEMENTARY  PARTS. 

§  19.  The  higher  elementary  parts  correspond,  genetically,  to  a  whole 
series  of  the  simple  ones,  and  it  is  the  cells  only,  so  far  as  we  know, 
which  possess  the  faculty  of  producing  them.  The  manner  in  which  this 
takes  place  varies.  Either  the  cells  while  they  coalesce  retain  their  cellu- 
lar nature,  and  to  a  certain  extent  their  independence,  in  which  case  we 
have,  according  as  they  are  fusiform  or  stellate  cells,  cell-fibres  or  cell- 
reticulations;  or  the  cells  in  uniting  totally  surrender  their  indepen- 
dence, in  which  case  they  form,  if  they  are  arranged  in  lines,  elongated 
elementary  parts  ;  or  are  united  by  many  offsets, — networks ;  or  are 
fused  together  upon  all  sides, — membranes.  The  two  former  of  these 
again,  according  to  the  kind  of  modification  undergone  by  the  contents 
of  the  united  cells,  appear  either  as  fibres,  bundles  offibrilla?  and  tubes, 
or  as  fibre-networks  and  tubular  plexuses.  Since  all  these  elementary 
parts  will  be  spoken  of  at  length  afterwards,  among  the  tissues,  we  may 
here  simply  enumerate  them  as  follows.  They  are  : — 

a.  The  cell-fibres  and  cell-networks. — To  these  belong  a  part  of  the 
nuclear  fibres  of  authors,  the  cartilage  cells  of  certain  Plagiostome 
fishes  (see  Leydig,  "  Beitrage  zur  mikr.  Anat.  u.  Entwickel.  d.  Rochen 
u.  Haie.,"  Leipzig,  1852),  the  pigment  cells  of  the  lamina  fusca,  pia 
mater,  and  of  Batrachian  larvae,  the  networks  of  the  nerve  cells  in  the 
brain  of  the  Torpedo  (R.  Wagner),  the  fatty  substance  of  the  Lepidoptera 
(H.  Meyer,  "  Zeitschrift  fur  wiss.  Zool.,"  Bd.  i.  st.  178). 


CELLS.  71 

b.  The  elastic  fibres,  fibrous  networks,  and  fibres. 

c.  The  fibres  of  connective  [areolar]  tissue,  the  networks  of  connective 
tissue  (reticulated   connective  tissue),  and  the  membranes  composed  of 
connective  tissue  (homogeneous  connective  tissue). 

d.  The  transversely  striated  muscular  fibres  and  muscular  fibre  net- 
^vorks. 

e.  The  nerve-fibres  and  nerve-fibre  networks. 

f.  The  capillary  plexuses  of  the  blood-vessels  and  lymphatics. 

g.  The  trachese  and  tracheal  plexuses  of  the  invertebrata. 

All  these  higher  elementary  parts  possess  essentially  the  same  proper- 
ties as  cells,  especially  growth  in  length  and  thickness,  absorption, 
metamorphoses,  and  excretion,  and  to  some  extent  contractility  ;  to- 
gether with  other  functions  which  may  perhaps  also  be  demonstrated  in 
cells.  Their  growth  is  manifested  by  the  fact,  that  all,  without  excep- 
tion, are  much  shorter  and  narrower  immediately  after  their  formation 
than  subsequently ;  their  absorptive  powers,  by  the  dependence  of  their 
functions  upon  the  circulation,  by  the  phenomena  of  resorption  in  the 
lymphatics  and  blood-vascular  capillaries,  and  by  the  above-mentioned 
growth,  which  can  only  take  place  by  the  reception  of  substances  into 
their  interior.  A  metamorphic  and  an  excretive  power  must  be  assumed 
to  exist  in  them ;  it  is  testified  by  the  well-known  peculiar  products  of 
decomposition  of  the  muscles,  and  also  by  the  continual  transmission 
of  blood-plasma  through  the  walls  of  the  capillaries.  The  muscular 
fibrils  possess  contractility,  and  the  processes  in  the  nerve-fibres,  though 
very  peculiar,  and  at  present  not  to  be  defined  more  nearly,  may 
nevertheless  in  some  respects  be  compared  to  the  functions  of  the  nerve- 
cells. 

With  regard  to  the  tracheae,  which  are  placed  here  only  for  complete- 
ness' sake,  I  long  since  found  that  their  terminations  are  formed  by  the 
coalescence  of  stellate  cells  into  tubes,  in  which  the  original  cell-contents 
either  remain  or  become  developed  into  a  spiral  fibre ;  and  I  published 
a  concise  notice  of  the  fact  in  the  year  1849  ("  Zeitschrift  fur  wiss. 
Zool.,"  Bd.  i.  p.  215,  Anmerkung),  a  view  which  has  since  been  con- 
firmed by  H.  Meyer  (Ibid.  Bd.  i.),  and  more  recently  by  Leydig  (Ibid. 
Bd.  iii.  Heft  4.) 

Literature  of  the  Elementary  Parts. — In  addition  to  Schwann's  work 
quoted  above,  may  be  named:  Kolliker,  "die  Lehre  von  der  thierischen 
Zelle,"  in  Schleiden  u.  Nageli's  "  Zeitschrift  fiir  wiss.  Botanik.,"  Heft 
ii.  1845;  Remak,  "  Ueber  extracellulare  Entstehung  thierischen  Zellen 
und  die  Vermehrung  derselben  durch  Theilung  u.  uber  Entstehung  des 
Bindegewebes  u.  d.  Knorpel,"  in  Muller's  "  Archiv,"  1852,  i.  (No  longer 
available.  Remak  assumes  quite  confidently,  what  I  only  indicated,  that 
animal  cells  have  a  primordial  utricle,  without  giving  any  demonstration  of 


72  GENERAL    ANATOMY    OF    THE    TISSUES. 

the  fact;  he  ascribes  the  multiplication  of  cells  by  division  to  be  widely 
extended  through  embryonic  tissues ;  finds  (what  others  will  not 
easily  succeed  in  doing)  two  membranes  in  the  later  cleavage-masses, 
and  wrongly,  denies  altogether  the  occurrence  of  free  cell-development) ; 
also  the  treatise  of  Donders,  cited  below  under  the  head  of  elastic  tissue ; 
and  the  embryological  monographs  of  Reichert,  Bischoff,  Vogt,  Remak, 
and  myself.  Inasmuch  also,  as  the  doctrine  of  the  vegetable  cell  is  impor- 
tant for  zoologists,  I  call  attention  to  Schleiden's  first  treatise  ("  Ab- 
handlung  Uber  die  Bildung  d.  Pflanzenzelle,"  Mull.  "Arch.,"  1837);  to 
his  "Elements  of  Botany ;"  to  Nageli's  Essay  "  Ueber  die  Pflanzenzelle," 
in  the  "Zeitschrift  flir  wissenschaftlich.  Botanik,"  Heft  ii.  ;  and  to 
Mohl's  monograph  upon  this  subject,  in  Wagner's  "Handworterbuch" 
("  Mohl  on  the  Vegetable  Cell,"  translated  by  A.  Henfrey,  London, 
1852).  [To  these  should  be  added  the  important  monographs  of 
Schleiden,  "Beitrage  zur  Phytogenesis,"  in  Muller's  Archiv,  p.  137; 
of  Rosenthal,  "  De  formatione  granulosa  in  nervis  aliisque  partibus 
organismi  animalis,"  Vratislavise,  1837  ;  of  Kramer  "Bemerkungen  Uber 
das  Zellenleben  in  der  Entwickelung  des  Froscheies"  in  Muller's  Archiv, 
1848,  and  the  more  recent  works  of  Dr.  Schacht,  on  the  "  Vegetable 
Cell"  (Die  "  Pflanzenzelle")  Berlin,  1852  ;  and  of  Alex.  Brown  on 
u  Rejuvenescence"  (Verjungung),  Leipzig,  1851. — DAC.] 

III.    OF   THE    TISSUES,    ORGANS,    AND    SYSTEMS. 

§  20.  The  elementary  parts  of  both  the  simpler  and  the  higher  kinds, 
are  not  dispersed  irregularly  in  the  body,  but  are  united  according  to 
determinate  laws,  into  the  so-called  tissues  and  organs.  Under  the 
first  denomination  comes  every  constant  arrangement  of  the  elementary 
parts  always  recurring  in  similar  modes  in  the  same  parts ;  under  that 
of  an  organ,  on  the  other  hand,  a  certain  sum  of  elementary  parts  of  a 
definite  form  and  function.  When  several  or  many  organs  of  a  similar 
or  different  kind  are  united  into  a  higher  unity,  this  is  called  a  system. 

The  tissues  are  of  different  kinds,  according  as  structural  elements  of 
one  kind  only  occur  in  them,  or  as  various  elements  and  even  organs 
take  part  in  their  formation.  We  can  thence  distinguish  simple  and 
complex  tissues,  which,  however,  cannot  be  sharply  separated  from  one 
another,  and  which  may  be  most  fittingly  arranged  in  the  following 
series : — 

(a.)  Simple  tissues. 

1.  Epidermic  tissue. 

2.  Cartilaginous  tissue. 

3.  Elastic  tissue. 

4.  Connective  tissue.* 

*  [Fibrous  tissue,  see  note,  p.  47. — ED.] 


TISSUES.  73 

(b.)   Complex  tissues. 

5.  Osseous  tissue. 

6.  Smooth  muscular  tissue. 

7.  Transversely  striated  muscular  tissue. 

8.  Nervous  tissue. 

9.  The  tissue  of  the  blood-vascular  glands. 
10.  The  tissue  of  the  true  glands. 

The  organs  may  be  divided  like  the  tissues,  into  simple  and  complex. 

To  the  simple  belong : — 

(a.)  Horny  tissue,  as  the  epidermis,  the  epithelia,  hairs,  nails,  and 
the  lens,  which  consist  solely  and  wholly  of  epithelial  cells  of  one  kind 
or  another. 

(b.)  The  true  cartilages  and  the  elastic  cartilages,  which  in  their  inte- 
rior, with  few  exceptions,  consist  only  of  cartilaginous  tissue,  though 
externally  they  possess  a  vascular  and  nervous  coat,  the  perichondrium. 

(c.)  The  elastic  ligaments,  consisting  of  elastic  fibres,  with  some  con- 
nective tissue,  and  containing  only  at  the  surface  a  few  vessels  and 
nerves. 

(d.)  The  tendons,  ligaments,  true  fibrous  membranes,  and  fibro-carti- 
lages,  containing  a  preponderance  of  connective  tissue,  intermixed  with 
fine  elastic  fibres,  and  sometimes  cartilage  cells  in  small  quantities,  and 
almost  entirely  devoid  of  vessels  and  nerves. 

Complex  organs  are  : — 

(e.)   The  smooth  muscles  and  muscular  membranes  ;  and — 

(/.)  The  transversely  striated  muscles  and  muscular  membranes,  both 
of  which,  besides  their  contractile  elements,  are  abundantly  intermingled 
with  connective  tissue,  nerves,  and  blood-vessels. 

(g.)  The  nerves,  ganglia,  and  higher  central  organs  of  the  nervous 
system,  contain  besides  gray  and  white  nervous  substance,  many  blood- 
vessels, and  special  fibrous  investments. 

(h.)  The  vessels  are  composed  of  connective  and  elastic  tissue,  muscles 
and  epithelium  in  various  proportions,  and  are  provided  with  vessels  and 
nerves,  only  in  their  outermost  layers. 

(i.)  The  bones  and  teeth,  which,  together  with  their  characteristic  tis- 
sues, have  peculiar  soft  structures,  containing  many  vessels  and  nerves, 
and  the  former  medulla  also. 

(&.)  The  blood-vascular  glands,  composed  of  a  peculiar  glandular  ele- 
ment, in  the  form  of  closed  follicles  of  different  kinds,  and  many  blood- 
vessels ;  with  nerves  also,  and  with  abundant  but  generally  non-con- 
tractile fibrous  tissue. 

(I.)  The  true  glands  ;  glandular  follicles,  vesicles  or  tubes  with  many 
vessels,  nerves,  and  investing  fibrous  tissue. 

(m.)  The  vascular  membranes,  as  the  skin,  the  mucous,  serous,  and 
proper  vascular  membranes,  which  in  a  matrix  composed  of  connective 


74  GE-NERAL    ANATOMY    OP    THE    TISSUES. 

and  elastic  tissue,  generally  contain  very  numerous  blood-vessels  and 
lymphatics,  in  part  also  simple  glands  and  nerves,  and  are  invested  by 
special  epithelial  layers. 

(n.)  The  separate  organs  of  the  tractus  intestinalis,  as  the  tongue, 
the  oral  cavity,  the  pharynx,  the  oesophagus,  the  stomach,  and  so  forth, 
into  the  constitution  of  which,  mucous,  muscular,  and  serous  membranes, 
grouped  in  various  ways,  enter. 

(o.)  The  hig'her  organs  of  sense,  into  which  almost  all  the  tissues  and 
many  more  simple  organs  enter. 

Lastly,  the  organs  enter  into  the  formation  of  peculiar  systems,  of 
which  we  may  distinguish  the  following : — 

1.  The  external  cutaneous  system,  consisting  of  the  corium,  the  epi- 
dermis, the  horny  tissues,  and  the  larger  (lacteal  gland)  and  smaller 
glands  of  the  skin. 

2.  The  osseous  system,  consisting  of  the  bones,  cartilages,  ligaments, 
and  articular  capsules. 

3.  The  muscular  system,  consisting  of  the  muscles  of  the  trunk  and 
of  the  extremities,  the  tendons,  fasciae,  tendinous  ligaments,  and  bursce 
mucosoe. 

4.  The  nervous  system,  composed  of  the  larger  and  smaller  central 
organs,  the  nerves  and  the  higher  organs  of  sense. 

5.  The  vascular  system,  consisting  of  the  heart,  the  blood  and  lymph- 
vessels,  and  the  lymphatic  glands. 

6.  The  intestinal  system,  composed  of  the  intestinal  canal,  the  organs 
of  respiration,  with  the  thymus  and  thyroid,  the  salivary  glands,  the 
liver,  and  the  spleen. 

7.  The  urinal  and  sexual  systems. 

As  the  separate  organs  and  systems  are  particularly  considered  in  the 
special  part  of  this  work,  it  is  not  necessary  to  speak  at  greater  length 
of  them  here,  and  it  is  only  requisite  to  define  the  tissues  somewhat 
more  closely — taking  occasion  at  the  same  time  to  refer  to  some  gene- 
ralities concerning  the  organs. 

§21.  Epidermic  Tissue. — The  morphological  character  of  the  epi- 
dermis is,  that  it  is  wholly  constituted  by  independent  cells  intimately 
united  together  without  any  visible  matrix,  which  are  generally  nucleated 
and  in  part  are  true  vesicles,  while  in  part  they  are  metamorphosed  into 
solid  scales.  In  its  chemical  characters  this  tissue  is  but  little  known, 
though  this  much  has  been  made  out,  that  its  cells  contain  chiefly  an 
albuminous  substance,  in  part  also  mucous  ;  and  at  first  all  possess  easily 
soluble  protein  membranes,  which  however,  subsequently,  become  par- 
tially changed  into  a  substance  which  more  or  less  resists  acids  and 
alkalies, — the  so-called  horn.  The  physiological  import  of  the  epidermic 
tissue  is  to  serve  as  a  defensive  covering  to  those  parts  of  the  organism 


TISSUES,     ORGANS,     AND     SYSTEMS.  75 

which  abound  in  vessels  and  nerves,  and  by  the  activity  of  its  elements 
to  take  part  in  secretion  and  absorption.  All  epidermic  tissues  are  non- 
vascular,  and  support  themselves  from  a  plasma  which  is  yielded  by  the 
deeper-seated  vessels.  They  are  very  easily  regenerated  when  their 
superficial  portions  are  removed,  and  in  this  case  they  grow  chiefly  by 
the  development  of  new  elements  in  the  deeper  layers  ;  even  when  wholly 
lost  they  are  readily  reproduced. 

The  epidermic  tissue  takes  the  following  forms : — 

1.  Corneous  tissue. — This  always  consists  of  compact  masses  of  cells, 
which  are  soft  in  the  neighborhood  of  their  vascular  basis,  but  at   a 
greater  distance  become  more  or  less  solid  and  hard  (corneous),  and  fre- 
quently lose  their   originally  vesicular  constitution  and  nucleus,   and 
become  the  so-called  horny  scales.     The  following  organs  are  formed  by 
this  tissue : — 

a.  The  Epidermis ;  which  invests  the  exterior  of  the  body,  and  is 
continuous  at  the  great  apertures  of  the  inter-  Fi-.i2. 

nal  cavities  with  the  epithelium.  It  consists  of 
two  tolerably  distinct  layers ;  the  mucous  layer 
(rete  mucosum),  with  soft,  rounded  polygonal 
cells,  which,  under  certain  circumstances,  con- 
tain coloring  matter.  This  layer  applies  itself 
accurately  to  all  the  inequalities  of  the  corium 
(which  nourishes  the  epidermis),  and  externally 
passes  into  the  polygonal  scales  of  the  horny 
layer. 

b.  The  Nails. — These  may  be  regarded  as  a  modification  of  the  epi- 
dermis, whose  horny  layer  has  attained  a  still  greater  density;  and, 
with  its  rete  mucosum,  lies  upon  a  special  depressed  surface  of  the  cutis, 
— the  bed  of  the  nail ;  and  is  partly  sunk  in  a  peculiar  cleft, — the  fold 
of  the  nail. 

c.  The  Hairs. — Filiform  epidermic*  structures,  seated  upon  a  vas- 
cular papilla,  in  a  peculiar  sac,  the  hair  sac,  which  is  a  process  of  the 
corium,  and  is  lined  by  a  continuation  of  the  epidermis.     The  structural 
elements  in  the  region  of  the  papilla  are  soft  and  vesicular ;  the  more 
distant  are  metamorphosed  into  three  kinds  of  cells — plates,  flat  fibres, 
and  more  or  less  rounded  irregular  cells. 

2.  Epithelium. — Soft   nucleated   cells,  nowhere    densely   corneous  ; 
rounded,  polygonal,  fusiform,  cylindrical  or  conical  in  shape ;  sometimes 
possessing  cilia,  sometimes  not,  arid  occurring  in  one  or  many  layers. 
Hence  we  have  the  following  forms  : — 

FIG.  12. — Plates  of  the  horny  layer  in  man,  magnified  350  diameters.    1,  without  addition, 
viewed  from  the  surface,  one,  with  a  nucleus :  2,  from  the  side. 

*  [It  is  to  be  questioned  if  the  hairs  are  truly  epidermic  structures,  vide  infra,  §  Hair. — TRS.] 


76 


GENERAL  ANATOMY  OF  THE  TISSUES. 


a.  Epithelium  in  a  single  stratum. 

(1.)  With  rounded,  polygonal  cells  (pavement-epithelium  in  a  single 
layer). 

This  exists  as  an  investment  of  the  true  serous  membranes,  of  most 
synovial  membranes,  of  the  cerebral  ventricles  (ependymd)  of  the  mem- 
brane of  Demours,  of  the  back  of  the  iris,  and  of  the  inner  surface  of  the 
choroid  (pigment  layer),  of  the  capsule  of  the  lens  and  of  the  retina,  of  the 
internal  ear,  of  the  endocardium,  of  the  veins,  ftf  many  glandular  vesicles 
and  canals  (racemose  glands,  kidneys,  sudoriparous  and  ceruminous 
glands,  lungs),  and  of  the  ductus  interlobulares  of  the  liver. 


Fig.  13. 


Fig.  14. 


(2.)  With  fusiform,  superficially-united  cells  (fusiform  epithelium). 

Epithelium  of  the  arteries,  and  of  many  veins. 

(3.)  With  cylindrical  cells  (cylinder-epithelium). 

In  the  intestine  from  the  cardia  to  the  anus,  in  Lieberkiihn's  glands, 
in  the  excretory  ducts  of  the  gastric  glands,  as  well  as  of  all  the  other 
glands  which  open  into  the  intestine ;  also  of  the  lacteal  and  lachrymal 
glands  ;  in  the  male  urethra,  the  vas  deferens,  the  vesiculce  seminales,  the 
excretory  ducts  of  the  prostate,  of  Cowper's,  Bartholini's,  and  the  ute- 
rine glands. 

Fig.  15.  Fig.  16. 


(4.)  With  cylindrical  or  conical  ciliated  cells  (simple,  ciliated  cylinder- 
epithelium). 

Epithelium  of  the  finest  bronchise,  of  the  nasal  cavities,  of  the  inner 
surface  of  the  membrana  tympani,  of  the  Eustachian  tube,  of  the  uterus, 

FIG.  13. — Epidermis  of  a  two  months' human  embryo,  still  soft  like  epithelium;  mag- 
nified 350  diam. 

FIG.  14. — Epithelial  cells  of  the  vessels,  the  longer  ones  from  the  arteries,  the  shorter 
from  the  veins. 

FIG.  15. — Epithelium  of  the  intestinal  villi  of  the  rabbit;  magnified  300  diam. 

FIG.  16. — Ciliated  cells  from  the  finer  bronchise;  magnified  350  diam. 


TISSUES,     ORGANS,     AND     SYSTEMS. 


77 


from  the  middle  of  the  cervix,  up  the  Fallopian  tubes,  as  far  as  the  outer 
surface  of  thefanbrite, 

(5.)  With  rounded  ciliated  cells  (simple  ciliated  pavement-epithelium). 

Epithelium  of  the  cerebral  cavities  of  embryos. 

b.  Epithelium  in  many  layers  : — 

(1.)  With  cylindrical  or  rounded  cells  below,  rounded,  polygonal,  more 
or  less  flattened  cells  above  (laminated  pavement-epithelium). 

Epithelium  of  the  oral  cavity,  of  the  lower  half  of  the  pharynx,  of 
the  oesophagus,  of  the  lachrymal  canals,  of  the  conjunctiva,  of  the  tym- 
panic cavity,  of  the  vagina  and  female  urethra,  of  the  urinary  bladder, 
of  the  ureters  and  pelves  of  the  kidneys,  and  of  certain  synovial  mem- 
branes. 

(2.)  With  rounded  cells  below,  more  elongated  ones  in  the  middle,  and 
ciliated  conical  ones  above  (laminated  ciliary  epithelium). 

Epithelium  of  the  larynx,  trachea,  and  larger  bronchise  ;  of  the  nasal 


Fig.  17. 


cavity,  with  the  exception  of  the  regio 
olfactoria ;  of  the  lachrymal  sac  and 
duct;  of  the  upper  half  of  the  pharynx. 
Among  the  epidermic  tissues,  we 
may  also  enumerate  the  crystalline  lens  and  the  enamel.*  The  former 
consists  of  long  tubular  cells  filled  with  albumen,  which,  as  the  study  of 
development  teaches,  are  formed  by  the  metamorphosis  of  a  part  of  the 
epidermis.  The  latter  contains  prismatic,  densely-ossified  long  fibres, 
which,  in  all  probability,  are  also  nothing  more  than  excessively  elon- 
gated epithelial  cells  of  the  enamel  organ  of  the  embryonic  tooth  sac. 

The  epidermic  tissue  is  found  through  almost  the  whole  animal  king- 
dom, and  as  regards  its  elements,  it  exhibits  no  very  considerable  devia- 

FIG.  17. — A  simple  papilla  with  manifold  vessels  and  epithelium,  from  the  gums  of  a 
child  ;  magnified  250  diarn. 

Fig.  18. — Ciliated  epithelium  from  the  trachea  of  a  man;  magnified  300  diam.;  a.  outer- 
most part  of  the  elastic  longitudinal  fibres ;  6,  homogeneous  outermost  layer  of  the  mucous 
membranes;  c,  deepest  round  cells  ;  rf,  median  long  cells;  e,  outermost  ciliated  cells. 

*  [Vide  infra,  note  §  on  the  Teeth.] 


78  GENERAL    ANATOMY    OF    THE    TISSUES. 

tions  in  animals.  One  of  its  kinds,  the  horny  tissue,  appears  to  occur 
more  generally,  and  to  some  extent  in  peculiar  forms.  To  it  belong  (a), 
among  structures  which  appertain  to  the  skin :  claws,  hoofs,  horns,  spines, 
plates,  and  discs,  bristles,  feathers,  and  penis-spines.  (6),  among  appen- 
dages of  the  mucous  membranes :  the  horny  sheaths  of  the  beaks  of 
birds,  of  Chelonia,  of  the  Siren  and  Ornithorhynchm ;  the  horny  teeth 
of  the  cyclostome  fishes;  of  the  Ornithorhynchus,  of  the  gill  rays  of 
fishes,  and  of  Batrachian  larvae ;  the  whalebone,  the  spines  and  plates 
of  the  tongue  of  Birds,  Mammalia,  and  some  Amphibia;  the  spines  of 
the  oesophagus  of  Chelonia;  the  jaws  of  Cephalopoda  and  other  inver- 
tebrata ;  the  gastric  teeth  of  many  mollusks ;  the  horny  plates  of  the 
bird's  stomach.  In  all  these  structures,  but  often  only  by  the  aid  of 
caustic  alkalies,  horny  plates  of  one  kind  or  another,  as  in  the  corneous 
structures  of  man,  are  discoverable.  On  the  other  hand,  the  hard  tis- 
sues of  the  Articulata  differ  not  only  morphologically,  but  also  chemically 
from  them,  consisting  as  they  do  of  a  peculiar  substance,  chitin,  and 
exhibiting  no  cellular  structure. 

[The  epidermic  tissue  is  a  frequent  constituent  of  pathological  for- 
mations. It  is  met  with  in  skin  and  mucous  membrane,  forming  epi- 
dermic hypertrophies,  as  corns  and  warts  ;  also  in  the  so-called  epidermic 
or  epithelial  tumors,  and  as  a  covering  on  the  surfaces  of  adhesions. 
The  variety  of  the  epidermic  tissue  generally  observed  in  these  forma- 
tions is  the  pavement-epithelium,  with  cells  slightly  modified  by  mutual 
pressure,  but  not  differing  otherwise  from  normal  pavement-epithelium. 
Cylindrical  and  ciliated  epithelium  occur  but  rarely  as  abnormal  pro- 
ducts. Chemically,  the  epithelium  of  pathological  tissues  presents  the 
same  reactions  as  that  of  normal  tissues. — DAC.] 

Literature. — Purkinje  et  Valentin,  "  De  phaenomeno  generali  et  fun- 
damental! motus  vibratorii  continui,"  Vratisl.  1835  (Discovery  of  ciliary 
movement  in  the  higher  animals);  Henle,  "  Symbol ae  ad  anatom.  vill. 
int.,"  Berol.  1837  ;  "  On  the  distribution  of  the  epithelium  in  the  human 
body,"  Berlin,  1838 ;  and  upon  the  development  of  mucus  and  pus,  and 
their  relation  to  the  epidermis  (first  exact  description  of  the  different 
epidermic  cells) ;  Valentin,  art.  Ciliary  Motion,  in  Wagner's  "  Hand- 
worterbuch;"  Jasche,  "De  telis  epithelialibus  in  specie  et  de  iis  vasorum 
in  genere,"  Dorp.  1847.  [Pathologically,  the  epidermic  tissue  is  con- 
sidered by  Mayer  ;  "  These  sur  les  tumeurs  epidermiques,"  Paris,  1846  ; 
by  Bennett,  "  On  Cancerous  and  Cancroid  Growths,"  Edinb.,  1849 ; 
by  Lebert,  in  his  Monograph,  "  Du  Cancer  et  du  Cancroide  de  la  Peau," 
Paris,  1851 ;  by  Virchow,  Wurzb.  Verhandl.,  1850,  and  in  the  recent 
works  of  Paget,  "  Surgical  Pathology,"  London,  1853,  and  of  Wedl, 
"  Grundziige  der  Pathologischen  Histologie,"  Wien,  1854. — DAC.] 

§  22.  Cartilage. — Cartilage  consists  of  a  solid,  but  elastic,  bluish,  milk- 
white  or  yellowish  substance,  which  presents  two  morphological  condi- 


TISSUES,     ORGANS,     AND     SYSTEMS.  79 

tions  ;  appearing,  firstly,  as  a  simple  parenchyma  composed  of  cells  ;  and 
secondly,  as  a  cellular  tissue,  with  an  intermediate  substance  or  matrix 
between  the  elements.  The  cartilage-cells  present  little  peculiarity  in  re- 
spect of  form ;  they  are  generally  round  or  elongated,  frequently  flat- 
tened or  fusiform,  very  rarely  stellate  (in  Cuttle-fishes  and  Sharks, 
and  in  enchondroma).  Their  membrane  is  ordinarily  thick,  frequently 
invested  by  concentric  laminae ;  the  contents  are  clear  and  more  fluid, 
with  a  single  nucleus,  and,  though  not  constantly,  with  one  or  many  fat 
globules.  The  interstitial  substance  is  either  homogeneous  or  finely 
granulated  or  fibrous,  even  with  clear  separable  fibres.  The  chemical 
characters  of  cartilage  are  in  some  respects  but  little  known.  It  is 
ascertained,  however,  that  the  cells  and  the  intermediate  substance  are 
composed  of  different  substances.  The  membranes  of  the  cartilage  cells, 
in  fact,  are  not  dissolved  by  boiling,  and  offer  a  lengthened  resistance  to 
alkalies  and  acids,  peculiarities  which  distinguish  them  from  the  sub- 
stances which  yield  gelatine,  but  approximate  them  to  elastic  tissue. 
The  contents  of  the  cells  coagulate  in  water  and  dilute  acids,  and  are 
readily  dissolved  by  alkalies.  The  interstitial  substance  is,  in  most  car- 
tilages, chondrin,  and  only  in  the  reticulated  cartilages  is  it  a  substance 
closely  allied  to  that  of  the  elastic  tissue.  Consequently  the  cartilages, 
which  consist  only  of  cartilage  cells,  yield  no  gelatine  upon  boiling,  and 
its  occurrence  is  no  essential  character  of  cartilage.  Physiologically, 
the  solidity  and  elasticity  of  the  cartilages  are  particularly  to  be  noted, 
as  by  these  properties  it  is  fitted  for  its  various  uses.  In  growing  carti- 
lages the  change  of  material  is  very  energetic ;  they  constantly  contain, 
in  certain  localities,  numerous  bloodvessels  in  peculiar  canals;  and,  as  I 
have  demonstrated  in  the  nasal  cartilage  of  the  calf,  even  nerves.  Their 
growth  takes  place,  firstly,  by  endogenous  multiplication  of  cells,  traces 
of  which  are  always  clearly  to  be  observed  in  perfect  cartilages  ;  and 
secondly,  by  the  deposition  between  the  cells,  which  originally  exist 
alone  in  all  cartilages,  of  an  interstitial  substance  from  the  blood-plasma, 
which,  according  to  Schwann,  at  first  yields  no  chondrin  even  in  the 
true  cartilages,  and  subsequently  gradually  increases  in  quantity.  In 
perfect  cartilages  the  nutrition  is  by  no  means  energetic ;  and  it  has, 
apart  from  the  vessels  of  the  perichondrium  which  invests  many  carti- 
lages, and  those  of  the  neighboring  bone,  no  particular  agent,  except  in 
the  cartilages  (septum  of  the  nose)  of  a  few  mammalia,  and  in  the  pla- 
giostome  fishes,  in  some  of  which  last,  according  to  Leydig,  even  in  old 
individuals,  vascular  canals  exist  (Raja\  in  others  anastomosing,  fusi- 
form, or  stellate  corpuscles  (Sharks).  With  age,  the  intermediate  sub- 
stance of  certain  true  cartilages  readily  becomes  fibrous,  and  very  similar 
in  its  chemical  characters  to  that  of  the  reticulated  cartilage,  which  de- 
monstrates that  these  two  kinds  of  cartilage  are  not  widely  separated ; 
the  true  cartilages  also  not  uncommonly  ossify,  vessels,  cartilage,  and 


80  GENERAL    ANATOMY    OF    THE    TISSUES. 

medulla  being  formed  in  them  at  the  same  time.  Cartilage  possesses  no 
power  of  regeneration,  nor  do  wounds  in  cartilage  unite  by  cartilage  ; 
on  the  other  hand,  an  adventitious  development  of  cartilage  is  not  un- 
common. 

The  different  cartilages  are  : — 

a.  Cartilage  without  interstitial  substance,  or  parenchymatous  carti- 
lage.    To  this  belong  the  chorda  dorsalis  of  the  embryo  and  of  many 
adult  fish  ;  many  foetal  cartilages ;   the  cartilages  of  the  gill  laminae  of 
fishes  in  part ;  and  those  of  the  external  ear  of  many  mammalia. 

b.  Cartilage  with  interstitial  substance. 

1.  With  a  more  homogeneous,  chondro-yielding  substance  :  true  carti- 
lage, hyaline  cartilage :  it  is  found  in  the  larger  cartilages  of  the  respi- 
ratory organs,  those  of  the  articulations,  of  the  ribs,  and  of  the  nose  ; 
also  in  all  8ymphy$e8  and   synchondroses  immediately  in  contact  with 
the  bones  ;  in  the  talus  ossis  cuboidei,  and  in  the  so-called  ossifying  carti- 
lages of  the  foetus. 

2.  With  a  fibrous  interstitial  substance,  yielding  no  chondrin,  or  but 
very   little:    reticulated  cartilage,  yellow  cartilage,   fibro-cartilage   in 

Fig.  19. 

i  Fig.  20. 


part  ;  epiglottis,  cartilagines  Santoriniance,  Wrisbergiance,  cartilage 
of  the  ear  and  of  the  Eustachian  tube  ;  ligamenta  intervertebralia  in 
part. 

In  the  Invertebrata  many  tissues  of  a  similar  consistence  to  cartilage 
are  found,  but  true  cartilage  has  hitherto  been  discovered  only  in  the 
Cuttle-fishes. 

[Cartilage  is  frequently  observed  in  situations  where  it  does  not 
occur  normally.  This  pathological  cartilage  resembles  morphologically 
and  chemically,  the  ordinary  cartilage,  and  more  especially  the  variety 
with  an  interstitial  substance.  — 


FiG.  19.  —  Portion  of  the  chorda  dorsalis  of  an  embryo  sheep,  6  lines  long:  a,  sheath  ;  b, 
cells,  with  clear  vascular  spaces. 

FIG.  20.  —  Cartilage  cells  from  the  white  layer  of  the  cricoid  cartilage:  from  man  —  magni- 
fied 350  diameters. 


TISSUES,     ORGANS,     AND     SYSTEMS.  81 

Literature. — Meckauer,  "  De  penitiori  cartilaginum  structura  Diss.," 
Yratisl.  1836;  J.  Miiller,  in  "Poggendorfs  Annalen,"  1836,  p.  293; 
Rathke,  in  Froriep's  "Notizen,"  1847,  p.  306;  A.  Bergmann,  "De  car- 
tilaginibus  Disq.  micr.,"  Mitaviae,  1850.  [Leidy,  "On  the  structure  of 
articular  cartilage,"  American  Journal  of  Med.  Sci.  April,  1849.] 

§  23.  Elastic  Tissue.* — The  elements  of  elastic  tissue  are  cylindrical 
or  band-like  fibres,  with  dark  contours,  which  vary  in  their  diameter 
from  immeasurable  fineness  up  to  a  thickness  of  0-003,  and  even  0§005 
of  a  line  (in  animals  even  to  as  much  as  O'OOS  of  a  line),  and  when  they 
are  present  in  quantity,  exhibit  a  yellowish  color.  These  so-called 
elastic  fibres  are,  when  perfectly  formed,  quite  solid,  but  may  subse- 
quently acquire  little  cavities  in  particular  spots  ;  and  these,  in  one 
animal,  the  Giraffe  (Quekett,  "Histological  Catalogue,"  i.),  are  so  regu- 
lar, that  the  fibres  present  a  pretty  transversely  striated  appear- 
ance. The  margins  of  the  elastic  fibres  are  in  general  quite  rectilinear, 
but  in  some  rare  cases  appear  to  be  notched  and  even,  as  Virchow  saw 
them,  in  newly-developed  tissues,  beset  with  a  great  number  of  shorter 
and  longer  pointed  processes.  Hitherto  the  elastic  fibres  have  been 
separated  from  the  nucleus-fibres :  since,  however,  the  latter  are  dis- 

Fig.  21.  Fig.  22. 


tinguished  from  the  former  in  nothing  but  their  diameter ;  furthermore, 
as  all  elastic  fibres  are  originally  as  fine  as  nucleus-fibres  ;  and  since, 
finally,  the  latter  are  not  formed  of  nuclei  alone,  it  will  be  better  wholly 
to  suppress  the  name  of  nucleus-fibres,  and  to  divide  the"  elastic  fibres  simply 
into  finer  and  coarser.  The  elastic  fibres  are  found  either  isolated  as 
longer  or  shorter  fibres,  which  may  be  straight  or  wind  spirally  round 
other  parts  (bundles  of  connective  tissue,  nerves),  and  in  this  case  they 
are  commonly  of  the  finer  kind  ;  or  by  the  anastomosis  of  fibres  of  dif- 
ferent sizes,  a  so-called  fibrous  elastic  network  is  formed,  which  is  some- 

FIG.  21. — Portion  of  a  human  epiglottis  ;  magnified  3rO  diameters. 

FIG.  22. — Elastic  network  from  the  tunica  media  of  the   pulmonary  artery   of  a  horse, 
with  lacunas  in  the  fibre  ;  magnified  350  diameters. 

*  [Yellow  fibrous  tissues — DaC.] 


GENERAL     ANATOMY     OF     THE     TISSUES. 


times  expanded  in  a  membranous  form,  and  sometimes  penetrates  other 
tissues  to  various  depths.  A  modification  of  this  fibrous  elastic  network 
is  formed  by  the  elastic  membranes,  in  which  the  fibres  are  so  closely 
interwoven,  that  a  connected  membrane  arises,  which  in  the  most  extreme 
cases  no  longer  exhibits  any  indication  of  its  previous  nature,  and  ap- 
pears as  a  perfectly  homogeneous  membrane  with  smaller  gaps  (the 
fenestrated  membrane  of  Henle). 

Fig.  23.  Fig.  24. 


Fig.  25. 


Chemically,  elastic  tissue  presents  very  decided  reactions,  but  the 
composition  of  its  substance  is  not  yet  exactly  known.  In  cold  concen- 
trated acetic  acid,  the  elastic  fibres,  except  that  they  swell  a  little,  are 
not  affected  ;*  if  boiled  for  a  whole  day,  however,  they  are  gradually  dis- 

FiG.  23. — Two  secondary  bundles  of  connective  tissue  from  the  arachnoid  of  man  with 
coiled  and  straight  (intestinal)  fine  elastic  fibres,  and  acetic  acid  added  ;  magnified  350 
diameters. 

FIG.  24. — Network  of  fine  elastic  fibre  from  the  peritoneum  of  a  child ;  magnified  350 
diameters. 

FIG.  25. — Elastic  membrane  from  the  tunica  media  of  the  carotid  of  the  horse;  magni- 
fied 350  diameters. 

*  [The  difficulty  with  which  acetic  acid  acts  on  elastic  (yellow  fibrous)  tissue,  presents  an 
important  means  of  distinction  between  it  and  the  connective  (white  fibrous)  tissue,  the 
fibres  of  which  are  readily  rendered  transparent  by  its  action.  In  tissues  in  which  the 
elastic  fibres  are  mixed  up,  or  concealed  by  the  fibres  of  connective  tissue,  acetic  acid 


TISSUES,     ORGANS,     AND     SYSTEMS. 


83 


Fig.  26. 


Fig.  27. 


solved:  nitric  acid  colors  them  yellow;  Millon's  test*  for  protein  tinges 
them  red ;  whilst  sulphuric  acidf  and  sugar  have  no  action  (red  colora- 
tion) upon  them.  In  a  moderately  diluted  solution  of  potassa,  elastic 
tissue  remains,  for  a  long  time,  unaltered  in  the  cold,  except  that  it 
swells  up  and  becomes  somewhat  paler.  Heated  for  a  day  with  it,  it 
becomes  converted  into  a  gelatinous  mass.  In  water  this  tissue  does 
not  alter,  even  after  sixty  hours'  boiling,  but  changes  by  boiling  for 
thirty  hours  in  Papin's  digester  into  a  brownish  substance,  smelling  like 
glue,  but  not  gelatinizing,  which  is  precipitated  by  tannic  acid,  tincture 
of  iodine,  and  corrosive  sublimate,  but  not  by  the  other  tests  for  chondrin. 
Physiologically,  the  prominent  characteristic  of  this  tissue  is  its  elas- 
ticity, in  consequence  of  which  it  forms  a  most  essential  support  to  the 
motor  organs,  and  also  plays  an  im- 
portant part  in  other  situations,  e.  g. 
in  the  vocal  ligaments.  With  respect 
to  its  development,  the  supposition  of 
Schwann,  that  this  tissue  proceeds 
from  cells,  receives  increasing  support 
from  modern  investigations ;  in  fact, 
in  all  those  organs  which  subsequently 
contain  elastic  tissue,  there  may  be 
discovered  in  embryos,  peculiar  fusi- 
form or  stellate,  sharply-pointed  cells, 
which  by  their  coalescence  produce 
long  fibres  or  reticulations,  in  which 
at  first,  those  localities  where  the 
bodies  of  the  cells  previously  existed 
may  still  be  recognized  as  enlarge- 
ments containing  elongated  nuclei  in 
their  interior.  In  this  condition  the 
fibres  not  unfrequently  remain,  and 
they  then  form  a  modification  of  what 
were  formerly  called  nucleus-fibres ,  or 
every  trace  of  their  previous  composi- 

FiG.  26. — Formative  cells  of  the  elastic  fibres,  from  the  tendo-Achillis :  a,  of  a  four  months' 
embryo ;  6,  from  a  seven  months'  foetus, — a  few  cells  free,  with  one  and  two  processes, 
others  united  by  twos  and  threes. — Magnified  350  diameters. 

FIG.  27. — Stellate  formative  cells  of  the  nucleus-fibres  out  of  the  tendo-Achillis  of  a  new- 
born infant. — Magnified  350  diameters. 


by  rendering  the  latter  transparent,  permits  us  to  investigate  the  former.  In  preparations 
thus  treated  the  subsequent  addition  of  ammonia,  by  neutralizing  the  acid,  causes  the  fibres 
of  the  connective  tissue  to  reappear,  and  those  of  the  elastic  tissue  to  recede. — DaC.] 

*  [Millon's  test  (see  Compt.  Rend.  t.  27,  p.  42-44),  is  the  most  delicate  test  for  protein 
known.  It  consists  in  heating  the  suspected  fluid  or  tissue  from  60°  to  100°  in  a  solution 
of  one  part  of  mercury,  in  two  parts  of  nitric  acid.  If  protein  be  present  an  intense  red; 
color  results,  which  does  not  disappear  on  prolonged  boiling. — DaC.]] 

t  [The  immediate  effect  of  sulphuric  acid  is  to  render  the  fibres  more  distinct. — DaC.] 


84  GENERAL    ANATOMY    OF    THE     TISSUES. 

tion  disappears,  so  that  quite  homogeneous  fibres  or  fibrous  reticulations 
are  produced.  These  may  then  either  remain  through  life  as  fine  elastic 
fibres  and  networks,  or  by  increasing  in  thickness  they  may  pass  into 
the  coarser  form  of  the  tissue.  The  more  homogeneous  elastic  mem- 
branes are  nothing  but  close  elastic  networks,  whose  fibres  have  so  much 
increased  in  diameter,  that  only  narrow  spaces  remain  between  them. 
The  perfect  elastic  tissue  appears  to  undergo  very  little  change  of  sub- 
stance— at  least  it  is,  so  to  speak,  non-vascular,  even  when  it  occurs  in 
large  masses ;  on  the  other  hand,  in  those  forms  which  still  present  in- 
dications of  the  original  cells,  a  certain  movement  of  the  juices  may 
still  take  place.  Elastic  tissue  is  not  known  to  be  regenerated,  but  new 
formations  of  it  are  not  rare. 

The  elastic  tissue  is  rarely  found  in  large  masses ;  but  it  is  very  fre- 
quently mixed  with  connective  tissue,  either  in  the  form  of  isolated 
fibres  or  of  networks  of  various  kinds.  As  true  elastic  organs  we  may 
mention : — 

a.  The  elastic  ligaments,  in  which  the  tissue,  with  only  a  slight  ad- 
mixture of  connective  tissue  and  hardly  any  vessels  and  nerves,  exists, 
so  to  speak,  in  a  pure  form.    As  such  we  have  the  ligamenta  subflava  of 
the  vertebrae,  the  ligamentum  nuclice,  certain  ligaments  of  the  larynx, 
the  stylo-hyoid  ligament,  and  the  ligamentum  suspensorium  penis. 

b.  The  elastic  membranes,  which  appear  in  the  form  either  of  fibrous 
networks  or  of  fenestrated  membranes,  and  are  found  in  the  walls  of 
the  vessels,  especially  in  those  of  the  arteries,  in  the  trachea  and  bron- 
chia?, and  in  the  fascia  superficialis. 

In  all  the  vertebrate  classes  the  elastic  tissue  is  found  in  the  same 
localities  as  in  man,  and  in  a  few  particular  situations  besides,  as  in  the 
ligaments  of  the  cat's  claw,  in  the  alary  membrane  of  mammals,  in  the 
folds  of  the  alary  membrane  and  in  the  lung  sacs  of  birds.  In  the  In- 
vertebrata  this  tissue  appears  to  be  rare,  and  it  is  not  even  certain  that 
the  elastic  ligaments  which  occur  in  them  (as,  for  example,  in  bivalves), 
agree  anatomically  and  chemically  with  the  elastic  tissues  of  the  higher 
animals. 

Of  the  different  parts  belonging  to  the  elastic  tissues,  the  so-called 
nucleus-fibres  of  Gerber  are  almost  alone  those  whose  development  has 
been  examined.  With  regard  to  these,  Henle's  view,*  that  they  arise 
by  the  coalescence  of  elongated  nuclei,  was  almost  universally  received, 
until  lately  Virchow  and  Bonders  nearly  contemporaneously  brought 
forward  another  conception.  Both  these  authors  proceed  from  the  in- 
vestigation of  the  connective  tissue,  and  show  that  what  in  it  have  been 
held  to  be  elongated,  isolated,  or  more  or  less  coalesced  nuclei,  are 
nothing  more  than  fusiform  or  stellate  cells,  with  fine  processes,  which 

*[See  article  "  Kernfasern,"  Mailer's  Archiv.  1838.— DaC.] 


TISSUES,     ORGANS,     AND     SYSTEMS.  85 

closely  surround  a  generally  elongated  nucleus,  and  are  partly  united 
into  fibres  or  networks.  With  regard  to  the  development  of  these  cells, 
Virchow  deduces  from  Schwann's  observations,  and  Donders  from  his 
own  investigations,  the  result  that  the  well-known  fusiform  cells  in  the 
rudimentary  areolar  tissue  of  embryos  are  nothing  more  than  the  forma- 
tive cells  of  the  so-called  nucleus-fibres ;  to  which,  then,  as  a  conse- 
quence, it  is  added  that  the  proper  connective  tissue  does  not  proceed 
from  cells,  but  is  nothing  else  than  fibrillated  cytoblastema.  Hence 
both  these  authors  agree  in  placing  connective  tissue  and  cartilage  side 
by  side  and,  in  comparing  the  formative  cells  of  the  so-called  nucleus- 
fibres,  which  Virchow  calls  "  connective-tissue  corpuscles,"  (Binde- 
gewebskb'rperchen),  with  the  cartilage-cells ;  the  interstitial  substance 
of  the  cartilage,  with  the  fibrous  part  of  the  connective  tissue.  Virchow 
goes  still  further,  and  compares  even  the  bone  substance  to  connective 
tissue ;  especially  that  which  is  developed  by  the  ossification  of  what  I 
have  called  soft  blastema,  in  which  the  bone  cavities,  he  supposes,  pro- 
ceed from  stellate  anastomosing  "  connective-tissue  corpuscles,"  a  view 
which  seems  chiefly  to  have  led  him  to  declare  that  the  nucleus-fibres 
are  hollow,  and  form  a  great  system  of  tubules  and  cavities  through  the 
connective  tissue,  thus  probably  subserving  nutrition.  It  could  be 
imagined  that  the  nutritious  fluid  might  thus  be  quickly  conducted  for 
considerable  distances,  and  uniformly  distributed  through  the  tissue,  in 
which  case  the  nuclei  must  be  considered  to  be  the  special  regulative 
portions  of  the  apparatus,  while  the  cells  are  simply  conductors. 

If  we  submit  these  different  views  to  the  test  of  observation,  it  results 
that  much  is  quite  correct,  but  that  some  points  are  untenable.  It  is 
true,  that  the  so-called  nucleus-fibres  are  developed  from  cells  ;  and  the 
fact  is,  indeed,  noted  in  certain  earlier  statements  and  figures  of  Valen- 
tin, Hassall,  Quekett,  and  others.  In  the  tissues  of  full-grown  animals, 
it  is  in  many  localities  unquestionably  impossible,  in  others  very  diffi- 
cult, to  attain  to  certainty  upon  these  points,  because  here,  even  when 
the  nucleus-fibres  still  present  indications  of  cells,  the  cell-membrane  so- 
closely  embraces  the  elongated  and  by  no  means  vanished  nucleus,  that 
it  is  often  quite  out  of  the  question  to  decide  whether  we  have  a  cell 
with  two  or  more  slender  processes,  or  a  fusiform  or  stellate  nucleus ; 
on  the  other  hand  in  young  animals,  in  which  also  Virchow  made  his 
first  observations,  and  especially  in  embryos,  it  is  easy  to  come  to  a 
clear  decision  upon  the  matter.  In  man,  I  find  the  tendons,  ligaments, 
and  the  aponeurosis  palmaris  and  plantaris,  to  be  especially  serviceable 
objects ;  but  in  all  the  places  in  which  elastic  tissue  is  mixed  with  con- 
nective tissue,  I  was  able  to  follow  their  development.  The  observation 
is  most  successful  in  the  foetus  of  three  to  four  months.  Here,  in  all 
the  more  solid  organs  composed  of  connective  tissue, — tendons,  liga- 
ments, fasciae,  corium, — the  proper  connective-tissue  fibrils  are  already 


86  GENERAL    ANATOMY    OF    THE    TISSUES. 

quite  well  developed,  while  of  nuclear  fibres,  so  to  speak,  there  are  no 
traces.  Instead  of  these,  however,  we  find  between  the  often  very  dis- 
tinct bundles  of  connective  tissue,  a  great  number  of  fusiform  cells  of 
O01--015  of  a  line  in  length,  which  in  their  middle  (of  0-002-0-003 
of  a  line  in  breadth)  enclose  an  elongated  roundish  clear  nucleus  with  a 
nucleolus,  which  completely  fills  them,  and  are  prolonged  at  their  ends 
into  fine  dark  threads.  If  we  trace  these  cells,  among  which  are  always 
scattered  many  round  and  elongated  cells  out  of  which  they  are  formed, 
and  in  older  embryos  a  few  stellate  ones,  with  from  3  to  5  processes, 
it  is  found  that  they  gradually  become  longer  and  narrower,  and  from 
the  sixth  month  begin  to  coalesce  with  one  another  into  elongated  fibres 
or  networks ;  up  to  a  late  period,  however  (even  7  to  8  months),  these 
formative  cells  of  the  elastic  tissue  may  be  easily  isolated  in  abundance 
from  all  forms  of  connective  tissue,  either  singly  or  combined  by  twos 
and  threes.  In  the  foetus  at  birth  this  can  no  longer  be  done ;  but  here 
the  complete  nucleus-fibres,  at  least  in  the  more  solid  forms  of  connec- 
tive tissue,  still  clearly  exhibit  their  composition  out  of  fusiform  and 
stellate  cells  with  nuclei ;  which,  as  we  have  already  seen,  is  occasion- 
ally in  some  localities  even  the  case  in  the  adult. 

What  holds  good  of  the  nucleus-fibres  may  be  asserted  also  of  the 
elastic  fibres,  which  are  not  further  treated  of  by  Donders  and  Virchow. 
Valentin  (Wagner's  "  Handw.  d.  Phys.,"  I.  p.  668)  found  that  the  elastic 
fibres  of  the  ligamentum  nuchce  of  the  calf  are  considerably  finer  than 
those  of  the  ox,  and  I  stated  ("  Zeitschrift  fur  Wiss.  Zool.,"L  p.  77,  Anm.) 
that  all  the  thick  elastic  fibres  of  the  adult  have  at  one  time  been  com- 
mon nucleus-fibres.  In  fact,  we  find  in  the  new-born  child  not  a  single 
true  elastic  fibre,  since  even  those  of  the  ligt.  nuchce,  of  the  ligt.  flava, 
and  of  the  aorta,  when  largest,  do  not  measure  more  than  0-0008--001 
of  a  line.  This  circumstance  alone,  might,  if  we  take  into  account  the 
close  resemblance  of  the  elastic  and  so-called  nucleus-fibres  in  other 
respects,  be  considered  as  a  demonstration  that  the  former  are  also 
developed  out  of  cells,  but  we  have  in  addition  direct  evidence  that 
this  is  their  mode  of  development 

In  the  aorta,  in  the  ligt.  nuchce,  and  in  the  fascia  superficialis  abdo- 
minis  of  human  embryos  of  the  fourth  and  fifth  months,  we  find  the 
same  short  fusiform  cells  as  in  the  common  connective  tissue  ;  and 
their  coalescence  into  originally  finer  fibres,  though  perhaps  not  quite 
so  readily  demonstrable  as  in  the  former  localities,  may  yet  be  made 
out  with  certainty,  so  that  the  agreement  in  their  genesis  of  the  finer 
with  the  coarser  elastic  fibres,  may  be  considered  to  be  established. 

Not,  however,  to  the  same  extent,  as  with  regard  to  the  genesis  of 
the  finer  elastic  fibres,  can  I  agree  with  the  authors  mentioned  in  other 
points.  In  the  first  place,  concerning  the  physiological  import  of  the 
so-called  nucleus-fibres,  I  grant  to  Virchow,  that  even  in  the  adult, 


TISSUES,     ORGANS,     AND     SYSTEMS.  87 

in  some  places,  the^  appear  to  retain  more  their  original  character  of 
a  system  of  canals ;  yet  I  can  by  no  means  allow,  that  these  nucleus- 
fibres  are  to  be  regarded  as  a  system  of  tubules  subserving  nutrition. 
In  my  opinion,  all  fine  elastic  fibres,  which  no  longer  present  any  trace  of 
the  original  cell,  i.  e.  those  of  the  areolar  connective  tissue  of  the  corium, 
fasciae,  of  the  perimysium,  of  the  periosteum,  of  the  dura  mater,  of  the 
serous  membranes,  of  the  walls  of  the  vessels,  and  of  mucous  membranes, 
are  solid  fibres,  and  only  of  service  to  the  organism  so  far  as  they  are 
elastic. 

A  relation  to  nutrition  can  only  be  supposed  of  those  elastic  elements 
of  the  tendons,  ligaments,  and  of  the  cornea,  which  present  condi- 
tions more  nearly  embryonic ;  but  even  with  respect  to  these  it  does  not 
appear  so  evident  that  it  can  be  decidedly  afiirmed.  In  the  tendons 
and  ligaments,  for  instance,  it  is  plain  that  a  part  only  of  the  elastic 
elements  are  not  quite  fully  developed,  so  that  possibly  cavities  may  still 
exist  in  them;  while  the  rest,  much  more  considerable,  are  as  com- 
pletely developed  as  elsewhere,  and  offer  no  trace  of  a  cavity.  If, 
now,  it  were  assumed  that  the  former  have  a  determinate  relation  to 
the  conduction  of  the  nutritive  fluid,  it  would  yet  remain  unexplained 
why,  in  certain  regions,  these  organs  were  more  favored  than  in  others. 
If  it  be  further  considered,  that  in  the  tendons  and  ligaments,  as  in  the 
connective  tissue  in  general,  vegetative  molecular  changes  and  nutri- 
tion are  assuredly  at  their  lowest  stage, — furthermore,  that  the  arrange- 
ment of  the  nucleus-fibres  (their  more  longitudinal  course,  the  want  of 
anastomosis  of  the  nucleus-fibres  of  the  different  secondary  bundles  in 
tendons)  appears  very  little  fitted  to  conduct  nutritious  fluids  from  the 
surfaces  of  these  organs,  where  only  the  vessels  are  found,  into  their 
interior, — there  will  appear  no  great  necessity  for  entering  further  into 
this  hypothesis.  For  the  cornea  alone,  where  the  elastic  tissue  remains 
in  a  quite  embryonic  stage,  should  I  be  inclined  to  adopt  Virchow's 
hypothesis ;  and,  as  respects  the  other  tissues,  I  can  only  grant  that, 
when  the  elastic  elements  are  in  such  an  imperfectly  developed  condi- 
tion that  they  still  contain  canals  for  greater  or  less  distances,  they 
may  have  a  share  in  the  distribution  of  the  nutritive  fluid  which  natu-. 
rally  interpenetrates  these  organs,  and,  therefore,  in  their  nutrition,  but 
that  this  must  rather  be  regarded  as  a  secondary  function,  and  will  not 
justify  their  approximation  to  the  fine  canals  of  the  teeth  and  bones, 
which  exist  specially  for  the  purpose  of  nutrition. 

Such  a  function  might  much  rather  be  ascribed  to  the  undeveloped 
nucleus-fibres  and  their  formative  cells  in  the  immature  (pathological 
or  normal)  connective  tissue  ;  for  here,  at  least,  the  anatomical  and 
physiological  relations  of  the  tissue  are  not  opposed  to  such  an  assump- 
tion ;  it  would  amount  to  little  more,  however,  than  what  may  be  asserted 
of  every  undeveloped  fibrous  tissue. 


88  GENERAL     ANATOMY     OF     THE     TISSUES. 

A  second  and  much  more  important  point  in  which  I  differ  from 
Donders  and  Virchow  is  the  general  mode  of  looking  at  the  connective 
tissue.  Both  these  writers  hold  that  it  is  not  composed  of  cells,  but  is 
developed  by  the  fibrillation  of  a  homogeneous  cytoblastema  ;  and  they 
believe  that  all  the  fusiform  embryonic  cells,  which  since  Schwanri's 
time  have  been  regarded  as  its  formative  cells,  belong  not  to  it,  but  to 
the  elastic  tissue.  I  can  by  no  means  admit  such  a  view,  and  it  seems 
to  me  to  be  comprehensible,  only  when  we  recollect  that  these  authors 
arrived  at  it  more  upon  theoretical  grounds,  than  by  direct  observation. 
With  Virchow,  a  passage  in  Schwann  appears  to  have  been  conclusive, 
where  he  describes  the  embryonic  connective  tissue  as  a  gelatinous  homo- 
geneous mass,  which  dissolves  upon  boiling,  and  contains  cells  distri- 
buted through  it  which  are  not  affected  by  the  boiling.  Yirchow  does 
not  hesitate  to  extend  this  to  all  connective  tissue,  and  to  assume  that 
the  substance  soluble  in  water  answers  to  the  subsequently  fibrous  con- 
nective tissue,  while  the  insoluble  cells  are  the  formative  cells  of  the  so- 
called  nucleus-fibres.  Here,  however,  he  has  omitted  to  notice  that 
Schwann  speaks  only  of  a  determinate  form  of  tissue,  the  lax  or  areolated, 
and  describes  in  a  totally  different  manner  the  formation  of  the  more 
solid  connective  tissue,  e.  g.  of  a  tendon.  In  this  case  we  find,  in  direct 
contrast  to  the  former,  no  trace  of  cytoblastema,  which  can  in  no  way 
be  directly  observed,  the  tendon  consisting  throughout  of  fibre-cells, 
either  isolated  or  united  into  bundles  of  connective  tissue. 

To  observe  this,  however,  the  examination  must  be  made  at  a  very 
early  period,  since,  as  Schwann  has  justly  remarked,  the  elements  of 
the  fibrous  tissue  are  very  early  developed  ;  a  circumstance  from  ne- 
glecting to  observe  which,  it  seems  that  Donders  has  been  led  to  adopt 
the  same  view  as  Virchow.  For  my  own  part  I  have  found  Schwann's 
statements  confirmed  in  all  essential  points,  with  the  single  exception 
that  he  was  unacquainted  with  the  formative  cells  of  the  elastic  fibres, 
and  confounds  them  with  those  of  the  connective  tissue.  My  observa- 
tions upon  these  points  are  to  be  found  in  the  following  section.  Hence 
I  cannot  admit  that  cartilage  and  connective  tissue  are  nearly  allied, 
inasmuch  as  the  fundamental  substances  of  both,  even  if  chemically 
agreeing,  yet,  genetically,  are  very  different. 

Literature. — A.  Eulenberg,  "  de  tela  elastica,"  1836;  Virchow,  "die 
Identitat  von  Knochen,  Knorpel  und  Bindegewebskorperchen,  sowie 
ueber  Schleimgewebe,"  in  the  "Verhandlungen  der  Phys.  Med.  Gesell- 
schaft  in  Wiirzburg,"  Bd.  II.  1851,  p.  150;  and  "  Weitere  Beitrage 
z.  Kenntniss  d.  Structur  der  Gewebe  der  Bindesubstanz."  Ebend.  II. 
p.  314  ;  Donders  in  the  "  Nederlansch  Lancet.,"  1851,  July  and  August; 
and  in  the  "  Zeitschrift  fur  wissen.  Zool.,"  Bd.  III.  p.  348  ;  Kolliker, 
"  Ueber  die  Entwicklung  der  sogenannten  Kernfasern,  der  elastichen 
Fasern  und  des  Bindegewebes;"  in  "  Verh.  d.  Phys.  Med.  Ges.  in 
Wurzburg,"  Bd.  III.  H.  1. 


TISSUES,     ORGANS,     AND     SYSTEMS. 


89 


Fijr.  2 


§  24.  Connective  Tissue  [fibrous  and  areolar  tissue]. — The  elemen- 
tary parts  which  are  found  in  connective  tissue  may  be  divided  into  the 
essential,  never-failing  components,  and  those  which  are  met  with  only 
in  certain  localities.  To  the  former 
belongs  the  fasciculated  as  well  as  the 
more  homogeneous  connective  tissue;  to 
the  latter,  elastic  fibres  in  their  different 
forms  and  conditions  of  development, 
fat  cells,  cartilage  cells,  and  pigment 
cells  of  different  kinds.  Besides  these, 
connective  tissue  contains  also  no  in- 
considerable quantity  of  a  gelatinous 
intermediate  substance.  The  bundles 
of  the  connective  tissue  are,  among 
the  essential  elements,  those  which 
occur  most  frequently ;  each  of  them 
consists  of  a  certain  number  of  very 
fine  fibrils,  the  connective  fibrils,  which 
are  distinguished  from  their  nearest 
allies,  the  finest  elastic  fibres  and  mus- 
cular fibrils,  by  their  smaller  diameter 
(0-0003-0-0005  of  a  line),  their  pale 
color,  their  homogeneous  appearance, 
and  the  complete  absence  of  striation. 
They  are  united  by  means  of  a  small 
quantity  of  a  clear  connecting  sub- 
stance, and  thus  form  the  bundles  in 
question,  which  in  many  respects  re- 
semble those  of  the  transversely  striated  muscles,  but  differ  from  them 
in  the  absence  of  any  special  investment  comparable  to  the  sarcolemma, 
and  in  their  smaller  mean  diameter  (0-004-0-005  of  a  line.)  They  are 
either  long,  slightly  wavy  cords,  of  uniform  thickness  throughout,  which 
are  not  directly  connected  together,  but  arranged  in  different  ways  near 
and  above  one  another,  forming  great  lamellae  and  bundles;  or  they 
coalesce  like  the  elastic  networks  into  meshes,  and  thus  form  what  I 
have  called  the  reticulative  connective  tissue.  In  rare  cases  the  bundles 
appear  not  to  be  composed  of  fibrils,  but  are  more  homogeneous,  as  in 
the  neurilemma,  where  they  are  known  as  Remak's  fibres.  Besides  this 
form  of  connective  tissue,  there  exists  a  second,  rarer  kind,  in  which 
neither  bundles  nor  fibrils  can  be  clearly  distinguished,  but  only  a  mem- 
branous or  more  or  less  solid,  finely  granulated,  or  slightly  striated,  even 
perfectly  homogeneous,  clear  tissue ;  homogeneous  (or  Reichert's)  connec- 
tive tissue.  The  other  elements  which  occur  in  connective  tissue  pre- 

FIG.  28. — Lax  connective  tissue  with  fat-cells  from  man;  magnified  350  diam. 


GENERAL    ANATOMY    OF    THE    TISSUES. 


sent  nothing  remarkable,  and  will  be  more  particularly  treated  of  in  their 
proper  places  in  the  special  part. 

The  chemical  relations  of  connective  tissues  are  well  known :  proper 
connective  substance  when  boiled  yields  common  gelatine,  and  contains 
besides  a  fluid,  whose  nature,  on  account  of  its  generally  minute  quantity, 
cannot  be  investigated.  Only  where  it  exists  in  considerable  proportion, 
as  in  the  gelatinous  connective  tissue  of  embryos,  can  the  presence  of 
much  albumen  and  mucus  be  easily  demonstrated  in  it.  The  chemical 
qualities  of  the  other  constituents  of  the  connective  tissue  will  be  spoken 
of  in  their  place. 

Connective  tissue  is  of  utility  to  the  organism  according  to  its  compo- 
sition,— sometimes  as  a  solid  unyielding  substance ;  sometimes  as  a  soft 
support  for  vessels,  nerves,  and  glands ;  sometimes,  finally,  as  a  yielding 
tissue,  filling  up  spaces,  and  facilitating  changes  of  position.  Where 
elastic  elements  are  present  in  it  in  great  quantities,  its  nature  alters; 
and  a  great  abundance  of  fat  or  cartilage  cells  gives  it  an  unusual  soft- 
ness or  resistance.  The  connective  tissue  is  invariably  developed  from 
cells,  and,  in  fact,  from  fusiform  or  stellate  vesicles,  which  become 
united  into  long  fibres  or  networks,  and  often  break  up  into  fibrils  before 
their  union.  The  mode  in  which  this  takes  place  is  not  yet  quite  made 

out,  but  it  is  most  proba- 


Fig.  30. 


ble  that  the  cells,  as  they 
elongate,  change  with 
their  membrane  and  con- 
tents, into  a  homogeneous 
softish  mass,  which  sub- 
sequently breaks  up  into 
a  bundle  of  fine  fibrils 
and  some  intermediate 
substance.  The  develop- 
ment of  the  homogeneous 
connective  tissue  has  as 
yet  been  little  investiga- 
ted, but  it  would  seem, 
like  the  other,  to  proceed 
from  a  fusion  of  rounded 
or  elongated  cells,  which 
are  perhaps  united  by  an  intermediate  substance,  in  which  the  meta- 
morphic  process  has  only  gone  so  far  as  the  development  of  a  homoge- 
neous mass,  but  has  not  attained  the  stage  of  fibrillation.  The  bundles 

FiG.  29. — Formative  cells  of  the  connective  tissues  from  the  skin  of  the  trunk  in  a  sheep's 
embryo,  7  lines  long :  a,  cell  without  any  indication  of  fibrils  5  6,  with  commencing ;  c,  with 
distinct  fibrils. — Magnified  350  diameters. 

FIG.  30. — Three  formative  cells  of  the  areolated  connective  tissue  from  the  allantois  of  a 
sheep's  embryo,  7  lines  long. — Magnified  350  diameters. 


TISSUES,     ORGANS,     AND    SYSTEMS.  91 

of  the  connective  tissue,  when  once  formed,  grow  in  length  and  thick- 
ness like  the  elastic  fibres,  until  they  have  attained  the  size  which  they 
possess  in  the  adult ;  however,  there  arise  subsequently,  in  many  places, ' 
additional  elements,  which  are  combined  with  the  original  ones.  The 
perfect  connective  tissue,  when  unmixed,  is  almost  non-vascular,  and  with 
regard  to  nutrition,  it  is  certainly  very  low  in  the  scale,  whence  it 
undergoes  hardly  any  morbid  changes.  The  vascular  connective  tissue 
is  an  exception  to  this  rule,  but  the  changes  in  this  case  depend  not 
upon  any  .peculiarity  in  the  connective  tissue  itself,  but  are  determined 
by  the  vessels,  fat-cells,  &c.,  contained  in  it.  The  bundles  of  fibrils  of 
the  connective  tissue  and  the  elastic  fibres  stand  at  the  bottom  of  the 
series  of  the  higher  elementary  parts,  and  thence  most  readily  adapt 
themselves  to  the  regeneration  of  lost  substance,  or  to  the  increase  of 
parts  which  already  exist. 

•The  union  of  the  different  elements  of  the  connective  tissue  is  effected 
in  many  ways,  but  the  following  forms  are  most  worthy  of  distinction : — 

1.  Solid  connective  tissue  (formed  connective  tissue,  Henle).  In  this 
the  elements  are  intimately  united,  and  in  such  a  manner,  that  simple 
organs  of  well-marked  form  proceed  from  them.  To  this  belong: — 

a.  The  tendons  and  ligaments,  with  parallel  bundles,  united  by  loose 
connective  tissue  into  larger  cords,  between  which  a    relatively  very 
small  number  only  of  fine  elastic  fibres,  and  fibrous  networks,  pene- 
trate. 

b.  The  fibro- cartilages  have  the  same  structure  as  the  tendons  and 
ligaments,  but  with  numerous  scattered  cartilage  cells,  and  without  finer 
elastic  fibres.     They  exist  either  as  special  organs,  such  as  the  cartila- 
gines  inter  articular  es  and  the  cotyloid  ligaments,  or  in  particular  parts 
of  other  organs  composed  of  connective  tissue,  especially  in  the  tendons, 
the  tendinous  sheaths,  and  the  ligaments. 

c.  The  fibrous  membranes  are  distinguished  from  a,  only  by  the  fre- 
quent interweaving  of  the  bundles,  and  generally  by  the  more  considera- 
ble number  of  the  elastic  fibres.     Here  may  be  enumerated : — 

1.  The  muscular  fascia?,  which  have  more  the  structure  of  tendons. 

2.  The  periosteal  membranes  and  the  perichondrial  membranes,  con- 
taining sometimes  a  great  number  of  elastic  elements. 

3.  The  white  dense  tunics  of  many  soft  organs,  as  the  dura  mater,  the 
neurilemma,  the  sclerotic  and  cornea,  the  fibrous  coat  of  the  spleen  and 
kidneys,  the   tunica  albuginea  of  the   ovaries   and  testes,  penis,  and 
clitoris.     In  the  last-mentioned  parts,  and  in  the  spleen,  these  coats, 
which  consist  of  a  solid  connective  tissue  and  numerous  fine  elastic  fibres, 
are  continued  into  the  interior,  where,  mixed  to  some  extent  with  smooth 
muscles,  they  constitute    a  more  or  less   complete   framework,  which 
appears  in  the  form  of  partitions,  or  of  a  stroma,  or  of  a  trabecular  net- 
work.   In  the  cornea  we  find  a  modification,  inasmuch  as  the  connective 


92  GENERAL     ANATOMY     OF     THE     TISSUES. 

tissue  is  transparent,  contains  fine  elastic  tissue  in  a  more  embryonic 
state,  and  when  boiled  in  water  yields  chondrin  and  not  gelatine. 

d.  The  serous  membranes  consist  of  a  connective  tissue,  rich  in  fine 
elastic  fibres,  whose  bundles  anastomose,  or  are  interwoven  in  different 
modes  ;  and  sometimes  also,  especially  at  the  surface  of  these  membranes, 
appear  more  homogeneous.  The  serous  membranes,  which  never  possess 
glands,  and  upon  the  whole  but  few  vessels  and  nerves,  line  the  cavities 
which  contain  the  viscera,  and  present  an  inner  surface,  which  is  smooth 
and  shining  from  the  presence  of  an  epithelial  investment.   They  do  not 
necessarily  form  closed  sacs,  as  was  formerly  believed,  but  may  have 
apertures  in  certain  localities  (abdominal   apertures   of  the  Fallopian 
tubes),  or  may  be  wholly  wanting,  as  upon  the  articular  cartilages ;  or 
the  areolar  foundation  may  be  absent,  as  in  the  so-called  external  lamina 
of  the  arachnoidea  cerebri.     To   these  membranes  belong  I.,  the  true 
serous  membranes,  as  the  arachnoidea,  the  pleura,  the  pericardium,  the 
peritoneum,   and   the   tunica  vaginalis  propria,   which   all,    normally, 
secrete  only  a  minute  quantity  of  serous  fluid  ;  and  2,  the  synovial  mem- 
branes or   capsules  of    the  joints,  bursce  mucosce,  and   the   tendinous 
sheaths,  which  afford  a  viscid  yellow  secretion, — the  synovia — contain- 
ing albumen  and  mucus. 

e.  The  corium  consists  of  a  dense  network  of  bundles  of  connective 
tissue,  which  at  the  surface,  and  in  the  papillae,  gives  place  to  an  indis- 
tinctly fibrillated,  in  part  even  more  homogeneous  tissue,  and  contains  a 
great  quantity  of  finer  and  coarser  elastic  networks,  as  well   as  very 
numerous  vessels  and  nerves. 

The  corium  supports  the  papillae  upon  its  outer  surface,  and  is  here 
covered  by  the  epidermis,  in  connection  with  which  it  forms  the  external 
skin ;  from  the  deeper  parts  it  is  separated  by  a  soft  tissue,  generally 
very  rich  in  fat,  the  subcutaneous  connective  tissue,  adipose  membrane, 
or  panniculus  adiposus. 

f.  The  mucous  membranes  essentially  consist  of  a  very  vascular  basis 
of  connective  tissue,  well  supplied  with  nerves, — the   proper  mucous 
membrane — of  an   epithelial  layer   covering  it,   and   of  a  submucous 
areolar  tissue,  which  in  the  intestine  is  also  called  the  tunica  nervea. 
The  former  is  of  the  same  structure  as  the  corium,  only  softer,  and  not 
unfrequently  ppor  in  elastic  tissue.     The  mucous  membranes  are  distin- 
guished from  the  serous,  in  general  by  their  greater  vascularity,  their 
more  considerable  thickness,  their  numerous  glands,  and  the  mucous 
secretion,  which  may  be  especially  ascribed  to  their  soft  epithelium ; 
though  there  are  mucous  membranes  which  are  as  delicate  and  glandless 
as  serous  membranes ;  and,  on  the  other  hand,  the  synovial  capsules  may 
approximate  the  mucous  membranes  in  their  vascularity  and  the  nature 
of  their  secretion.     The  mucous  membranes  and  the  external  skin  are 
analogous  in   all  their  principal  components,   whence  the  transitions 


TISSUES,     ORGANS,     AND    SYSTEMS.  93 

between  the  two,  such  as  exist  upon  the  lips,  eyelids,  and  elsewhere, 
are  not  surprising.  To  the  mucous  membranes  belong  the  innermost 
coat  of  the  tractus  intestinalis ;  the  lining  of  the  nasal  passages,  and  of 
their  secondary  cavities  ;  the  Eustachian  tube,  the  tympanum  and  mas- 
toid  cells,  and  the  conjunctiva.  Among  the  glands,  all  the  larger,  pre- 
sent in  their  excretory  ducts,  a  distinct  mucous  membrane,  as  the  lungs 
from  the  glottis  to  the  finest  bronchia? ;  the  liver  in  the  larger  gall-ducts 
and  in  the  gall-bladder ;  the  pancreas  in  the  ductus  pancreaticus  ;  the 
urinary  and  sexual  organs ;  in  the  urethra,  bladder,  ureters,  pelvis  of 
the  kidneys,  vagina,  uterus,  and  oviducts ;  and  in  the  ducts  and  follicles 
of  the  mammary  gland;  in  the  seminal  vesicles,  and  in  the  vas  deferens. 
In  all  these  glands  the  coats  of  the  mucous  membrane  pass  immediately 
into  the  walls  of  the  glandular  tubes  and  vesicles,  which  might  thus  be 
regarded  as  composed  of  a  more  delicate  mucous  membrane.  The  same 
might  be  said  of  the  smaller  glands,  as  those  of  the  intestine,  which  are 
directly  connected  with  the  larger  mucous  expansions,  only  in  that  case 
the  smaller  glands  of  the  skin  must  be  regarded  as  attenuated  processes 
of  it.  Inasmuch  as  both  physiology  and  development  support  this  view, 
it  would  seem  to  be  at  any  rate  justifiable ;  yet  every  one  is  free,  not- 
withstanding, to  look  more  to  the  differences  which  certainly  do  exist 
between  the  parts  in  question,  and  to  consider  them  as  distinct  struc- 
tures. 

g.  The  membranes  of  the  veins,  lymphatics,  the  adventitious  coat  of 
the  arteries,  and  the  endocardium,  consist  of  a  loose  connective  tissue 
not  altogether  dissimilar  to  that  of  the  fibrous  membranes,  and  of  finer 
or  coarser  elastic  fibrous  networks,  with  which  in  the  veins  smooth 
muscles  are  also  partly  mixed. 

h.  The  so-called  vascular  membranes  (tunica?  vasculosce),  to  which 
belong  the  pia  mater,  with  the  plexus  choroidei,  the  choroid  coat  and  the 
iris,  all  contain  very  numerous  vessels,  which,  however,  appear  to  have  less 
reference  to  the  membranes  themselves  than  to  the  nutrition  of  other 
organs.  Supporting  these  vessels  we  have  either  a  common  connective 
tissue,  in  which  there  are  no  elastic  fibres  (iris,  pia  mater],  with  paral- 
lel, matted,  and  anastomosing  bundles,  or  a  homogeneous  connective 
tissue  (plexus  choroidei,  choroided),  to  which,  as  in  the  choroid,  peculiar 
elements,  namely,  anastomosing  cells,  generally  filled  with  more  or  less 
pigment,  may  be  added. 

i.  The  homogeneous  connective  tissue. — In  many  organs  we  find  mem- 
branes whose  chemical  nature  agrees  with  that  of  connective  tissue,  but 
which  neither  contain  distinct  bundles  nor  fibres,  and  appear  to  be  more 
homogeneous.  Such  is  the  homogeneous  tissue  which  often  invests  the 
bundles  of  the  arachnoid  singly,  or  in  a  number  together  ;  the  coats  of 
the  Malpighian  corpuscles  of  the  spleen,  and  of  the  glandular  follicles 
of  the  intestine  (tonsils,  lingual-follicles,  the  solitary  and  Peyerian 


GENERAL     ANATOMY     OF    THE     TISSUES. 

glands),  certain  of  the  so-called  membrance  proprice  of  the  glands  ap- 
pear to  come  under  this  head  also ;  yet,  since  some  of  them  do  not 
belong  here,  and  consist  of  a  very  different  substance  from  connective 
tissue,  as,  for  example,  that  of  the  kidneys,  and  since  we  have  no  thorough 
investigation  of  these  structures,  for  the  present  nothing  decided  can  be 
said  upon  the  subject. 

7c.  Loose  orareolated  connective  tissue*  ("  amorphous  connective  tissue" 
of  Henle),  consists  of  a  soft  meshwork  of  reticulated,  or  variously  inter- 
woven bundles  of  connective  tissue,  which  in  larger  or  smaller  quantity 
constitute  a  filling  up  and  uniting  mass  between  the  organs  and  their 
parts,  and  appear  under  two  forms  : — 

1.  As  adipose  tissue,  when  numerous  fat-cells  are  contained  in  the 
meshes  of  an  areolated  tissue  which  is  usually  very  poor  in  elastic  fibres. 

2.  As  common  lax  connective  tissue,  when  the  latter  are  few  or  want- 
ing.    The  adipose  tissue   occurs  principally  in   the   skin  forming  the 
panniculus  adiposus  ;  in  the  larger  cylindrical  bones,  as  yellow  bone- 
medulla  ;  in  the  orbit ;  around  the  kidneys ;  in   the  mesentery  and  the 
omentum  ;  around  the  spinal  marrow  ;   in  the  nerves   and  vessels,  and 
in  muscles.     The  areolated  connective  tissue  is  widely  distributed  be- 
tween the  separate  organs  and  the  viscera  of  the  neck,  thorax,  abdomen, 
and  pelvis,  and  everywhere  along  the  course  of  the  vessels  and  nerves, 
and  in  the  interior  of  the  muscles,  nerves,  and  glands. 

The  connective  tissue  is  found  in  all  the  four  classes  of  the  vertebrata 
in  about  the  same  condition  as  in  man ;  while,  on  the  other  hand,  in  the 
invertebrata  it  is  very  rare,  and  when  present  is  more  homogeneous, 
or  consists  of  isolated  cells  and  intermediate  substance,  rarely  more 
fibrous,  as  in  Cephalopoda,  in  the  mantle  of  bivalves,  in  the  peduncle 
of  the  Lingulse,  and  of  the  Cirripeds.  Fat-cells  also  do  not  occur 
among  the  lower  animals  to  the  same  extent  as  among  the  higher.  The 
firm  connective  tissue  is  here  replaced  by  a  chitinous  substance,  or  by 
one  consisting  of  cellulose,  and  by  calcareous  or  horny  tissues. 

Opinions  are  still  divided  as  to  the  structure  and  development  of  the 
connective  tissue.  Whilst  the  majority  ascribe  a  distinctly  fibrous  struc- 
ture to  it,  and  suppose  it  to  consist  of  bundles,  and  these  again  of  fibrils, 
Reichert  considers  this  tissue  to  be  more  homogeneous,  and  regards  the 
fibrillation  partly  as  artificial,  partly  as  the  expression  of  a  folding,  a 
view  to  which  Bidder  and  Virchow  are  also  inclined.  For  my  own 
part,  I  find  a  certain  amount  of  truth  in  Reichert's  conception,  inso- 
much as  it  is  not  to  be  denied  that  there  also  exists  a  non-fibrillated, 
more  homogeneous  connective  tissue,  which  had  previously  been  little 
investigated ;  but  I  am  nevertheless  of  opinion,  that,  as  applied  to  the 

*  [This  second  variety,  "loose  or  areolated  connective  tissue,"  is  generally  described  as 
areolar  tissue,  or  under  the  faulty  name  of  cellular  tissue. — DaC.J 


TISSUES,     ORGANS,     AND     SYSTEMS.  95 

great  mass  of  the  organs  composed  of  connective  tissue,  it  is  incorrect. 
The  possibility  of  making  out  fibrils  in  delicate  membranes,  even  with- 
out preparation,  the  ease  in  which  these  may  be  isolated  in  tendons  and 
ligaments,  and  lastly,  the  circumstance  that  the  fibrils  may  be  demon- 
strated upon  transverse  sections  of  the  tendons,  and  of  the  more  solid 
connective  tissue  in  general,  are  for  me  sufficient  reasons  for  retaining 
the  old  view. 

With  respect  to  the  development  of  the  connective  tissue,  I  distinguish 
two  types  which  correspond  with  its  two  principal  forms,  the  solid  and 
the  areolated.  The  former  is  developed  out  of  masses  of  cells  without 
any  demonstrable  matrix,  by  the  elongation  of  the  cells,  their  breaking 
up  into  fibrils,  and  their  coalescence.  This  is  most  obvious  in  the  ten- 
dons and  ligaments,  which,  as  observations  upon  Batrachian  larvye  and 
upon  mammalian  embryos  show,  at  first  consist  entirely  of  common, 
rounded,  formative  cells,  which  about  the  same  time  as  the  transversely 
striated  muscles  are  formed  (in  mammalia  in  the  second  month),  become 
fusiform.  The  further  development  demonstrates  (what  had  escaped 
Schwann)  that  only  one  portion  of  these  fusiform  cells,  and  in  fact  cells 
which  are  remarkable  for  their  size  and  paler  contours,  become  bundles 
of  connective  tissue,  while  the  others,  which  Schwann  in  part  depicts 
rightly  (Tab.  III.  fig.  11  ;  the  smallest  cell,  fig.  6,  from  connective 
tissue,  the  cell  6,  and  the  lowest  cell  upon  the  right  side),  remain  for  a 
time  as  fusiform  elements,  and  only  subsequently  become  fused  into 
elastic  fibres.  There  arises,  at  last,  out  of  the  cells  alone,  with  no  dis- 
tinguishable matrix,  a  compact  tissue  composed  of  two  chemically  quite 
distinct  fibres.  The  areolated  connective  tissue  differs  from  the  former 
in  the  circumstance  that,  if  not  from  the  beginning  yet  from  the  time 
at  which  the  cells  become  elongated,  an  abundant  gelatinous  interme- 
diate substance  is  developed  between  them,  which  does  not  yield  gela- 
tine, ami  never  becomes  converted  into  it,  but  contains  albumen  and  a 
substance  similar  to  mucus  ;  Schwann,  indeed,  found  a  substance  re- 
sembling pyin,  in  this  tissue.  Although  all  embryologists  know  that 
the  areolated  connective  tissue  is  at  first  of  a  gelatinous  consistence, 
as  for  example,  under  the  skin,  in  the  neck,  in  the  omentum,  behind  the 
peritoneum,  in  the  orbit,  and  in  the  bones,  no  one  has  yet  drawn  atten- 
tion to  the  general  occurrence  of  that  intermediate  substance  which 
was  observed  by  Schwann  in  a  single  locality.  I  originally  became  ac- 
quainted with  this  tissue  between  the  chorion  and  amnion,  and  at  first 
paid  more  attention  to  its  reticulated  anastomosing  cells.  Subsequently 
when  I  examined  it  more  closely  in  the  enamel  organ  of  the  embryonic 
tooth  sac,  I  paid  attention  to  the  peculiar  intermediate  substance,  and 
at  the  same  time  Virchow  described  this  tissue  from  the  umbilical  cord, 
where  the  gelatinous  tissue  of  Wharton  entirely  consists  of  it.  Virchow 
believed  that  it  ought  to  be  distinguished  from  connective  tissue,  and 


96  GENERAL    ANATOMY    OF    THE    TISSUES. 

proposed  the  denomination  of  mucous  tissue  (tissu  muqueux)  for  it.  I 
considered  it  from  the  first  to  be  connective  tissue,  and  I  now  feel  the 
more  inclined  to  remain  of  this  opinion,  because  I  find  that  every  de- 
scription of  the  areolated  connective  tissue  of  embryos  originally  com- 
mences under  (his  form,  and  therefore  the  circumstance  that  the  tissue 
in  the  umbilical  cord  never  arrives  at  perfection,  cannot  determine  its 
nature. 

The  mode  in  which  the  gelatiniform  connective  tissue  is  developed  is 
this :  one  portion  of  the  cells  contained  in  the  gelatinous  basis  changes 
into  connective  tissue  by  becoming  fusiform,  and  breaking  up  into  common 
or  reticulated  anastomosing  connective  tissue,  which,  however,  as  Schwann 
has  already  stated,  at  first  yields  no  gelatine.  In  this  manner  a  closer  or 
denser  network  arises,  in  the  interspaces  of  which  the  intermediate  sub- 
stance or  matrix,  and  a  remainder  of  the  previous  formative  cells,  are 
contained.  In  the  further  course  of  development,  new  cells  proceed 
from  the  matrix,  which  hereby  diminishes  by  degrees  in  quantity,  and 
at  the  same  time  the  original  network  consolidates,  fresh  cells  being 
added  to  it,  a  part  of  which  also  become  elastic  fibres  and  vessels.  If 
subsequently  the  areolated  connective  tissue  includes  no  adipose  cells, 
the  gelatinous  tissue  ends  by  completely  disappearing,  and  nothing  re- 
mains but  a  loose  fibrous  tissue,  containing  at  most  somewhat  less  fluid, 
and  loose  cells  in  its  meshes ;  if,  on  the  other  hand,  it  becomes  con- 
verted into  an  adipose  tissue,  the  spaces  remain,  and  a  great  part  of  the 
cells  which  have  arisen  at  the  expense  of  the  gelatinous  substance,  sub- 
sequently pass,  by  the  development  of  fat  in  their  interior,  into  fat- 
cells. 

In  the  gelatinous  tissue  of  Wharton,  between  the  chorion  and  amnion, 
and  in  part  of  the  enamel  organ,  the  areolated  connective  tissue  remains 
more  in  its  foetal  condition  of  a  gelatinous  tissue,  yet  there  exists  no 
natural  line  of  demarcation  from  ordinary  connective  tissue,  *so  much 
the  less,  since  in  the  gelatinous  substance  of  Wharton,  in  older  embryos 
even  fibrils  are  quite  evident,  and  in  the  enamel  organ  the  passage  of  a 
part  of  the  gelatinous  tissue  into  common  connective  tissue  is  demon- 
strable. 

So  much  for  the  two  types  of  development  of  the  connective  tissue. 
We  have  yet  to  state  how  the  bundles  become  chemically  and  morpho- 
logically what  they  are.  In  the  first  place,  I  may  observe  that  the  for- 
mative cells  of  the  connective  tissue  are  not  originally  distinguishable 
from  the  other  formative  cells  of  the  embryo,  do  not  dissolve  by  boiling 
in  water,  and  therefore  contain  no  gelatine.  Even  when  the  cells  have 
evidently  become  fusiform,  and  have  already  coalesced  into  bundles  and 
networks,  they  still,  as  Schwann  has  already  stated,  yield  no  gelatine. 
Therefore,  in  this  case,  the  change  of  the  cells  into  a  collagenous  sub- 
stance, goes  on  as  slowly  as  in  the  matrix  of  the  cartilages,  which, 


TISSUES,     ORGANS,     AND     SYSTEMS.  97 

according  to  Schwarm,  also,  at  first,  yields  no  gelatine,  and  therefore  it 
is  no  objection  to  the  above  view  of  the  nature  of  Wharton's  gelatinous 
tissue,  that  it  yields  no  gelatine  on  boiling,  as  Scherer  has  found.  How 
the  collagenous  matter  is  formed  out  of  cells,  whether  the  contents  only, 
or  the  membrane  also,  takes  part  therein,  it  is  very  difficult  to  say ;  in 
any  case,  from  what  we  know  of  the  contents  of  embryonic  cells,  it  can 
hardly  be  any  but  a  protein  substance  which  yields  the  gelatine,  and, 
from  what  takes  place  in  the  ossification  of  the  cartilage  cells,  it  seems 
very  probable  that  the  cell-membranes  and  contents  together  become 
metamorphosed  into  a  collagenous  substance. 

The  morphological  change  which  the  formative  cells  of  the  connective 
tissue  undergo,  in  the  course  of  their  passage  into  bundles  of  fibrils,  is 
very  probably  this,  that  after  their  membranes  and  contents  are  fused 
into  a  homogeneous  semi-solid  mass,  they  then  secondarily  break  up  into 
fibrils ;  the  latter  process  taking  place  in  the  same  manner  as  we  see  it 
occur  in  the  contents  of  the  animal  muscular  fibres.  Herewith,  as  a 
rule,  the  nuclei  of  the  cells  eventually  disappear,  or  if  they  remain,  as 
we  see  occasionally  in  connective  tissue,  still  they  never  become  changed 
into  the  so-called  nucleus  fibres. 

Though  in  physiological  connective  tissue,  development  from  cells 
must  be  most  decidedly  affirmed,  it  does  not  therefore  follow  that  a  sub- 
stance which  chemically  and  morphologically  closely  resembles  con- 
nective tissue,  may  not  arise  in  a  different  manner.  We  know,  in  fact, 
that  the  collagenous  basis  of  cartilage,  when  it  breaks  up  into  fibres, 
becomes  deceptively  similar  to  connective  tissue,  and  furthermore,  that 
fibrous  exudations  may  become  changed  into  a  fibrous  substance  which 
is  scarcely,  perhaps  not  at  all,  to  be  distinguished  from  genuine  con- 
nective tissue.  There  also  exists,  however,  a  pathological  true  connective 
tissue  in  cicatrices  of  all  kinds,  and  perhaps  elsewhere,  which  is  deve- 
loped from  cells ;  and  for  my  own  part,  therefore,  I  am  opposed  to  the 
classing  together  of  all  connective  tissues.  We  must  in  our  classifica- 
tions not  only  distinguish  similarity  or  identity  in  structure  and  chemi- 
cal composition,  but  embrace  all  the  conditions,  and  especially  the 
genesis;  and  thence  we  must  distinguish  both  the  collagenous  fibrous 
cartilage  and  the  collagenous  organized  fibrine,  from  true  connective 
tissue, — just  as  we  separate  the  true  elastic  fibre,  from  the  chemically 
and  morphologically,  very  similar  fibres  of  the  reticulated  cartilages  and 
from  certain  forms  of  metamorphosed  fibrine.  On  the  other  hand,  the 
connective  tissue  which  has  not  been  developed  from  cells,  may  justly 
and  properly  be  arranged  with  cartilage.* 

*  [The  arguments  brought  forward  by  Professor  Kolliker  in  support  of  his  views  with 
regard  to  the  nature  and  mode  of  development  of  connective  tissue,  appear  to  us  not  to 
preponderate  against  those  of  Reichert,  Virchow,  and  Remak,  and  to  be  opposed  to 


98  GENERAL    ANATOMY    OF    THE     TISSUES. 

Literature. — C.  B.  Reichert,  "  Vergleichende  Beobachtungen  Uber 
das  Bindegewebe  und  die  verwandten  Gebilde,"  Dorpat,  1845;  Luschka, 

our  own  observations,  which   agree  in  all  essential  points  with  those  of  the  last-named 
authors. 

There  are  two  questions  in  dispute.  The  first,  the  structure  of  the  connective  tissue;  the 
second,  the  homology  of  its  various  constituents  with  those  of  other  tissues,  and  of  cells  in 
general. 

With  respect  to  the  first  question,  it  is  admitted  on  all  hands  that  ordinary  connective 
tissue  (e.  g.  of  the  tendons)  is  composed  of  two  elements :  a,  a  network  of  elastic  tissue, 
which  is  not  acted  upon  by  cold  acetic  acid ;  b,  a  substance  which  is  swollen  up  by  acetic 
acid,  and  has  a  more  or  less  fibrillated  appearance,  contained  in  the  meshes  of  the  elastic 
tissue.  Now  it  has  been  demonstrated  by  Virchow,  and  the  fact  is  admitted  by  both  Kdl- 
liker  (supra)  and  Reichert  (Zur  Stre"itfrage  uber  die  Gebilde  der  Binde-substanz,  fiber  die 
Spiralfaser,  &c.,  Miiller's  "  Archiv,"  1852),  that  the  elastic  fibres  are  originally  cells,  and 
therefore  that  they  are  homologous  with  the  cartilage-cell,  i.  e.  the  cartilage-cavity  with  its 
wall  plus  the  cartilage-corpuscle  or  nucleus.  That  this  is  the  case  is  very  evident  upon  ex- 
amining in  a  young  animal  (e.  g.  kitten)  the  insertion  of  the  tendo-Achillis  into  the  cartila- 
ginous extremity  of  the  os  calcis.  It  is  here  easy  enough  to  see  that  the  oval  or  rounded  cells 
of  the  true  cartilage  pass  in  the  most  gradual  manner  into  the  elongated  elastic  fibres  of  the 
true  tendon.  The  cells  retain  their  cavities  for  a  considerable  time,  but  eventually  the  nuclei 
and  the  thin  layer  of  substance  which  immediately  forms  the  wall  of  the  cavity,  become 
fused  into  one  mass,  and  altered  in  chemical  composition.  A  like  alteration  affects  the 
matrix  in  various  irregular  directions,  so  that  the  delicate  elastic  connecting  fibres  are  formed, 
and  constitute  a  network  through  the  whole  tendon.  These  connecting  fibres  are  often 
branched,  and  even  Appear  fibrillated  at  the  ends,  especially  if  torn  out  from  their  connection 
with  one  another,  and  in  this  condition  they  exactly  resemble  the  bodies  figured  by  Professor 
Kdlliker  as  the  "  fusiform  formative  cells"  (Fig.  29.)  That  they  have  nothing  to  do  with  the 
development  of  the  "fibrillated"  collagenous  substance  is,  however,  obvious,  from  this  very 
simple  circumstance, — that  the  latter  lies  between  them,  and  in  part  replaces  the  rest  of  the 
matrix  of  the  cartilage,  into  which  it  can  be  directly  traced.  It  will  not  be  said  in  this  case, 
that  the  "fibrillated"  tissue  of  the  tendo-Achillis  is  only  "deceptively  similar"  to  true  con- 
nective tissue — and  yet  the  transition  of  true  cartilage  into  true  connective  tissue,  is  not  less 
certainly  demonstrable  in  the  intervertebral  cartilages,  &c. 

As  Reichert,  then,  long  since  indicated,  in  illustrating  his  "  law  of  continuity''  (a  law  whose 
full  importance,  it  may  be  observed,  has  yet  to  be  developed),  and  as  he  and  Virchow  have 
since  demonstrated,  the  elastic  element  of  fully-formed  connective  tissue  represents  the  car- 
tilage-cells, while  the  collagenous  element  represents  the  matrix  of  the  cartilage,  and  is  not 
developed  from  distinct  cells. 

With  regard  to  the  structure  of  the  latter  element,  Reichert,  in  his  last  communication, 
after  considering  Kdlliker's  arguments,  denies  the  truth  of  his  statement,  that  the  ends  of  the 
fibrils  may  be  seen  in  transverse  sections  of  the  tendons  (§  Tendon,  tn/ra,)  and  retains  his 
opinion  that  it  is  not  truly  fibrillated  in  the  uninjured  state,  but  that  it  is  simply  plaited. 
Some  remarkable  observations  upon  the  behavior  of  the  "connective  fibril  bundles"  with 
acids  and  alkalies,  to  which  Reichert  first  drew  attention  in  184G,  and  which  have  been 
since  extended  by  Dr.  Paulsen  (Bericht.,  Miiller's  "Archiv,"  1849),  are,  as  the  former  points 
out,  of  the  greatest  importance  in  determining  the  nature  of  this  tissue,  and  remind  one 
somewhat  of  the  equally  puzzling  structure  of  the  starch-corpuscle.  Dr.  Paulsen  states,  that 
if  a  piece  of  tendon  be  kept  for  twenty-four  hours  in  a  solution  of  caustic  potash  of  ten  per 
cent,  strength,  it  changes  into  a  viscid  hyaline  mass,  so  transparent  that  it  can  hardly  be  dis- 
tinguished from  the  surrounding  fluid.  This  substance  can  be  torn  with  equal  ease  in  any 
direction,  and  no  fibrous  structure  can.  in  any  way  be  detected  in  it.  Under  the  microscope 
the  mass  is  quite  transparent,  and  shows  no  trace  of  the  well-known  striation.  However, 
the  connective  tissue  is  at  this  time  by  no  means  dissolved,  nor  is  its  texture  destroyed.  If 
the  potass  be  removed  by  acetic  acid,  and  this,  if  it  be  in  excess,  by  washing,  the  original 


"Die  Structur  der  serosen  Haute."     Besides  which,  consult  the  works 
of  Virchow,  Donders,  Remak,  and  myself,  cited  above. 

§  25.   Osseous  Tissue. — Morphologically,  the  osseous  tissue  consists 
essentially  of  a  matrix,  and,  Fig  31 

scattered  through  it,  of  a 
multitude  of  microscopic 
cavities,  the  bone  corpuscles,  j^r 
or  lacunce,  of  0-006-0-014 
of  a  line  in  length,  0-003- 
0-006  of  a  line  in  breadth, 
and  0-002-0-004  of  a  line  in 
thickness.  The  former,  of  •/ 

a  white  color,  is  sometimes  more  homogeneous,  sometimes  finely  granular, 

FIG.  31. — A  portion  of  a  perpendicular  section  of  a  parietal  bone  ;  magnified  350  diameters  : 
a.  lacunae  with  pale  only  partially  visible  canaliculi,  filled  as  in  the  natural  condition  with 
fluid;  6,  granulated  matrix.  The  striated  parts  indicate  the  boundaries  of  the  lamellae. 


texture  returns.  The  author  justly  remarks,  that  if  the  connective  tissue  consisted  of  separate 
fibrils  the  impossibility  of  isolating  them  in  the  distended  condition  would  be  quite  inex- 
plicable. It  is  however  intelligible,  that  in  consequence  of  such  an  alteration  in  the  con- 
nective tissue  its  cleavability  may  be  diminished  or  destroyed,  which  does  away  with  the 
necessity  of  supposing  a  fibrous  structure.  On  the  other  hand,  if  a  piece  of  tendon  be 
hardened  by  a  strong  solution  of  caustic  potash,  or  by  nitric  or  hydrochloric  acids,  no  fibres 
can  be  demonstrated  in  it  (Bericht.,  pp.  40,  41).  It  is  easy  enough  to  verify  the  truth  of  these 
statements,  by  treating  a  piece  of  tendinous  tissue  with  acetic  acid,  when,  as  is  well  known, 
the  fibrillated  appearance  disappears;  then  keeping  in  view  one  of  the  distended  and  trans- 
parent "bundles,"  slowly  add  a  solution  of  caustic  ammonia,  the  transparent  mass  will  be 
seen  gradually  to  shrink,  and  eventually  to  resume  what  appears  to  be  a  most  distinctly 
fibrous  appearance. 

The  gelatinous  or  rather  gelatiniform  areolated  connective  tissue  of  Professor  Kolliker  is  simply 
ordinary  connective  tissue,  in  which  the  collagenous  element  is  not  yet  or  but  little  formed. 
Its  development  may  be  readily  traced  to  the  most  superficial  layer  of  the  skin  and  mucous 
membranes,  or  in  th£,  tooth-pulp,  or  the  so  called  actinenchyma  of  the  enamel  organ  in  the 
calf,  &c.  The  epiglottis  of  the  kitten  is  particularly  to  be  recommended,  as  this  tissue  can 
be  observed  passing  on  the  one  side  into  the  homogeneous  layer  of  the  corium  next  to  the 
epithelium,  and  on  the  other  into  the  so-called  fibro-cartilage  of  the  epiglottis. 

In  all  these  cases,  the  mode  of  development  of  the  areolated  connective  tissue  is  essen- 
tially similar  to  that  observed  by  Remak  (Ueber  die  Entstehung  des  Bindegewebes,  &c., 
Mull.  "  Archiv,"  1852,  I.)  in  the  frog.  The  layer  of  the  tissue  next  the  epidermis  or  epi- 
thelium, is  composed  of  a  nearly  homogeneous  substance  (matrix,)  in  which  lie  corpuscles 
(so-called  nuclei),  the  whole  in  fact  corresponding  exactly  with  embryonic  cartilage.  In- 
ternal to  this,  vacuolar  cavities  have  been  formed  in  the  rnatrix  between  the  corpuscles,  the 
substance  of  the  matrix  appearing  as  bands  or  fibres  between  these  vacuolce.  The  latter 
enlarging,  the  substance  of  the  matrix  is  more  and  more  broken  up  into  bands,  in  which 
dilatations  remain  where  the  "nuclei"  are  situated,  so  that  the  bands  often  resemble  fusiform 
or  stellate  cells.  A  structure  of  this  kind  which  undergoes  no  further  chemical  or  morpho- 
logical alteration,  constitutes  the  gelatiniform  connective  tissue  •  and  it  is  unquestionable,  that 
its  subsequent  conversion  into  perfect  areolated  connective  tissue  is  effected,  as  Professor 
Kolliker  states,  by  the  direct  passage  of  these  fusiform  bodies  into  the  pseudo-fibrillated 


100  GENERAL    ANATOMY     OF    THE    TISSUES. 

very  frequently  lamellated,  and  hard  and  brittle  from  its  being  inti- 
mately combined  with  calcareous  salts  ;  the  lacunce  are  for  the  most  part 
lenticular,  and  are  united  by  very  numerous  fine  processes,  the  canali- 
culi ;  by  which  some  of  them  also  open  upon  the  outer  surface  of  the 
bones  and  into  the  larger  and  smaller  medullary  and  vascular  spaces  in 
the  interior.  The  lacunce  and  canaliculi  contain  a  clear  substance  which 
may  be  regarded  as  the  nutritive  fluid  of  the  bones,  and  besides,  a  cell- 
nucleus  appears  in  many  cases,  perhaps  constantly,  to  be  enclosed  within 
the  lacunae.  Besides  these  two  most  essential  elements,  which  exist  in 
all  bones,  numerous  vessels  and  nerves  occur  in  most,  as  well  as,  fre- 
quently, a  peculiar  substance,  the  medulla,  which  supports  them,  and 
consists  either  of  common  fatty  tissue,  or  of  a  loose,  scanty,  connective 
tissue,  with  few  fat-cells  and  many  peculiar,  so-called  medulla-cells. 
These  soft  parts  fill  up  the  larger  cavities  in  the  interior  of  the  bones 
and  in  the  spongy  substance  ;  but  are  to  be  found  also,  at  least  partially, 
in  narrow  canals  which  penetrate  the  compact  substance,  the  vascular  or 
Haversian  canals,  which  open  in  all  directions  upon  the  outer  and  inner 
surfaces  of  the  bones. 

The  matrix  of  the  osseous  tissue  is  composed  of  an  intimate  combina- 
tion of  an  organic  substance,  which  perfectly  agrees  with  that  of  the 
connective  tissue,  and  of  inorganic  compounds,  among  which  the  phos- 
phate and  carbonate  of  lime  are  the  principal  constituents.  The  fluid 
contained  in  the  cavities  and  canals  is  not  thoroughly  understood,  but  it 
probably  presents  a  preponderance  of  albumen,  fat,  and  salts,  like  the 
serum.  The  bones,  from  their  solidity  and  inflexibility,  serve  as  sup- 
ports  to  the  softer  organs  or  for  their  more 
secure  enclosure ;  and  also  perform  special  func- 
tions ;  as,  for  example,  the  auditory  ossicles  and 
the  parts  of  the  labyrinth  which  conduct  the 
sonorous  vibrations.  The  development  of  the 
bones  takes  place  in  two  modes :  firstly,  by  the 
metamorphosis  of  genuine  cartilage,  and  secondly, 
by  that  of  a  soft  blastema  composed  of  indifferent 

FIG.  32. — Six  developing  bone-cells  from  a  rickety  bone,  as  yet  sharply  defined  from  the 
interstitial  substance:  a,  simple  bone-cells ;  6,  compound  ones  running  to  a  parent  cell,  with 
two  secondary  cells ;  c,  such  arising  from  three  cells. — Magnified  350  diameters. 


bundles  of  the  collagenous  substance.  But  it  is  their  outer  portion  only,  that  therefore 
which  corresponds  with  the  matrix  of  cartilage,  which  becomes  thus  changed — the  elastic 
element  being  developed  as  before,  not  from  separate  cells,  but  by  the  chemical  metamor- 
phosis of  the  matrix  immediately  around  the  cavity  which  contains  the  il  nucleus,"  and  in 
various  other  directions. 

That  the  pseudo-fibrillated  portion  of  the  connective  tissue  corresponds  with  the  matrix 
of  the  cartilages  is  then,  we  think,  certain.  Whether  with  Remak  we  are  to  regard  both 
these  as  cell- walls,  or  with  Reichert  as  intercellular  substances,  must  be  discussed  hereafter. 
(See  General  Appendix.) — TRS.] 


TISSUES,     ORGANS,     AND     SYSTEMS.  101 

cells  and  of  a  fibrous  substance  similar  to  connective  tissue.  In  both 
cases  it  is  the  cells — in  the  one  the  cartilage  cells,  in  the  other,  cells 
•without  any  defined  character — which  form  the  lacunae  and  canalicidi 
by  the  thickening  of  their  walls,  with  a  contemporaneous  development 
of  pore  canals,  which  subsequently  grow  into  the  matrix  and  unite  with 
one  another;  whilst  the  matrix  of  the  cartilage  and  the  fibrous  sub- 
stance harden  into  the  matrix  of  the  bone  by  the  deposition  of  calca- 
reous salts,  which  likewise  infiltrate  the  thickened  cell-walls.  The 
nutrition  of  the  bones  is  very  energetic,  and  is  effected  by  the  vessels  of 
the  investing  periosteum,  and,  if  they  be  present,  by  those  of  the 
medulla  and  the  Haversian  canals  also.  The  bones  have  a  great  capa- 
city of  regeneration,  and  readily  unite ;  in  fact,  very  great  losses  of 
substance  are  repaired,  or  even  whole  bones,  if  the  periosteum  be  left : 
adventitious  development  of  bone  is  also  very  common. 

The  osseous  tissue  is  found,  firstly,  in  the  bones  of  the  skeleton,  to 
which  also  the  auditory  ossicles  and  the  hyoid  bone  belong ;  secondly, 
in  the  bones  of  the  muscular  system,  as  the  sesamoid  bones  and  the 
ossifications  of  tendons ;  thirdly,  in  the  substantia  osteoidea,  or  tooth 
cement.  Many  cartilages  ossify  with  tolerable  regularity  as  they  grow 
older  ;  as  the  costal-cartilages,  and  those  of  the  larynx. 

Dentine  may  be  regarded  as  a  modification  of  osseous  substance, 
which,  instead  of  solitary  lacunce,  presents  long  canals, — the  dental 
canals ;  besides  which,  it  exhibits  some  chemical  modifications.  The 
development  of  the  dentine  leads  to  the  conclusion  that  it  is  an  osseous 
structure,  whose  cells,  in  the  course  of  their  ossification  and  thickening, 
become  united  into  tubes,  and  have  very  little  or  no  intermediate  sub- 
stance ;  a  view  which  gains  additional  support  from  the  numerous  transi- 
tional forms,  to  be  observed  in  animals,  between  typical  dentine  and 
osseous  tissue. 

In  the  Vertebrata,  bone  is  found  more  extensively  distributed  than  in 
man.  It  exists  in  the  skin  (Armadillo,  Tortoises,  Lizards,  Fishes),  in 
the  heart  (the  cardiac  bone  of  the  Ruminants  and  Pachydermata),  in 
the  muscular  system  (diaphragmatic  bone  of  the  Camel,  Lama,  and 
Porcupine,  ossified  tendons  of  birds),  in  the  eye  (sclerotic  ring  of  Birds, 
Chelonians,  and  Saurians,  bony  scales  of  the  sclerotic  of  many  Fishes), 
in  the  external  portion  of  the  nose  (proboscis  of  the  Pig  and  Mole,  os 
prcenasale  of  the  Sloth),  in  the  tongue  (os  entoglossum  of  Fishes  and 
Birds),  in  the  respiratory  organs  (laryngeal,  tracheal,  and  bronchial 
bones  of  many  Birds),  in  the  sexual  organs  (penis-bone  of  Mammalia), 
in  the  osseous  system  (ossa  sterno-costalia  of  birds  and  some  mammals). 
In  the  Invertebrata  true  bones  are  never  found,  being,  in  them,  replaced 
by  the  so-called  calcareous  skeletons,  which  principally  consist  of  car- 


102  GENERAL    ANATOMY    OF    THE    TISSUES. 

bonate  of  lime,  and  arise  in  different  structures  as  incrustations  of  homo- 
geneous tissues  and  of  cellular  parenchymata,  as  solidifying  excretions  of 
calcareous  matter,  or  as  deposits  of  calcareous  concretions.  The  teeth 
are  limited  to  the  three  well-known  classes  of  vertebrata.  In  the 
Plagiostomata,  structures  precisely  similar  to  the  teeth  occur  as  cuta- 
neous spines. 

Literature. — Deutsch,  "  De  periitiori  ossium  structura  Observationes," 
Diss.  Vrat.,  1834 ;  Miescher,  "  De  inflammatione  ossium  eorumque  ana- 
tome  generali."  Accedunt  observat.  auct.  J.  Mailer,  Berol.,  1836 ; 
Schwann,  article  "  Knochengewebe,"  in  "  Berl.  encyclop.  Worterbuch 
der  med.  Wiss.,"  Bd.  xx.  p.  102 ;  Tomes,  article  Osseous  Tissue,  in 
"  Cyclop,  of  Anatomy,"  vol.  iii.* 

§  26.  Structure  of  the  Smooth  Muscles. — The  smooth  muscles  consist 
essentially  of  microscopic,  usually  fusiform,  more  rarely  shorter  and 
broader  fibres,  to  which  I  have  given  the  name  of  "  contractile  or  mus- 
cular fibre-cells."  Each  of  these  elements,  in  the  mean  from  0-02- 
0-04  of  a  line  long,  0-002-0-003  of  a  line  broad,  is  an  elongated  cell, 
wherein,  however,  no  difference  between  contents  and  membrane  can  be 
distinguished  ;  but  which  consists  of  an  apparently  homogeneous,  often 
finely  granulated  or  slightly  striated,  soft  substance,  in  which  without 
exception  in  the  middle  of  the  fibre  a  generally  columnar  elongated 
nucleus  exists.  These  fibre-cells  are  united  by  means  of  a  substance 
which  cannot  be  directly  demonstrated,  into  flattened  or  rounded  cords, 
the  bundles  of  the  smooth  muscles ;  which  are  then  united,  by  delicate 
investments  of  connective  tissue  with  fine  elastic  fibres  (a  kind  of  peri- 
mysium),  into  more  considerable  masses,  in  which  numerous  vessels  and 
a  relatively  small  number  of  nerves  are  distributed.  Chemically,  the 
principal  constituent  of  smooth  muscle  is  a  nitrogenous  substance  similar 
to  fibrin,  the  so-called  muscular  fibrin  or  syntonin  (Lehmann),  which, 
from  the  observations  that  have  hitherto  been  made,  is  distinguished 
from  blood  fibrin  only  in  this,  that  it  is  not  dissolved  by  solution  of 
nitre,  nor  by  carbonate  of  potass,  but  very  easily  by  dilute  hydrochloric 
acid. 

*  [While  perfectly  agreeing  with  Professor  Kdlliker's  general  view  of  the  relations  between 
dentine  and  bone,  namely,  that  the  canals  in  the  former  represent  the  cavities  and  canaliculi 
which  exist  in  the  latter  structure,  we  do  not  think  that  his  statement  of  the  mode  in  which 
the  process  of  calcification  of  the  dentine  takes  place  is  correct.  So  far  as  we  have  seen, 
the  dentine  is  never  developed  by  the  immediate  ossification  of  cells,  nor  do  the  latter  take 
any  direct  share  in  its  formation.  (See  Quarterly  Journal  of  Micros.  Sc.,  April,  1852.)  It 
may  be  said  that  dentine  is  bone,  in  which,  in  consequence  of  the  early  disappearance  of  the 
u  nuclei"  from  the  ossifying  blastema,  the  lacunce  are  not  formed,  the  dentinal  tubes  present- 
ing only  the  canaliculi. — TRS.] 


TISSUES,     ORGANS,     AND    SYSTEMS.  103 

The  physiological  importance  of  the  smooth  muscles  lies  in  their  con- 
tractile power ;  in  consequence  of  which  they  afford 
considerable  assistance  to  the  functions  of  the  differ-  Yls- 34- 

ent  viscera.  The  development  of  their  elements  takes 
place  simply  by  the  elongation  of  rounded  cells,  the 
membranes  and  contents  uniting  into  a  homogeneous 
soft  substance.  The  nutrition  of  the  smooth  muscles 
would  seem  to  go  on  very  actively,  according  to  the 
later  investigations  upon  the  fluid  which  bathes  them, 
which,  according  to  Lehmann,  has  most  generally  a 
distinctly  acid  reaction,  and  together  with  lactic, 
acetic,  and  butyric  acid,  contains  creatin  and  inosit ; 
and  the  same  conclusion  may  be  deduced  from  the  fre- 
quent occurrence  of  physiological  (in  the  uterus)  and 
pathological  hypertrophies  and  atrophies  of  them. 
Whether  smooth  muscles  are  regenerated,  or  whether 
loss  of  their  substance  is  replaced  by  a  similar  tissue, 
is  unknown ;  on  the  other  hand,  new  formations  of 
them  appear  to  occur  in  uterine  tumors. 

The  smooth  muscular  fibres  never  form  large  iso- 
lated muscles  in  the  human  body ;  as,  for  example, 
is  the  case  in  the  genito-rectal  muscles  of  mammalia, 
but  exist  either  scattered  in  the  connective  tissue,  or 
in  the  form  of  muscular  membranes.  In  both  cases 
the  bundles  are  either  parallel  or  interwoven  into  net- 
works. Their  distribution  is  as  follows  : — 

1.  In   the   Intestinal   canal   the    smooth    muscle 
forms  :  first,  the   tunica  musculosa  from  the  lower 
half  of  the  oesophagus,  where  smoth  bundles  are  still 
mingled  with  transversely   striated  fibres,  as  far  as 

the  sphincter  ani  internus  :  secondly,  the  muscular  layers  of  the  mucous 
membrane,  from  the  oesophagus  to  the  anus:  and  thirdly,  scattered  mus- 
cular bundles  in  the  villi. 

2.  In  the  Respiratory  organs,  a  layer  of  smooth  muscles  appears  in 
the  posterior  wall  of  the  trachea,  and  accompanies  the  bronchia?,  even 
to  their  finest  ramifications,  as  a  complete  circularly  fibrous  membrane. 

3.  In  the  Salivary  glands,  this  tissue  is  found  solely  in  Wharton's 
duct ;  and  here  only  scantily,  and  forming  an  incomplete  coat. 

4.  The  Liver  has  a  perfect  muscular  layer  in  the  gall-bladder,  and 
scattered  smooth  muscles  also  in  the  ductus  choledochus. 

5.  The  Spleen  has  this  kind  of  muscle  in  many  animals  in  its  outer 

FIG.  33. — Muscular  fibre-cell  from  the  small  intestine  of  man. 

FIG.  34. — Muscular  fibre-cell  from  the  fibrous  investment  of  the  spleen  of  the  dog;  magni- 
fied 350  diam. 


104  GENERAL    ANATOMY     OF    THE     TISSUES. 

coat,   and  in  the  trabeculce,  mixed  with   connective   tissue   and  elastic 
fibres. 

6.  In    the    Urinary  organs  the    smooth  muscles  are    found  in  the 
calices  and  pelves  of  the  kidneys,  form   a   complete  muscular  layer  in 
the  ureters  and  urinary  bladder,  but  are  only  sparingly  to  be   found  in 
the  urethra.* 

7.  The  Female  sexual  organs  possess  smooth  muscles  in  the  oviducts, 
the  uterus,  where  during  pregnancy  their  elements  become  excessively 
developed,  and  attain  a  length  of  J  of  a  line,  the  vagina,  the  corpora 
cavernosa,  and  in  the  broad  ligaments  of  the  uterus  in  different  places. 

8.  In  the  Male  sexual  organs  they  are  found  in  the  dartos,  between 
the  t.  vaginalis  communis  and  propria,  in   the  vas  deferens,  vesiculse 
seminales,   the   prostate,   around   Cowper's  glands,  and  in  the  corpora 
cavernosa  penis. 

9.  In  the    Vascular  system  smooth  muscles  exist  in  the  tunica  media 
of  all,  especially  of  the  smaller  arteries  ;  also  in  that   of  most  veins, 
and  of  the  lymphatics,  with  the  exception  of  the  finest ;  furthermore, 
in  the  lymphatic  glands  (Heyfelder) ;  and  lastly  in  the  tunica  adventitia 
of  many  veins.     The  elements,   in  vessels  of  middle  dimensions,  are 
everywhere  fusiform    fibre-cells  ;    in  the  large  arteries,   on  the  other 
hand,  shorter  plates,  which  often  resemble  certain  forms  of  pavement 
epithelium  ;  and  in  the  smallest  arteries   they  are  more  elongated,  or 
even  round  cells,  forms  which  must  be  considered  as  less  developed. 

10.  In  the  Eye,  smooth  muscles  form  the  sphincter  and  dilator  pu- 
pillce  and  the  tensor  choroidece. 

11.  In   the  Skilly  lastly,   this   tissue  appears  besides   in  the  dartos, 
in  the  form  of  minute  muscles  upon  the  hair  sacs,  in  the  areola,  and 
in  the  nipple,  and  in  many  of  the  sudoriparous  and  sebaceous  follicles. f 

The  elements  of  the  smooth  muscles  were  formerly  universally  re- 
garded as  elongated  bands  containing  many  nuclei,  which  were  sup- 
posed to  be  developed  by  the  coalescence  of  numerous  mutually  applied 
cells.  In  1847  I  showed  that  this  is  not  the  case  ;  that,  on  the  other 
hand,  the  elements  of  these  muscles  are  only  modified  simple  cells  ;  and 
at  the  same  time  I  demonstrated,  that  these  contractile  fibre-cells  occur 
wherever  contractile  connective  tissue  had  previously  been  assumed  to 

*  [Mr.  Hancock  (On  the  Anatomy  and  Physiology  of  the  Male  Urethra,  London,  1852), 
who  had  made  out  the  existence  of  the  organic  muscular  layer  in  the  urethra  indepen- 
dently, attributes  to  it  much  more  anatomical  and  physiological  importance.  (See  below, 
§  Urinary  Organs.) — TRS.] 

*j"  [These  muscles  have  also  been  seen  by  Mr.  Lister  (Quart.  Journal  of  Microscop. 
Science,  vol.  i.  p.  203),  in  the  scalp.  Mr.  Lister  found  the  muscles  in  this  situation  smaller 
(^l^th  of  an  inch)  than  those  measured  by  Ko' Hiker.  They  possessed  extremely  distinct 
nuclei,  but  instead  of  uniting  in  flat  bundles  were  often  circular,  sometimes  elliptical  or 
polygonal. — DaC.J 


TISSUES,     ORGANS,     AND     SYSTEMS/  105 

exist,  and  also,  that  they  are  to  be  found  in  many  localities  in  which 
their  presence  had  not  been  suspected.  These  views,  notwithstanding 
contradiction  at  first  from  certain  quarters,  are  now  universally  con- 
firmed ;  a  result  to  which  Reichert,  by  the  discovery  of  a  reagent,  which 
readily  enables  even  those  who  are  less  practised,  easily  to  isolate  the  con- 
tractile fibre-cells,  viz. :  nitric  and  hydrochloric  acids  of  20  per  cent. 
(Miiller,  "  Archiv,"  1849,  and  Paulsen,  "  Obs.  Microchem.,"  1849) ; 
and  Lehmann,  by  his  chemical  investigations  upon  this  tissue,  have 
contributed  their  share.  Contractile  fibre-cells  occur  in  all  four  classes 
of  the  Vertebrata,  but  appear  to  be  wholly  wanting  in  the  Invertebrata, 
since  the  smooth  fibres  of  these  creatures,  which  have  been  thought  to 
be  such,  are  allied  genetically  to  the  transversely  striated  muscles  of  the 
higher  animals. 

Their  occurrence  in  the  Vertebrata  is  in  some  respects  peculiar, 
and  I  will  here  mention  the  following  localities  in  which  they  are  found  : 
In  the  skin  of  Birds,  as  the  muscles  of  the  quill-feathers — in  this  case 
with  tendons  of  elastic  tissue ;  in  that  of  the  Orang-outang,  in  the  hair- 
sacs,  as  in  man;  in  the  iris  of  the  Amphibia;  in  the  campanula  Hal- 
leri  of  the  osseous  Fishes  (Leydig);  in  the  swimming  bladder  of  Fishes; 
in  the  lungs  of  the  Frog  (in  Triton  they  are  here  wanting) ;  in  the  me- 
sentery of  the  Plagiostomata,  or  Psammosaurus  and  Leposternon  (Ley- 
dig  u.  Briicke) ;  in  the  genito-rectal  muscle  of  Mammals.  In  the  giz- 
zard of  birds  these  muscles  are  of  a  bright  red  color,  and  are  united 
with  a  tendinous  membrane. 

Literature. — Kolliker,  "Ueber  den  Bau  und  die  Verbreitung  der 
glatten  Muskeln.,"  in  the  "  Mittheilungen  der  Naturf.  Gesellschaft  in 
Zurich,"  1847,  p.  18,  and  "  Zeitschrift  fur  wiss.  Zool.,"  Bd.  I.  1849; 
C.  R.  Walther,  "  Nonnulla  de  musculis  Isevibus.,"  Diss.  Lips.  1851.* 
[Jos.  Lister,  "  Observations  on  the  Contractile  Tissue  of  the  Iris," 
Quart.  Journ.  Mic.  Sc.,  vol.  I.  p.  8,  PL  i.,  and  "  Observations  on  the 
Muscular  Tissue  of  the  Skin,"  Quart.  Journ.  Mic.  Sc.  vol.  I.  p.  263. — 
DaC.] 

*  [Reichert  (Bericht,  1849,  Miiller,  "  Archiv.,':)  states  that,  according  to  Paulsen,  the  action 
of  a  solution  of  caustic  potass  of  50  per  cent,  causes  the  smooth  muscles  to  become  wavy, 
and  thus  to  assume  a  transversely  striated  appearance  under  the  microscope.  Macerated 
in  such  a  solution  for  three  days,  they  breakup  into  small  globules  ;  striated  muscle  behaves 
in  a  similar  manner,  and  the  globules  correspond  in  size  to  the  interval  between  two  striae. 

Eylandt  (Obs.  Microscop.  de  musculis  organicis  in  hominis  cute  obviis.  Diss.  inaug.,  Dorp. 
1850,  c.  Tab.  lithog.),  denies  the  existence  of  free  smooth  muscles  in  the  papilla  and  areola 
mamnuzjin  the  scrotum,  in  the  skin  of  the  penis  or  of  the  prepuce,  and  in  the  perinoeum.  Nor  does 
he  find  them  in  the  outer  layers  of  the  hair-sacs  (apart  from  the  arrectores  pill),  in  the  glan- 
dules sudoriferte  of  the  axilla,  of  the  anus,  &c.,  nor  in  the  glandulce  ceruminosce.  The  smooth 
muscles  observed  in  the  papilla  and  areola  mammce,  in  the  skin  of  the  penis,  and  the  peri- 
neum, he  considers  to  belong  to  a  greatly  developed  vascular  layer.  (See,  however,  the 
remarks  of  Prof.  Kclliker  upon  Eylandts  statements,  at  the  end  of  §  34.) — TRS.] 


106 


GENERAL    ANATOMY     OF    THE    TISSUES. 


§27.  Transversely  Striated  Muscular  Tissue. — The  elements  of  this  tis- 
sue consist  essentially  of  the  so-called  muscular  fibres  or  primitive  muscu- 
lar bundles,  each  of  which,  0-004-0*08  of  a  line  thick,  consists  of  fine 
fibrils  surrounded  by  a  special  homogeneous,  delicate,  elastic  investment, 
the  sarcolemma :  the  fibrils  are  generally  enlarged  at  regular  intervals, 
so  that  they  appear  to  consist  of  a  series  of  many  portions,  and  give  a 

transversely  striated  as- 

Fig-35<  Fi*-36-  pect    to    the     muscular 

fibres,  or  they  appear 
more  even,  and  then  the 
primitive  bundles  pre- 
sent a  longitudinal  stria- 
tion.  Besides  these 
fibrils,  the  muscular 
fibres  contain  nothing 
but  a  small  quantity  of 
viscid  substance  uniting 
them,  and  a  certain  num- 
ber of  rounded  or  elon- 
gated cell-nuclei,  which 
generally  lie  against 
the  inner  surface  of  the 
sarcolemma.  The  associ- 
ation of  the  muscular 
fibres  into -^muscles  and 
muscular  membranes  occurs  in  such  a  manner  that  they  either  apply 
themselves  parallel  to  one  another,  or  are  united  into  true  networks  of 
transversely  striated  muscles.  They  then  receive  an  investment  of  more 
delicate  or  firmer  connective  tissue,  the  so-called  perimysium,  with  which 
finer  elastic  fibres  and  also  fat-cells  are  frequently  mingled ;  and  are, 
besides,  surrounded  by  numerous  blood-vessels  and  nerves. 

In  chemical  characters  the  principal  substance  of  the  transversely 
striated  muscular  fibres  agrees  perfectly  with  the  syntonin  referred  to  in 
the  previous  section.  The  sarcolemma  is  very  resistant  to  acids  and 
alkalies,  whilst  the  nuclei  present  the  common  characters  of  those  organs. 
A  fluid  with  an  acid  reaction  may  be  expressed  from  the  muscles,  in 
which  Liebig  and  Scherer  have  discovered  an  interesting  series  of  non- 
nitrogenous  and  nitrogenous  products  of  the  decomposition  of  the  mus- 
cular tissue. 

The  transversely  striated  muscles  are  in  a  high  degree  contractile,  and 

FlG.  35. — Two  muscular  fibres  of  man  ;  magnified  350  diam.  In  one  the  bundle  of  fibrils, 
6,  is  torn,  and  the  sarcolemma,  a,  is  to  be  seen  as  a  mere  empty  tube. 

FIG.  36. — Primitive  fibrils  from  a  primitive  bundle  of  the  Axolotl  (Siredon  pisciformis)  ; 
a,  a  small  bundle  of  them ;  b,  an  isolated  fibril,  magnified  GOO  diam. 


TISSUES,     ORGANS,     AND    SYSTEMS.  107 

are  the  chief  instruments  of  the  animal  motions.  Their  elements  are 
developed  by  the  coalescence  of  round  or  stellate  cells,  whose  contents 
change  into  a  homogeneous,  semi-fluid  suhstance,  and  then  break  up 
into  fibrils.  Once  formed,  the  muscular  fibres  grow  by  the  elongation 
and  thickening  of  their  elements,  and  in  their  complete  condition  they 
enjoy  a  very  energetic  nutrition,  which  is  especially  manifested  by  the 
multiform  products  of  their  decomposition,  as  well  as  by  the  circum- 
stance that  their  powers  are  exhausted  in  a  short  time  when  the  circula- 
tion is  suspended.  Wounds  of  the  muscles  never  heal  by  transversely 
striated  muscular  substance  ;  but  an  adventitious  formation  of  this  tissue 
appears  to  occur  sometimes,  though  rarely. 

Transversely  striated  muscular  tissue  is  found  in  the  following  parts: 

1.  In   the  muscles  of  the  trunk  and  extremities  ;  of  the  globe  of  the 
eye,  and  all  those  of  the  ear. 

2.  In  the  muscles  of  many  organs  ;  as  the  larynx,  pharynx,  tongue, 
and  oesophagus  (upper  half),  the  end  of  the  rectum  (sphincter  externus, 
levator  ani),  the  genital  organs  (bulbo-ischio-cavernosus,  urethralis  trans- 
versus,  transversi  perincei,  cremaster,  muscular  fibres  of  the  round  liga- 
ments of  the  uterus,  in  part). 

3.  In  certain  parts  of  the  vascular  system,  e.  g.  in  the  heart  and  in 
the  walls  of  the  great  veins  which  open  into  it. 

The  muscular  fibres  of  animals  are  not  all  composed  of  bundles  of 
transversely  striated  fibrils,  but  present  a  series  of  other  forms,  which 
may  best  be  grouped  in  the  following  manner  : — 

1.  Muscular  tubes,  with  homogeneous,  semi-solid,  not  transversely  stri- 
ated contents  (most  Mollusks,  Worms,  and  Radiata). 

2.  Muscular  tubes  with  a  membrane,  a  semi-fluid,  homogeneous,  cor- 
tical layer  in  contact  with  it,  and  a  fluid  or  granular,  frequently  trans- 
versely striated  or  nucleated  central  substance.     (Muscles  of  Petromy- 
zon  in  part,  certain  muscles  [of  the  lateral  line  and  of  the  spiracles]  of 
the  plagiostome  and  osseous  Fishes.     Muscles  of  the  Hirudinidce,  Lum- 
bricidce,  of  Paludina  in  part,  and  of  Carinaria.) 

3.  Similar  muscular  tubes  with  a  transversely  striated  cortical  layer 
without  distinct  fibrils.    (Many  muscular  fibrils  of  the  Hirundinidce,  and 
of  the  muscles  of  Fishes  enumerated  under  2.) 

4.  Muscular  fibres  without  any  internal  cavity,  with   a  sarcolemma 
and  transversely  striated  contents,  which  do  not  break  up  into  fibrils, 
but  frequently  into  discs  (Bowman),  Salpce,  some  Radiata,  many  Arti- 
culata. 

5.  Similar  muscular  fibres,  which  readily  break  up  into  fibrils.   (Most 
Vertebrata,  certain  muscles  of  Insects.) 

6.  Simple  isolated  cells,  whose  contents  are  changed  into  a  trans- 
versely striated  substance,  which  either  fills  the  whole  cell  or  forms  only 
a  thin  layer  upon  its  membrane.  Here  my  observations  lead  me  to  place 


108  GENERAL    ANATOMY     OF    THE    TISSUES. 

the  peculiar  cartilaginous  striae,  which  Purkinje  (Mikr.  neurol.  Beobach- 
tungen,  in  Miill.  "  Arch.,"  1845)  found  in  the  endocardium  of  Ruminants. 
They  consist  of  large  polygonal  cells  with  beautiful  nuclei,  which  in- 
ternally, but  as  it  seems  only  upon  their  wall,  contain  a  transversely 
striated  substance,  which  is  not  distinguishable  from  that  in  the  muscular 
fibres. 

All  these  forms  are  readily  comprehended,  if  the  genesis  of  the  true 
transversely  striated  muscular  fibres  in  the  higher  vertebrata  be  properly 
understood  (see  the  special  part,  Muscles) ;  and  I  cannot  agree  with  the 
supposition  of  Stannius  (Gott.  Nachr.,  1851,  p.  17),  that  the  transversely 
striated  muscular  fibrils  are  developed  according  to  many  essentially 
different  types.  Even  the  gap  which  has  hitherto  separated  the  smooth 
from  the  transversely  striated  muscles  becomes  less,  when  we  remember 
that  the  so-called  transversely  striated  muscular  fibrils  may  also  have 
homogeneous  non-striated  contents,  and  also  that  even  when  transversely 
striated  they  may  appear  as  isolated  cells.* 

Muscuhtr  fibres  of  the  same  description  as  the  transversely  striated 
muscles,  and  in  part  actually  striated,  are  very  widely  distributed.  In 
the  Vertebrata  such  muscles  are  found  in  the  oesophagus  of  some  Mam- 
malia and  of  the  plagiostome  fishes,  in  the  intestine  of  Tinea  chrysitis, 
in  the  stomach  of  Qobitis  fossilis,  around  the  poison  gland  of  Snakes, 
and  in  the  contractile  organ  of  the  pharynx  of  the  Carp  ;  in  the  skin  of 
Mammalia,  Birds,  Snakes,  and  tailless  Batrachians  (so  called  cutaneous 
muscles),  in  the  tactile  hairs  of  mammals,  in  the  lymph  hearts  of  many  Birds 
and  Amphibia  ;  in  the  auriculo-ventricular  valve  of  the  right  side  in  Birds, 
and  the  Ornithorhynchus;  upon  the  vena  cava  inferior  of  the  Seal, 
close  above  the  diaphragm  :  in  the  interior  of  the  eye  of  Birds  ;  and  round 
Cowper's  and  the  anal  glands  of  mammals.  In  the  Invertebrata,  as  we 
have  mentioned,  all  the  muscles  belong  to  this  category,  whether  they 
be  transversely  striated  or  not ;  and  they  are  found,  therefore,  in  the 
heart,  the  intestine,  the  genitalia,  and  often  clearly  striated. 

The  anastomosis  of  the  primitive  bundles  of  the  muscles,  with  which 
Leeuwenhoek  was  already  acquaintedf  and  which  I  rediscovered  in  the 
heart  of  the  frog,  has  now  been  seen  in  many  places,  and  appears  to  be 
constant  in  the  hearts  of  the  lymph  and  blood-vascular  systems  of  all 
animals,  and  in  the  muscles  of  the  Invertebrata,  especially  those  of  the 
vegetative  and  generative  organs.  (Hessling,  Leydig.)  Simple  arbores- 

*  [The  muscles  of  the  Medusas  consist  of  flat,  fusiform  bands,  whose  ends  are  interlaced 
like  those  of  smooth  muscle,  but  which  present  the  most  distinct  transverse  stride. — TRS.] 

f  [It  has  been  pointed  out  to  us  by  Professor  Sharpey,  that  Leeuwenhoek  was  not 
acquainted  with  the  anastomosis  of  the  primary  bundles  of  the  cardiac  muscles,  but  has 
described  and  figured  only  that  of  the  secondary  bundles,  which  is  indeed  obvious  upon 
reference  to  Leeuwenhoek's  Plate  ("  Experimenta  et  Contemplationes,"  Op.  Om.  Lugd.Bat. 
torn.  i.  p.  409,  1722);  the  ascription  in  the  text  is  therefore  an  error.  For  other  remarks  upon 
the  muscular  tissue,  vide  infra,  §  Muscle. — TRS.] 


TISSUES,     ORGANS,     AND     SYSTEMS.  109 

cent  branchings  of  muscular  fibres,  which  Corti  and  I  noticed  in  the 
tongue  of  the  frog,  are  on  the  other  hand  rare,  and  have  been  seen  else- 
where only  in  Artemia  salina  and  in  the  oral  and  anal  disc  of  Piscicola 
(Leydig).* 

Literature. — W.  Bowman,  article  Muscle  and  Muscular  Motion,  in 
Todd's  "  Cyclopaedia  of  Anatomy,"  and  "  On  the  Minute  Structure  of 
Voluntary  Muscle,"  in  "  Phil.  Trans.,"  1840  II.  1841,  I. ;  J.  Hoist,  "De 
Structura  Musculorum  in  genere  et  annulatorum  Musculis  in  Specie," 
Dorp.  1846 ;  M.  Barry,  "  Neue  Unters.  uber  die  schraubenformige  Be- 
schafferiheit  der  Elementarfasern  d.  Muskeln,  nebst  Beobachtungen  uber 
die  musculos.  Natur  d.  Flimmerharchen"  (Miill.  "Arch.,"  1850,  p.  529). 

§  28.  Nervous  tissue. — The  essential  elements  of  this  tissue  are  of 
two  kinds,  the  nerve-fibres  and  nerve-cells  (ganglion-globules).  The  pri- 
mitive fibres  or  tubules  of  the  nerves  have  either  a  distinct  medulla  or 
they  have  none.  The  former  consist  of  three  parts :  of  a  structureless 
delicate  membrane,  the  sheath  of  the  primitive  tubules ;  of  a  central, 
soft,  but  elastic  fibre,  the  central  or  axis  band  (axis  cylinder,  Purkinje  ; 
primitive  band  of  Remak) :  and  of  a  viscid  white  layer  placed  between 
them,  the  medulla?^  sheath.  In  the  tubules  without  medulla,  which  in 
man  occur  only  in  certain  peripheral  expansions  (retina,  olfactory  organ, 
cornea,  Pacinian  corpuscles),  the  structureless  coat  contains  nothing  but 
a  homogeneous  or  finely-granular,  clear  substance,  which  appears  to  be 
identical  with  the  central  band  of  the  other  tubules,  and  at  any  rate 
may  be  considered  analogous  to  it,  so  that  the  medullary  layer  may  be 
supposed  to  be  absent  in  these.  The  primitive  nerve-tubules  of  both 
kinds,  especially  of  the  former,  occur  of  very  different  dimensions,  and 
may  thence  be  divided  into  fine  ones  of  0-0005-0-002  of  a  line,  those  of 
a  medium  size  of  0-002-0-004,  and  thick  ones  of  0-004-0-01  of  a  line. 
Their  course  is  either  isolated,  so  that  one  tubule  runs  from  the  centre  to 
the  periphery ;  or  they  divide,  especially  in  their  terminal  expansions, 
into  a  greater  or  smaller  number  of  branches;  or,  lastly,  they  form 
actual  anastomoses  and  networks.  Besides  this,  many  nerve-tubules  are 
connected  with  nerve-cells,  so  that  they  either  arise  from  them  or  are 
interrupted  in  their  course  by  interposed  nerve-cells.  These  nerve-cells, 
or  as  they  are  called  in  the  ganglia,  ganglion-cells,  or  ganglion-globules, 
are  endowed  with  the  common  attributes  of  cells.  Their  membrane 
presents  no  peculiarity,  except  that,  frequently,  it  is  very  delicate,  and 
even,  as  in  the  great  central  masses,  eventually  perhaps  wholly  disap- 
pears. The  contents  are  finely-granulated,  semi-solid,  often  contain 

*  [Such  branched  muscular  fibres  may  be  found  beautifully  marked  in  the  upper  lip  of  the 
Rat,  and  in  the  tongue  oi'Man  and  Animals.  See  article  "  Tongue,"  by  Dr.  Hyde  Salter,  in 
Todd's  c;  Clycopsedia."— TBS.] 


110 


GENERAL    ANATOMY    OF    THE    TISSUES. 


pigment,  and  without  exception  enclose  a  distinct  vesicular  nucleus  with 
a  large  nucleolus.  In  size,  the  nerve-cells  vary  from  0-003-0-04  of  a 
line,  and  as  regards  their  form,  they  may  be  distinguished  principally 


Fig.  37. 


Fig.  38 


into  round,  fusiform,  and  stellate.  The 
two  latter  kinds  are  produced  by  the 
prolongation  of  many  nerve-cells  into 
two,  three,  to  eight  and  more,  pro- 
cesses, which  in  some  cases,  after  a  short  course,  pass  into  medullated 
nerve-fibres,  in  others,  present  a  more  marked  independence,  since, 
preserving  a  complete  resemblance  to  non-medullated  nerves,  they 
often  run  for  a  considerable  distance,  and  branch  out  in  manifold  ways. 
In  what  manner  finally  these  processes  end,  whether  free  or  in  con- 
nection with  nerve-tubules  or  by  anastomosis  with  similar  processes,  is 
not  yet  made  out ;  though,  upon  the  whole,  it  would  seem  to  be  not  im- 
probable that  all  three  possibilities  may  occur  in  different  localities. 

Nerve-fibres  and  nerve-cells  are  combined  into  two  substances,  which  in 
extreme  cases  present  very  wide  differences,  the  gray  and  the  white  sub- 
stances. The  former  constitutes  the  so-called  white  medulla  or  medullary 
substance  of  the  spinal  cord  and  brain,  and  the  nerves ;  it  consists  essen- 
tially of  nerve -tubules,  united  into  bundles  or  interwoven  into  plexuses, 
with  bloodvessels ;  added  to  which,  in  the  peripheral  nerves,  we  have 

FIG.  37. — Tubular  nerve-fibres  of  man.  Four  of  them  fine,  two  of  them  being  varicose, 
one  of  a  medium  thickness  with  a  simple  contour,  and  four  thick  ones;  two  having  double 
contours,  and  two  with  granular  contents. — Magnified  350  diameters. 

FIG.  38. — Nerve-cell  of  the  Pike  (so-called  bipolar),  passing  at  its  two  ends  into  dark-bor- 
dered nervous  tubules,  treated  with  arsenious  acid:  a,  membrane  of  the  cell;  b,  nerve- 
sheaths  ;  c,  medulla  of  the  nerve ;  d,  axis-fibres  connected  with  the  contents  of  the  nerve- 
cell  ;  e,  retracted  from  the  membrane. — Magnified  350  diameters. 


TISSUES,     ORGANS,     AND     SYSTEMS. 


Ill 


special  investments  of  connective  tissue,  the  so-called  neurilemma.  The 
gray  substance  contains  a  great  preponderance  of  nerve-cells,  besides 
which,  in  certain  localities,  there  is  a  finely-granular  matrix  and  free 
nuclei ;  but  it  is  rarely  found  quite  unmixed,  being  usually  mingled  more 


Fig.  39. 


or  less  with  nerve-fibres.  This  is  more  especially  the  case  in  most  gan- 
glia, in  the  gray  substance  of  the  spinal  cord,  and  in  the  so-called  gan- 
glia of  the  cerebrum ;  while,  on  the  other  hand,  in  the  gray  cortex  of 
the  cerebrum  and  cerebellum,  it  is  found  in  some  localities  almost  with- 
out nervous  fibres.  This  substance  possesses  vessels  even  in  much 
greater  abundance  than  the  white ;  and  in  the  peripheral  ganglia  there 
are  also  different  forms  of  connective  tissue,  which  serve  to  invest  their 
separate  parts. 

The  chemical  composition  of  the  nervous  substance  has  hitherto,  by 
no  means,  been  sufficiently  investigated.  In  the  white  substance,  the 
central  bands  of  the  nerve-tubules  consist  of  a  protein  compound  very 
similar  to  the  fibrin  of  the  muscles  ;  the  medullary  sheath,  chiefly  of  fats 
of  different  kinds,  and  the  membrane,  of  a  substance  similar  to  the  sar- 
colemma.  The  gray  substance  contains  a  preponderance  of  albuminous 
matter,  besides  a  considerable  quantity  of  fat. 

The  physiological  importance  of  the  nervous  tissue  consists,  in  the 
first  place,  in  its  subserving  movement  and  sensation ;  secondly,  in  its 

FIG.  39. — Nerve-cells  of  the  substantiaferruginea  from  the  floor  of  the  fourth  ventricle  in 
man  ;  magnified  350  diameters. 


112  GENERAL    ANATOMY    OF    THE    TISSUES. 

exerting  a  certain  influence  upon  the  vegetative  functions  ;  and  thirdly, 
in  its  serving  as  a  substratum  to  the  psychical  activities ;  in  all  which 
capacities,  according  to  what  we  know  at  present,  the  gray  substance 
performs  the  more  important  part,  the  white  acting  rather  as  a  con- 
necting conductor  between  it  and  the  organs.  The  nerve-cells  are 
developed  from  the  common  formative  cells  of  the  embryo,  whilst 
the  nervous  tubules  proceed  from  the  coalescence  of  the  membrane 
and  contents  of  many  such  cells,  of  a  rounded,  fusiform,  or  stellate 
shape ;  with  this,  in  the  medullary  tubules  a  peculiar  modification  of  the 
contents  occurs,  in  consequence  of  which  it  is  divided  into  a  central 
solid  filament  and  a  softer  investment.  The  nutrition  in  the  nervous 
tissue  must  be  very  active,  especially  in  the  gray  substance,  as  the  great 
quantity  of  blood  which  flows  into  it  clearly  shows,  but  the  products  of 
its  decomposition  are  wholly  unknown.  The  white  nervous  substance  is 
regenerated  pretty  readily  in  the  peripheral  nerves,  and  as  it  would 
seem,  in  the  spinal  cord  also.  The  adventitious  formation  of  nervous 
tubules  has  been  observed  in  pathological,  new  formations,  and  according 
to  Virchow's  observations,  it  would  even  appear  that  an  abnormal  de- 
velopment of  gray  substance  may  occur. 

The  organs  composed  of  nervous  substance  are  :  the  peripheral  nerve- 
cords,  nerve-membranes  and  nerve-tubules,  the  ganglia,  the  spinal  cord, 
and  the  brain. 

Medullated  nerve-fibres  are  found  only  in  the  Vertebrata,  and  even 
in  that  class  not  in  every  division,  as  for  example,  in  Petromyzon  (Stan- 
nius).  Fibres  without  medulla  always  occur  together  with  the  former, 
and  in  general  in  the  same  localities  as  in  man ;  but  in  other  situations 
also,  as  in  the  skin  of  the  Mammalia,  in  the  electric  organs  of  Fishes, 
and  in  the  sympathetic  nerve  of  the  Plagiostomata  (Leydig).  Where 
nerves  are  found  in  the  Invertebrata,  they  contain  only  pale  fibres  with- 
out medulla,  whose  structure  often  completely  resembles  that  of  the 
embryonic  fibres  of  higher  animals,  especially  as  regards  the  occurrence 
of  great  nucleated  enlargements  in  the  terminal  expansions,  which  re- 
mains of  the  original  formative  cells,  have,  recently,  less  properly  been 
considered  to  be  ganglion-globules. 

Literature. — Gr.  Valentin,  "  On  the  course  and  termination  of  the 
nerves,"  in  the  "Nov.  Act.  Natur.  Curios.,"  vol.  xviii.  t.  i. ;  R.  Remak, 
"  Observations  anatomicse  et  microscop.  de  syst.  nerv.  struct.,"  Berol., 
1838;  A.  Hannover,  "Recherches  microscopiques  sur  le  systeme  ner- 
veux,"  Copenhague,  1844  ;  R.  Wagner,  "  Neue  Unters.  iiber  den  Bau  und 
die  Endigungen  der  Nerven  und  die  Structur  der  Ganglien,"  Leipzig, 
1847;  and  "Neurologische  Untersuchungen,"  in  Gottingen  "Anzeige," 
1850;  Bidder  andReichert,  "Zur  Lehre  vom  Verhaltniss  der  Ganglien- 
korperzuden  Nervenfasern,"  Leipzig,  1847;  Ch.  Robin,  in  "1'Institut.," 


TISSUES,     ORGANS,     AND    SYSTEMS. 


113 


1846,  Nos.  687-699,  and  1848,  No.   733 ;    Kolliker,  "  Neurologische 
Bemerkungen,"  in  "  Zeitsch.  fur  wiss.  ZooL,"  i.  p.  135. 

§29.  True  G-landular  Tissue. — The  most  essential  constituents  of  the 
true  glands  are  the  secreting  elements,  which  appear  as  aggregations  of 
cells,  as  closed  glandular  vesicles,  and  as  open  glandular  vesicles  and 
glandular  tubes,  containing  as  their  most  important  constituent  the  so- 
called  gland-cells.  These  cells  are  for  the  most  part  polygonal  or  cylin- 
drical, and  perfectly  resemble  certain  epithelial  cells,  but  upon  the  other 
hand,  they  are  frequently  distinguished  and  characterized  by  peculiar 
contents.  The  union  of  these  cells  into  the  secreting  parts  of  the  glands 
is  effected  either  directly  or  with  the  co-operation  of  homogeneous  mem- 
branes, the  so-called  membranes  proprice,  and  of  connective  tissue.  In 
this  manner  the  secreting  glandular  elements,  different  in  nature  accord- 
ing to  the  different  glands,  are  formed ;  and  becoming  invested  with 
vessels,  nerves,  and  connective  tissue,  with  which  elastic  fibres,  fat- 
cells,  and  even  muscles,  are  mingled,  they  are  combined  into  the  larger 
and  smaller  divisions  of  the  glands.  The  principal  forms  of  the  secret- 
ing glandular  elements  in  man  are  the  following : — 

1.  Solid  networks  of  cells  without  investing  membrane.     In  the  liver 
(Fig.  40). 

2.  Closed  vesicles  with  a  fibrous  membrane  and  epithelium.     Graafian 
vesicles,  mucous  follicles  (so-called  ovula  Nabothi),  in  the  cervix  uteri. 


Fig.  40. 


Fig.  41. 


3.  Hounded  or  elongated  glandular  vesicles,  with  a  membrana  propria 
and  an  epithelium.  In  the  racemose  glands  (Fig.  41). 

FIG.  40. — Network  of  hepatic  cells,  b  ;  and  finest  ductus  interlobnlares,  a  ;  of  man  after 
nature;  the  union  of  both  diagrammatic;  c,  vascular  spaces. — Magnified  350  diameters. 

FIG.  41. — Two  of  the  smallest  lobes  of  the  lung,  a  a;  with  air-cells,  bb  ;  and  the  finest 
bronchial  ramifications,  c  c;  upon  which  also  air-cells  are  seated.  From  a  new-born  child ; 
semi-diagrammatic  figure. — Magnified  25  diameters. 

8 


114 


GENERAL    ANATOMY    OF    THE    TISSUES. 


Fig.  42. 


4.  Glandular  tubes,  with  a  membrana  propria,  or  a  fibrous  membrane 
and  an  epithelium.  Tubular  glands  (Fig.  42). 

To  these  elements  are  also  added  (except  in  those  glands  enumerated 
under  2,  which  become  emptied  of  their  contents  by  the  occasional 
bursting  of  their  follicles,  and  the  simplest  tubular  glands)  special  excre- 
tory ducts,  which,  after  manifold  ramifications  either  pass  directly  into 
the  glandular  vesicles  and  glandular  tubes,  or,  as  in  the  liver,  are  simply 
applied  to  the  secreting  networks  of  cells.  These  ducts  are  at  first 
similar  in  their  structure  to  the  secreting  parts,  but  they  always  possess 
epithelial  cells,  which  have  not  the  specific  contents  of  the  proper  gland 
cells,  and  mostly  also  exhibit  a  different  form.  The  wider  excretory 
ducts  consist  of  a  fibrous  investment  and  of  an  epithelium,  and  often 
also,  possess  a  muscular  layer,  and  in  their  ultimate  divisions,  a  fibrous, 
a  muscular,  and  a  mucous  layer  very  frequently  exist  as  special  struc- 
tures. 

Chemically,  the  glands  are,  as  yet,  little  known.  The  glandular 
cells,  the  most  important  structures,  are  allied  in  this  respect  also  to  the 
epithelial  structures,  only  that  frequently,  they  contain  in  their  interior 
peculiar  substances, — as  fat,  the  constituents  of  the  bile,  of  the  urine,  of 
the  gastric  juice,  mucus,  &c.,  and  thence  assume  a  specific  character. 

The  true  glands  either  separate  certain  constituents 
from  the  blood,  or  by  means  of  it,  elaborate  peculiar 
substances  of  structural  elements,  and  according  as 
they  do  the  one  or  the  other,  is  the  import  of  their 
separate  parts  different.  In  the  former  glands  the 
cells  play  a  more  subordinate  part,  and  are  at  most 
of  importance,  so  far  merely,  as  they  impede  the 
passage  of  this  or  that  constituent  of  the  blood,  and 
allow  only  certain  of  them  to  pass  (kidneys,  lachrymal 
glands,  small  sudoriparous  glands,  lungs) ;  whilst  in 
others,  the  cells  take  a  very  important  share  in  the 
formation  of  the  glandular  fluid,  by  producing  within 
them  the  specific  secretion,  which  then  either  drains 
out  of  them  (liver,  mucous  glands,  gastric  glands,  pro- 
state, Cowper's  glands,  salivary  glands,  pancreas),  or  be- 
comes free  by  the  gradual  dissolution  and  breaking  up  of 
the  cells  themselves  (lacteal  glands,  fat  glands,  testis, 
larger  sudoriparous  and  ceruminous  glands).  In  the  for- 
mer case,  as  in  the  Graafian  follicles,  a  peculiar  cell- 
development  may  take  place  in  the  secretion  which  is 
formed,  whilst  in  the  latter,  new  elements  continually  arise  in  place  of 
those  gland-cells  which  are  removed  as  they  attain  their  full  develop- 

FiG.  42. — Gastric  gland  from  the  pylorus  of  the  dog,  with  cylinder-epithelium  :  a,  larger 
glandular  cavity  ;  6,  tubular  appendages  of  it. 


TISSUES,     ORGANS,    AND    SYSTEMS.  115 

ment,  in  consequence  of  which  the  character  of  these  cells  as  a  coating 
of  the  glandular  canals  is  frequently  lost,  and  they  appear  simply  as 
a  part  of  the  secretion  (testis,  lacteal  gland  during  lactation).  All  the 
glands  here  mentioned,  with  the  exception  of  the  sexual,  are  developed 
from  the  internal  and  external  epithelial  structures  of  the  body,  con- 
joined with  the  vascular  membranes  which  support  these  epithelia. 
Some  of  them  originate  as  involutions  of  these  membranes,  and  retain 
the  cavities  throughout  the  course  of  their  development  (lungs,  small 
intestinal  glands),  others  are  at  first  hollow,  but  afterwards  increase  by 
the  addition  of  solid  out-growths  (liver) ;  others,  again,  are  solid  from 
the  very  first,  continue  to  grow  in  this  condition,  and  only  secondarily 
come  to  possess  cavities  (cutaneous  glands,  racemose  glands).  The 
nutrition  of  the  glands  goes  on  with  great  energy,  and  they  belong  to 
the  most  vascular  organs  of  the  body.  Except  in  the  uterine  glands 
no  regeneration  of  the  glandular  substance  takes  place,  but  hypertrophy 
occurs  in  them,  and  even  the  accidental  formation  of  minute  glands. 

The  true  glands  of  the  human  body  may,  according  to  the  form  of 
their  ultimate  elements,  above  described,  be  divided  as  follows  : — 

1.  Glands  with  closed  glandular  vesicles,  which  dehisce  periodically. 
Ovary,  follicles  of  the  uterus. 

2.  Crlands  whose  parenchyma  consists  of  cells  united  into  a  network. 
Liver. 

3.  Racemose  glands,   in  which  rounded    and   elongated   glandular 
vesicles  are  seated  upon  the  ultimate  ends  of  the  excretory  ducts. 

a.  Simple,  with  one  or  few  glandular  lobules.     Mucous  glands,  seba- 
ceous glands,  Meibomian  glands. 

b.  Composite,  with  many  glandular  lobules.     Lachrymal  glands,  sali- 
vary glands,  pancreas,  prostate,  Cowper's  and  Bartholini's  glands,  lac- 
teal glands,  lungs. 

4.  Tubular  glands,   whose   secreting   elements   have   the   form   of 
canals. 

a.  Simple,  consisting  of  only  one  or  a  few  cgecal  tubes.   .  Tubular 
glands  of  the  stomach  and  intestine,  uterine  glands,  sudoriparous  and 
ceruminous  glands. 

b.  Composite,  with  many  branched  glandular  canals,  which  may  also 
be  united  into  a  network.     Testis,  kidney. 

The  forms  of  the  glands  of  animals,  notwithstanding  their  variety, 
may,  with  few  exceptions,  be  brought  under  one  of  the  four  categories 
here  established.  The  following  are  worthy  of  particular  notice  :  1. 
The  glandular  cells,  with  peculiar  excretory  ducts,  to  be  found  in  some 
Articulata,  which  either,  singly,  form  glands,  or  are  united  together 
in  numbers  by  a  membrana  propria.  2.  The  occurrence  of  a  structure- 
less, chitinous  membrana  intima  in  many  glands  of  the  Articulata.  3. 


116  GENERAL    ANATOMY    OF    THE    TISSUES. 

The  formation  of  certain  secretions  [  Uric  acid  and  bilin  in  Mollusks, 
bilin  in  Crustacea]  within  special  spontaneously  enlarging  "  secreting 
vesicles,"  (Nageli,  H.  Meckel),  which  may  be  compared  to  the  yelk 
vesicles  (§  6).  4.  The  colossal  size  (up  to  0-1  of  a  line)  of  many  glan- 
dular cells  of  Insects,  and  the  peculiar  ramifications  of  their  nuclei. 

Literature. — J.  Miiller,  "  De  Glandularum  secernentium  structural 
penitiori,"  Lips.  1830;  H.  Meckel,  "  Micrographie  einiger  Drlisenappa- 
rateniederer  Thiere,"in  Mull.  "Arch.,"  1846;  Fr.  Leydig's  "Verglei- 
chend-anatomische  Abhandlungen,"  in  "Zeitschrift  fur  wiss.  Zool." 

§  30.  Tissue  of  the  Blood-vascular  G-lands. — Under  this  denomination 
are  most  appropriately  comprised,  a  series  of  organs,  which  agree  in  this, 
that  in  a  peculiar  glandular  structure,  they  elaborate  from  the  blood  or 
other  juices  certain  substances  which  are  not  excreted  by  special,  per- 
manent, or  periodically-formed  excretory  ducts,  but  simply  by  infiltra- 
tion from  the  tissue,  and  are  afterwards  applied  in  one  way  or  another 
to  the  general  purposes  of  the  organism. 

It  may  be,  that  this  wide  definition  includes  organs,  which  it  will  be 
necessary  to  separate  in  future ;  but  with  our  present  slight  knowledge 
of  these  structures,  it  is  the  only  one  which  is  possible  without  entering 
more  fully  into  the  subject. 

The  essential  glandular  tissue  of  the  organs  in  question  appears  under 
the  following  forms  : — 

1.  As  a  parenchyma  of  larger  and  smaller  cells,  imbedded  in  a  stroma 
of  connective  tissue.     Supra-renal  bodies,  anterior  lobes  of  the  hypo- 
physis cerebri.     Some  of  the  cells  here  attain  the  great  size  of  0*04  of 
a  line ;  and  then  contain,  together  with  a  granular  substance,  many 
nuclei,  and  perhaps  secondary  cells. 

2.  As  closed  follicles,  each  of  which  consists  of  a  membrana  propria 
with  an  epithelium  upon  its  inner  side,  and  has  clear  contents:  thyroidea. 
The  follicles,  which  are  not  enlarged  cells,  are  surrounded  by  a  large 
quantity  of  connective  tissue,  and  are  united  by  it  into  smaller  and 
larger  lobules. 

3.  As  closed  follicles,  with  a  membrane  of  connective  tissue,  and  con- 
tents consisting  of  nuclei,  cells  and  some  fluid.     Among  these  I  enume- 
rate— 

a.  The  solitary  follicles  of  the  stomach  and  intestine  ;  and 

b.  The  aggregated  follicles  of  the  small  intestine,  or  Peyer's  patches 
(in  animals  those  of  the  stomach  and  large  intestine  also),  both  of  which 
contain  numerous  bloodvessels  in  the  interior  of  the  follicles. 

c.  The  follicular  glands  in  the  root  of  the  tongue,  the  tonsils,  and 
the  pharyngeal  follicles,  which  in  the  walls  of  their  sacs,  contain  many 


TISSUES,     ORGANS,    AND    SYSTEMS. 


117 


closed  follicles  like  those  above  mentioned,  but,  so  far  as  we  as  yet 
know,  without  vessels  in  their  interior. 


Fig.  43. 


Fie.  44. 


d.  The  lymphatic  glands,  which  appear  to  consist  of  follicles  like 
those  of  the  Peyerian  patches. 

4.  As  a  cellular  parenchyma,  which  contains  numerous  closed  follicles 
like  those  just  described:  Spleen. 

5.  As  racemose,  aggregated,  glandular  vesicles  opening  into  a  common 
closed  canal  or  broad  space,  whose  thick  walls  are  formed  of  a  delicate 
investment  of  connective  tissue,  and  of  a  soft  substance  consisting  of 
many  nuclei  and  of  vessels  :  Thymus. 

We  know  little  of  the  chemical  nature  of  these  organs,  which  are  all 
more  or  less  richly  supplied  with  bloodvessels.  Those  enumerated 
under  1,  2,  3,  and  5,  contain  much  protein  and  fat  in  their  tissue,  as 
also  do  the  follicles  of  those  included  under  the  fourth  form,  while  the 
remaining  parenchyma  of  the  spleen  possesses  peculiar  corpuscles,  not 
yet  completely  investigated,  which  seem  to  indicate  an  energetic,  retro- 
gressive metamorphosis.  We  know  little  of  the  physiological  functions 
of  these  glands ;  and  here  it  need  merely  be  remarked,  that  in  the 
spleen,  the  thyroid,  the  thymus,  the  supra-renal  capsules,  and  the  pitui- 
tary body,  it  can  only  be  the  blood  which  yields  material  to  them,  and 
only  the  blood-  and  lymph-vessels  which  again  receive  the  substances 
given  off  externally  or  internally  (thymus)  by  them.  In  the  follicular 
glands  of  the  mouth  and  pharynx,  the  secretions  are  poured  into  the 
wider  cavities  of  the  glands,  and  ultimately  into  those  organs,  whilst  in 

FIG.  43. — A  few  of  the  glandular  vesicles  from  the  thyroid  gland  of  a  child:  a,  connective 
tissue  between  them  ;  6,  membrane  of  the  glandular  vesicles ;  c,  their  epithelium — Magni- 
fied 250  diameters. 

FIG.  44. — A  Malpighian  corpuscle  from  the  spleen  of  the  ox :  a,  wall  of  the  corpuscle  ;  6, 
contents;  c,  wall  of  the  artery  upon  which  it  is  seated  ;  d,  sheath  of  the  latter. — Magnified 
150  diameters. 


118  GENERAL    ANATOMY    OF    THE    TISSUES. 

the  intestinal  follicles,  it  is  doubtful  whether  they  excrete  substances 
into  the  intestine,  or  receive  them  from  thence  to  give  them  up  again  to 
the  vessels.  In  the  lymphatic  glands,  the  ducts  supply  the  glandular 
follicles  with  matters  which  they  take  up  again  when  further  elaborated. 

The  development  of  the  blood-vascular  glands  is  still  very  obscure ; 
although  this  much  appears  certain,  that  most  of  them  are  developed 
without  the  participation  of  the  intestinal  epithelium,  either  from  the 
fibrous  wall  of  the  intestine  or  from  the  same  blastema  as  that  which 
produces  the  sexual  glands.  The  thymus  and  thyroid  alone  are  to  be 
regarded,  according  to  Remak,  as  diverticula  of  the  intestinal  canal. 

The  nutrition  of  most  of  these  glandular  structures  is  very  energetic, 
as  the  abundance  of  the  blood  they  contain  and  their  frequent  morbid 
alterations  show:  the  hypophysis  cerebri  and  the  supra-renal  capsules 
alone,  in  this  respect,  occupy  a  lower  grade. 

Literature. — A.  Ecker,  art.  "Blood-vascular  Glands,"  in  "Wagner's 
Handw.  d.  Phys.,"  Bd.  IV.  1849.  [H.  Gray,  "  On  the  Development  of 
the  Ductless  Glands  in  the  Chick,"  Philosoph.  Trans.,  1852.— TRS.] 


SPECIAL  HISTOLOGY. 


OF  THE  EXTERNAL  INTEGUMENT. 


Fig.  45. 


._— -c 


I.— OF  T^E  SKIN  IN  THE  STRICTER  SENSE. 

A.  CUTIS. 

§  31.  The  external  skin,  Integumentum  commune  (Fig.  45),  consists 
essentially  of  an  internal 
layer  formed  principally 
of  connective  tissue,  and 
rich  in  vessels  and 
nerves,  the  true  skin, 
cutis,  derma  (Fig.  45, 
c,  d) ;  and  of  an  external 
layer  composed  of  cells 
only,  the  epidermis  (Fig. 
45,  a,  b) ;  and  it  contains 
in  addition  many  pecu- 
liar, glandular  and  horny 
organs. 

The  cutis  may  be 
again  subdivided  into 
two  layers,  the  subcu- 
taneous cellular  tissue, 
tela  cellulosa  subcutanea 
(Fig.  45,  d);  and  the 
proper  corium  (Fig.  45, 
c) ;  the  latter  of  which,  from  its  rich  nervous  and  vascular  supply,  forms 
the*  most  important  part  of  the  skin. 

§  32.  The  subcutaneous  cellular  tissue  is  a  tolerably  firm  membrane, 
constituted  chiefly  of  connective  tissue,  which  in  by  far  the  most  parts 

FIG.  45. — Perpendicular  section  through  the  whole  skin  of  the  ball  of  the  thumb,  trans- 
versely through  three  ridges  of  the  cutis:  a,  horny  layer  of  the  epidermis;  b,  its  mucous 
layer ;  e,  corium  ;  rf,  panniculus  adiposus  (upper  part)  ;  e,  papillse  of  the  cutis  ;  /,  fat  masses  ;  g, 
sudoriparous  glands;  A,  their  canals;  i,  sweat-pores. — Magnified  20  diameters. 


120  SPECIAL     HISTOLOGY. 

of  the  body  encloses  within  its  meshes  a  considerable  quantity  of  fat-cells 
(Fig.  45,  /),  thus  forming  the  pannieulus  adiposus  ;  in  some  situations, 
however,  as  for  example  in  the  scrotum,  the  penis,  and  the  nympJice,  &c., 
it  contains  but  little  or  even  no  fat.  The  innermost  layer  of  the  subcu- 
taneous cellular  tissue,  which  upon  the  trunk  and  thighs  forms  a  tolera- 
bly firm  fatless  texture,  the  fascia  superficialis,  rests  upon  different 
organs,  as  muscular  fascia?,  periosteum,  and  pericJiondrium,  muscles, 
and  the  deeper  accumulations  of  fat,  and  is  more  or  less  closely  united 
with  them.  The  union  is  looser  upon  the  trunk,  the  two  distal  divisions 
of  the  limbs,  the  back  of  the  hand  and  foot,  the  neck,  and  especially  on 
the  eyelids ;  the  penis,  scrotum,  and  on  the  extensor  side  of  the  articu- 
lations, where  the  subcutaneous  mucous  lursce,  as  they  are  called,  are 
frequently  situated,  as,  for  instance,  in  the  knee,  elbow,  and  phalangeal 
joints.  A  more  close  connection  sometimes  exists — as  where  tendinous 
fibres  or  processes  (aponeurosis  palmaris  and  plantaris,  linea  alba),  or 
muscles  (palmaris  brevis,  levator  labii  superioris  alceque  nasi,  levator 
labii  superioris,  &c.),  are  inserted  into  the  skin ;  sometimes, — as  where 
the  innermost  layers  of  the  subcutaneous  cellular  tissue  are  blended,  as 
it  were,  by  means  of  short,  strong,  filaments  of  connective  tissue  with 
the  subjacent  muscle,  fascia?,  tendons,  &c.,  particularly,  therefore,  on  the 
head,  especially  on  the  alee  nasi  and  lips,  the  forehead  and  temples,  the 
ear,  mouth,  and  occiput ;  on  the  glans  penis,  beneath  the  nails,  &c.  In 
general,  where  the  fat  forms  a  thick  layer,  the  skin  is  less  movable  than 
when  from  any  cause  it  is  less  abundant  or  entirely  absent. 

The  external  surface  of  the  subcutaneous  cellular  tissue,  is  connected 
by  means  of  numerous  filamentary  processes  of  connective  tissue,  with 
the  corium,  arid  is  not  everywhere  clearly  distinct  from  it ;  but  a  sepa- 
ration between  the  subcutaneous  cellular  tissue  and  the  corium  may  be 
pretty  readily  effected,  especially  when  the  former  contains  an  abun- 
dance of  fat,  with  the  exception  of  certain  situations  (head,  cheeks,  chin, 
&c.),  where  the  follicles  of  the  larger  and  more  closely  set  hairs  pene- 
trate deeply  into  the  pannieulus  adiposus.  The  subcutaneous  cellular 
tissue  of  the  penis,  scrotum  (dartos),  &c.,  passes  into  the  corium  without 
any  distinct  limitation. 

The  thickness  of  the  subcutaneous  cellular  tissue  varies  very  con- 
siderably, as  is  well  known,  according  to  situation,  age,  sex,  and  the 
individual.  The  fatless  subcutaneous  cellular  tissue  of  the  eyelids,  and 
of  the  upper  and  outer  part  of  the  ear,  measures,  according  to  Krause 
J,  on  the  penis  J,  on  the  scrotum  f  of  a  line.  The  pannieulus  adiposus 
is  1  line  thick  on  the  cranium,  brow,  nose,  lobe  of  the  ear,  neck,  dorsum 
of  the  hand  and  foot,  the  knee  and  elbow ;  in  most  other  situations  it  is 
2  to  6  lines,  though  in  fat  persons  it  may  exceed  1  inch  in  thickness, 
and  in  thin  ones  may  sink  below  1  line. 

§  33.  The  proper  corium  is  a  tough,  slightly- elastic  membrane,  and  is 


OF    THE    SKIN.  121 

composed  principally  of  connective  tissue,  which  in  the  thicker  parts 
presents  two,  though  not  very  well-defined  layers,  which  may  be  desig- 
nated the  "reticular"  and  the  "  papillary"  portions  (p.  reticularis  and  p. 
papillaris).  The  former  constitutes  the  inner  layer  of  the  corium,  and 
consists  of  a  white,  reticulated  membrane,  frequently  distinctly  lami- 
nated in  its  deeper  portions,  and  containing  in  special,  narrow  or  wide, 
scanty  or  numerous  meshes,  the  hair  follicles  and  cutaneous  glands, 
together  with  much  fat.  The  papillary  part  of  the  corium  is  the  reddish- 
gray  external  superficial  layer  (Fig.  45),  which  in  its  dense,  firm  tissue, 
contains  the  upper  portion  of  the  hair-follicles,  and  cutaneous  glands, 
and  the  terminal  expansions  of  the  vessels  and  nerves  of  the  skin.  Its 
most  important  element  consists  in  the  cutaneous  or  tactile  papillae, 
papillce  tactus  (Fig.  46) ;  small,  semi-transparent,  flexible,  but  tolerably 
solid  elevations  of  the  external  surface  of  the  corium,  which  are  ordi- 
narily conical  or  clavate  in  form,  but  in  certain  places  present  numerous 
points  (compound  papillce).  With  regard  to  their  number  and  position, 
the  papillce  of  the  bed  of  the  nail,  of  the  palm  of  the  hand,  and  of 
the  sole  of  the  foot  are  very  numerous  (E.  H.  Weber  enumerates 
upon  1  square  line  of  the  vola  manus,  81  compound  or  150  to  200 

Fig.  46.  Fig.  47. 

MBA~~^  r,-<    F: /v:-"\      A  /T)  An 

rKh  fVr\.$  wJ HI 

s- 


.jULmKjL 

smaller  papillce),  and  disposed  with 
tolerable  regularity  in  two  principal 
series,  each  of  which  has  2  to  5  papillae 
in  the  transverse  direction,  placed  upon 
linear  elevations,  TV  to  J  of  a  line  broad, 
by  0*0  to  J  of  a  line  high, — the  ridges  of 
the  corium.  The  course  of  these  ridges 
is  visible,  even  externally  in  the  epidermis, 


FIG.  46. — Compound  papillse  of  the  surface  of  the  hand,  with  two,  three,  and  four 
points :  a,  base  of  a  papilla ;  b  6,  their  separate  processes ;  c  c,  processes  of  papillae  whose  base 
is  not  visible. — Magnified  60  diameters. 

FIG.  47. — Horizontal  section  of  the  skin  of  the  heel  through  the  apices  of  the  papillae  of  one 
entire  and  two  half  ridges.  The  serial  arrangement  of  the  papillae  corresponding  with  the 
ridges  of  the  cutis,  is  obvious,  a,  Horny  layer  of  the  epidermis  between  the  ridges,  which 
from  their  undulating  course  are  cut  through  in  making  a  section  through  the  points  of  the 
papillae.  6,  Stratum  Malpighii  of  the  epidermis,  c,  Papillae  which  are  placed  in  more  than 
two  rows;  since,  however,  many  of  them  are  always  seated  upon  a  common  base,  there  are, 
so  to  say,  only  two  rows  of  compound  papillae  present,  rf,  Stratum  Malpighii  between  the 
papilla;  belonging  to  a  common  base,  which,  because  it  has  a  less  thickness  here,  appears 
somewhat  clearer,  e,  Sweat  canals. — Magnified  60  diameters. 


122 


SPECIAL     HISTOLOGY. 


and  therefore  needs  no  further  description.  Elsewhere  the  papillae  are 
more  irregularly  scattered,  either  very  close  together,  as  in  the  labia 
minora,  the  clitoris,  the  penis,  and  the  nipple,  or  somewhat  more  widely 
apart,  as  upon  the  extremities,  with  the  exception  of  the  places  named, 
on  the  scrotum,  the  neck,  chest,  abdomen,  and  back. 

The  size  of  the  papillae  varies  considerably ;  the  shortest  (J$  to  4*0, 
of  a  line)  occur  in  the  face,  especially  upon  the  eyelids,  brow,  nose, 
cheeks,  and  chin,  where  they  are  even  wholly  wanting,  or  are  replaced  by 
a  network  of  depressed  ridges ;  next  upon  the  female  breast  (g1^  to  g^), 
upon  the  scrotum,  and  at  the  base  of  the  penis  (^  to  ^  of  a  line).  In 
most  other  situations  their  length  is  from  -J2  to  -^  of  a  line.  The 
longest,  (33  to  3*3  of  a  line)  exist  on  the  surface  of  the  palm  of  the 
hand,  sole  of  the  foot,  and  the  nipple,  where  they  are  generally  of  the 
compound  kind ;  further,  the  anterior  and  posterior  extremities  of  the 
bed  of  the  nail  (y^  to  j^),  and  the  labia  minora  (^  to  ^  of  a  line). 
The  breadth  of  the  base  in  most  of  the  papillae  about  equals  or  is  some- 
what less  than  the  length  ;  in  a  few,  as  in  those  of  the  scrotum,  prepuce, 
and  root  of  the  penis,  it  even  exceeds  the  length  by  J  or  more,  whence 
these  papillae  exactly  resemble  warts,  or  even  short  ridges ;  in  the 
longest  papillae,  lastly,  the  breadth  is  J  to  J  the  length. 

The  thickness  of  the  corium  varies  from  J  to  1 J  of  a  line,  and  in  most 
places  is  about  J  to  f  of  a  line.  It  is  the  thinnest  (J  to  J  of  a  line)  in 
the  meatus  auditorius  externus,  in  the  eyelids,  the  red  border  of  the  lip, 
the  glans  penis,  and  clitoridis',  and  thickest  (J  to  1  line)  on  the  back, 
chin,  upper  and  lower  lip,  (the  hairy  part),  the  alee  nasi,  upon  the  ball 
of  the  sole,  the  extremity  of  the  great  toe,  the  scapula,  and  the  nates  ; 
on  the  heel,  1  to  1J  lines. 

The  principal  chemical  characters  of  the  corium  agree  with  those  of 

the  connective  tissues,  of  which  it  is 
principally  constituted.  It  putrefies 
with  difficulty,  and  not  at  all  when 
tanned;  it  may  be  easily  dried, 
and  then  becomes  yellowish,  trans- 
parent, and  hard,  but  flexible  and  no 
longer  subject  to  putrefaction.  In 
boiling  water,  it  at  first  shrinks, 
eventually  however  dissolving,  but 
not  with  equal  facility  in  all  animals, 
and  in  the  young,  more  quickly  than 
in  the  old,  into  gelatine,  colla ;  and 
the  same  change  is  effected  at  the 

FIG.  48. — Two  papillae  of  the  surface  of  the  hand,  from  a  slightly  macerated  skin  ;  magni- 
fied 350  diameters,  a,  Wavy,  remarkably  distinct  fibrils  of  connective  tissue;  b,  Transverse 
elastic  fibrils  lying  in  the  axis  of  a  papilla  and  transverse  nuclei,  axile  corpuscles,  the  corpus- 
cula  tactus  of  R.  Wagner  (see  §  37) ;  of  nerves  no  trace  is  to  be  seen  without  reagents. 


Fiar.  48. 


OF    THE    SKIN. 


123 


ordinary   temperatures,    when    it    is    treated   with    dilute    acids  and 
alkalies. 


§  34.  The  corium  is  principally  composed  of  connective  and  elastic 
tissue,  containing  in  addition,  smooth  muscles,  fat-cells,  bloodvessels, 
nerves,  and  lymphatics,  in  great  abundance. 

The  connective  tissue  consists  of  the  ordinary  bundles,  which  are  in 
part  united  into  a  network,  as  in  the  subcutaneous  cellular  tissue  ;  in  part 
into  large  secondary  bundles,  trabeculce  and  lamince,  which,  in  the  pan- 
niculus  adiposus,  circumscribe  larger  and  smaller  spaces  filled  with  fat ; 
whilst  in  the  fascia  superficial,  and  in  the  cerium,  their  connection  is 
very  intimate,  and  they  form,  especially  in  the  latter,  a  very  dense  tissue, 
with  indications  of  lamination.  In  the  papillce  the  fibrous  structure  is 
not  everywhere  distinct,  and  instead  of  it  there  often  exists  a  more 
homogeneous  tissue,*  which  frequently  appears  to  be  bounded  by  a 

Fig.  49. 


structureless  membrane,  which,  however,  does  not  admit  of  being  actually 
isolated. 

The  bursce  mucosce  subcutanece  are  nothing  but  larger,  simple,  or  par- 
tially subdivided  reticular  spaces  in  the  subcutaneous  cellular  tissue,  in 

FIG.  49. — ^,  Elastic  fibres  from  the  inner  part  of  the/asaa  lata  of  man,  closely  interwoven, 
and  appearing  like  an  elastic  membrane;  magnified  450  diameters.  JB,  An  elastic  fibre 
with  a  serrated  edge,  such  as  may  also  be  seen  occasionally  in  the  cutis. 

*  [The  most  superficial  layer  of  the  cutis  is  invariably  composed  of  a  transparent  matrix, 
homogeneous  or  nearly  so,  in  which  nuclei  are  imbedded.  The  "  indications  of  lamination" 
are  simply  the  commencement  of  the  breaking  up  of  this  tissue  into  areolated  connective 
tissue,  such  as  we  have  already  described ;  see  note,  p.  83. — TRS.] 


124  SPECIAL    HISTOLOGY. 

the  fascia  superficial^  (bursa  olecranii),  or  between  the  larainse  of  the 
fascia  muscularis  (bursa  patella*).  The  internal  walls,  smooth  but  un- 
even, are  formed  of  common  connective  tissue,  possess  no  epithelium, 
and  include  a  somewhat  viscid,  clear  fluid. 

The  elastic  tissue  exists  abundantly  in  almost  all  parts  of  the  cutis  ; 
but,  in  general,  far  more  sparingly  than  the  connective  tissue.  More 
rarely  it  occurs  in  the  form  of  true  elastic  membranes,  which  may  even 
resemble  the  densest  elastic  networks  of  the  arteries,  as  in  the  fascia 
superficialis  of  the  abdomen  and  thigh  ;  while  more  commonly  it  repre- 
sents a  loose  reticulation  of  coarser  or  finer  fibres,  as  in  the  corium. 
The  papillce  (but  not  all),  and  the  panniculus  adiposus,  in  which  they 
are  sometimes  wholly  wanting,  contain  only  fine  elastic  (nucleus)  fibre. 

1.  Smooth  muscles,  according  to  my  observations,  occur  far  more  exten- 
sively in  the  skin  than  has  hitherto  been  supposed,  arid  particularly  in 
the  subcutaneous  cellular  tissue  of  the  scrotum,  or  the  tunica  dartos, 
which  has  thence  received  the  name  of  u  muscular  membrane"  (Fleisch- 
haut),  and  of  the  penis,  including  the  prepuce  and  the  anterior  part 
of  its  body,  where  they  run  in   the  form  of  yellow  bundles  (whose  ele- 
ments are  figured  in  §  26),  measuring  J  to  J  a  line,  partly  contiguous 
to  the  vessels  and  nerves,  partly  more  isolated  in  the  connective  tissue  ; 
they  are  sometimes  converted  into  a  network,  but  are  more  usually  dis- 
posed parallel  to    the  raphe  of  the  scrotum  and  the  longitudinal  axis 
of  the  penis,  though,  more  particularly  in  the  latter  situation,  they  not 
unfrequently  form  large  transverse  bundles. 

2.  In  the  areola  of  the  nipple,  the  smooth  muscles,  which  are  especially 
well  developed  in  the  female,  are  disposed  circularly  in  a  delicate  layer, 
which  becomes  thicker  internally  towards  the-  base  of  the  nipple,  and 
are,  for  the  most  part,  visible  to  the  naked  eye,  on   account   of  their 
yellowish  red  color,  and  the  thickness  of  their  bundles  (up  to  J  of  a  line) ; 
in  the  nipple  itself  they  run  in  part  circularly,  in  part  perpendicularly, 
and  are  united  into  a  close  network,  through  whose  meshes  the  excretory 
ducts  of  the  lacteal  glands  pass. 

3.  Lastly,  smooth  muscles  are   also  found  in  the  superficial  portions 
of  the  corium,  and  in  fact  in  all  situations  where  hairs  occur,  in  the 
form  of  flat  bundles,  0*1— 0*16  of  a  line  broad,  which,  singly  or  in  pairs, 
are  invariably  placed  near  the  upper  part  of  the  hair-follicles  and  seba- 
ceous glands.*     They  arise,  probably,  from  the  superficial  part  of  the 
corium,  and  running  obliquely  from  without  inwards,  towards  the  hair- 
follicles,  surround  the  sebaceous  glands,  and  are  inserted  close  behind 
and  near  the  base  of  those  glands  into  the  hair-follicles. 

Quite  recently  Eylandt  and  Henle  have  added  to  our  knowledge  of 
the  smooth  muscles  of  the  skin.     The  existence  of  the  little  muscles  of 

*  [Smooth  muscular  fibres  have  also  been  found  in  the  scalp.     See  note  p.  104. — DaC.] 


OF    THE     SKIN.  125 

the  hair-follicles,  termed  by  Eylandt,  arrectores  pili,  has  been  confirmed 
by  both  writers,  only  that  they  find  them  to  be  more  delicate  (Eylandt 
0-02,  Henle  0-04  of  a  line).  Eylandt  never  noticed  more  than  one 
bundle  passing  to  a  hair-follicle,  and  Henle  states  that  they  subdivide 
upwards  into  many  bundles  of  0-004  of  a  line,  and  may  be  traced  im- 
mediately under  the  epidermis  as  far  as  the  papillae.  In  the  scrotum, 
in  the  skin  of  the  penis,  the  perinceum,  the  areola  mammce,  and  in  the 
nipple,  Eylandt  could  not  find  smooth  muscles ;  and  he  imagines  that  I 
have  confounded  the  circular  muscles  of  the  vessels  with  them,  a  sup- 
position which  I  should  not  have  allowed  myself  to  entertain  even 
against  a  beginner.  Henle  has  seen  the  smooth  muscles  in  all  these 
situations,  which  it  is,  in  fact,  very  easy  to  do,  though  I  think  that  he 
goes  to  the  other  extreme  in  assuming  the  existence  of  smooth  muscular 
fasciculi  in  the  hairless  portions  of  the  skin  also,  in  the  sudoriparous 
glands,  and  in  the  vascular  ramuscules  (on  their  exterior),  and,  I  believe, 
that  in  these  cases,  he  has  been  misled  by  fine  nervous  twigs,  which,  as 
he  himself  states,  may  readily  be  confounded  with  smooth  muscles,  in 
the  boiled  preparations  which  he  employed. 

§  35.  Fat-cells. — These  cells  are  especially  developed  in  the  pannicu- 
lus  adiposus.  In  this  situation  the  fat-cells  do  not  form  large  conti- 
nuous expansions,  but  occupy,  in  larger  or  smaller  clusters,  the  variously 
formed  meshes  of  the  connective  tissue  (Fig.  45/).  Each  of  the  yellow 
clusters,  or  fat-lobules,  which  appear  to  the  naked  eye  clearly  defined, 
has  a  special  coating  of  connective  tissue,  in  which  the  vessels  intended 
for  the  nutrition  of  the  fat-cells  are  distributed,  and  consists  either  of 
a  simple  aggregation  of  cells,  or  of  a  number,  varying  according  to  its 
size,  of  smaller  and  smallest  lobules,  each  of  which  again  has  its  proper 
delicate  investment  of  connective  tissue.  According  to  Todd  and  Bow- 
man, every  cell  even,  has  its  own  special  covering  and  vessels ;  but  this 

though    true    in    many  Fig<  51> 

cases,  is  certainly  not  so 

in  all.     In   the   corium 

the   fat-cells  are   found 

more  in  the  deeper  part  l>- 

round  the    hair-follicles 

and    sebaceous    glands, 

while   they   are   wholly 
wanting  in  the  pars  papillaris.     In  persons  in  tole- 

FiG.  50. — Normal  fat-cells  from  the  breast ;  magnified  350  diameters:  a,  without  reagents; 
6,  after  being  treated  with  ether,  whereby  the  fat  is  exhausted,  and  the  folded  delicate 
membrane  remains. 

FIG.  51. — Fat-cells  with  crystals  of  margarin 5  magnified  350  diameters:  a,  cell  with  a 
star  of  crystalline  needles,  as  they  maybe  found  not  uncommonly  in  normal  fat;  b,  cell  quite 
filled  with  crystals,  from  the  white  fat-lobules  of  an  emaciated  subject. 


126  SPECIAL    HISTOLOGY. 

rably  good  condition,  the  fat-cells  are  always  rounded  or  oval,  0-01-0-06  of 
a  line  in  diameter,  with  a  dark  border,  filled  with  fluid,  pale  yellow  fat, 
which  forms  a  single  drop — and  with  a  parietal  nucleus  which  is  not 
readily  rendered  visible  (Fig.  50).  In  emaciated  subjects,  on  the  other 
hand,  hardly  any  cells  of  this  kind  are  met  with,  but  instead,  more 
or  less  abnormal  forms :  1.  Crranular  cells,  with  numerous  small  fat- 
drops,  forming  whitish-yellow  clustered  lobules  ;  2.  Fat-cells  containing 
serum,  in  yellow  or  reddish-brown  minute  lobular  masses,  which,  to- 
gether with  the  fat  (which  has  become  more  or  less  diminished  in  quan- 
tity, and  usually  appears  as  a  single  dark-colored  globule),  contain  a 
clear  fluid  and  a  distinct  nucleus,  and  are  considerably  smaller  than 
the  normal  cells,  0-01-0-015  of  a  line;  3.  Cells  which  contain  no  fat, 
but  only  serum,  with  a  distinct  nucleus,  and  having  a  delicate  or 
thickened  membrane  ;  they  occur  in  more  gelatinous  fatty  tissue,  or 
mingled  with  the  others  ;  they  are  also  met  with  in  oedema;  4.  Lastly, 
Fat-cells  containing  crystals,  either  presenting  1  to  4  stars  of  acicular 
crystals  (margarin),  together  with  a  drop  of  fat,  or  being  completely 
filled  with  crystalline  needles.  The  former  occur  among  our  normal 
cells,  the  latter  only  in  the  white,  more  isolated,  fat-lobules. 

The  nuclei  in  the  fat-cells  of  the  adult  have  not,  as  far  as  I  am  aware, 
yet  been  observed,  excepting  by  Bendz  (Almind.  "Anat."  p.  122,  tab. 
I.  fig.  4),  who  rarely,  very  rarely,  noticed  even  two  pale  nuclei  with 
nucleoli.  It  is  true  that  Mulder  (p.  601),  states  that  they  are  furnished 
with  one,  rarely  with  two,  nuclei,  but  Bonders  and  Moleschott  (ib.,  p. 
602,  et  seq.},  upon  whom  Mulder  appears  principally  to  rely,  expressly 
say  that  they  did  not  detect  the  nuclei;  nor  does  Bonders  (in  the  "Hol- 
land. Beitr.,"  I.  pp.  57,  61),  say  anything  about  nuclei.  I  invariably 
find  them  when  the  fat  has  partially  disappeared  from  the  cell.  In  cells 
completely  filled,  I  first  distinctly  noticed  them,  in  some  cases  in  the 
marrow,  and  in  the  fat-cells  in  the  muscles;  but  I  do  not  hesitate  in  the 
least  to  affirm  their  constant  occurrence  in  all  fat-cells,  since  no  one  can 
suppose  that  they  are  not  formed  until  after  the  disappearance  of  the 
fatty  contents.  With  respect  to  what  Donders  and  Moleschott  observe, 
as  to  the  existence  of  two  membranes  in  the  fat-cells,  the  outer  of  which 
is  said  to  be  soluble  in  concentrated  acetic  acid,  and  in  potass,  and  the 
inner  not;  the  former,  as  Donders  himself  elsewhere  supposes,  can  be 
regarded  merely  as  connective  tissue,  which,  in  many  instances,  also 
penetrates  between  the  separate  cells  and  connects  them  together,  or,  pro- 
bably, is  occasionally  replaced  by  a  homogeneous  connective  substance 
(modified  cytoblastema).  The  crystals  in  the  fat-cells  are  considered  by 
Vogel  to  be  margarin.  As  the  forms  of  margarin  and  margaric  acid 
are  very  similar,  the  question  can  be  decided  only  on  chemical  grounds, 
and  these  appear  to  favor  the  latter. 


OF     THE     SKIN.  127 

The  pathological  conditions  of  the  fat-cells,  although  as  yet  but  little 
investigated,  corroborate  my  assertion  of  the  constant  occurrence  of  the 
nucleus.  Without  relying  upon  Schwann's  observation,  that  the  fat- 
cells  of  the  subcutaneous  cellular  tissue  of  a  rachitic  child  a  year  old,  all 
contained  a  nucleus,  I  would  more  particularly  adduce  the  condition  of 
the  fat-cells  in  cutaneous  dropsy.  In  this  affection,  as  long  as  the  fat 
in  the  panniculus  adiposus  has  not  entirely  disappeared,  cells  containing 
serum,  and  but  a  small  quantity  of  fat,  are  extremely  abundant,  and 
exactly  of  the  same  form  as  those  which  are  found  in  emaciated  subjects, 
all  with  distinct  nuclei ;  and,  besides  these,  there  are  numerous  cells  con- 
taining nothing  but  serum  and  also  nucleated.  In  cases  where  the  fat 
may  be  said  to  have  altogether  disappeared,  and  the  colorless  subcuta- 
neous cellular  tissue  is  infiltrated  throughout  with  water,  I  find  the  last- 
mentioned  cells  in  greatly  preponderating  quantity,  and  associated  with 
them,  others  of  peculiar  form.  In  the  first  place,  fusiform  or  stellate 
cells,  with  from  three  to  five  irregular,  oftea  tolerably  long  processes, 
with  a  distinct  nucleus,  and  mostly  only  scanty  and  minute  dark  fat- 
granules  ;  these,  as  the  very  numerous  and  various  transitionary  forms 
indicate,  being  developed  from  diminished  cells  containing  serum,  and 
from  which  the  fat  has  been  partially  or  wholly  removed  ;  secondly, 
roundish  or  elongated  minute  cells  (0-003-0-006  of  a  line)  closely  filled 
with  dark  granules,  and  without  a  visible  nucleus,  which,  as  is  also 
easy  to  be  perceived,  owe  their  origin  to  a  diminution  of  the  fat-cells 
coincident  with  a  change  in  their  contents,  and,  on  the  other  hand,  are 
metamorphosed  into  the  cellules  with  little  or  no  fat,  and  containing 
serum,  with  which  they  are  found  associated.  I  may  also  mention  that, 
in  the  inflamed  medulla  in  the  articular  ends  of  the  bones,  as,  according 
to  Hasse,  appears  to  be  the  case  in  rheumatism,  I  have  seen  the  com- 
mon fat  cells  transformed  into  round  and  even  fusiform  cells,  contain- 
ing serum  and  little  fat,  and  occasionally  furnished  with  nuclei.  (From 
Kolliker,  "Mikrosk.  Anat.,"  Vol.  II.  p.  18.) 

§  36.  Vessels  of  the  Skin. — In  the  subcutaneous  cellular  tissue  the 
arteries  entering  the  skin  give  off  many  branches  to  the  hair-follicles 
(see  below),  the  fat-lobules  and  the  smooth  muscles,  which,  for  the  most 
part,  form  wide-rneshed  networks  of  fine  capillaries;  more  rarely,  par- 
ticularly in  the  fat-lobules,  the  network  is  closer.  More  externally  they 
supply  the  sudoriparous  and  sebaceous  glands  (see  below),  and  also  form 
terminal  expansions  in  the  inner  part  of  the  corium  (pars  reticularis), 
but  not  many  :  finally,  they  penetrate  into  the  outermost  part  of  the 
papillary  layer,  and  into  the  papillce  themselves,  where  they  terminate 
in  a  close  network  of  capillaries  with  narrow  meshes.  This  consists, 
wherever  there  are  papillce,  of  two  portions  ;  firstly,  of  a  horizontal 


128 


SPECIAL    HISTOLOGY. 


plexus  lying  immediately  under  the  surface   covered  by  the  epidermis, 
and  which  is  composed  of  larger  vessels  (of  O'Ol— 0*005  of  a  line)  with 


Fig.  52. 


53- 


wide,  and  of  capillaries  (of  0-003-0-005  of  aline)  with  narrow  meshes  ;  and 

secondly,  of  very  many  separate 
loops  of  the  finest  vessels  (0-003 
—  0'004  of  a  line)  which  are  given 
off  to  the  papillce.  With  cer- 
tain exceptions  (v.  §  37)  every 
papilla  possesses  its  own  capil- 
lary loop  (Fig.  53),.  (the  branched 
papillce  have  many),  which  runs 
either'  in  the  axis  of  the  papilla 
or  near  the  surface,  almost  as 
far  as  its  apex. 

The  larger  trunks  of  the  lym- 
phatic vessels  are  very  easily  recognizable  in  the  subcutaneous  cellular 
tissue,  and  are  very  numerous.  In  the  corium  itself  different  anatomists, 
Hasse,  Lauth,  Fohmann,  &c.,  have  demonstrated  the  lymphatics  by  in- 
jecting them  with  quicksilver.  All  agree  in  this,  that  they  form  an  ex- 
cessively close  network  of  fine  vessels  in  its  outermost  part,  —  according 
to  Krause  (1.  c.,  p.  Ill)  of  j5-^o  of  a  line  in  diameter;  the  meshes  of 
which  become  wider  internally,  and  finally  open  by  single  trunks  into 
the  vessels  of  the  subcutaneous  cellular  tissue.  However,  it  is  not  by 
any  means  known,  whether  the  vessels  composing  these  plexuses  are 
really  the  true  commencement  of  the  cutaneous  lymphatics. 

FIG.  52.  —  Vessels  of  the  fat-cells.  J$.  Vessels  of  a  small  fat  lobule  ;  a,  artery  ;  b,  vein. 
JB.  Three  fat-cells  with  their  capillaries  more  magnified  :  after  Todd  and  Bowman.  Magni- 
fied 100  diameters. 

FiG.  53.  —  Vessels  of  \\iepapillce  of  one  entire  and  two  half  ridges  of  the  cutis  5  after  Berres. 


OF    THE    SKIN. 


129 


§  37.  Nerves. — The  skin,  in  those  parts  of  it  which  border  upon  the 
epidermis,  particularly  in  some  localities,  is  one  of  the  structures  most 
richly  provided  with  nerves  in  the  human  organism,  whilst  in  its  deeper 
parts  it  is  remarkable  for  their  scantiness.  In  the  panniculus  adiposus, 
and  in  the  fascia  superficialis,  as  yet,  no  nerves  are  known  besides  those, 
which,  giving  off  a  succession  of  branches,  traverse  those  parts  to  reach 
the  corium,  or  to  supply  the  hair-glands,  smooth  muscles,  and  Pacinian 
corpuscles,  of  which  we  shall  speak  further  on.  In  the  corium  itself, 
the  trunks  which  enter  through  the  meshes  of  the  deeper  layers  ascend 
by  degrees,  continually  ramify-  Fig.  54. 

ing,  but  without  actually  form- 
ing, terminal  expansions,  to- 
wards the  pars  papillaris.  Here 
they  anastomose  frequently,  and 
form  rich  terminal  plexuses,  in 
which  deeper  and  more  superfi- 
cial portions  may  be  clearly  dis- 
tinguished, the  former  consist- 
ing of  fine  branches  still  con- 
taining many  primitive  tubules, 
with  wide  meshes  ;  the  second 
of  fibres  single  or  united  in  pairs, 
with  narrow  meshes.  In  this  last  or  the  fine  terminal  plexus,  there  also 
occur  (whether  in  all  the  fibres  is  as  yet  undecided)  in  man  and  in  ani- 
mals actual  divisions  of  the  primitive  tubules,  so  that  they  divide,  gene- 
rally at  an  acute  angle,  into  two ;  and  from  the  plexus  itself,  the  tubules 
finally  enter  the  base  of  the  papilla?  in  pairs,  in  order  to  run  to  their 
extremities,  and  there  unite  in  a  loop. 

The  elements  of  the  nerves  of  the  skin  exhibit  no  striking  peculi- 
arities ;  the  diameter  of  some,  in  the  trunks  in  the  subcutaneous  cellular 
tissue,  is  still  as  much  as  0-005-0-006  of  a  line,  and  also  in  the  deepest 
part  of  the  corium,  whilst  they  become  finer  and  finer  outwards.  In 
the  terminal  plexus  I  find  they  vary  according  to  the  locality,  from 
0-003  to  0-0016,  in  the  papilla  from  0-0008-0-002  of  a  line.  In  the 
hand  and  foot  the  finest  tubules  vary  between  0-0012-0-002  of  a  line; 
in  the  glans  penis,  in  the  lips  and  nose,  on  the  other  hand,  only  from, 
0-0008-0-0012  of  a  line. 

R.  Wagner  has  recently  published  some  statements  ("Allg.  Zeitung," 
Jan.,  Feb.,  1852;  "Getting.  Nachricht,"  Feb.,  1852),  according  to- 

FIG.  54. — Two  papilla  from  the  extremities  of  the  fingers,  without  epithelium  and  with 
axile  corpuscles,  a,  and  nerves,  b.  A.  Simple  papilla,  with  four  nerve-fibres  and  two  termi- 
nal loops,  c.  B.  Compound  papilla,  with  two  vascular  points  with  capillary  loops,  d;  and 
one  nervous  point  with  a  terminal  loop,  e. 

9 


130  SPECIAL    HISTOLOGY. 

which  the  relations  of  the  nerves  of  the  skin  have  hitherto  been  entirely 
misconceived.  From  the  investigations  of  G.  Meissner  and  himself, 
which  were  instituted  upon  the  nerves  of  the  palm  of  the  hand,  Wagner 
divides  the  papillce  into  nervous  and  vascular.  The  former  are  said  to 
contain  a  peculiar  oval  corpuscle  in  their  axis,  which  consists  of  super- 
imposed saccular  or  band-like  laminae,  resembling  a  fir-cone,  and  this 
structure  is  regarded  by  Wagner,  as  a  peculiar  sensory  apparatus,  and 
named  by  him  "  tactile  corpuscle"  (corpusculum  tactus).  Into  these 
the  nerves — 1  to  3  fine  dark-bordered  tubules — are  said  to  enter  from 
below,  or  from  the  side,  and  to  terminate  within  them,  either  free,  or 
perhaps  divided  into  many  delicate  branches.  Wagner  found  these 
corpuscles  to  be  most  abundant  in  the  points  of  the  fingers,  and  that 
they  were  more  and  more  rare  towards  the  wrist.  I  have  considered 
it  requisite  to  investigate  these  assertions,  which  are  made  with  much 
confidence,  particularly  as  Wagner  grounds  upon  them  great  expecta- 
tions of  the  physiology  of  the  sense  of  touch,  and  the  following  are  the 
results  at  which  I  have  arrived. 

Independently  of  the  vessels  and  nerves,  the  papillae  consist,  in  the 
main,  of  a  sometimes  more  homogeneous,  sometimes  more  distinctly 
fibrillated  collagenous  substance,  which  there  is  no  reason  to  distinguish 
from  connective  tissue,  and  of  fine  elastic  fibres  in  different  stages  of 
development,  as  fusiform  cells  (corpuscles  of  the  connective  tissue,  of 
Virchow),  cell  networks,  isolated  fine  elastic  fibres  and  fibrous  networks. 
These  elements  are  so  distributed,  that  in  most  papillce  a  cortical  layer 
and  an  axile  tract  can  be  distinguished.  In  the  former  the  fibrous 
elements  are  disposed  longitudinally,  and  the  connective  tissue  is  often 
distinctly  fibrillated,  with  the  exception  of  the  most  superficial  layer, 
which  forms  a  clear,  homogeneous  but  not  separable  margin.  In  the 
latter,  on  the  other  hand,  the  substance  is  more  uniform  and  clear,  and 
in  many  places  is  separated  from  the  outer  layer  by  transverse  elastic 
fibres.  When  these  latter,  true  elastic  fibres,  are  not  very  closely  dis- 
posed, no  one  would  be  led  to  consider  that  there  is  anything  peculiar 
in  this  arrangement ;  but  undeveloped  and  very  close  together,  as  they 
are  in  Wagner's  corpuscle,  it  is  otherwise.  These  are,  in  fact  nothing 
but  the  clear  axis  marked  by  transverse  nuclei  and  nucleated  fibres, 
which  I  have  already  described ;  and,  if  no  reagents  be  added,  they  pre- 
sent no  other  appearance  than  that  which  I  have  figured  in  my  "Micro- 
scopic Anatomy,"  Fig.  4,  or  in  Fig.  48  of  this  work. 

Dilute  solution  of  soda,  of  which  almost  solely  I  have  availed  myself 
in  investigating  the  course  of  the  nerves  in  the  papillae,  often  does  not 
render  their  contour  at  all  more  distinct,  and  I  therefore  paid  no  fur- 
ther attention  to  their  structure  ;  while,  on  the  Other  hand,  acetic  acid, 
which  was  also  employed  by  Wagner  and  Meissner,  brings  out  the  axes 
of  the  papillae  generally,  though  not  always,  as  oval,  or  cylindrical, 


OF    THE    SKIN.  131 

more  sharply-defined  bodies,  to  which  the  numerous  transverse  striae 
give  a  certain  vague  similarity  to  a  fir-cone  (Fig.  54).  In  its  more  inti- 
mate structure,  such  an  "  axile  corpuscle,"  as  I  call  it,  does  not  con- 
sist of  superimposed  discs,  as  Wagner  supposes,  but  of  an  internal  mass 
of  homogeneous  connective  tissue,  which  is  most  distinct  in  transverse 
sections,  and  when  viewed  from  above  ;  and  of  an  external  generally 
single  layer  of  undeveloped  elastic  tissue,  which,  in  the  form  of  fusi- 
form cells  probably  connected  together  and,  more  or  less,  drawn  out 
into  fine  fibres,  with  shorter  or  longer  nuclei  (these  last  were  also  seen 
by  Wagner),  closely  surrounds  the  internal  substance  in  which  here 
and  there  similar  corpuscles  also  appear  to  be  contained.  Morphologi- 
cally, then,  such  a  corpuscle  is  by  no  means  peculiarly  constructed,  but 
resembles  the  axis  of  certain  other  papillae  (e.  g.  of  the  sole  of  the  foot), 
which  are  surrounded  by  true  elastic  fibres,  particularly  their  often  less- 
developed  summits ;  it  is  very  similar,  again,  to  the  bundles  of  connec- 
tive tissue,  with  elastic  fibres  wound  round  them,  such  as  are  found  in 
the  corium;  indeed,  the  difference  consists  principally  in  this,  that  the 
axis-corpuscles  contain  more  undeveloped  elastic  tissue  ;  a  circumstance 
easily  comprehensible,  since  the  papillce,  as  compared  with  the  cutis 
itself,  consist  altogether  of  a  tissue  which  is  in  a  more  embryonic  state. 
With  regard  to  their  occurrence,  axile  corpuscles  of  the  kind  here  de- 
scribed occur  only  in  certain  papillae ;  arid,  in  fact,  so  far  as  my  inves- 
tigations hitherto  extend,  only  in  those  of  the  palm  and  surface  of  the 
hand,  the  red  edges  of  the  lips,  and  the  tip  of  the  tongue,  not  in  those 
of  the  toes,  thorax,  back,  glans  penis,  nymphse,  and  only  rarely  in  those 
of  the  back  of  the  hand  and  of  the  sole  of  the  foot.*  In  the  hand  they 

*  [I  have  recently  succeeded  in  detecting  these  tactile  corpuscles  in  the  toes.  They  cor- 
respond exactly  to  the  tactile  corpuscles,  as  described  by  Wagner  and  Kolliker  in  other 
parts,  only  they  were  far  less  numerous  than  on  the  palm  of  the  hand,  or  on  the  edges 
of  the  lip.  I  first  discovered  them  in  the  papillae  of  the  toe  of  an  infant,  and  have  twice 
since  verified  my  observation.  Their  minute  structure  apparently  consisted  of  superim- 
posed discs,  such  as  described  by  Wagner.  They  may  be  most  conveniently  studied  in  fine 
transverse  or  perpendicular  sections,  which  have  been  treated  with  acetic  acid,  or  a  dilute 
solution  of  soda. 

The  nature  of  these  so-called  "tactile"'  or  "axile"  corpuscles  is  as  yet  a  matter  of  dispute. 
Most  recent  observers  seem  to  entertain  regarding  them  the  same  views  as  Kolliker  (see 
Mr.  Dalzell's,  in  the  Edinburgh  "Monthly  Journal  of  Medical  Science,"  March,  1853;  also 
Mr.  Huxley,  "Quart.  Journal  of  Micr.  Sc.,"  Oct.  1853,  and  in  Appendix  to  this  work)  ;  yet 
Wagner,  (in  his  reply  to  Kolliker,  in  "Miiller's  Archiv.  1852,'')  and  more  recently  Meissner, 
("Beitrage  Zur  Anatomic  und  Physiologie  der  Haut,"  Leipsig,1853)  add  additional  observa- 
tions in  confirmation  of  the  nature  of  these  "corpuscula  tactus"  as  first  described  by  them. 
Meissner  has  presented  us  with  some  very  interesting  researches  on  the  relative  frequency 
of  their  occurrence  in  the  papillae  in  different  parts  of  the  body.  Thus  he  found  on  a  sur- 
face of  7  lines  in  length  on  the  lips  and  apex  of  the  tongue,  only  4  or  5  ;  on  one  square 
line  comprising  400  papillae  of  the  last  joint  of  the  index  finger,  108,  but  only  40  on  the 
second  joint,  18  on  the  first.  In  the  papillae  at  the  root  of  the  tongue,  he  was  not  able  to 
discover  any  of  these  bodies. 

The  tactile  corpuscles  are  probably  surrounded  by  a  special  membrane,  since  they  can 
be  isolated.  They  have  as  yet  only  been  observed  in  Man,  and  in  the  Ape. — DaC.] 


132  SPECIAL    HISTOLOGY. 

appear  especially  in  the  compound  papilla,  in  particular  cusps,  one  or 
two  together,  which  may  project  more  or  less,  and  are  sometimes  shorter, 
frequently  longer  ;  they  occur  more  rarely  in  the  simple  papillae,  as 
oval  or  cylindrical  bodies,  occupying  J  to  f-  the  width  of  the  summits  of 
the  papillae,  and  \  to  J,  or  as  much  as  f  the  length.  In  the  points  of 
the  fingers,  they  occur  in  the  proportion  of  1  to  every  2-4  papillce ; 
in  the  first  phalanx,  on  the  other  hand,  in  the  length  of  1  line,  only 
2-6  are  to  be  found,  and  in  the  palm  they  are  still  more  rare.  Fre- 
quently the  axile  corpuscles  exhibit  local  constrictions,  especially  after 
the  addition  of  acetic  acid,  are  even  spirally  contorted,  so  tlfat  they 
often  have  a  certain  similarity  to  a  bundle  of  connective  tissue  treated  in 
the  same  way,  or  with  a  spiral  sudoriparous  duct.  Upon  the  back  of 
the  fingers  and  in  the  heel  there  appeared,  in  many  individuals  to  be 
no  axile  corpuscles  in  the  papillae  ;  in  a  small  number,  however,  they 
were  to  be  found  even  here,  but  scattered  and  small,  in  a  few  papillae. 
In  the  lips,  I  saw  in  two  individuals  axile  corpuscles  similar  to  those 
in  the  hand  ;  in  one  they  were  wanting.  They  existed  only  in  that  part 
of  the  red  margin  of  the  lip,  which  is  visible  when  the  mouth  is  closed ; 
they  were  very  minute,  and  were  placed  partly  in  small  projecting  points 
of  the  larger  papillae,  partly  in  depressions  between  two  of  their  pro- 
cesses. In  the  tongue,  in  which,  according  to  Wagner,  something 
similar  to  his  corpuscles  appears  to  exist,  I  met,  in  two  cases,  with  no 
axile  corpuscles ;  whilst,  in  a  third,  I  found  them  tolerably  well  deve- 
loped in  the  papillce  fung if ormes  of  the  point  of  the  tongue  (whether 
they  are  to  be  found  in  the  posterior  ones  I  know  not),  whilst  they  were 
wanting  in  the  p.  filif ormes  and  p.  circumvallatw.  In  the  p.  fungif or- 
mes, one  or  many  were  situated  in  the  point  of  the  principal  papilla, 
without  extending  into  its  simple  processes,  and  therefore  lay,  as  it 
were,  at  the  bottom  of  a  terminal  pit,  surrounded  by  the  simple  papillae. 
With  regard  to  the  course  of  the  nerves  of  the  skin,  Wagner  confirms 
the  fact  discovered  by  me,  that  even  in  man,  the  primitive  tubules  divide 
in  the  terminal  plexuses  (which  I  have  recently  also  observed  in  the 
hand,  the  lips,  and  the  tongue) ;  and  he  further  states  that,  in  the 
palm  at  least,  only  those  papillae  contain  nerves  which  possess  the  axile 
corpuscles,  while  they  have  no  vessels.  As  regards  the  latter  impor- 
tant circumstance,  all  those  who  have  occupied  themselves  more  parti- 
cularly with  the  investigation  of  the  skin,  must  be  aware  that  nerves 
are  not  to  be  found  in  all  the  papillae ;  but  seeing  the  difficulty  of  dis- 
covering the  nerves  in  a  dense  organ  like  the  skin,  no  one  has  thought 
it  requisite  on  this  account  to  depart  from  the  old  notion  that  every 
papilla  contains  a  nerve,  and  is  therefore  a  tactile  process.  Wagner 
having  observed  the  sharply-defined  axile  corpuscles  of  the  hand,  ap- 
pears to  have  been  surprised  that  they  occurred  only  in  certain  papillae, 
and  that  these  had  nerves  ;  and  struck  with  this  circumstance,  adopted 


OF    THE    SKIN.  133 

the  view  referred  to.  As  for  myself,  having  again  made  long-continued 
investigations  into  the  skin  of  the  palm  of  the  hand,  I  find  that  those 
points  of  the  papillae,  or  those  independent  papilla,  which  contain  axile 
corpuscles,  do  generally  exhibit  dark-bordered  nerve-tubules  very  dis- 
tinctly ;  but  from  this  I  should,  for  the  present  at  any  rate,  by  no  means  be 
led  to  conclude  that  the  other  papillae  contain  no  nerves,  but  only  vessels. 

If  it  be  considered  that  dark-bordered  nerve-tubules,  though  indeed 
rarely  in  proportion,  are  contained  in  vascular  papillae  without  axile 
corpuscles,  in  the  hand ;  furthermore  that  in  other  places,  as  in  the  sole 
of  the  foot  and  the  lips,  such  papillae  are  found  ;*and  finally,  that  the 
investigation  of  the  cutaneous  nerves  is  very  difficult,  it  seems  more 
judicious  to  suspend  one's  judgment  upon  this  question,  especially  as  it 
is  possible,  that  pale,  non-medullated,  nerve-tubules,  similar  to  those 
which  I  discovered  in  the  skin  of  the  Mouse,  exist  in  man  also.  How- 
ever, I  am  by  no  means  disinclined  to  agree  with  Wagner  this  far, 
that  in  the  palm  it  is  almost  exclusively  the  papillae  with  axile  corpuscles 
which  contain  dark-bordered  nerves,  for  to  say  the  least,  it  is  very  re- 
markable that  in  these  papillae  the  nerves  are  so  readily  and  satisfac- 
torily displayed.  As  to  the  possible  existence  of  non-medullated  fibres 
in  the  papillae  without  axile  corpuscles,  it  is  certainly  too  soon  to  express 
any  definite  opinion.  With  regard  to  the  vessels,  it  is  incorrect,  uncon- 
ditionally to  deny  their  existence  in  those  papillae  which  contain  nerves. 
In  the  compound  papillae  it  is  unquestionably  true,  that  the  cusps  with 
axile  corpuscles  and  nerves  frequently  contain  no  vessels ;  at  other  times, 
however,  even  these  contain  a  capillary  loop,  and  this  is  still  more  fre- 
quently the  case  in  the  simple  papillae  with  nerves.  In  the  lip,  the 
papillae  containing  nerves,  whether  they  possess  axile  corpuscles  or  not 
contain  vessels  for  the  most  part,  if  not  always,  and  there  are  rela- 
tively very  few  papillae  in  which  no  nerves  are  visible.  The  tongue  pos- 
sesses vessels  and  nerves  in  all  the  larger  papillae  ;  on  the  other  hand, 
I  have  as  yet  been  unable  to  discover  nerves  in  the  simple  papillae 
buried  in  the  epithelium.  It  is  yet  to  be  ascertained  how  the  nerves  are  dis- 
posed in  other  parts  of  the  skin.  It  is  surprising  to  me,  that  even  in  the 
sole  of  the  foot,  dark-bordered  nerve-tubules  can  so  rarely  be  perceived 
in  the  papillae,  while  in  many  situations  they  cannot  be  found  at  all. 

Further  investigations  are  required  to  determine  to  what  extent  dark- 
bordered  nerves  are  distributed  in  the  papillae  of  the  skin ;  whether, 
perhaps,  non-medullated  fibres  occur  instead  of  them ;  or  whether,  in 
certain  situations,  the  nerves  do  not  enter  the  papillae  at  all,  but  end  in, 
the  well-known  superficial  plexus  at  their  base. 

With  respect  to  the  dark-bordered  nerves  in  the  papillae  of  the  hand, 
Wagner  is  wrong  in  asserting  that  the  nervous  loops  which  I  have 
figured  are  bloodvessels.  He  has  only  imperfectly  seen  the  nerves  of  the 
papillae  in  question,  perhaps  on  account  of  his  having  preferred  the  use 
of  caustic  soda,  which  more  easily  destroys  them.  Latterly,  in  making 


134  SPECIAL    HISTOLOGY. 

very  delicate  investigations,  I  have  used  only  acetic  acid,  and  have 
arrived  at  the  following  results: — Each  point  of  a  papillae,  or  each 
papilla  with  an  axile  corpuscle,  generally  contains  two,  or  as  frequently 
happens  at  the  points  of  the  fingers  four,  dark-bordered  tubules,  which, 
surrounded  by  a  neurilemma*  which  has  escaped  previous  observers, 
pass  upwards  through  the  axis  of  the  papilla  to  reach  the  base  of  the 
axile  corpuscle,  as  a  fine,  convoluted  nervous  twig  of  0-006--012  of  a  line 
in  thickness.  Here  the  nerve  frequently  becomes  invisible,  so  that,  as  has 
happened  to  Wagner,  one  may  be  led  to  believe  that  it  enters  the  cor- 
puscle, which  is  seatetl  upon  it,  as  upon  a  stalk,  and  there  ends.  How- 
ever, if  a  number  of  fresh  preparations  be  treated  with  acetic  acid  and 
examined,  the  conviction  is  soon  arrived  at  that  this  is  merely  apparent, 
the  nervous  tubules  in  reality  proceeding  along  the  outer  surface  of  the 
corpuscle,  either  as  far  as  its  point,  or  very  nearly  so.  In  the  mean- 
while they  either  remain  together  or  take  an  isolated  course.  In  both 
cases  their  neurilemma  becomes  excessively  delicate,  appearing  finally 
to  vanish  entirely,  while  the  nerves  themselves  surround  the  axile  cor- 
puscle, passing  round  it  either  more  directly,  though  in  a  slightly  undu- 
lating course,  or  forming  one  or  several  spiral  coils  (Fig.  54,  B}.  As 
regards  the  actual  termination  of  the  nervous  tubules,  I  retain  the  opi- 
nion I  formerly  expressed,  inasmuch  as,  in  at  least  six  cases,  I  have 
again  most  distinctly  seen  loops  (Fig.  54).  It  is,  however,  always  difficult 
to  observe  them,  and  very  frequently  impossible,  in  spite  of  every  exer- 
tion; and  therefore,  as  we  are  all  liable  to  error,  I  will  blame  no  one  for 
considering  the  termination  of  the  nerves  of  the  papillae  to  be  unknown, 
or  for  believing  in  the  existence  of  free  ends,  which  perhaps  also  exist, 
and,  at  any  rate,  very  frequently  appear  to  exist.  I  only  state  what, 
according  to  my  best  belief,  I  have  seen ;  and  while  I  have  no  prejudice 
in  favor  of  loops,  neither  can  I  see  anything  alarming  in  their  existence. 
This  much,  however,  is  certain,  that  Wagner  has  not  traced  the  nerves 
in  the  papillae  so  far  as  they  may  be  traced,  and  therefore,  at  present 
at  all  events,  can  lay  no  claim  to  a  decisive  voice  in  the  matter.  How 
the  nerves  in  the  papillae  of  the  lips,  tongue,  and  elsewhere,  are  disposed, 
I  have  not  yet  ascertained  with  certainty ;  but  with  regard  to  the  first 
of  these,  I  believe  I  can  also  affirm,  that  they  do  not  terminate  in  the 
axile  corpuscles,  but  either  merely  pass  by  them  or  wind"  round  them. 
In  the  lips,  in  a  single  instance,  I  found  well-marked  nerve-coils  in  small 
papillae,  or  at  the  base  of  the  large  ones. 

§  38.  Development  of  the  Outis. — The  following  may  be  taken  as  a 

*  [It  is  by  no  means  easy  to  recognize  this  nenrilemma.  Indeed,  even  its  existence  is  ques- 
tioned by  Meissner,  who  states  that  after  the  most  careful  observation,  he  has  not  been  able  to 
detect  a  neurilemma  in  one  single  instance.  The  nerve  itself  he  thinks  does  not  terminate  in 
loops,  as  supposed  by  Kolliker,  but  penetrates  into  the  tactile  corpuscles.  The  cross-striae 
considered  by  Kolliker  as  elastic  tissue,  he  justly  describes  as  the  termination  of  the  dark- 
bordered  nerve-tubules,  for  the  action  of  soda  on  them  proves  them  to  be  such. — DaC.] 


OF    THE    SKIN.  135 

general  sketch  of  the  development  in  the  foetus,  of  the  cutis  in  the 
broadest  sense  of  the  term.  It  consists  at  first  of  cells,  which  though 
not  in  man,  yet  in  animals  (the  Frog,  for  instance)  may  be  easily  traced 
back  to  the  earliest  formative  cells  of  the  embryo.  A  considerable  pro- 
portion of  these  cells  are  changed  into  connective  tissue,  becoming  fusi- 
form, coalescing,  and  eventually  being  converted  into  bundles  of  fibrils; 
a  process  which  appears  to  occur  first  in  the  fascia  superficialis,  the  sub- 
cutaneous connective  tissue,  then  in  the  pars  reticularis  of  the  corium, 
and  finally  in  the  papillary  layer.  Another  portion  of  the  cells  are 
converted  into  vessels  and  nerves,  as  can  be  seen  even  in  man,  and  very 
beautifully  in  the  Batrachia  (see  my  Memoir  in  the  "Annales  des 
Sciences  Naturelles,"  1846) ;  while  a  third,  growing  and  developing  fat 
in  its  interior,  becomes  elastic  fibres  and  fat-cells  (vide  supra,  §  23). 
The  first  foundations  of  all  these  parts  having  been  laid,  they  continue  to 
increase  in  a  manner  which  is  not  yet  exactly  made  out.  The  cutis  ob- 
viously grows  from  within  outwards  (so  that  the  papillae  arise  and  are 
developed  last  of  all),  partly  by  the  growth  of  its  primitive  elements, 
partly  at  the  expense  of  cells,  which  are  perhaps  mostly  of  new  forma- 
tion, and  do  not  proceed  from  the  original  formative  cells.  The  panni- 
culus  adiposus  also  increases,  partly  by  the  increase  of  the  cells  of  which 
it  at  first  consists,  partly  by  the  subsequent  development  of  others,  as 
well  as  of  connective  tissue  and  vessels.  In  this  manner,  the  skin  grows 
for  a  long  time  after  birth.  In  children  below  seven  years  of  age,  for 
example,  the  cutis  is,  according  to  Krause,  only  half  as  thick  as  in  the 
adult,  until  at  last,  though  at  a  time  which  is  yet  undetermined,  the  new 
development  of  cells  ceases,  as  at  a  later  period,  perhaps,  does  the  ex- 
tension of  those  elements,  cells,  fibres,  &c.,  which  are  already  formed. 
The  fat-cells  of  adults,  in  which  the  process  of  growth  is  especially  ob- 
vious, according  to  Harting,  are  in  the  orbit  twice,  in  the  palm  three 
times  as  large  as  in  the  new-born  infant ;  whence  it  results  that  they  in- 
crease in  size  in  proportion  to  the  parts  of  the  body  to  which  they  belong. 

In  embryos  of  two  months  the  skin  is  0'006-0*01  of  a  line  thick, 
and  wholly  composed  of  cells.  At  the  third  month  it  is  about  0-06  of 
a  line,  and  already  presents  tolerably  distinct  connective  tissue.  In  the 
fourth  month  the  first  lobules  of  fat  appear,  and  the  ridges  of  the  hand 
and  sole  of  the  foot.  From  the  seventh  month  onwards  the  panniculus 
adiposus  is  rapidly  developed,  and  at  birth  it  is  relatively  thicker  than 
in  the  adult. 

§  39.  Physiological  Remarks. — If  we  attempt  to  harmonise  the  ana- 
tomical data  here  brought  together,  with  the  phenomena  of  sensation 
exhibited  by  the  skin,  we  meet  with  considerable  difficulties.  The  more 
intimate  anatomy  of  the  skin,  as  it  is  here  detailed,  fails  to  demonstrate 
nerves  in  all  the  papillae,  or  even  in  the  majority  of  them ;  and  yet  ex- 


136  SPECIAL    HISTOLOGY. 

periment  teaches  that  though  all  points  of  the  skin  may  not  feel  with 
the  same  delicacy,  they  are  all  nevertheless  sensitive.  I  hoped  to  be 
able  to  submit  Wagner's  doctrine  of  the  absence  of  nerves  in  many 
papillae  to  experimental  proof,  by  examining  the  sensitiveness  of  various 
parts  of  the  body  with  the  finest  possible  English  sewing  needle.  At 
first  I  really  thought  that  I  had  found  some  places  which  were  quite  in- 
sensible, whilst  in  others  the  slightest  touch  produced  sensation ;  bat  on 
carrying  the  investigation  further,  it  appeared  that  the  very  same  place 
was  often  sometimes  sensible,  sometimes  not ;  so  that,  finally,  I  came 
to  the  conclusion  that  the  very  smallest  portions  of  the  skin  are  sensitive. 
But  since  even  in  the  palm  of  the  hand  the  papillae  containing  nerves 
are  widely  dispersed,  and  in  other  places  occur  but  rarely,  or  even  not 
at  all,  it  only  remains  either  to  assume  the  existence  of  non-medullated 
nerve-fibres  in  all  the  papillae,  or  to  have  recourse  to  the  nervous  plexus 
at  the  base  of  the  papillae.  I  should  unhesitatingly  prefer  the  latter 
explanation,  were  it  not :  (1)  that  these  plexuses  are  in  many  places  so 
very  scanty,  and  (2)  that  the  slightest  touch  of  the  epidermis  produces 
sensation  ;  for  the  present,  therefore,  I  believe  this  must  remain  an  open 
question. 

If  we  are  not  in  a  condition  to  understand  how  it  is  that  every  point 
of  the  skin  is  sensitive,  still  less  are  we  competent  to  explain  the  different 
kinds  of  sensations.  In  this  respect  the  following  very  general  state- 
ment may  be  made. 

The  excitement  of  the  terminations  of  the  nerves  in  the  outermost 
parts  of  the  cutis  and  the  papillae  is  either  direct  or  indirect.  The 
former  as  it  is  produced,  for  example,  when  the  cutis  is  laid  bare,  by 
penetrating  instruments  and  by  fluids,  is  much  more  intense  than  that 
which  takes  place  through  the  mediation  of  the  epidermis,  one  of  the  func- 
tions of  the  latter  being  to  act  as  a  defence  against  too  violent  impressions, 
and  to  blunt  them  according  to  its  greater  or  less  thickness.  It  can  now 
be  partly  explained  on  anatomical  grounds,  why  the  delicacy  and  viva- 
city of  the  sense  of  touch  are  not  everywhere  equal,  why  they  are  less 
upon  the  hairy  scalp,  the  back,  the  two  upper  divisions  of  the  extremities, 
than  on  the  face,  on  the  genitalia,  the  hand  and  foot,  the  chest,  and  ab- 
domen. In  the  first  place,  where  the  tactile  sense  is  delicate,  the  epi- 
dermis is  in  itself  thin,  as  upon  the  eyelids  and  face,  or  has,  at  least  a 
thin  horny  layer,  as  upon  the  penis  and  clitoris,  whilst  upon  the  back 
and  extremities  it  is  considerably  thicker.  Yet  this  circumstance  is  not 
a  sufficient  explanation,  for  parts  with  a  thicker  epidermis,  as  the  palm  of 
the  hand  and  the  sole  of  the  foot  are  delicately  sensitive,  more  so,  in  fact 
than  others  with  a  thinner  covering,  as  the  back  of  the  hand  and  foot. 
Another  condition  must  here  obviously  come  into  play,  and  it  is,  I  think, 
that  the  skin  is  not  equally  well  provided  with  nerves  in  all  its  parts.  Sim- 
ple inspection  teaches  that  the  nerves  upon  the  palm  of  the  hand  and 


OP    THE    SKIN.  137 

the  sole  of  the  foot  are  more  numerous  than  upon  the  back  of  the  hand 
and  foot ;  upon  the  glans  penis  and  clitoridis,  the  nipple,  the  face,  they 
are  more  abundant  than  upon  the  abdomen,  back,  and  thigh,  &c.  &c.  ; 
and  this  is  to  some  extent  confirmed  bj  my  measurement  of  the  sensi- 
tive roots  of  the  spinal  nerves  (vide  "Mic.  Anat.,"  p.  433).  With  the 
number  of  the  nerves,  is  connected  that  of  the  actually  demonstrable 
dark-contoured  nerves  in  the  papillae  and  the  superficial  nervous  plexus, 
for  nowhere  is  this  more  considerable  than  in  the  points  of  the  fingers, 
the  lips,  the  tip  of  the  tongue,  and  the  glans  penis. 

As  to  the  local  sensibility  of  the  skin,  it  is  the  province  of  anatomy, 
especially,  to  afford  information,  with  regard  to  these  two  points  :  1, 
how  it  is  that  we  do  not  distinguish  with  the  same  clearness  and  exact- 
ness, in  all  parts  of  the  body,  the  point  at  which  a  single  irritation 
is  applied :  and  2,  why  two  stimuli  operating  at  the  same  time,  under 
certain  circumstances,  appear  double,  under  others  single  (Weber's 
experiment).  I  think  that  Weber's  experiment  cannot  be  explained  by 
the  mode  of  distribution  of  the  peripheral  nerves,  but  depends  very  pro- 
bably upon  their  central  relations.  It  seems  to  me  to  be  simplest  to  as- 
sume, that  every  peripheral  end  of  a  nerve  is  capable,  when  irritated,  of 
producing  a  conscious  sensation,  but  that,  on  account  of  the  small  num- 
ber of  nervous  fibres  (in  the  cerebrum)  which  unite  these  with  the  seat  of 
consciousness,  if  many  contiguous,  or  even  more  distant,  cutaneous  nerves 
are  excited,  only  a  single  conscious  sensation  results.  In  this  case,  the 
nerves  of  acutely  sensitive  parts  must  be  connected  with  the  seat  of  con- 
sciousness by  more  numerous  intermediate  fibres  than  those  of  other  locali- 
ties, and  at  the  ends  of  these  fibres,  also,  we  must  suppose  a  sort  of  inter- 
lacement to  take  place.  Upon  this  hypothesis,  the  former  of  the  two  points 
might  be  explained.  A  local  irritation  is,  indeed,  felt  locally ;  but,  accord- 
ing as  the  nerves  implicated  are  united  with  the  brain  by  more  or  fewer 
conductors  in  the  spinal  cord,  are  we  able  to  assign,  more  or  less  exactly, 
the  precise  spot ;  so  that,  in  some  cases  the  limits  of  error  will  not  exceed 
J-l  line,  while  in  others,  they  may  extend  to  1  or  1J  inch  and  more. 

E.  H.  Weber  has  endeavored  to  demonstrate,  in  his  last  able  Treatise 
upon  the  sense  of  touch,  that  it  is  only  the  termination  of  the  nerves  in 
the  skin,  not  the  fibres  in  the  nervous  trunks,  which  are  the  mediators 
of  the  sensations  of  pressure,  warmth,  and  cold ;  and  he  has  expressed 
a  supposition,  that  tactile  organs  as  yet  unknown  may  exist  in  the  skin. 
R.  Wagner  believes  that  he  has,  in  fact,  found  these  organs  in  his  so-called 
corpuscula  tacttis,  and  he  supposes  that,  composed  as  they  are,  accord- 
ing to  him,  of  superimposed  membranes,  in  the  interspaces  of  which  a 
very  minute  quantity  of  fluid  is  lodged,  like  elastic  cushions,  or  a  bladder 
filled  with  water,  they  are  specially  fitted  to  receive  impressions  from  the 
epidermis  at  the  extremity  which  is  directed  towards  it,  and  to  transmit 
them  to  the  ends  of  the  nerves  which  lie  in  and  upon  them. 

In  my  opinion,  Weber's  view  of  the  greater  sensibility  of  the  termi- 


138  SPECIAL    HISTOLOGY. 

nations  of  the  nerves  in  the  skin,  can  hardly  be  doubted ;  but,  on  the 
other  hand,  there  is  no  obvious  reason,  a  priori,  why  peculiar  hitherto 
unknown  organs  should  exist  to  that  end ;  nor  why  the  condition  to 
which  I  have  already  referred,  the  more  isolated  course  of  the  fibres  of 
the  nervous  tubules  in  the  papillae  and  terminal  plexuses,  their  fineness, 
superficial  position,  and  the  delicacy  or  absence  of  the  neurilemma,  may 
not  abundantly  suffice  as  an  explanation.  That  Wagner's  so-called  cor- 
puscula  tactus,  my  axile  corpuscles,  are  not  tactile  organs  in  the  sense 
intended  by  Weber,  is  easily  demonstrable.  Independently  of  the  erro- 
neousness  of  his  views  of  their  structure,  and  of  the  fact  that  the  nerves 
are  not  distributed  in  them,  but  only  proceed  along  them,  outside,  in 
order,  in  many  cases,  to  terminate  even  beyond  them — we  find  that  all 
the  essential  functions  of  the  skin  are  also  performed  without  such  cor- 
puscles. The  feeling  of  warmth  and  cold,  of  orgasm,  of  tickling,  of 
pressure,  of  pricking,  of  burning,  of  pain,  are  found  partly  over  the 
whole  surface  of  skin,  partly  in  places  where  these  corpuscles  are  cer- 
tainly absent,  which  sufficiently  shows  that  they  have  not  in  the  remotest 
degree  the  signification  ascribed  to  them  by  Wagner.  However,  it  is  not 
likely  that  they  exist  for  nothing  in  those  particular  localities,  in  which 
the  sensibility  to  pressure  is  the  greatest,  and  which  we  use  especially 
as  tactile  organs,  as  the  ends  of  the  fingers,  the  point  of  the  tongue,  and 
the  border  of  the  lips ;  and  I  consider  them  as  parts,  which  in  conse- 
quence of  their  being  composed  principally  of  dense,  imperfectly -formed 
elastic  tissue,  confer  a  certain  solidity  upon  the  points  of  the  papillse, 
and  serve  as  a  firm  support  for  the  nerves,  in  consequence  of  which,  a 
pressure,  which  in  other  situations  is  not  sufficient  to  affect  the  nerve, 
here  takes  effect.  They  would,  in  fact,  be  organs,  like  the  nails  and 
phalangeal  bones,  not  essential  and  indispensable  to  the  sense  of  touch, 
but  only  conferring  upon  it  a  greater  acuteness  than  elsewhere.  If,  in 
this  sense,  they  are  to  be  called  tactile  corpuscles,  I  have  nothing  to  say 
against  the  term,  but  then  the  phalanges  and  the  nails,  the  "  whiskers" 
of  animals,  &c.,  equally  deserve  the  name  of  tactile  organs. 

The  contractility  of  the  skin  is  exhibited  in  the  wrinkling  of  the 
scrotum  and  of  the  skin  of  the  penis,  the  erection  of  the  nipple,  and  the 
occurrence  of  the  so-called  cutis  anserina.  It  depends  upon  the  smooth 
muscles  of  the  skin  already  described,  which,  as  Froriep  and  subse- 
quently Brown-Sequard  and  I  have  found,  contract  by  electricity,  inas- 
much as  by  this  means,  even  in  the  living  subject,  the  cutis  anserina, 
the  erection  of  the  nipple,  and,  in  recently-executed  persons,  a  wrinkling 
of  the  scrotum  can  be  produced.  In  the  erection  of  the  nipple  by  gentle 
mechanical  irritation,  the  whole  areola  becomes  diminished  by  the  con- 
traction of  its  circular  fibres,  and  thus  protrudes  the  nipple  whose  mus- 
cular fibres,  in  this  case,  seem  to  be  relaxed.  Cold  causes  the  areola 
and  the  nipple  to  contract,  both  becoming  small  and  firm.  The  cutis 
anserina,  which  consists  in  wholly  local  contractions  of  the  portions  of 


OF    THE     SKIN. 


139 


the  skin  around  the  hair  sacs  by  which  their  apertures  are  protruded 
conically,  is  explained  simply  by  the  existence  of  the  muscles  which  I 
discovered,  and  which  pass  obliquely  from  the  superficial  part  of  the 
cutis  down  to  the  hair  sacs,  and  when  they  act,  extrude  the  sacs,  and 
retract  those  portions  of  the  skin  whence  they  arise.  The  assumption 
of  a  contractile  connective  tissue  in  the  skin,  as  well  as  in  other  parts, 
I  must  repudiate  here,  as  I  have  already  done  (Mittheil.  der  Zuricher 
Gresellschaft,  1847,  p.  27),  because  the  smooth  muscles,  which  can  be 
microscopically  demonstrated  in  the  skin,  and  whose  contraction  by 
galvanism  may  be  experimentally  shown,  sufficiently  account  for  all  the 
contractile  phenomena  which  it  exhibits. 

B.  EPIDERMIS. 

§  40.  The  corium  is  everywhere  covered  by  a  semitransparent  mem- 
brane formed  wholly  of  cells,  and  containing  neither  vessels  nor  nerves, 
— the  epidermis,  which  applies  itself  exactly  to  all  the  elevations  and 


-6' 


depressions,  and  which  accordingly  upon  its  inner  surface  presents  an 
exact  cast  of  the  outer  surface  of  the  corium^  the  convexities  and  con- 
cavities of  course  being  reversed.  Upon  its  outer  surface,  also,  the 
epidermis,  to  some  extent,  represents  the  form  of  the  corium  since  the 

FIG.  55^2. — Surface  of  the  palm,  from  within:  a,  ridge  answering  to  the  groove  between 
the  ridges  of  the  cutis ;  6,  a  similar  one  corresponding  with  the  cleft  between  the  rows  of 
papillae;  c,  sweat  ducts;  d,  broader  points  of  insertion  of  these  into  the  epidermis ;  e,  depres- 
sions for  the  simple  and  compound  papillae. 


140 


SPECIAL    HISTOLOGY. 


more  marked  elevations  and  depressions,  such  as  the  ridges  of  the  palm 
of  the  hand  and  of  the  sole  of  the  foot,  the  folds  at  the  joints,  muscular 
insertions,  &c.  are  expressed  in  it, — the  latter  even  more  strongly  ;  on 
the  other  hand,  the  papillae  produce  either  no  perceptible  projection,  or 
hardly  any. 

The  epidermis  consists  of  two  layers,  chemically  and  morphologically 
distinct,  and  which  are  separated  by  a  tolerably  sharp  line  of  demarca- 
tion, viz.,  the  mucous  layer  and  the  horny  layer. 

§  41.  The  mucous  layer,  stratum  Malpighii,  rete  or  mucus  Malpighii 
(rete  mucosum),  of  many  authors,  is  that  part  of  the  epidermis  which  lies 
immediately  upon  the  corium,  and  almost  everywhere  appears  undulated; 
in  many  places  it  is  distinguishable  even  to  the  naked  eye  by  its  color, 
which  is  whitish  or  variously  tinged  with  brown,  and  it  is  further  cha- 
racterized by  its  small,  soft,  easily  destroyed,  peculiarly  disposed  cells. 
Fig.  555.  The  form  of  these  cells  and  their  dispo- 

sition are  not  the  same  in  all  localities. 
The  innermost  of  them  (Fig.  55  5),  which, 
without  interspersed  free  nuclei  or  semi- 
fluid substance,  form  a  single  layer  resting 
immediately  upon  the  free  surface  of  the 
coriutn,  are  elongated,  and  not  unfre- 
quently  resemble  the  cells  of  cylinder- 
epithelium  ;  they  are  placed  perpendicu- 
larly upon  the  corium ;  their  length  is 
about  from  0-0033-0-006,  their  breadth 
0-0025-0-003  of  a  line.  Upon  these  im- 
mediately follow  in  most  places,  elongated 
or  even  round  cells  of  0-003-0-004  of  a 
line  in  many  layers ;  but  in  a  few  locali- 
ties, as  in  the  hand  and  foot,  at  the  free 

margin  of  the  eyelids,  in  the  mucous  layer  of  the  nails  and  hairs  (vide 
infra),  there  are  interposed  here  and  there,  between  the  rounded  and 
elongated  cells,  one,  two,  or  even  three  layers  of  similarly  elongated  and 
perpendicularly  disposed  elements,  so  that  the  mucous  layer,  on  account 
of  the  numerous  strata  of  perpendicular  cells,  has  a  striated  appearance 
in  its  deepest  part,  under  a  low  power.  This  character  is  the  more 
striking,  since  the  other  elements  of  the  mucous  layer,  the  further  they 
are  followed  from  the  first,  round  cells  outwards,  become  thinner  in 
another  direction,  i.  e.  become  horizontally  flattened  (Fig.  55  c),  and 
finally  in  the  uppermost  layers  are  transformed  into  thick  vesicles, 
0-006-0-016  of  a  line  broad,  and  0-002-0-008  of  a  line  thick.  At  the 

FIG.  555. — Perpendicular  section  of  the  skin  of  the  Negro  (from  the  leg),  a  a,  cutis- 
papillse;  b,  deepest  intensely-colored  layer  of  perpendicularly  elongated  cells  of  the  stratum 
mucosum;  c,  upper  layer  of  the  stratum  mucosum:  rf,  horny  layer. — Magnified  250  diameters. 


OF    THE    SKIN.  141 

same  time,  from  their  mutual  pressure,  they  acquire  a  polygonal  form 
which  may  even  be  recognized  in  isolated  cells. 

All  the  cells  of  the  mucous  layer  agree,  in  essential  points,  in  their 
structure,  and  are  nucleated  vesicles  distended  with  fluid.  Their  mem- 
brane is  pale,  often  difficult  of  demonstration  in  the  smallest,  frequently 
quite  distinct,  always  delicate,  thicker  in  the  larger  ones,  yet  by  no 
means  to  be  compared  to  that  of  the  cells  in  the  horny  layer.  The 
contents  are  never  quite  fluid ;  but  also,  excepting  in  the  colored  epi- 
dermis (vide  infra),  never  normally  contain  larger  particles,  granules  or 
fat-drops  for  example ;  but  are  finely  granulated,  with  more  or  less 
clearly-defined  granules,  wrhich  invariably  diminish  in  number  in  the 
more  external  cells.  The  nucleus,  lastly,  is  small  in  the  smallest  cells, 
(0-0015-0-0025  of  a  line),  in  the  large,  of  greater  size  (0-003-0-005  of 
a  line) ;  globular  or  lenticular  in  the  round  and  flattened  cells;  elongated 
in  the  elongated  cells.  In  the  larger  cells  it  appears  obviously  vesicular, 
often  with  a  nucleolus,  and  lies  centrally  in  the  midst  of  the  contents  ; 
in  the  smaller  it  is  apparently  more  homogeneous,  without  any  visible 
nucleolus,  and  so  disposed  that  it  is  not  unfrequently  in  contact  with 
one  part  or  other  of  the  cell-walls. 

[Most  authors  admit  the  existence  of  a  special  membrane  between 
the  cuticle  and  the  corium.  Krause  (loc.  cit.  p.  112)  describes  on  the 
upper  surface  of  the  corium  a  perfectly  transparent,  textureless,  semi- 
fluid, tough  mass  of  ^-J^th  to  -^50^  °f  a  ^ne  in  thickness,  which  he  be- 
lieves to  be  the  cytoblastema  of  the  epidermic  cells,  covered  by  a  layer 
of  free  nuclei  and  real  cells.  Henle  (loc.  cit.  p.  1010)  considers  the 
inferior  layer  of  the  cuticle  as  a  continuous  cytoblastema  with  inter- 
spersed nuclei,  and  calls  it  the  "intermediate  skin."  Such  free  nuclei 
are  admitted  by  Bruns  (loc.  cit.  p.  358),  by  Gunther  (loc.  cit.  p.  257),  by 
Hyrtl  (p.  379),  by  Hassall  (loc.  cit.  p.  242),  and  others,  whilst  Reichert 
(Miiller's  Archiv,  1845),  denies  their  occurrence,  and  also  that  of  the 
structureless  membrane  of  Krause.  Todd  and  Bowman  (loc.  cit.  p.  413, 
Fig.  84),  regard  the  lower  portion  of  the  epidermis  as  consisting  of  fully- 
developed  cells  (loc.  cit.  p.  404-411),  and  admit  as  the  external  border  of 
the  corium  a  simple  homogeneous  and  transparent  membrane,  "  basement 
membrane,"  which  view  Carpenter  seems  to  share.  My  own  observations 
lead  me  to  believe  with  Reichert,  that  the  lowest  layers  of  the  epidermis 
consist  of  fully-formed  cells,  as  may  be  easily  ascertained  in  most  cases 
by  the  addition  of  acetic  acid,  or  diluted  alkalies  to  fine  vertical  sections. 
We  are,  therefore,  not  justified  in  drawing  conclusions  from  those  cases  in 
which  the  cells  are  not  distinct,  which,  it  is  true,  does -not  unfrequently 
occur  ;  for  even  then  the  regularity  of  distance  separating  the  nuclei,  the 
traces  of  cell-membranes  observable  as  delicate  stride  between  them,  and 
the  distinct  limitation  of  the  Malpighian  stratum,  as  it  approaches  the 
corium,  afford  certain  evidences  of  the  existence  of  fully-formed  cells. 
The  homogeneous  membrane  of  Krause,  and  the  basement  membrane  of 


142 


SPECIAL    HISTOLOGY. 


Fig.  56. 


the  English  authors,  I  believe  to  be  identical.  They  are  but  the  external 
portion  of  the  corium,  which  appears,  especially  around  and  between  the 
papillae,  as  a  structureless  and  homogeneous  membrane.  A  separation 
from  the  corium  of  this  narrow,  and  on  its  under  surface,  by  no  means 
distinctly  limited  membrane,  ought  not  to  be  attempted ;  for  although  a 
distinct  membrane  in  the  embryo,  it  cannot  be  obtained  as  a  special  layer 
in  the  adult.  (From  Kolliker's  Microsc.  Anat.  vol.  ii.  p.  47. — DaC.)] 

§  42.  The  horny  layer  (stratum  corneum\  forms  the  external  semi- 
transparent  part  of  the  epidermis,  which  in  white  people  is  colorless, 
and  is  composed  almost  wholly  of  uniform  cells  metamorphosed  into 
plates.  The  deepest  plates  are  still  very  similar  to  the  uppermost  cells 
of  the  stratum  mucosum;  but  even  in  the  second  or  third  layer  we  find 
the  widely  different  epidermic  or  horny  plates.  They  (Fig.  56,  1,  2,  3) 
are,  in  fact,  plates  of  moderate  thickness,  which 
in  the  lower  and  middle  parts  of  the  horny  layer 
retain  tolerably  regular  polygonal  (4-5-6-sided) 
and  smooth  surfaces ;  in  the  upper  layers,  on 
the  other  hand,  they  present  more  irregular 
outlines,  are  variously  crooked  and  curved,  and 
thence  often  appear  to  be  wrinkled  and  folded. 
These  plates  must  be  regarded  as  cells,  com- 
pletely flattened,  and  containing  a  very  minute 
quantity  of  viscid  fluid;  and  not,  as  might  at 
first  be  imagined,  as  homogeneous  lamellae, 
composed  throughout  of  the  same  substance ; 
for  by  the  addition  of  various  reagents,  espe- 
cially of  acetic  acid  and  potassa,  they  swell  up 
and  assume  the  form  of  vesicles  (Fig.  57) ;  at 
the  same  time,  a  rudimentary  nucleus  becomes 
obvious  in  a  few,  particularly  in  those  from  the 
middle  and  inner  layers,  but  by  no  means  in 
the  majority  of  them,  in  the  form  of  a  flat, 
homogeneous,  rounded  or.  elongated  corpuscle, 
0-003-0-004  of  a  line  in  length,  and  0-002- 
0-003  of  a  line  in  breadth,  which,  especially 
when  seen  from  the  side,  is  easily  recognized 
by  the  dark  contours  which  it  then  presents. 
The  size  of  the  plates  of  the  ordinary  horny 
layer  varies  from  0-008-0-016  of  a  line,  and 
in  the  outer  layer  it  is  commonly  somewhat 

FiG.  56. — Horny  plates  of  man:  1,  without  addition,  viewed  from  the  surface  one  with  a 
nucleus;  2,  from  the  side;  3,  treated  with  water,  granular  and  dark;  4,  nucleated  plate, 
such  as  occur  on  the  outer  surface  of  the  labia  minora  and  on  the  glans  penis. — Magnified 
350  diameters. 


OF    THE    SKIN.  143 

greater  than  in  the  inner.  Upon  the  body  of  the  penis  the  cells  mea- 
sure 0-008-0-012  of  a  line;  upon  the  glans,  the  largest  are  0-016-0-02 
of  a  line ;  upon  the  outer  side  of  the  labia  minora  0-012-0-02;  on  the 
labia  major  a  0-01—0-016  of  a  line.  These  last,  larger  cells,  all  possess 
distinct  nuclei,  and  are  almost  identical  with  the  epithelial  plates,  e.  g. 
of  the  cavity  of  the  mouth  and  of  the  vagina  (Fig.  56,  4). 

Whilst  the  stratum  Malpighii,  except  in  its  upper  layer,  is  but  indis- 
tinctly laminated,  a  clear  lamination  is  obvious  in  the  horny  layer,  inas- 
much as  its  plates  applied  together  horizontally,  form  strata  in  number 
proportionate  to  the  thickness  of  the  horny  layer  (Fig.  55).  It  must 
not  be  imagined  that  these  strata  are  distinctly  defined  from  one  another  ; 
they  are  connected  by  their  surfaces,  and  can  only  be  detached  and  de- 
monstrated adhering  together  in  numbers,  by  dissection,  which  is  much 
facilitated  by  boiling  or  macerating  the  epidermis.  The  innermost,  like 
the  stratum  Malpighii,  taken  together,  exhibit  a  wavy  course  wher- 
ever papillae  exist,  projecting  outwards  over  the  points  of  the  papillae, 
and  following  the  depressions  between  them.  This  takes  place  in  the 
most  striking  manner  where  very  much  developed  papillae  coexist  with 
a  moderately  thick  rete  Malpighii,  especially  in  the  palm  and  in  the  sole 
of  the  foot,  in  which  (see  the  figure  in  the  section  on  the  sudoriparous 
glands),  the  horny  layer  penetrates  so  deeply  between  the  papillae,  that 
its  deepest  cells  are  on  a  level  with  half  their  height :  where  the  papillae 
are  smaller,  the  horny  layer  sinks  less  deeply  between  them,  or  even  lies 
quite  flat  upon  the  stratum  Malpighii,  as  is  the  case  where  the  papillae 
are  absent.  From  this  cause  the  boundary-line  between  the  horny  layer 
and  the  stratum  mucosum  in  perpendicular  sections,  is  sometimes  straight, 
sometimes  wavy,  with  smaller  or  greater  elevations  and  depressions. 
The  other  parts  of  the  horny  layer  take  a  more  even  course  the  further 
they  are  from  the  mucous  layer ;  yet  not  merely  in  the  hand  and  foot, 
where,  as  is  well  known,  the  ridges  of  the  corium  are  marked  externally 
upon  the  epidermis,  but  in  many  other  localities,  a  slightly  wavy  course 
of  the  uppermost  layers  may  be  perceived  in  perpendicular  sections,  and 
slight  elevations  indicate  externally  the  points  beneath  which  the  papillae 
are  seated.  In  the  separate  lamellae  the  plates  are  sometimes  irregular, 
sometimes  arranged  circularly,  as  around  the  excretory  ducts  of  the 
glands  and  hair-follicles,  and  also  round  the  papillae  on  the  palm  of  the 
hand  and  sole  of  the  foot,  as  may  be  seen  most  readily  at  the  apertures 
of  the  sudoriparous  glands. 

§  43.  As  regards  the  color  of  the  epidermis,  in  the  white  races,  as 
has  been  said,  the  horny  layer  is  colorless  and  transparent  or  slightly 
yellowish,  the  mucous  layer  yellowish  white  or  brownish.  The  color  is 
deepest  in  the  areola  and  in  the  nipple,  passing  even  into  blackish- 
brown,  especially  in  women  during  pregnancy  and  after  they  have  borne 


144  SPECIAL    HISTOLOGY. 

children ;  it  is  less  intense  in  the  labia  majora,  the  scrotum,  and  the  penis, 
where  for  the  rest  it  varies  greatly,  being  sometimes  almost  entirely 
absent,  sometimes  very  distinct,  and  is  least  considerable  in  the  axilla 
and  round  the  anus.  Besides  these  situations,  which  in  most  individuals 
are  more  or  less  tinged,  in  the  dark-complexioned  more  than  in  the 
fair,  a  lighter  or  more  deeply  colored,  frequently  very  dark  pigment  is 
deposited  in  various  other  localities  in  the  stratum  MalpigJiii;  in  preg- 
nant women  in  the  linea  alba,  and  in  the  face  (rhubarb-colored  spots) ; 
in  persons  who  are  exposed  to  the  sun,  in  the  face,  especially  the  brow, 
chin,  and  cheeks  ;  in  the  neck,  the  thorax,  the  back  of  the  hands,  the 
forearm  ;  and  in  dark  persons  over  almost  the  whole  body.  These 
tints  are  not  produced  by  special  pigment  cells,  but  are  seated  in  the 
common  cells  of  the  mucous  layer,  round  whose  nuclei  a  finely  granular 
or  more  homogeneous  coloring  matter  or  actual  pigment  granules  are 
deposited.  When  the  skin  is  only  slightly  colored,  it  is  mostly  only  the 
neighborhood  of  the  nuclei  and  in  fact  only  of  the  lowermost  layers  of 
cells  which  is  implicated,  so  that  in  perpendicular  sections  the  papillse 
are  seen  to  be  surrounded  by  a  yellowish  fringe;  darker  shades  are  pro- 
duced by  the  extension  of  the  color  to  two,  three,  four,  and  more  layers 
of  cells,  and  over  the  whole  cell  contents ;  sometimes  by  a  darker 
coloration  of  the  deepest  layer  of  cells ;  the  two  conditions  commonly 
coexisting.  The  horny  layer  also  of  the  colored  places  of  the  skin, 
has  according  to  Krause,  its  cell  walls  slightly  tinged;  this  appears, 
however,  only  upon  comparing  them  with  those  of  uncolored  parts  of  the 
skin,  and  only  in  the  more  deeply-tinged  parts.  In  the  negro,  and  the 
other  colored  human  races,  it  is  also  only  the  epidermis  which  is  colored, 
whilst  the  corium  completely  resembles  that  of  Europeans.  The  pig- 
ment, however,  is  far  darker  and  more  abundant.  In  the  Negro  (Fig. 
55),  in  whom,  as  regards  the  arrangement  and  size  of  the  cells,  the  epi- 
dermis is  precisely  like  that  of  the  European,  it  is  the  perpendicular 
cells  of  the  deepest  part  of  the  mucous  layer  which  are  darkest  (dark 
brown  or  blackish-brown),  and  they  form  a  sharply  marked  fringe  con- 
trasted against  the  clear  corium.  To  these  succeed  clearer  but  still 
brown  cells,  which  are  accumulated  particularly  in  the  depressions  be- 
tween the  papillae,  but  are  also  found  on  their  points  and  lateral  por- 
tions in  many  layers  ;  finally  at  the  boundary  close  to  the  horny  layer 
there  follow  brownish-yellow  or  yellow,  often  rather  pale,  more  trans- 
parent layers.  All  these  cells  are  colored  throughout,  with  the  excep- 
tion of  their  membranes,  and  especially  the  parts  round  the  nuclei, 
which,  in  the  internal  layers,  are  by  far  the  darkest  portions  of  the 
cells.*  The  horny  layer  of  the  negro  also  inclines  to  yellow  or  brownish. 

*  [The  pigment  in  these  cells  seems  of  two  kinds:  a  less  intense  yellowish  pigment,  and 
a  dark  granular  pigment.  The  latter  is  irregularly  dispersed  throughout  the  contents  of  the 
cell,  and  in  some  parts  it  is  conglomerated  into  small  masses.  It  is  generally  especially 


OF     THE     SKIN.  145 

In  the  yellowish  skin  of  a  Malay  head  in  the  anatomical  collec- 
tion at  Wurzburg,  I  find  the  same  appearance  as  in  a  dark-colored 
European  scrotum.  It  follows,  then,  that  the  epidermis  of  the  colored 
races  is,  in  no  essential  point,  distinguishable  from  the  colored  regions 
in  the  white  man,  and  it  even  agrees  in  nearly  all  respects  with  that 
of  certain  localities  (the  areola  of  the  nipple,  for  instance). 

Pathological  coloration  of  the  epidermis  (freckles,  mothers'  marks, 
&c.),  according  to  Simon,  Krause,  Barensprung,  and  my  own  observa- 
tions, is  produced  exactly  as  the  more  intensely  colored  spots  in  the 
white  man,  and  as  the  color  of  the  negro's  skin.  Pigment  deposits  in 
the  corium  and  in  the  papillae,  such  as  may  be  seen  in  cicatrices,  after 
chronic  inflammation  of  the  skin,  and  frequently  as  in  ichthyosis  and 
many  ncevi,  associated  with  a  colored  epidermis,  in  which  the  pigment 
is  developed  directly  from  the  blood-corpuscles  and  their  coloring  mat- 
ter, must  be  carefully  distinguished  from  the  foregoing.*  Numerous 
instances  of  partially  or  entirely  white  negroes  and  of  black  Europeans, 
not  as  a  consequence  of  change  of  climate,  but  as  a  congenital  or  sub- 
sequently arising  abnormal  condition  of  the  skin,  have  been  noticed  (see 
Hildebrandt.— Weber,  II.  fig.  526  ;  Flourens,  Compt.  rendus  XVII.) 
But,  for  the  future,  it  will  have  to  be  remembered,  so  far  as  the  dark 
coloration  of  Europeans  is  concerned,  that  it  may  also  arise  from  a  de- 
position of  the  coloring  matter  of  the  bile. 

§  44.  The  thickness  of  the  epidermis  as  a  whole,  varies  exceedingly,  de- 
pending especially  upon  that  of  the  horny  layer.  It  measures  : — 

l-75th  to  l-50th  of  a  line,  upon  the  chin,  the  cheeks,  and  brow,  in  the 
external  auditory  passages,  and  upon  the  eyelids: 

l-50th  to  l-25th  of  a  line,  upon  the  bridge  of  the  nose,  on  the  breast 
and  nipple  of  a  female,  on  the  back  of  the  toes  and  fingers,  upon  the 
neck  and  back,  on  the  inner  and  outer  side  of  the  thigh,  on  the  scro- 
tum and  the  labia  minor  a  : 

l-25th  to  1-1 6th  of  a  line,  on  the  edge  of  the  eyelids,  on  the  male  chest 
and  nipple,  the  hairy  scalp,  the  chin,  penis,  prepuce,  and  ylans 
penis : 

l-16th  to  l-10th  of  a  line,  on  the  red  external  parts  of  the  lips,  on  the 
back  of  the  hand : 

1-1  Oth  to  l-7th  of  a  line,  on  the  flexor  side  of  the  fingers  and  toes : 

dense  around  the  nucleus,  which  is  itself  but  rarely  recognizable,  except  by  the  aid  of 
reagents,  and  does  not  seem  to  contain  any  of  these  darker  granules. — DaC.] 

*  [A  colored  epidermis  may  also  be  produced  by  a  parasitic  vegetable  growth,  as  in  the 
disease  called  pityriasis  versicolor,  in  which  the  yellowish  color  of  the  epidermis,  is  owing  to 
layers  of  filaments  and  spores  deposited  under  the  epidermic  cells. — DaC.] 

10 


146  SPECIAL    HISTOLOGY. 

1-3  to  1-2  of  a  line,  on  the  palm:  and — 

3-4ths  to  IJd  of  a  line,  on  the  sole  of  the  foot,  in  which  tAvo  latter 
localities  the  variations  are  greatest,  independently  of  the  circum- 
stance, that  in  the  furrows  and  at  the  joints  the  skin  is  thinner  than 
elsewhere. 

With  regard  to  the  proportionate  thickness  of  the  horny  and  mucous 
layers  I  find,  in  some  localities,  that  the  latter  is  constantly  thicker 
than  the  former  ;  i.  e.,  in  all  parts  of  the  face,  in  the  hairy  scalp,  in  the 
penis,  the  glans,  the  scrotum,  the  nipple,  and  the  skin  of  the  thorax 
in  man ;  in  the  labia  majora  and  minor  a,  on  the  back  and  neck.  Here 
the  mucous  layer  is  3-6  times,  or  2-3  times  as  thick  as  the  horny  layer, 
according  as  its  thickness  is  measured  from  the  bases  or  from  the  points 
of  the  papillae. ;  in  a  few  of  the  localities  mentioned,  however,  the  stra- 
tum Malpighii  is,  in  its  thinnest  parts,  of  the  same  thickness  as  the 
epidermis,  as  in  the  glans.  In  the  rest  of  the  body  both  layers  are 
either  equal  in  thickness,  as  in  the  external  auditory  passage,  and  here 
and  there  upon  the  flexor  side  of  the  first  two  sections  of  the  extremities, 
or  the  horny  layer  is  2  to  5  times  thicker  than  the  mucous,  and  in  the 
thickest  places  even  10  to  12  times  as  thick. 

The  absolute  thickness  of  the  stratum  MalpigJiii  varies  (at  the  base 
of  the  papilla?)  between  0-007  and  0-16  of  a  line;  where  it  is  thicker 
than  the  horny  layer,  it  measures  in  the  mean  0-04  of  a  line,  where  it 
is  thinner,  0*01— 0-02  of  a  line.  The  horny  layer  by  itself  measures  in 
many  places  only  0-005  of  a  line,  in  others  1  line  or  more  ;  when  its 
thickness  exceeds  that  of  the  stratum  Malpigliii,  it  is  generally  about 
0-1-04  of  a  line,  when  it  is  less,  0-01  of  a  line. 

§  45.  Pliysical  and  Vital  Properties. — The  epidermis  is  but  little 
elastic,  flexible  in  the  living  condition  and  not  easily  frangible,  softer 
in  the  deeper  than  in  the  superficial  layers.  The  cells  contain,  neither 
in  their  membranes  nor  between  them,  any  demonstrable  pores  (apart 
from  the  sudoriparous  ducts  and  hair-sacs,  which,  in  a  manner,  have 
their  outermost  portions  hollowed  out  in  the  epidermis),  and  form  a 
very  solid,  hardly  a  permeable  substance.  Many  experiments,  especially 
those  of  Krause,  show,  that  the  horny  layer  of  the  epidermis  permits 
no  fluids,  except  those  which  act  chemically  upon  it,  as  the  mineral  acids 
and  the  caustic  alkalies,  to  pass  through  it,  either  by  pores  or  by 
imbibition,  or  by  endosmose  and  exosmose,  while  it  readily  takes  up 
gaseous  matters,  or  easily  vaporizable  substances  (alcohol,  ether,  acetic 
acid,  ammonia,  solutions  of  chloride  of  iron  in  ether,  of  acetate  of  lead  in 
alcohol),  and  gives  them  off  (cutaneous  evaporation).  This  conclusion 
is  not  invalidated  by  the  undeniable  passage  of  water,  liquid  substances, 
ointments,  and  even  solid  matter  (sulphur,  cinnabar),  through  the  unin- 


OF    THE    SKIN.  147 

jured  epidermis,  since  in  these  cases  a  mechanical  intrusion  of  the  sub- 
stances, in  and  through  the  sudoriparous  ducts  and  hair-sacs,  or  their 
penetration  into  the  sweat-ducts,  and  mingling  with  the  sweat,  explains 
their  absorption.  The  mucous  layer,  at  any  rate,  is  easily  penetrated 
by  liquids,  as  is  sufficiently  shown  by  pathological  anatomy  (exudations 
which  penetrate  the  mucous  and  raise  up  the  horny  layer  into  a  vesicle 
the  ready  occurrence  of  absorption  after  the  separation  of  the  horny 
and  the  superficial  portion  of  the  muceus  layer,  by  the  action  of  vesi- 
cants). 

In  their  chemical  relations,  it  is  indeed  well  known  how  the  cells  and 
plates  of  the  epidermis  behave  with  regard  to  certain  reagents,  but 
there  exists,  at  present,  no  perfectly  satisfactory  total  analysis  of  the 
epidermis,  with  regard  to  its  two  layers  which  differ  so  widely ;  and  the 
organic  combinations,  also,  which  occur  in  it,  are  not  sufficiently  known. 

The  so-called  horn,  which  forms  the  membranes  of  the  horny  plates, 
is  insoluble  in  water,  easily  soluble  in  concentrated  al-kalies  and  con- 
centrated sulphuric  acid,  whence  the  skin,  if  wetted  with  these  sub- 
stances, feels  slippery  and  greasy ;  there  remains,  however,  a  small  residue 
insoluble  in  alkalies  ;  concentrated  acetic  acid,  also,  dissolves  it,  first 
rendering  it  gelatinous,  by  which  it  is  distinguished  from  the  protein 
compound  of  the  hair.  It  contains  less  sulphur  than  the  hair  and  nails, 
which  is  perhaps  the  reason  why  salts  of  lead,  mercury,  and  bismuth, 
color  the  hair  but  not  the  epidermis.  Besides  these,  Mulder  finds  in 
the  horny  layer  a  gelatinous  matter,  which  is  obtained  by  long  boiling 
in  water,  and  which  would  appear  to  be  of  a  collagenous  nature.  The 
epidermis  does  not  putrefy — it  melts  in  the  fire  without  bending  or 
swelling  up,  and  burns  with  a  clear  flame. 

The  behavior  of  the  epidermis  towards  reagents  is  particularly  of 
importance  for  the  microscopist,  on  whose  behoof  I  add  the  following 
account. 

After  long  maceration  in  water,  the  epidermis  becomes  detached  in 
portions,  and  under  moderate  pressure  is  resolved  into  a  white  powder, 
consisting  of  the  isolated  horny  plates,  and  the  uppermost  cell  of  the 
rete  MalpigJiii.  Boiled  in  water,  pieces  of  the  horny  layer  break  up 
into  their  elements  much  more  readily.  Boiled  in  concentrated  acetic 
acid  from  15  to  25  minutes,  all  the  horny  plates  become  perfectly  isola- 
ted, forming  a  cloudy,  whitish  deposit  in  the  test  tube ;  they  are  ex- 
ceedingly pale,  so  that  they  are  often  hardly  visible  under  a  full  illu- 
mination ;  and  are  completely  swollen  up  and  changed  into  globular  or 
elongated,  distended,  but  always  more  or  less  flattened  vesicles  of  0-02- 
0-032  of  a  line  in  breadth,  and  0-006-0-01  of  a  line  in  thickness,  the  nuclei 
when  they  are  present  being  also  pale  and  hardly  to  be  perceived.  The 


148  SPECIAL     HISTOLOGY. 

Malpighian  layer  becomes  pale  under  the  action  of  cold,  concentrated 
acetic  acid,  the  cells  and  nuclei  being  rendered  more  distinct.  The 
cell-contents  are  partially  dissolved:  by  longer  action  the  contours  of 
the  deepest  layers  of  cells  become  invisible.  The  same  thing  occurs 
after  boiling  for  four  minutes. 

Caustic  potass  and  soda  act  differently,  according  as  the  solutions  used 
are  concentrated  or  diluted.  In  the  latter  case,  immediately  after  the 
addition  of  the  reagent,  the  horny  layer  is  rendered  more  clear,  it  swells 
up  and  changes  in  a  short  time  into  a  beautiful  tissue  of  pellucid,  glo- 
bular vesicles,  without  nucleus  or  granules,  and  with  sharp,  moderately- 
thick  contours,  O02--032  of  a  line  in  breadth,  and  0-016-0-02  of  a  line 
in  thickness.  If  concentrated,  solutions  of  the  caustic  alkalies  render 
the  plates  at  first  smaller,  so  that  they  measure  only  0-012-0-016  of  a 
line,  and  are  at  the  same  time  more  wrinkled  and  pale,  but  with  defined, 
dark  contours ;  in  the  course  of  an  hour  they  swell  up  so  as  to  appear 
as  cells,  but  it  takes  two  or  three  hours  to  give  them  the  aspect  of  the 
plates  which  have  been  heated  with  dilute  solutions.  Boiled  with  these 
fluids,  even  the  dry  horny  layer  swells  up,  in  an  instant,  into  the  most 
beautiful  tissue  of  cells,  without  either  granules  or  nuclei  (Fig.  57),  and 
at  the  same  time  the  dissolving  cell- contents  mixed  with  the  alkali,  are 

collected  in  the  cells,  into  greater  and 
smaller  granular  masses ;  after  the 
action  of  the  heat  for  five  hours,  all  the 
cells  disappear  without  leaving  a  trace, 
and  yellowish  and  pale  fat-drops  in  no 
great  number,  swim  in  the  liquid.  The 
cells  of  the  Malpighian  layer  are  still 
more  acted  upon  by  alkalies  than  those 
of  the  horny  stratum :  they  swell  up 
at  once,  and  appear  distinctly  as  deli- 
cate vesicles;  these  then  dissolve,  all 
but  the  uppermost  two  or  three  layers, 
which  require  a  longer  time,  like  those  of  the  horny  stratum,  though 
less  than  the  latter.  The  nuclei  of  all  the  cells  withstand  the  operation 
of  this  reagent  even  less  than  the  cells ;  whilst,  when  the  latter  are  dis- 
solved, a  granular  or  striated  substance  remains  behind,  which  is,  pro- 
bably, partly  fat.  Concentrated  sulphuric  acid,  in  five  minutes,  causes 
the  horny  layer  to  swell  up  so  much,  that  its  elements,  although  still 
remaining  flattened  and  irregular,  appear  quite  distinctly  to  be  vesicles; 
after  half  an  hour  they  are  somewhat  more  distended,  and  easily  sepa- 
rable from  one  another.  By  boiling  with  this  acid  the  plates  swell  up 

FIG.  57. — Horny  plates  boiled  with  caustic  potassa  and  distended ;  the  contents  partially 
and  wholly  distended. — Magnified  350  diameters. 


OF     THE     SKIN.  149 

even  in  a  minute,  without  exhibiting  nuclei,  and  in  two  minutes  they  dis- 
appear without  leaving  any  trace.  Boiling  in  dilute  sulphuric  acid  ren- 
ders the  horny  layer  hard  and  transparent,  and  dissolves  it  wholly  in  4-5 
hours.  The  cells  of  the  stratum  Malpighii*  are  little  altered  by  cold 
sulphuric  acid  :  on  boiling,  their  contours  and  nuclei  at  first  become  more 
distinct,  but  in  about  two  minutes  the  whole  is  dissolved.  Nitric  acid  colors 
the  epidermis  yellow,  softens  and  changes  it  into  xantho-proteic  acid. 
The  cells  of  the  horny  layers  swell  up  somewhat,  after  a  time,  in  the  cold, 
and  become  granular  ;  the  stratum  Malpighii  is  rendered  granular  and 
indistinct,  and  sharply  defined  from  the  horny  layer.  Upon  boiling,  the 
whole  epidermis  is  entirely  dissolved  in  half  a  minute.  Hydrochloric 
acid  does  not  tinge  the  epidermis,  and  in  the  cold  renders  the  cells  of 

*  [I  have  recently  investigated  the  reaction  of  the  pigmental  cells  in  the  Malpighian 
layer  of  the  Negro,  and  with  the  following  results.  Macerated  in  water  they  remain 
unchanged.  Caustic  potassa  renders  the  outline  of  the  cell  more  distinct,  but  produces  no 
effect  on  the  enclosed  pigment.  After  acting  for  three  or  four  hours  it  dissolves  the  cell, 
and  allows  the  dark  pigment  granules  to  escape.  Boiled  for  ten  minutes  in  a  solution 
of  caustic  potassa,  the  cells  become  larger  and  more  distinct;  in  many,  nuclei  and  dark 
granules  are  visible ;  and  their  color  becomes  changed  to  a  yellowish  brown.  Prolonged 
boiling  dissolves  the  cells,  but  does  not  act  on  the  granular  pigment ;  caustic  soda  brings  the 
pigment  cells  distinctly  into  view  and  causes  them  to  swell  up.  Continued  action  for  one 
or  two  hours,  dissolves  the  cell  and  permits  the  unchanged  black  pigment  to  escape.  Upon 
boiling  for  about  four  minutes  in  caustic  soda,  rupture  of  the  cell-wall  with  escape  of  the 
contents  ensues. 

Concentrated  sulphuric  acid  has  no  effect  on  the  Malpighian  layer.  When  first  added  the 
cells  are  rendered  more  distinct ;  after  twenty-four  hours  no  further  effect  is  observable. 
Boiling  in  sulphuric  acid  produces  no  change  on  the  cells;  after  a  few  minutes  the  whole 
epidermis  is  dissolved.  Nitric  acid  when  first  added  had  no  decided  action  ;  but  after  a  few 
hours  it  rendered  the  cells  more  indistinct,  dissolving  some,  and  staining  the  intermediate 
tissue  yellow.  Soaked  for  twenty-four  hours  in  nitric  acid,  the  whole  pigmentary  layer 
assumes  a  yellow  color;  the  separate  cells  are  scarcely  recognizable.  The  rapidity  with 
which  the  whole  epidermis  when  boiled  in  nitric  acid  is  dissolved,  makes  it  difficult  to 
determine  its  effect  upon  the  Malpighian  layer. 

Hydrochloric  acid  does  not  act  as  powerfully  as  nitric  acid.  At  first  its  addition  produces 
no  effect  on  the  cells;  in  the  course  of  a  few  hours,  they  become  more  indistinct,  but  are  not 
dissolved.  The  same  result  is  obtained  by  allowing  this  acid  to  act  for  twenty-four  hours. 
The  cells  are  then  indistinct,  but  of  a  black  color;  boiled  for  two  minutes  they  swell  up, 
enlarge,  but  are  not  rendered  more  distinct.  More  prolonged  boiling  (four  or  five  minutes) 
dissolves  the  whole  epidermis.  Acetic  acid  causes  the  pigment-cells  to  be  more  easily  dis- 
tinguished. In  a  preparation  that  had  been  placed  for  five  weeks  in  concentrated  acetic 
acid,  the  cells  were  very  distinct;  but  not  otherwise  altered.  No  effect  was  produced  upon 
the  pigment. 

The  action  of  Nitrate  of  silver,  as  it  stains  the  horny  tissue,  cannot  be  well  ascertained.  In 
a  preparation,  that  had  been  placed  in  a  concentrated  solution  for  twenty-four  hours,  the 
pigment  cells,  as  far  as  they  could  be  studied,  were  of  a  more  intense  color,  but  not  otherwise 
altered.  In  alcohol  and  ether  the  epidermis  is  hardened  and  the  pigment-cells  of  the 
Malpighian  layer  are  well  and  distinctly  seen,  but  these  reagents  exert  no  action  on  them. 
Boiled  in  ether  the  cells  become  distinct  and  of  a  lighter  color.  A  solution  of  Iodine,  colors 
the  whole  epidermis  immediately,  and  thus  prevents  the  study  of  its  special  action  upon 
the  pigmental  cells  of  the  Malpighian  layer. — DaC.] 


150  SPECIAL    HISTOLOGY. 

the  horny  layer  somewhat  more  distinct  than  nitric  acid.  After  boil- 
ing for  a  minute  the  horny  layer  becomes  a  beautiful  cellular  tissue, 
exactly  as  after  the  addition  of  dilute  solution  of  potass.  In  carbonate 
of  potass  the  epidermis  is  hardly  changed  at  all.  After  seventeen 
weeks  it  is  hardened  and  easily  cut  with  a  knife.  Nitrate  of  silver 
colors  it  violet  or  brownish-black,  by  the  formation  of  oxide  of  silver, 
of  chloride  of  silver,  and  of  black  sulphuret  of  silver,  in  consequence 
of  the  chloride  of  sodium  and  sulphur  which  it  contains.  Investigated 
microscopically  with  the  help  of  acetic  acid,  the  tissue  of  the  epider- 
mis is  seen  to  remain  quite  unchanged,  and  minute  dark  granules  are 
visible  between  its  elements.  Nitrate  of  mercury  gives  the  epidermis  a 
reddish-brown  hue,  sulphurets  of  the  alkalies  render  it  brown  and 
black:  many  vegetable  colors  unite  with  it.  In  alcohol  and  ether  it 
is  insoluble,  with  the  exception  of  a  small  quantity  of  fat  which  it 
contains. 

From  all  this,  it  results,  with  regard  to  the  elementary  parts  of  the 
epidermis,  that  they  are  cells,  which,  however,  as  the  alkalies  show,  do 
not  everywhere  present  the  same  characters.  In  the  stratum  mucosum 
they  are  actual  vesicles  and  easily  soluble — in  the  horny  layer,  scarcely 
so  ;  and  here,  in  fact,  a  distinction  must  be  drawn  between  the  resisting 
cell-membrane  and  the  cell-contents,  which  swell  up  and  disappear  more 
readily;  these,  in  the  natural  condition,  form  an  apparently  homogene- 
ous simple  plate,  but  the  difference  between  them  may  be  readily  ex- 
hibited by  reagents.  In  what  parts  the  small  quantity  of  collagenous 
substance,  which  has  been  noticed,  has  its  seat,  is  not  clear  ;  perhaps 
it  forms  a  portion  of  the  contents,  especially  of  the  cells  of  the  mucous 
layer,  or  belongs,  it  may  be,  to  an  intermediate  substance  between  the 
cells,  which,  however,  is  not  microscopically  demonstrable.  If  the  fat 
of  the  epidermis  is  not  merely  accidental,  arising  from  the  cutaneous 
secretions,  it  is  most  probably  contained  within  the  Malpighian  cells. 

Cruns,  Todd  and  Bowman,  Valentin  and  Bruch,  recommend  the  use 
of  alkalies  for  the  investigation  of  the  epidermic  tissues,  but  their  full 
importance  was  first  shown  by  Donders  (Mulder's  "  Phys.  Chemie,"  p. 
257,  et  seq.,  and  "  Hollandische  Beitrage,"  I.  u.  11).  They  are  now 
generally  recognized  as  quite  indispensable  reagents  for  the  investiga- 
tion of  the  horny  tissues  ;  but,  as  Paulsen  ("  Obs.  Microchem.,"  &c. 
Dorpat,  1848)  and  Reichert  (Mull.  "Arch,"  1847,  Jahresbericht.)  ad- 
vise, it  is  well  always  to  use  only  definite  solutions.  I  may  add,  that  a 
great  saving  of  time  is  effected  by  the  heating  of  the  tissues  to  be  inves- 
tigated in  test  tubes,  with  these  and  other  reagents,  as  I  have  already 
done  in  examining  those  tissues  of  animals  which  contain  cellulose 
("Annales  d.  Sc.Nat.,"  1846). 

§  46.  Gf-rowth  and  Regeneration. — The  epidermis  possesses  no  power 
of  continually  active  growth  depending  upon  intrinsifc  causes  and  founded 


OF    THE    SKIN.  151 

upon  the  vital  relations  of  its  cells,  or  those  which  it  has  with  the  corium  ; 
it  is  essentially  a  stable  tissue,  which  does  not  change  in  its  elementary 
parts,  but,  somewhat  like  a  cartilage,  has  all  its  vital  energies  directed 
to  its  unchanged  self-maintenance  as  a  whole  (thickness  of  the  whole 
epidermis,  proportion  of  the  rete  Malpighii  to  the  horny  layer),  and  in 
its  separate  parts.  However,  since  a  throwing-oif  of  the  external 
layers,  if  not  necessarily,  yet  accidentally,  takes  place  almost  con- 
tinually over  the  whole  body  to  a  greater  or  less  extent,  the  epidermis 
is,  so  to  speak,  continually  occupied  in  replacing  what  is  lost,  or  in  grow- 
ing, and  thus  exhibits  its  vegetative  life  in  a  more  remarkable  manner. 
Whichever  takes  place,  it  is  the  corium  and  its  vessels  from  which  the 
fluids  required  by  the  epidermis  are  derived.  In  every  locality,  we  may 
suppose,  that  a  certain  determinate  quantity  of  plasma,  corresponding  with 
the  anatomical  and  physiological  relations  of  the  vessels  of  the  corium 
and  the  thickness  of  the  epidermis,  permeates  the  latter,  and,  when  it 
is  not  growing,  simply  fills  its  cells  and  plates  (independently  of  that  more 
watery  fluid  which  subserves  the  cutaneous  evaporation),  maintaining 
their  vital  activity,  and  at  the  most  causing  temporary  deposits  of  pig- 
ment in  the  rete  Malpighii.  If,  on  the  other  hand,  its  outer  layers  be 
removed,  a  certain  amount  of  plasma  becomes  free  and  disposable,  and 
then  regeneration  takes  place,  which,  if  it  proceed  continuously,  may 
even  be  called  growth.  It  is  in  this  process  that  the  vegetative  life  of 
the  epidermis-cells  is  most  distinctly  evidenced,  particularly  in  the  rete 
Malpighii,  where  it  is  unquestionably  most  intense,  exhibiting  itself 
especially  in  the  multiplication  and  growth  of  the  cells,  and  in  their 
chemical  changes.  In  the  horny  stratum  the  phenomena  are  less  strik- 
ing, though  it  must  not  be  considered  to  be  inactive  even  in  the  uppermost 
layer ;  being  by  no  means  dead  matter,  as  we  evidently  see,  when  under 
certain  conditions,  especially  under  abnormal  states  of  the  corium — '• 
the  source  of  its  nutrition — it  sometimes  becomes  hypertrophied,  some- 
times completely  dies  away.  We  have  not  as  yet,  however,  attained  to 
an  exact  insight  into  the  vital  manifestations  of  the  epidermic  cells,  and 
are  therefore  not  in  a  condition  to  decide  which  of  the  phenomena  pre- 
sented by  them  are  to  be  ascribed  to  their  own  activity,  and  which  to 
the  nature  of  the  plasma  which  nourishes  them.  The  latter  is  certainly 
of  the  greatest  importance  for  the  epidermis,  and  it  is  more  than  pro- 
bable that  most  of  its  peculiarities,  as,  for  instance,  its  typically  different 
thickness  in  different  parts  of  the  body,  the  different  relations  of  the 
stratum  Malpighii  to  the  horny  layer,  and  its  pathological  states,  depend 
upon  qualitative  and  quantitative  differences  in  the  plasma.  Upon  what 
condition,  furthermore,  it  depends,  that  in  the  Malpighian  layer,  the 
changes  of  the  cells  are  far  more  considerable  than  in  the  horny  layer, 
whose  elements  all  closely  resemble  one  another,  is  as  little  obvious  as 


152  SPECIAL    HISTOLOGY. 

the  cause  of  the  somewhat  defined  line  of  demarcation  between  the  two 
layers,  a  condition  which  appears  still  more  strikingly  in  the  nails,  and 
would  lead  one  to  suppose  that,  at  the  first  formation,  and  in  the  course 
of  the  development  of  the  epidermis  and  nails,  a  very  considerable  altera- 
tion suddenly  takes  place  at  one  point  in  their  cells,  thus  determining 
their  separation  into  two  layers. 

In  the  deep  fold  of  the  skin  which  surrounds  the  glans  penis  and  clito- 
ridis, a  continual  desquamation  and  reproduction  of  the  epidermic  scales, 
which  are  here  soft  and  nucleated,  takes  place,  in  consequence  of  which 
a  peculiar  secretion,  the  smegma  preputii,  is  produced.  Hitherto  this 
secretion  has  been  erroneously,  but  almost  universally,  supposed  to  be  a 
sebaceous  matter  secreted  by  the  preputial  glands.  The  microscope 
shows :  1,  that  in  the  female,  where  the  presence  of  smegma  preputii 
is  constant,  neither  sebaceous  nor  any  other  glands  exist  upon  the  pre- 
puce or  glans  clitoridis  ;  2,  that  in  the  male,  in  whom  such  glands  are 
indeed  found,  they  are  commonly  but  insignificant  in  relation  to  the 
quantity  of  smegma,  and  are  often  very  few  and  scattered;  3,  finally, 
that  the  smegma,  in  both  sexes,  consists  principally  of  cells  of  the  same 
form  as  those  of  the  prepuce  and  glans  penis  and  clitoridis ;  whence, 
taking  also  into  account  the  fact,  that  in  the  male  it  is  generally  dis- 
tinctly composed  of  superimposed  layers  covering  the  whole  prepuce  con- 
tinuously, whilst  the  sebaceous  glands  occur  only  isolated,  it  naturally 
follows  that  the  smegma  is  principally  constituted  of  desquamated  epi- 
dermis. However,  this  does  not  exclude  the  preputial  sebaceous  matter 
in  the  male  from  also  taking  a  share  in  proportion  to  the  number  and 
size  of  Tyson's  glands,  in  the  formation  of  what  goes  under  the  common 
name  of  smegma.  There  would  in  this  locality  then,  really  be  a  con- 
stant desquamation  of  the  external,  and  a  new  development  of  the  in- 
ternal layers  of  the  epidermis,  but  here  there  are  special  purposes  in 
view  which  elsewhere  do  not  enter  into  consideration.  The  preputial 
fold,  in  fact,  is  to  be  compared  to  a  gland  ;  and  as  the  secretions  of  these 
are  very  often  formed  only  by  the  continual  casting  off  of  the  cells  which 
line  them  (e.  g.  sebaceous  glands),  so  is  that  of  the  prepuce.  We  must 
recollect  that  in  many  animals,  e.  g.,  the  Weasel,  the  Beaver  (E.  H. 
Weber),  without  essentially  changing  the  character  which  it  possesses 
in  man,  the  prepuce  takes  on  a  highly  glandular  nature,  and  that  even 
in  man  it  yields  a  secretion  which  differs  considerably  from  common  epi- 
dermis. According  to  Lehtnann,  the  yellow,  fatty,  strongly-odorous 
preputial  smegma  of  man  contains,  when  dried,  in  100  parts  :  Ethereal 
extract,  52*8 ;  alcoholic  extract,  7*4;  aqueous  extract,  6*1;  earthy  salts, 
9'7  ;  albuminous  substances  soluble  in  dilute  acetic  acid,  5-6;  insoluble 
residuum,  18'5.  The  ethereal  extract  contained  saponifiable  fat,  choles- 


OF    THE    SKIN.  153 

terin,  a  non-saponifiable  and  uncrystallizable  fat  and  bilin  (Gallenstoff). 
The  smegma  of  the  horse  possessed  nearly  the  same  constituents  ;  and 
among  the  salts,  oxalate  of  lime;  while  in  man,  ammonio-phosphate  of 
magnesia  occurred.  The  watery  extract  contained  neither  albumen  nor 
casein. 

An  extensive  desquamation  of  the  entire  horny  layer  of  the  epidermis, 
such  as  takes  place  in  the  embryo  and  in  many  animals,  does  not  occur 
in  man  except  in  certain  morbid  states.  On  the  other  hand,  its  power 
of  regeneration  is  exhibited  in  other  modes  than  those  which  have  been 
mentioned.  Excised  portions  of  the  epidermis,  for  instance,  are  very 
readily  replaced,  and  with  tolerable  rapidity,  so  long  as  the  corium  be 
not  injured  ;  and,  in  fact,  not  by  the  immediate  deposition  of  epidermis 
in  the  wound,  but  only  by  the  growing  up  of  the  whole  epidermis  from 
below.  If  the  corium  be  injured  as  well,  an  epidermis  is,  indeed,  formed 
upon  the  substance  of  the  cicatrix,  but  without  any  of  the  previous  ele- 
vations and  depressions  of  the  internal  and  external  surface,  because 
the  new  corium  has  neither  papillae  nor  ridges.  If  the  epidermis  be 
raised  up  into  a  vesicle  by  acrid  substances,  e.  g.,  Tartar  emetic,  a  slight 
burn,  &c.,  the  wall  of  the  vesicle,  which  consists  of  the  horny  layer  and 
some  few  layers  of  cells  of  the  mucous  layer,  never  again  becomes  adhe- 
rent; but  from  the  main  substance  of  the  mucous  layer,  which  mostly 
remains  lying  upon  the  papillae,  a  new  horny  layer  is  by  degrees  deve- 
loped. 

If  we  inquire  more  minutely  into  the  mode  of  regeneration  of  the  epi- 
dermis, there  can,  in  the  first  place,  be  no  doubt  that  it  takes  place  in 
the  Malpighian  layer,  inasmuch  as  losses  of  substance  of  the  horny  layer, 
e.  g.  a  piece  cut  out,  are  restored  not  by  the  formation  of  a  new  portion 
in  the  gap,  but  by  the  growth  outwards  of  a  horny  layer  from  below 
(the  wound  remaining  wholly  unchanged),  which  gradually  raises  the 
bottom  of  the  wound,  and  brings  it  to  a  level  with  the  surrounding  epi- 
dermis, the  latter,  in  consequence  of  the  pressure  that  it  suffers  from  the 
growing  portion,  becoming  everted  and  exfoliating.  The  reason  of  this 
phenomenon  is  to  be  sought,  simply  in  this,  that  the  non-vascular  epider- 
mis draws  the  materials  which  it  requires  for  its  nutrition  and  regenera- 
tion from  the  superficial  vessels  of  the  corium.  It  is  more  difficult  to 
ascertain  from  what  portion  of  the  Malpighian  layer  the  regeneration 
proceeds.  If  a  layer  of  cytoblastema  and  of  free  nuclei  existed  upon 
the  surface  of  the  corium,  as  many  authors  suppose,  we  might  acquiesce 
in  the  view,  that  the  epidermis  grows  by  free  cell-development  in  those 
innermost  layers  which  rest  immediately  upon  it ;  but  such  a  cytoblas- 
tema, as  we  have  seen,  does  not  exist,  the  stratum  Malpighii  being  in- 
variably formed  by  perfect  cells ;  and  thence  nothing  remains,  but  to 
suppose  an  endogenous  cell-development  around  portions  of  contents  in 


154  SPECIAL    HISTOLOGY. 

the  deepest  round  cells,  or  a  multiplication  by  division,  for  which 
latter  view  the  occasional  occurrence  of  two  nuclei  in  some  of  the  softer 
epidermic  cells,  seems  to  speak.  It  can  be  more  easily  made  out,  how, 
in  the  course  of  the  growth  of  the  epidermis,  the  youngest  epidermic 
cells  become  changed  into  horny  plates.  The  small  and  round  vesicles 
of  the  deeper  layers  of  the  stratum  Malpighii  become  larger  and  flatter 
the  more  they  approach  the  surface,  until  at  last  they  are  completely 
converted  into  flattened  plates.  In  the  meanwhile  their  nuclei  at  first 
grow  a  little,  and  then,  as  a  general  rule,  disappear  wholly  in  the  horny 
layers  ;  whilst  the  cell-contents,  which  are  granular  in  the  mucous  layer, 
clearly  distinct  from  the  cell-membrane,  and  probably  semi-fluid,  become 
more  solid  and  homogeneous  in  the  horny  layer,  and  finally  coalesce  with 
the  cell-membranes.  At  the  same  time  the  latter  are  chemically  altered, 
becoming  less  and  less  soluble  in  caustic  alkalies. 

§  47.  Development  of  the  Epidermis. — The  first  layers  of  the  epi- 
dermis are  developed,  in  the  Mammalia,  by  the  metamorphosis  of  the 
most  superficial  of  the  original  formative  cells  which  compose  the  young 
embryo.  When  the  rudiments  of  the  stratum  Malpighii *n&  horny  layer 
are  once  indicated,  the  former  continues  to  increase  in  thickness,  in  con- 
sequence of  the  multiplication  of  its  elements,  whilst  the  horny  layer, 
for  the  increase  of  its  proper  substance  and  to  replace  what  it  loses  by 
desquamation,  recruits  itself  from  it  exactly  as  in  the  adult.  How  the 
multiplication  of  the  cells  goes  on  in  the  rete  Malpigliii  has  not  been 
directly  observed  ;  but  it  is  certainly  not  by  free  cell-development,  since 
in  embryos  of  all  ages  the  mucous  layer  consists  wholly  of  cells,  and  free 
nuclei  are  altogether  absent.  As  regards  the  horizontal  extension  of  the 
epidermis,  it  appears,  as  Harting  ("  Rech.  microme'tr,"  p.  47)  justly  ob- 
serves, from  the  circumstance  that  the  epidermic  scales  of  the  foetus  and 
of  the  adult  differ  very  little  in  superficial  size,  that  it  can  only  in  a 
very  slight  degree  be  ascribed  to  the  growth  of  its  elements.  In  fact 
the  horny  plates  of  the  embryo  of  fifteen  weeks  already  measure  0-009 
-0-012,  in  the  sixth  month  0-01-0-012,  in  the  seventh  month  0-01- 
0-014,  in  the  new-born  infant  0-012-0-016,  in  the  adult  0-008-0-016 
of  a  line.  Since,  however,  keeping  in  mind  the  structure  of  the  horny 
layer,  it  cannot  well  be  supposed  that  new  scales  are  continually  inter- 
calated from  below  between  its  elements,  and  since  a  superficial  multi- 
plication of  the  cells  of  the  rete.  which  also  do  not  increase  in  size,  must 
certainly  be  granted,  it  seems  impossible  to  admit  any  other  conclusion 
than  that,  in  agreement  with  the  great  superficial  growth  of  the  cutis 
and  of  the  rete,  and  the  small  extensibility  of  the  horny  layers,  a  series 
of  desquamations  of  the  latter  take  place,  which,  if  this  view  be  correct, 
must  likewise  obtain  after  birth. 


OF    THE    SKIN.  155 

In  an  embryo  of  five  weeks  I  found,  in  the  place  of  the  epidermis, 
nothing  but  an  external  layer  of  polygonal  cells  of  0-012-0-02  of  a  line 
in  diameter,  and  an  internal  layer  of  small  cells  of  0-003-0-004  of  a  line  ; 
in  embryos  of  fifteen  weeks  the  epidermis  is  0-01-0-012,  of  a  line  thick, 
and  composed  as  before,  only  that  the  deep  layer  of  cells  answering  to 
the  stratum  mucosum  is  often  already  double,  and  the  external  cells 
measure  only  0-009-0-012  of  a  line. 

In  the  fifth  month  the  epidermis  in  one  instance  measured  on  the  heel 
and  ball  of  the  hand  0-02-0-024  of  a  line,  over  the  ridges  of  the  cutis 
0-036-0-04,  in  the  furrows  between  them  on  the  back  0-02-0-024  of  a  line, 
of  which  thickness  one-third  may  be  regarded  as  belonging  to  the  horny 
layer  and  two-thirds  to  the  rete  Malpigliii.  In  a  somewhat  older  embryo 
it  was,  on  the  heel  0-06--064  of  a  line  (mucous  layer  0-05,  horny  layer 
0-01-0-014),  on  the  surface  of  the  hand  0-05  of  a  line  (mucous  layer  0-04, 
horny  layer  0*01),  on  the  back  0-02-0-024  of  a  line  (mucous  and  horny 
layers  of  equal  thickness).  The  mucous  layers  consisted  of  many  layers 
of  smaller  cells,  the  lowest  of  which  were  already  elongated, and  stood 
perpendicularly ;  the  horny  layer,  of  at  least  two  layers  of  polygonal 
flattened  cells,  with  round  nuclei. 

In  the  sixth  month  the  epidermis  upon  the  thorax  measures  0*02— 
0-022,  on  the  palm  of  the  hand  0-06,  on  the  sole  of  the  foot  0*07  of  a 
line,  and  everywhere  it  consists  of  many  layers  of  cells.  The  outermost 
one  or  two  are  composed  of  horny  plates  without  nuclei  0-01-0-14  of  a 
line,  perfectly  similar  to  those  of  the  external  horny  layer  in  adults ; 
then  follow  3-4  layers  of  polygonal  cells,  the  largest  0-01-0-012  of  a 
line,  with  nuclei  0-004  of  a  line;  finally  a  mucous  layer,  whose  thickness 
equals  about  one-half  or  two-fifths  that  of  the  whole  epidermis,  with  at 
least  3  or  4  layers  of  rounded  cells  of  0-003-0-004  of  a  line,  the  lowest 
of  which  are  somewhat  elongated,  and  are  seated  perpendicularly  upon 
the  cutis. 

In  the  seventh  month,  I  found  in  one  embryo,  that  the  epidermis 
on  the  heel  measured  0-12  of  a  line  (mucous  layer  0-072,  horny  layer 
0-048),  upon  the  back  0-07  of  a  line,  (mucous  layer  0-04  horny  layer 
0*03):  in  another  it  measured  on  the  heel  0-12—0-14  of  a  line  (mucous 
layer  0-05-0-06,  horny  layer  0-07-0-08),  on  the  knee  0-046-0-064  of 
a  line  (mucous  layer  0-016-0-024,  horny  layer  0-03-0-04).  Both  layers 
of  the  epidermis  are  as  sharply  separated  from  one  another  as  in  adults, 
and  their  elements  similar  to  those  of  the  perfect  epidermis,  especially 
the  lowest  parts  of  the  stratum  Malpighii  and  the  plates  of  the  horny 
layer,  which  have  no  nuclei,  and  measure  0-01—0*014  of  a  line  in  the 
uppermost  layers. 

In  the  new-born  infant,  apart  from  the  thickness  of  the  epidermis, 
which  in  one  case  measured  on  the  heel  0-1—0-11  of  a  line  (mucous 
layer  0-04-0-05,  horny  layer  0-06),  nothing  particular  is  to  be  observed, 


156  SPECIAL    HISTOLOGY. 

except  that  by  maceration,  &c.,  it  is  much  more  easily  separated  from 
the  corium  than  in  the  adult.  The  non-nucleated  horny  plates  measured 
0*012— '016,  on  the  labia  minora,  where  they  possess  nuclei  0*016— 0*02 
of  a  line. 

During  embryonic  life  a  desquamation  of  the  epidermis  occurs,  which 
is  perhaps  repeated  several  times.  Such  is  the  fate,  probably,  of  the 
layer  of  polygonal  cells  which  arises  first  of  all,  and  which  in  the  second 
to  the  fourth  months,  becomes  metamorphosed  into  an  almost  structure- 
less membrane,  and  is  then  no  longer  to  be  found ;  perhaps  also  of  the 
layer  of  epidermis,  which  covers  the  points  of  the  hairs  which  have  not 
yet  appeared  externally  (vide  infra  §  Hairs);  and  in  the  second  half  of 
the  foetal  period  it  may  be  easily  demonstrated  as  an  actively  occurring 
process.  From  the  fifth  month  onwards,  in  fact,  continually  increasing 
desquamation  of  the  external  epidermic  cells  takes  place,  and  these 
becoming  in  most  parts  mixed  up  with  the  sebaceous  secretion  of  the 
skin,  form  the  so-called  vernix  caseosa  or  smec/ma  embryonum.  This  is 
a  whitish  or  yellowish,  viscid,  inodorous  material,  which,  especially  from 
the  sixth  month  onwards,  covers  the  whole  surface  of  the  foetus  with  an 
often  considerably  thick  and  even  laminated  substance,  which  is  most 
abundant  upon  the  genitalia,  on  the  flexor  side  of  the  joints  (axilla, 
knee,  nates),  on  the  sole,  the  palm,  the  back,  the  ear,  and  on  the  head 
in  large  quantity,  and  when  microscopically  examined  consists  mainly 
of  epidermic  cells,  but  also  contains  sebaceous  cells  and  fat  globules. 
According  to  Davy  ("Lond.  Med.  Gaz.,"  March,  1844)  the  vernix 
caseosa  contains  in  100  parts,  5*75  elain,  3*13  margarin  (8*88  fat) ;  the 
rest,  91*12  per  cent.,  must  be  reckoned  as  epidermic  scales,  for  since 
the  vernix  caseosa  contains  no  free  fluid,  the  77*87  per  cent,  water  and 
13*25  solid  substance  found  by  Davy  must  be  laid  to  the  account  of 
epidermic  cells.  This  also  holds  good  of  Buck's  analysis  ("  De  Vernice 
caseosa,"  Halis,  1844)  who  found  in  100  parts,  10*15  fat,  5*40  epithe- 
lium, and  84*45  water  (so  that  there  was  89*85  of  epithelium) ;  and  also 
in  two  other  cases,  in  which  the  water  was  not  exactly  determined,  he 
found  14-80  and  9*31  per  cent,  of  fat,  and  therefore  86*20  to  89*69  of 
moist  epithelium.  According  to  Buek,  the  fat  of  the  vernix  caseosa 
contains  no  cholesterin,  as  had  been  stated  by  Fromherz  and  Gugert, 
but  oleic  acid,  and  either  stearic  or  margaric  acid,  which  are  probably 
not  free,  but  combined  with  glycerine, — a  circumstance  which  also 
evidences  its  origin  from  the  sebaceous  glands,  in  which,  normally,  no 
cholesterin  is  formed.  Lehmann  found  (1.  c.)  in  the  dry  vernix  caseosa 
of  a  nearly  full-grown  foetus,  47*5  per  cent,  of  ethereal  extract,  15*0  of 
alcoholic  extract,  3*3  of  watery  extract,  4*0  of  acetic  acid  extract  (earthy 
phosphates  and  albuminous  substances),  epidermis  and  lanugo  23*7.  In 
the  ethereal  extract  the  reaction  of  bilin  was  absent  and  the  fresh  vernix 
contained  a  large  quantity  of  water,  which  in  all  probability  had  entered 


OF    THE     SKIN.  157 

its  cells  from  the  liquor  amnii.  The  smegma  generally  appears  about 
the  sixth  month,  varies  greatly  in  quantity,  and  is,  especially  in  newly- 
born  infants,  sometimes  very  greatly  developed  (as  much  as  3J  drachms, 
Buek),  sometimes  wholly  wanting ;  in  which  latter  case  it  either  becomes 
mixed  with  the  liquor  amnii,  which  in  fact  often  contains  epidermic 
cells  as  well  as  fat  (Mark,  in  Heller's  "  Archiv,"  1845,  p.  218),  or  may 
have  been  from  the  first,  less  developed.  After  birth  the  smegma  is 
thrown  off  in  the  course  of  from  two  to  three  days,  and  the  permanent 
epidermis  appears,  of  whose  further  changes  up  to  the  adult  state  there 
is  little  to  be  said.  In  a  child  four  months  old  the  epidermis  measured: — 

Epidermis  in  toto.  Rete  Malp.  Horny  layer. 

On  the  heel,         .         .       O26  of  a  line.  0-12  of  a  line.  0-14  of  a  line. 

On  the  back  of  the  foot,     O048-OOG  of  a  line.  0  032-0-04  of  a  line.  O'OlG-0'02  of  a  line. 

On  the  palm,        .         .       0-07-0' 1  "  0-04-0-07         "  0'03  « 

On  the  back  of  the  fingers,  0-050-0-07        «  0'04-0'05         »  O-OlG-0'02       " 

On  comparing  this  with  the  adult,  it  is  to  be  observed  that  the  epidermis 
of  the  young  child  is  disproportionately  thick,  and  that  this  thickness 
depends  especially  upon  the  rete  Malpigliii,  whilst  the  horny  layer 
exhibits  only  a  slight  development.  The  pigment  of  the  rete  Malpigliii 
arises,  in  the  colored  races,  only  after  birth.  P.  Camper  ("  Kleinere 
Schriften,"  1782,  Bd.  I.  p.  24)  saw  a  negro  child,  which  at  its  birth  was 
reddish,  and  hardly  differed  from  that  of  a  European,  rapidly  become 
tinged  black  at  the  edges  of  the  nails  and  round  the  nipple.  On  the 
third  day  the  genitalia  became  colored,  and  on  the  fifth  and  sixth  the 
blackness  spread  over  the  whole  body.  In  Europeans  also,  at  birth,  the 
pigment  of  the  areola  and  of  the  other  places  which  have  been  men- 
tioned, is  not  yet  present:  it  is  gradually  developed  in  the  course  of  the 
first  year,  so  that  in  children  of  two  or  three  months  old  it  is  only  indi- 
cated. 

In  investigating  the  skin,  perpendicular  and  horizontal  sections  of 
fresh,  dried,  and  boiled  preparations  are  serviceable:  they  may  be  mois- 
tened with  an  indifferent  fluid  or  with  various  reagents,  the  most  impor- 
tant points  in  regard  to  whose  effects  have  been  noticed  in  the  foregoing 
paragraphs.  The  epidermis  is  separated  from  the  corium  by  maceration, 
by  boiling,  and  where  it  is  not  thick,  as  on  the  genitalia,  by  acetic  acid 
and  soda,  easily  and  in  large  flakes,  so  that  its  lower  surface  and  the 
papillae  of  the  corium  become  visible  in  the  most  beautiful  manner,  and 
the  latter  may  be  examined  singly  or  in  groups.  In  the  fresh  skin  their 
position  and  number  are  quickly  and  easily  to  be  recognized  in  horizon- 
tal sections,  passing  through  the  papillae  and  the  deep  layers  of  the 
epidermis.  Its  vessels  are  to  be  studied  in  thin  parts  of  the  skin  (geni- 
talia, lips),  in  the  fresh  condition,  or  in  injected  preparations  with  those 
of  the  rest  of  the  skin ;  its  nerves  in  perpendicular  sections,  in  isolated 


158  SPECIAL    HISTOLOGY. 

papillae,  or  in  thin  portions  of  the  skin  (prepuce,  glans,  eyelids,  conjunc- 
tiva bulbi)  after  the  addition  of  acetic  acid  and  dilute  solution  of  caustic 
soda,  or  according  to  Gerber's  and  Krause's  method.  Gerber  boils  the 
skin  until  it  is  transparent,  lays  it  a  few  hours  in  oil  of  turpentine  until 
the  nerves  are  white  and  glistening,  and  then  examines  them  in  fine 
perpendicular  sections  made  with  the  double  knife.  According  to 
Krause,  the  nerves  are  seen  very  well  after  treating  the  skin  with  nitric 
acid,  if  the  right  amount  of  action  is  hit  upon.  The  elastic  tissue  of  the 
skin  comes  out  well  under  the  action  of  acetic  acid,  soda,  arid  potassa. 
The  smooth  muscles  may  be  readily  isolated  in  the  tunica  dartos — with 
more  difficulty  in  the  penis  and  in  the  areola,  where  it  needs  familiarity 
with  them,  in  order  in  all  cases,  to  recognize  them  with  the  naked  eye. 
On  the  hair-sacs  they  are  rendered  visible  microscopically,  if  a  sac,  with 
the  sebaceous  glands  which  appertain  to  it,  be  isolated,  especially  after 
the  application  of  acetic  acid,  as  small  bundles  near  and  in  front  of  the 
sebaceous  glands,  but  best  and  very  easily  in  perpendicular  sections  of 
boiled  skin  (Henle).  The  examination  of  the  fat-cells  is  especially  in- 
structive in  thin  persons,  in  whom  their  membranes  and  nuclei  are 
readily  visible:  in  other  cases  their  membranes  are  readily  demonstrable 
by  the  aid  of  ether,  which  extracts  the  fat ;  but  the  nuclei  are  seen  with 
difficulty,  though  they  may  occasionally  be  discovered  here  and  there 
even  in  full  cells.  The  epidermis  must,  for  its  Malpighian  layer  espe- 
cially, be  examined  fresh,  in  fine  perpendicular  sections,  to  which  acetic 
acid  and  dilute  solution  of  soda  may  be  added ;  the  horny  layer,  par- 
ticularly by  the  addition  of  alkalies,  in  perpendicular  and  horizontal 
sections  ;  however,  mere  maceration  in  water  separates  its  elements  from 
one  another,  and  those  who  are  practised  can  discover  them  in  fresh 
preparations,  when  viewed  both  laterally  arid  from  the  surface. 

Literature. — Gurlt,  "  Vergleichende  Unters.  liber  die  Haut  des  Men- 
schen  u.  d.  Haus-saugethiere,"  &c.,  in  Mull.  "  Archiv,"  1835,  p.  399 
(good  figures  for  the  period) ;  Raschkow,  "  Meletemata  circa  Mammal, 
dentium  evolutionem,"  Vratisl,  1835  (first  more  complete  description 
of  the  elements  of  the  epidermis  under  Purkinje's  guidance) ;  Simon, 
"Ueber  die  Structur  der  Warzen  u.  liber  Pigmentbildung  in  der  Haut," 
Mull.  "Arch.,"  1840,  p.  167  (pigment-cells  in  the  rete  of  white  persons) ; 
Krause,  article  "Haut,"  in  Wagner's  "  Handworterbuch,"  II.  1844,  p. 
127  (a  detailed  and  excellent  treatise);  Kolliker,  "  Zur  Entwicklungs- 
geschichte  der  aussern  Haut,"  in  "  Zeitschrift  fur  wiss.  Zool.,"  Bd.  II. 
p.  67 ;  "  Histological  Observations,"  ibid.  II.  p.  118  ;  Eylandt,  "  De 
musculis  organicis  in  cute  humana  obviis,"  Dorp.  Liv.,  1850.  Besides 
these  refer  particularly  to  the  works  of  Simon  ("  Die  Hautkrankheiten 
durch  anatomische  Untersuchungen  erlautert,"  2  Aufll.,  Berl.,  1851); 
Yon  Barensprung  ("  Beitrage  zur  Anat.  u.  Pathol.  der  menschlichen 


OF     THE     NAILS.  159 

Haut,"  1848);  and  Kramer  ("Ueber  Condylome  u.  Warzen,"  Getting. 
1847).  [Meissner,  "  Beitrage  zur  Anatomic  und  Physiologic  der  Haut ;" 
Leipzig,  1853.]  Figures  are  given  by  R.  Wagner,  "  Icon.  phys. ;"  Ber- 
res,  tab.  vi.  vii.  xxiv.  (middling,  with  the  exception  of  what  regards  the 
vessels) ;  Arnold,  "  Icones  org.  sens.,"  tab.  xi.  (very  pretty,  but  drawn 
with  too  low  magnifying  powers) ;  Hassall,  tab.  xxiv.  xxvi.  xxvii.  (among 
others,  the  skin  of  the  negro  also,  and  the  areola  of  the  white  from 
within,  colored);  and  myself,  "Mikr.  Anatomic,"  Taf.  i. 

II. — OF   THE    NAILS. 

§  48.  The  nails,  ungues,  are  nothing  but  peculiarly  metamorphosed 
parts  of  the  epidermis,  and  like  it  they  consist  of  two  layers, — of  a  soft 
mucous,  and  a  horny  layer,  or  the  proper  nail. 

That  part  of  the  corium  upon  which  the  nail  lies,  or  the  bed  of  the 
nail,  corresponds  exactly  in  form  with  it,  is  elongated,  quadrangular, 
arched  in  the  middle,  shelving  off  anteriorly  and  posteriorly,  and  espe- 
cially on  the  sides.  When  the  nail  is  removed  by  maceration  in  con- 
nection with  the  epidermis,  its  anterior  and  middle  parts  are  uncovered 
whilst  its  lateral  edges  and  its  posterior  segment,  on  the  other  hand, 
are  invested  by  a  process  of  the  cutis,  the  wall  of  the  nail,  which  is 
anteriorly  depressed  and  rounded  off,  posteriorly  more  acute  and  longer, 
and,  taken  together  with  the  bed,  forms  a  fold,  the  fold  of  the  nail, 
which  receives  the  lateral  edges  and  the  posterior  (2-3  lines)  portion  of 
its  root  (Figs.  58,  60). 


The  bed  of  the  nail  presents  upon  its  surface  peculiar  ridges,  similar 
to  those  of  the  palm  and  of  the  sole  of  the  foot  (Fig.  58  a).  They 
begin  at  the  bottom  of  the  fold  of  the  nail,  at  the  posterior  border  of 
its  bed,  and,  as  Henle  (p.  270)  justly  remarks,  they  run  from,  the  mid- 
dle of  it  almost  as  from  a  pole.  The  middle  ones  pass  directly  for- 
wards ;  the  lateral  at  first  describe  an  arc,  which  is  the  more  convex 

FIG.  58. — Transverse  section  through  the1  body  and  bed  of  the  nail,  a,  bed  of  the  nail, 
with  its  ridges  (black)  ;  6,  corium  of  the  lateral  parts  of  the  wall  of  the  nail;  c,  stratum  Mal- 
pighii  of  the  nail  with  its  ridges  (white)  ;  e,  horny  layer  on  the  wall  of  the  nail ;/,  horny  layer 
of  the  nail,  or  proper  nail  substance,  with  short  notches  upon  its  under  surface. — Magnified 
8  diameters. 


1GO  SPECIAL    HISTOLOGY. 

the  further  out  the  ridges  lie,  and  eventually  are  directed  forwards  like 
the  others.  At  a  distance  of  2J  to  3J  lines  from  their  origin,  they  all 
at  once  become  more  prominent,  and  take  on  the  form  of  true  laminae 
of  0-024  to  0-1  of  a  line  in  depth,  which  run  directly  almost  to  the  anterior 
edge  of  the  bed  of  the  nail,  and  then  end  suddenly,  as  if  truncated. 
The  line  of  transition  of  the  ridges  into  the  lamince  is  convex  anteriorly, 
and  divides  the  bed  of  the  nail  into  two  sections,  differing  both  in  their 
extent  and  in  their  color  :  the  posterior  smaller  one  is  nearly  covered 
by  the  wall  of  the  nail  and  underlies  its  root,  the  anterior  and  reddish- 
colored  division  underlying  its  body.  The  ridges  and  laminae  of  the  bed 
of  the  nail,  the  number  of  which  varies  between  50  and  90,  are,  at  their 
edges,  beset  with  a  series  of  short  papillae  of  0'008-0-016  of  a  line.  In 
addition,  I  can  confirm  Henle"s  statement  that  the  bottom  of  the  fold  of 
the  nail  exhibits  a  few  transverse  ridges  with  larger  papillae  directed 
forwards  ;  further  forwards  where  the  lamince  cease,  there  are  also  long 
isolated  papillae.  On  the  nail  of  the  little  toe,  the  papillae  are  frequently 
not  seated  upon  ridges,  but  are  more  dispersed. 

The  wall  of  the  nail  has  no  ridges  upon  its  lower  surface,  and  rarely 
a  papilla  here  and  there.  These  commence  again  upon  its  margin, 
where  they  are  of  some  length,  and  are  continued  thence  upon  its  upper 
surface,  which  is  in  no  respect  distinguishable  from  the  cutis  of  the  back 
of  the  fingers  and  toes. 

The  corium  of  the  wall  and  of  the  bed  of  the  nail 
is  dense,  and  for  a  considerable  distance  contains 
but  little  fat;  in  the  ridges  and  laminae  with  their 
papillae,  it  is  abundantly  provided  with  fine  elastic 
fibres.  The  vessels  are  particularly  numerous  in 
the  anterior  segment  of  the  bed  of  the  nail ;  behind, 
where  the  root  of  the  nail  lies,  and  in  the  wall  they 
are  more  scanty;  their  capillaries,  0'005— O'OOS  of 
a  line,  form  very  distinct  simple  loops  in  the  papillae, 
and  single  trunks  often  pass,  even  into  many  papillae. 
The  nerves  have  the  same  relations  below  as  in  the  skin,  but  I  have 
hitherto  been  unable  to  detect  their  terminal  loops  or  divisions  in  them. 
In  the  nail  itself  we  may  distinguish,  the  root,  the  body,  and  the  free 
edge  (Fig.  60).  The  soft  root  (Fig.  60  t)  corresponds  in  its  extent  to  the 
posterior  ridged  segment  of  the  bed  of  the  nail,  and  is  either  wholly  hidden 
in  the  fold,  or  exposes  a  small  semilunar  surface,  the  lunula.  The  poste- 
rior edge  is  attenuated,  slightly  bent  upwards,  and  is  the  thinnest  and  most 
flexible  part  of  the  nail.  The  hard  body,  which  increases  in  thickness  and 
breadth  from  behind  forwards  (&),  lies  for  the  most  part  with  its  upper  sur- 
face uncovered;  its  somewhat  sharp  thin  edges  are  hidden  in  the  lateral 

FIG.  59. — Capillaries  of  the  bed  of  the  nail,  after  Berres. 


OF    THE    NAILS.  161 

parts  of  the  fold,  and  its  under  surface  reposes  upon  the  anterior  segment 
of  the  bed  of  the  nail :  lastly,  the  free  edge  (m)  is,  in  cut  nails,  directed 

Fig.  60. 

/> 

\<nmmmmmm\i 

m 


straight  forwards,  but  if  uncut,  it  curves  downwards  round  the  ball  of 
the  finger  and  with  the  rest  of  the  nail,  attains  to  a  length  of  as  much 
as  two  inches. 

The  lower  surface  of  the  body  and  of  the  root  answer  in  their  form 
exactly  to  the  bed  of  the  nail,  and  we  therefore  find  laminae  and  ridges 
upon  them,  as  well  as  furrows,  in  the  same  order  as  on  the  latter,  only 
here  the  edges  of  the  laminae  are  straight  and  not  papillated,  whilst  the 
furrows,  instead  of  having  an  even  bottom,  as  in  the  nail-bed,  are  pro- 
vided with  shallow  pits  for  the  reception  of  the  papillae.  By  the  mutual 
interlocking  of  the  elevations  and  depressions,  the  intimate  union  of 
the  nail  with  the  corium  is  effected,  which  becomes  still  more  close  by 
the  application  of  the  under  surface  of  the  wall  of  the  nail  upon  its  base 
and  edges. 

The  color  of  the  nail,  so  long  as  it  remains  in  its  natural  condition, 
is  whitish  and  transparent,  at  its  free  edges  ;  reddish  in  the  body,  with 
the  exception  of  a  very  narrow  clear  margin  close  behind  the  commence- 
ment of  the  free  edge  ;  in  the  lunula,  whitish ;  the  color  of  the  last  two 
portions  arising  principally  from  the  corium  and  its  blood-vessels  which 
shine  through  them.  Separated  from  the  corium  and  epidermis,  the 
nail  is  of  a  tolerably  uniform  whitish  color,  and  transparent,  though 
somewhat  whiter  at  the  root  than  in  the  body. 

§  49.  Structure  of  the  Nail. — The  nail  consists  in  its  deeper  parts  of 
a  soft,  somewhat  pale  stratum  mucosum,  which  is  distinguished  from  the 
hard  external  horny  layer,  or  proper  nail,  still  more  sharply  than  in 
the  common  epidermis.  It  covers  the  whole  of  the  lower  surface  of  the 
root  and  body  of  the  nail,  frequently  also  a  small  part  of  the  upper  surface 

FIG.  60. — Longitudinal  section  through  the  middle  of  the  nail  and  bed  of  the  nail:  a,  bed 
of  the  nail,  and  cutis  of  the  back  and  points  of  the  fingers;  6,  mucous  layer  of  the  points  of 
the  fingers ;  c,  of  the  nail ;  d,  of  the  bottom  of  the  fold  of  the  nail ;  e,  of  the  back  of  the  finger ; 
/,  horny  layer  of  the  points  of  the  fingers;  g,  beginning  of  them  under  the  edge  of  the  nail; 
A,  horny  layer  of  the  back  of  the  fingers  ;  i,  ends  of  it  upon  the  upper  surface  of  the  root  of 
the  nail ;  fc,  body ;  /,  root ;  m,  free  edge  of  the  proper  substance  of  the  nail. — Magnified  8 
diameters. 

11 


162 


SPECIAL    HISTOLOGY. 


Fig. 


of  the  root,  and  forms  by  itself  the  above-mentioned  laminge  on  the  under 
surface  of  the  nail.     Its  thickness  at  the  posterior  part  of  the  root  upon 

the  under  side  measures  0-12,  on 
the  upper,  0-14  of  a  line ;  close  be- 
hind the  margin  of  the  root,  direct- 
ly from  behind  forwards,  0-24— 
0-26  of  a  line  ;  on  the  body  of  the 
nail  on  the  laminae,  more  poste- 
riorly and  at  the  edge  0-04-0-05 
of  a  line;  in  the  middle,  0*06  even 
0-08-0-96  and  0-12;  between 
these,  0-032-0-04  of  a  line. 

The  Malpighian  layer  of  the 
nail,  like  that  of  the  epidermis, 
consists  wholly  of  nucleated  cells, 
and  agrees  in  all  essential  points 
with  it,  except  that  the  deep  por- 
tion contains  many  layers  of  elon- 
gated (of  0-004-0-007  of  a  line) 
perpendicular  cells,  in  conse- 
quence of  which  a  striated  appearance  is  produced,  which  has  misled 
Gunther,  and  probably  Rainey  also,*  into  supposing  the  existence  of 
peculiar  glands  under  the  nail.  In  the  Negro,  according  to  Be'clard 
(Anat.  Gene'rale,  p.  309),  the  stratum  Malpighii  of  the  nail  is  black ; 
and  according  to  Krause  (1.  c.  p.  124),  its  cells  would  in  this  case  appear 
to  contain  dark-brown  nuclei,  as  well  as  yellowish-brown  ones,  in  dark 
Europeans.  According  to  Hassall  (p.  252),  the  younger  cells  of  the 
nail  (i.  e.,  those  of  the  stratum  mucosum\  generally  contain  pigment, 
which  I  can  confirm,  at  least  in  some  cases. 

The  horny  layer  of  the  nails,  or  its  proper  substance  (Figs.  58  /;  60 
&,  I,  m;  61  c),  is  that  hard  brittle  portion  which  forms  its  upper  part 
and  its  free  edge.  The  under  surface  of  this  layer  is  quite  smooth,  pos- 
teriorly at  the  root ;  further  forward  it  exhibits  sharp  ridges  separated 
by  broad  furrows,  which  are  inserted  into  the  furrows  of  the  mucous 
layer  of  the  nail.  These  ridges  of  the  proper  nail  substance  appear  in 

FIG.  61. — Transverse  section  through  the  body  of  the  nail;  magnified  250  diameters. 
.>#,  cutis  of  the  bed  of  the  nail ;  jB,  mucous  layer  of  the  nail ;  C,  horny  layer  of  it,  or  proper 
nail  substance ;  a,  layers  of  the  bed  of  the  nail ;  6,  layers  of  the  stratum  Malpighii  of  the 
nail ;  c,  ridges  of  the  proper  substance  of  the  nail ;  d,  deepest  perpendicular  cells  of  the 
mucous  layer  of  the  nail;  e,  upper  flat  cells  of  it;  /,  nuclei  of  the  proper  substance  of  the 
nail. 

*  [With  respect  to  Rainey's  observations,  Reichert,  in  his  Report  for  1849-50  ("  Mull.  Arch.," 
1850-51)  says,  that  the  observation  as  to  the  follicles  is  quite  correct,  and  that  with  Dr. 
Ammons,  who  had  studied  the  growth  and  regeneration  of  the  nails  for  some  years,  he  had 
seen  such  capsules  containing  horny  cells,  with  especial  distinctness  upon  the  bed  of  the 
nail  of  the  great  toe. — TES.] 


OF    THE    NAILS. 


163 


transverse  sections  (Figs.  58,  61),  as  pointed  processes  of  0-01-0-02  of 
a  line  in  length,  which,  as  a  rule,  are  most  strongly  developed  at  the 
edges  of  the  nail,  even  to  0-04—0-06  of  a  line,  and  answer  precisely  in 
their  number  to  the  laminye  of  the  under  side  of  the  stratum  Malpighii. 
The  upper  surface  of  the  substance  of  the  nail  is  smooth,  taken  as  a 
whole,  yet  sometimes  even  here,  very  distinct,  parallel,  longitudinal 
streaks  appear  as  the  last,  almost  effaced  indications,  of  the  inequalities 
of  its  bed. 

Usually,  the  thickness  of  this  part  of  the  nail  continually  increases 
from  the  root  to  near  the  free  edge,  so  that  the  body  of  the  nail  is,  an- 
teriorly, at  least  three  times  thicker  (from  0-3  to  0-4  of  a  line)  than  the 
former ;  at  the  free  edge  again,  it  becomes  somewhat  less.  In  its  trans- 
verse diameter  also,  with  the  exception  of  the  posterior  edge  of  the  root, 
the  substance  of  the  nail  is  not  everywhere  equally  thick ;  it  thins  con- 
siderably towards  the  lateral  edges,  so  that  at  last  the  nails,  where  they 
lie  in  the  fold,  measure  not  more  than  0-06-0-12  of  a  line,  and  finally 
terminate  quite  sharply. 

With  regard  to  the  structure  of  the  proper  substance  of  the  nail,  it 
can  hardly  be  made  out  without  the  action  of  reagents.  In  perpen- 
dicular sections  we  see,  particularly  in  the  body,  nothing  but  horizontal, 
fine,  straight,  or  curved,  closely-approximated  lines,  which  one  would  be 
inclined  to  consider  as  the  optical  expression  of  delicate,  superimposed 
lamellae,  and  between  these,  a  multitude  of  elongated,  horizontal, 
opaque  or  peculiar  reddish-transparent  striae,  evidently  nuclei.  Only 
upon  the  most  posterior  part  of  the  root,  and  on  the  under  surface,  where 
it  meets  the  stratum  Malpighii,  do  more  or  less  distinctly  flattened  cells 
with  nuclei  appear  disposed  in  layers.  Horizontal  sections  show  even 
less  than  the  perpendicular  ones ;  exhibiting  a  pale  transparent  sub- 
stance, granular  here  and  there,  and 
mostly  without  indication  of  any 
structure  whatsoever,  occasionally 
with  very  indistinct  contours  of  plates 
similar  to  those  of  the  horny  layer  of 
the  epidermis.  Very  different  are  <f 
the  appearances  presented  after 
treating  the  nail  with  alkalies  and 
certain  acids. 

If  the  substance  of  the  nail  be 
boiled  in  dilute  caustic  soda,  it  be- 
comes changed  upon  the  first  bub- 
bling of  the  fluid  into  a  beautiful 
cellular  tissue  (Fig.  62,  J.,  B\  whose 

FIG.  62. — Nail  plates  boiled  with  caustic  soda.  A,  from  the  side;  B,  from  the  surface: 
a,  membranes  of  the  distended  elements  of  the  nail ;  6,  their  nuclei,  from  the  surface ;  c, 
from  the  side. — Magnified  350  diameters. 


Fig.  62. 


164  SPECIAL    HISTOLOGY. 

polygonal  elements  all,  without  exception,  the  deep  as  well  as  the 
superficial,  possess  nuclei  of  0-0030-0-0046  of  a  line  in  length  and 
breadth,  and  0-002  of  a  line  in  thickness,  which,  according  as  they 
turn  their  surfaces  or  their  edges  to  the  observer,  appear  as  rounded, 
very  pale,  and  finely-granulated  discs,  or  as  long,  narrow,  dark-con- 
toured rods ;  it  deserves  further  to  be  noted,  that  together  with  these, 
large  and  very  pale  nuclei  of  0*006-0-01  of  a  line,  and  more,  occur  in 
considerable  numbers,  probably  owing  their  existence  to  the  excessive 
action  of  the  reagent  which  has  swollen  them  up.  Caustic  soda  and 
potass  also  (which  has  a  similar  action  upon  the  whole,  though  it  acts 
more  upon  the  nuclei)  demonstrate  the  important  fact,  that  the  cells  of 
the  nail  are  flatter  in  the  superficial  than  in  the  deeper  layers.  If,  in 
fact,  a  fine  perpendicular  section  be  moistened  with  cold,  or  better,  with 
hot  solution  of  soda,  we  see  the  cellular  structure  of  the  nail  appear 
almost  at  the  very  instant  it  becomes  moistened,  without  any  obvious 
enlargement  of  its  elements ;  and  it  is  observable,  at  the  same  time,  that 
its  deepest  cells  are  at  least  as  thick  again  as  the  most  superficial. 

If  the  soda  solution  acts  longer,  the  section  gradually  swells  up,  in 
the  under  cells  first,  on  account  of  their  greater  softness,  and  only  sub- 
sequently in  the  flat  and  hard  upper  elements.  By  treating  the  nail 
with  cold  sulphuric  and  nitric  acids,  and  also  by  boiling  with  hydro- 
chloric acid,  its  elements  are  isolated. 

Taking  these  facts,  together  with  what  we  see  in  the  unaltered  nail, 
it  results  that  its  horny  layer  consists  of  closely  united  but  not  sharply 
defined  lamellae;  each  lamella  being  composed  of  one  or  many  layers  of 
nucleated,  polygonal,  flat  scales  or  plates,  which,  excepting  their  nuclei, 
are  very  similar  to  those  of  the  horny  layer  of  the  epidermis,  and  in 
their  deepest  layers  are  thicker  and  somewhat  less  in  circumference  than 
in  the  upper  and  uppermost  layers.  Those  of  0-012—0*016  of  a  line, 
may  be  regarded  as  of  an  average  size,  as  may  be  seen  upon  the  addition 
of  sulphuric  acid,  which  otherwise  exerts  but  little  action,  and  at  the 
commencement  of  the  operation  of  soda  and  potass. 

i 

§  50.  With  respect  to  the  relation  of  the  nail  to  the  epidermis,  I  must 
especially  refer  to  the  perpendicular  and  transverse  sections  figured  in 
Figs.  58  and  60.  They  show,  in  the  first  place,  that  the  epidermis  ap- 
plies itself  upon  the  root,  the  posterior  part  of  the  body,  and  upon  the 
margins  of  the  nail,  and  that  it  meets  it  under  the  free  edge  and  on  the 
anterior  parts  of  the  lateral  edges.  This  happens  in  such  a  manner, 
that  whilst  the  mucous  layer  of  the  epidermis  passes  continuously,  and 
without  any  line  of  demarcation,  into  that  of  the  nail,  the  horny  layer 
is,  properly  speaking,  never  continued  directly  into  the  actual  substance 
of  the  nail,  but  partly  applies  itself  with  its  lamellae  parallel  upon  the 
nail,  partly  abuts  upon  it  at  various  oblique  angles.  At  the  root,  the 
horny  layer  passes  more  or  less  deeply  into  the  fold  of  the  nail,  and  at 


OF    THE    NAILS.  165 

the  same  time  runs,  in  a  thin  layer  which  becomes  very  fine  anteriorly, 
upon  the  upper  free  part  of  the  nail,  as  far  as  the  end  of  the  lunula  or 
the  beginning  of  the  body.  Anteriorly  and  posteriorly,  in  which  latter 
region  this  layer  not  uncommonly  reaches  the  posterior  margin  of  the 
root,  its  cells  lie  parallel  to  the  upper  surface  of  the  nail ;  while  in  the 
middle,  where  it  is  thickest  (Fig.  60  i),  they  are  oblique  or  perpendicular 
to  it.  At  the  free  edge  of  the  nail  the  relations  of  the  parts  are  similar, 
where  the  horny  layer  meeting  the  end  of  the  under  surface  of  the  body 
of  the  nail,  partly  with  more  horizontal,  partly  with  oblique  lamellae,  is 
perhaps  also  continued  upon  the  commencement  of  the  free  edge.  On 
the  lateral  edges,  again,  the  horny  layer  passes  anteriorly,  in  horizontal 
strata,  under  the  nail ;  more  posteriorly  it  is  arranged  as  upon  the  root, 
or  simply  rests  against  the  edge  of  the  nail.  The  horny  layer  thus 
forms  a  kind  of  sheath  for  the  nail,  which  bears  some  resemblance  to 
the  sheath  of  the  hair,  though  it  is  much  more  imperfect.  If  we  com- 
pare the  nail  with  the  epidermis,  we  find,  in  the  structure  of  its  mucous 
layer,  not  the  slightest  peculiarity  of  any  importance,  while  the  horny 
layer  is  distinguished  from  that  of  the  epidermis  by  its  cells  being 
nucleated,  harder,  and  chemically  different ;  by  their  flattening  and  in- 
timate union.  For  the  rest,  the  agreement  of  the  two  structures  is  so 
close,  that  the  proper  nail  may  justly  be  considered,  as  it  has  long  been, 
a  modified  portion  of  the  horny  layer  of  the  last  joints  of  the  fingers 
and  toes. 

According  to  the  chemical  investigations  of  Scherer  and  Mulder,  the 
nails  agree  very  closely  with  the  epidermis ;  and,  according  to  Mulder, 
they  are  distinguished  from  it,  only  by  their  somewhat  greater  propor- 
tion of  sulphur  and  carbon.  In  his  last  essay,  he  considers  them  to  be 
composed  of  protein  +  sulphamid  (6'8  per  cent,  of  the  latter).  This 
agrees  with  the  observed  action  of  reagents,  with  which  the  plates  of  the 
nail  behave  almost  exactly  like  horny  plates,  only  they  are  attacked 
with  more  difficulty  and  possess  nuclei.  According  to  Lauth,  the  nails 
contain  more  phosphate  of  lime  than  the  epidermis,  whence  they  derive 
their  hardness :  this  may  be  correct,  although,  as  Mulders  tates  (a  Phys. 
Chemie,"  p.  536),  both  yield  about  the  same  proportion  of  ash  (1  per 
cent.). 

As  regards  the  lamellar  structure  of  the  proper  nail,  it  is  to  be  re- 
garded in  the  same  light  as  that  of  the  horny  layer  of  the  epidermis  ;  but 
it  is  not  so  distinct,  because  the  plates  of  the  nail  are  more  intimately 
connected  than  the  elements  of  the  epidermis.  Reagents,  however, 
render  the  lamellar  structure  very  evident,  and  it  is  also  clear  in  patho- 
logically thickened  and  curved  nails. 

§  51.  G-rowth  of  the  Nails. — The  nails  grow  continually,  as  long  as 
they  are  cut ;  on  the  other  hand,  if  uncut,  their  growth  is  limited.  In 


166  SPECIAL    HISTOLOGY. 

this  case,  as  may  be  observed  in  those  who  are  long  confined  to  their 
beds  by  sickness,  and  in  the  Eastern  Asiatics,  the  nails  become  1J-2 
inches  long  (in  the  Chinese,  according  to  Hamilton,  2  inches),  and  to 
curve  round  the  points  of  the  fingers  and  toes. 

During  the  growth  of  the  nail,  the  mucous  layer  does  not  change  its 
position  at  all,  but  its  horny  layer  is  constantly  being  thrust  forward. 
The  formation  of  the  latter  goes  on  continually  wherever  it  is  in  contact 
with  the  stratum  Malpighii^  in  other  words  upon  its  whole  under  sur- 
face, with  the  exception  of  the  free  anterior  edge  ;  further,  in  many  nails, 
upon  a  very  small  portion  of  the  upper  surface  of  the  root,  finally,  at 
the  posterior  edge  of  the  root  itself.  It  is,  however,  the  root  portion 
which  grows  fastest,  whilst  the  body  of  the  nail  is  more  slowly  developed, 
which  is  demonstrated  especially  by  the  fact  that  it  is  not  much  thinner 
at  the  boundary  between  the  root  and  the  body  than  it  is  anteriorly  upon 
the  body  itself,  and  that  the  transition  of  the  cells  of  the  stratum  Malpighii 
into  nail-cells  is  easily  shown  at  the  root,  but  with  difficulty  in  the  body. 
By  the  constant  addition  of  new  cells  at  the  edge  of  the  root,  the  nail 
grows  forward ;  by  their  addition  to  its  under  surface,  it  is  thickened. 
The  longitudinal  growth  exceeds  that  in  thickness,  because  the  first 
rounded  cells,  as  they  move  from  behind  and  below,  forwards  and  up- 
wards, become  more  and  more  flattened  and  elongated. 

The  mode  in  which  the  plates  of  the  nail  arise  from  the  cells  of  the 
mucous  layer,  is  easily  demonstrable  at  the  root  of  the  nail.  Here,  in 
fact,  the  uppermost  cells  of  the  mucous  layer  are  constructed  very  dif- 
ferently from  the  deeper  ones  ;  they  are  more  or  less  flattened,  and  closely 
resemble  the  cells  of  the  epidermis,  but  they  possess  a  nucleus,  which, 
however,  is  only  to  be  discovered  by  adding  caustic  soda,  and  then  with 
difficulty.  If  we  follow  these  cells,  which  form  a  layer  of  0'06-0'12  of 
a  line  in  thickness,  toward  the  proper  substance  of  the  nail,  we  find 
that  they  become  more  and  more  flattened,  and  at  last  pass  without  any 
defined  boundary  into  the  latter,  uniting  together  more  closely,  and 
taking  on  a  more  transparent  appearance. 

In  the  body  of  the  nail,  the  formation  of  nail  substance  is  demonstrated 
with  more  difficulty,  yet  here,  in  opposition  to  Reichert,  we  must  assume 
that  it  does  take  place,  because  the  nail  almost  invariably  increases  in 
thickness  even  in  the  body,  from  behind  forwards.  However,  there  is 
unquestionably,  in  this  part,  a  sharper  demarcation  between  the  two 
layers  of  the  nail,  than  in  the  root ;  but  in  fine  sections  it  appears  by 
no  means  so  sharp  as  in  those  which  are  commonly  examined,  and  I  find, 
in  fact,  that  the  transition  of  the  cells  of  the  mucous  layer  into  the  plates 
upon  the  body  of  the  nail,  is  demonstrable  with  tolerable  readiness,  par- 
ticularly on  the  addition  of  alkalies,  where  the  ridges  of  the  under  sur- 
face of  the  proper  nail  are  well  developed.  Between  the  ridges  also, 
though  no  direct  transition  is  recognizable,  yet  it  may  be  observed  that 


OF    THE    NAILS.  167 

the  plates  of  the  proper  nail  which  border  upon  the  mucous  layer  are 
much  less  flattened  than  in  the  interior  and  on  the  surface,  which  also 
indicates  that  they  are  developed  upon  the  spot.  In  conclusion  I  must 
add,  in  support  of  my  view,  that  it  is  only  in  this  way,  that  it  becomes 
explicable  why  the  under  surface  of  the  proper  nail  substance  upon  the 
root  of  the  nail  is  almost  smooth,  while  on  the  body  of  the  nail  it  pre- 
sents more  or  less  prominent  ridges.  The  origin  or  increase  of  these 
ridges  demonstrates  clearly  that  nail-substance  is  also  formed  here. 
Corresponding  with  these  ridges  and  with  the  grooves  between  them,  we 
also  find  that  the  lowest  layers  of  the  nail  plates,  which  are  quite  hori- 
zontal upon  the  root,  run  with  an  undulating  course  upon  the  body  (Fig. 
61).  The  general  result  then  is,  that  whilst  the  formation  of  the  nail 
goes  on  especially  at  its  root,  yet  that  plates  are  added  to  the  body  of 
the  nail  from  below,  though  more  slowly  and  scantily,  thus  producing  the 
anterior  thickening,  or  at  least  preventing  the  necessary  thinning  of  the 
nail  anteriorly.  It  is  to  be  remarked  further,  that  the  development  of 
nail-substance  takes  place  in  all  parts  of  the  middle  line  of  the  nail 
more  rapidly  than  in  the  lateral  portions,  which,  anteriorly,  are  almost 
as  thin  as  in  the  root,  though  they  possess  longer  processes  below.  But 
even  there,  substance  must  be  added  to  the  body  of  the  nail,  because  it 
becomes  broader  anteriorly. 

The  plates  of  the  substance  of  the  nail  once  formed,  alter  in  certain 
respects,  as  they  are  pushed  forwards  and  upwards  by  those  which  come 
after  them.  In  the  first  place,  their  nature  becomes  altered  in  a  man- 
ner which  is  little  understood,  the  change  consisting  partly  in  the  depo- 
sition of  more  phosphate  of  lime,  partly  in  a  solidification  (conversion 
into  horn)  of  their  organic  elements,  particularly  of  the  cell-mem- 
branes, in  consequence  of  which,  from  being  soft,  as  at  the  root  and 
under  surface  of  the  nail,  they  become  gradually  harder  and  harder. 
In  the  second  place,  like  the  horny  cells  of  the  epidermis,  they  are 
very  considerably  flattened,  and  at  the  same  time  increase  somewhat  in 
their  longitudinal  and'  transverse  diameters ;  finally,  they  coalesce  more 
completely,  so  that  they  cannot  be  separately  recognized,  without  the 
action  of  reagents,  in  the  upper  and  anterior  parts  of  the  nail,  which 
appear  to  be  composed  of  nothing  but  a  homogeneous  substance  which 
tears  in  all  directions;  whilst  in  the  lower  parts  the  separate  nail- 
plates  are,  at  least,  indicated,  and  are  occasionally  tolerably  distinct. 
On  the  other  hand,  the  nuclei  of  the  nail-plates  do  not  disappear,  and 
in  this  lies  a  characteristic  distinction  between  the  horny  layer  of  the 
nail  and  that  of  the  epidermis.  They  are  to  be  seen  in  perpendicular  sec- 
tions, of  fresh  nails,  and  after  treatment  with  caustic  soda,  and  even  in 
the  most  superficial  layers,  though  somewhat  smaller  and  flatter  than  in 
the  deep  layer.  It  follows  then,  that  certain  metamorphoses  go  on  in 
the  proper  substance  of  the  nail,  which  as  in  the  epidermis,  are  to  be 
ascribed  to  a  peculiar  growth  and  vital  process  in  the  nail-cells  them- 


168  SPECIAL     HISTOLOGY. 

selves.  These  seem  to  occur,  however,  almost  solely  in  the  lower  and 
posterior  parts  of  the  nail,  for  if,  as  Schwann  states  (Fig.  91),  two  points 
be  marked  upon  the  posterior  portion  of  the  free  surface  of  the  nail, 
one  behind  the  other,  by  piercing  it  with  a  needle  and  coloring  with 
nitrate  of  silver,  they  in  no  wise  alter  their  relative  position  in  the  course 
of  the  two  or  three  months,  during  which  they  are  moving  towards  the 
point  of  the  nail. 

As  to  the  pathological  conditions  of  the  nails,  they  are  readily  regene- 
rated when  they  have  been  detached,  in  consequence  of  crushing,  burn- 
ing, freezing,   cutaneous   disorders  (scarlet  fever,   &c.),  inflammations, 
exudations,  suppurations,  and  effusions  of  blood  in  the  bed  of  the  nail; 
in  fact,  as  Pechlin  ("  Obs.  Phys.  Med.,"  p.  315)  narrates,  this  regene- 
ration may  take  place  periodically;  in  a  boy,  the  nails,  every  autumn 
became  bluish-black  and  desquamated,  together  with  the  epidermis  (the 
horny  layer  ?),  and  were  subsequently  regenerated.  In  such  a  case,  accord- 
ing to  Lauth  ("  Me'm.  sur  divers  points  d'Anatomie,"  in  the  "  Annales  de 
la  Socidte  d'Histoire  Naturelle  de  Strasbourg,"  t.  i.  1834),   and  Hyrtl 
("  Anatomic,"  p.  382),  the  whole  bed  of  the  nail  becomes  covered  by  soft 
horny  plates,  which  harden  by  degrees,  grow  into  a  regular  nail,  and 
eventually  project  with  their  free  edges  beyond  the  end  of  the  finger. 
When  the  last  joint  of  the  finger  has  been  lost,  rudimentary  nails  fre- 
quently appear  upon  the  back  of  the  second  and  even  of  the  first  phalanx. 
The  older  cases  are  quoted  in  Pauli  ("De  vulneribus  sanandis,"  Got- 
tingse,  1825,  p.  98),  more  recently  Hyrtl  (1.  c.)  saw  such  a  nail  2  lines 
long  and  3  lines  broad  on  the  first  phalanx  of  the  thumb.     As  the  for- 
mation of  nail-substance  depends  upon  the  vessels  of  the  bed  of  the  nail, 
we    may,   with  Henle,   assume  that  varying   conditions  of    the  latter 
may  frequently  produce  local  thickening,  thinning,  or  even  detachment 
of  the  nail,  and  that  their  deformities  in  cyanosis  and  phthisis  depend 
on  these  causes.      The  thickening  and  abnormal  development  of  the 
nails,  however,  arise  very  frequently,  as  I  have  observed,  from  a  partial 
obstruction  of  the  capillaries  of  their  bed.     Thus  in  the  lamellated  nails 
of  old  people,  greatly  thickened  and  curved  downwards  in  front,  I  find 
all  the  capillaries  of  the  anterior  segment  of  the  bed  of  the  nail  closely 
filled  with  fat  granules  of  different  sizes,  and  wholly  impermeable  to  the 
blood ;  in  such  a  case  the  development  of  nail-substance  can  take  place 
only  in  small  lamellae  in  the  fold,  which  then,  as  may  be  readily  under- 
stood, are  raised  up  by  those  which  are  growing  behind  into  a  continu- 
ally more  and  more  oblique  position  ;  their  posterior  extremities  forming, 
on  the  surface  of  the  nail,  transverse  streaks  one  behind  another  at 
short  intervals.     After  dividing  the  nervus  ischiadicus,  Steinriick  ("  De 
nervorum  regeneratione,"  pp.  45-49)  observed,  in  the  Rabbit,  that  the 
nails  and  hair  fell  off,  which  is  a  result  of  the  influence  of  the  nerves 
upon  the  vessels.     Finally,  the  shape  of  the  bed  of  the  nail  also  in- 
fluences its  formation.    It  is  thus  explained,  how  (see  Henle,  1.  c.),  after 


OF    THE    NAILS.  169 

inflammation  and  closure  of  the  fold  of  the  nail,  the  formation  of  new 
nail  at  the  posterior  edge  ceases,  the  nail  no  longer  growing  forwards, 
but  at  all  its  edges  exactly  covering  its  bed. 

§  52.  The  development  of  the  nail  begins  in  the  third  month  with  the 
formation  of  the  bed  and  fold,  which  are  marked  off  from  the  surround- 
ing parts  by  the  gradual  growth  of  the  skin  into  the  wall  of  the  nail. 
At  first  the  bed  of  the  nail  is  lined  by  the  same  cells  as  those  which  form 
the  other  parts  of  the  epidermis  (see  §  47),  only  that  even  in  the  third 
month  the  cells  of  the  stratum  Malpighii  are  distinguished  by  their 
elongated  and  polygonal  form  (length  0-004,  breadth  0-001-0-0016  of 
a  line).  In  the  fourth  month  there  arises  between  the  stratum  Mal- 
pighii and  the  horny  layer  of  the  bed  of  the  nail,  which  latter  is  formed 
by  a  simple  layer  of  polygonal  clearly  nucleated  cells,  a  simple  lamina 
of  pale,  flat,  but  also  quadrangular  and  nucleated  cells,  0*009  of  a  line 
in  diameter,  which  are  closely  united  together,  and  must  be  regarded  as 
the  first  indication  of  the  proper  substance  of  the  nail ;  at  the  same  time 
also,  the  stratum  Malpighii  under  these  cells  become  thickened  so  that 
it  is  certainly  composed  of,  at  least,  two  layers.  The  nail  is  therefore 
at  first  wholly  included  within  the  epidermis  ;  it  is  formed  over  the  whole 
surface  of  the  led  of  the  nail  as  a  quadrangular  plate,  and  arises  between 
the  embryonic  mucous  layer  and  the  horny  layer,  without  doubt  by  a 
metamorphosis  of  the  cells  of  the  mucous  layer,  as  is  probable,  especially 
from  the  minute  size  of  the  original  cells  of  the  nails.  In  the  course  of 
its  further  development,  the  nail  is  thickened  by  the  addition  of  new 
cells  from  below  (in  the  fifth  month  its  thickness  is  about  0'024,  in 
the  sixth  0-04  of  a  line,  of  which  in  the  latter  0'025  must  be  reckoned 
as  proper  nail-substance);  it  increases  by  the  extension  of  its  elements, 
and  by  the  addition  of  new  ones  at  its  edges ;  but  it  remains,  even  to 
the  end  of  the  fifth  month,  hidden  under  the  horny  layer  of  the  epider- 
mis, until  finally  it  becomes  free,  and  in  the  seventh  month,  even  begins 
to  grow  longitudinally,  so  that  at  this  period,  except  in  its  greater 
softness  and  its  smaller  dimensions,  it  presents  no  essential  difference 
from  the  perfect  nail.  With  regard  to  the  bed  of  the  nail,  its  ridges 
are  already  indicated  at  the  end  of  the  fourth  month,  and  in  the  fifth 
they  are  well-marked,  0-02-0-024  of  a  line  deep,  0-004-0-005  of  a 
line  broad,  and  0-008-0-014  of  a  line  distant;  these  measurements  also 
indicate  the  breadth  of  the  laminae  of  the  stratum  Malpighii.  At  the 
sixth  month  they  are  somewhat  larger  and  further  apart. 

In  the  new-born  infant,  the  whole  nail  is  0-3-0-34  of  a  line  thick ; 
0-16  of  a  line  being  proper  nail-substance,  0-14-0-18  of  a  line  stratum 
Malpighii.  Its  elements  are  still  almost  identical  with  those  at  the  sixth 
month,  and  they  appear  with  tolerable  distinctness  in  the  nail  proper 
without  any  reagents,  as  elongated  polygonal  nucleated  plates  0-002-0*28 
of  a  line,  as  Schwann  has  already  partly  remarked.  The  free  edge, 


170  SPECIAL    HISTOLOGY. 

projecting  far  forwards,  which  is  presented  in  all  nails,  is  worthy  of 
remark.  It  is  considerably  thinner  and  narrower  than  the  body,  and  is 
separated  from  it  by  a  semilunar  line ;  it  is  rounded  anteriorly,  as  much 
as  2  lines  long,  and  is  plainly  nothing  but  the  nail  of  an  earlier  period 
which  has  been  thrust  forward  by  the  longitudinal  growth  of  the  nail  in 
the  course  of  its  development.  In  fact  it  nearly  corresponds  in  size  with 
a  nail  of  the  sixth  month. 

Soon  after  birth  the  long  free  edge  of  the  nail  of  the  new-born  infant 
is  cast  off,  at  least  once  (according  to  Weber  many  times),  in  all  pro- 
bability in  consequence  of  external  mechanical  violence,  which  it  is 
unable,  owing  to  its  delicacy,  to  resist.  In  the  sixth  and  seventh  months 
after  birth,  I  find  that  the  nails  which  the  child  brought  into  the  world, 
are  completely  replaced  by  new  ones,  and  in  the  second  and  third  years 
the  nail-plates  are  not  distinguishable  from  those  of  the  adult,  whence 
it  follows  that  the  nail  increases  in  thickness,  less  in  consequence  of  any 
enlargement  of  its  elements,  than  by  the  addition  of  new  ones  to  its 
edges  and  under-surface. 

The  investigation  of  the  nail-cells  and  plates  is  best  made  in  fine 
sections  of  recent  nails,  with  and  without  the  addition  of  reagents, 
especially  caustic  soda  and  sulphuric  acid,  concerning  whose  operation 
the  most  important  points  have  already  been  noted.  To  examine 
the  relations  of  the  parts  of  the  nail  to  one  another,  and  to  the  epi- 
dermis, the  nails  must  be  separated  from  the  cutis  by  maceration,  or  by 
boiling  in  water.  It  is  then  seen,  that  the  nail  is  detached,  with  the 
cuticle,  from  the  finger ;  and  in  transverse  and  longitudinal  sections,  its 
mode  of  connection  with  the  former  is  perceived.  The  bed  of  the  nail 
also,  its  lamince  and  ridges,  the  fold  and  the  lamince  in  the  stratum 
Malpigliii  of  the  nail,  are  easily  seen,  in  this  way.  Since  fine  sections, 
in  such  a  nail,  are  not  readily  made,  precisely  in  the  most  important 
parts — the  margins  and  roots, — it  is  necessary,  for  this  purpose,  to 
employ  fresh  nails  separated  from  the  bone  with  the  cutis,  and  dried. 
These  afford  all  the  information  required,  portions  of  them  swelling  up 
readily  in  water,  and  exhibiting  the  structure  of  the  different  layers, 
with  acetic  acid  and  caustic  soda,  in  the  most  distinct  manner. 

Literature. — A.  Lauth,  "  Sur  la  disposition  des  ongles  et  des  poils," 
Mem.  de  la  Socie'te'  d'hist.  nat.  de  Strasbourg,  1830-4 ;  Gurlt,  "  Ueber 
die  hornigen  Gebilde  des  Menschen  u.  der  Haussaugethiere,"  Mull. 
"Arch.,"  1836,  p.  262;  Reichert,  in  Mull.  "Arch.,"  1841,  Jahresbe- 
richt;  0.  Kohlrausch,  "Recension  von  Henle's  allgem.  Anat.,"  in  Get- 
ting. "  Anzeigen,"  1843,  p.  24;  Rainey,  "On  the  structure  and  forma- 
tion of  the  nails  of  the  fingers  and  toes,"  in  "Trans,  of  Microsc.  Society," 
March,  1849;  Berthold,  "Beobachtungen  uber  das  quantitative  Verhalt- 
niss  der  Nagel-  u.  Haarbildung  beim  Menschen,"  in  Mull.  "Arch.,"  1850. 


OF    THE    HAIRS. 


171 


Fig.  63. 


III.— OF  THE  HAIRS. 

§  53.  In  every  hair  we  distinguish  the  free  part  or  shaft,  scapus,  with 
its  tapering  point,  from  the  portion  enclosed  within  the  sac,  the  root, 
radix.  In  straight  hairs  the  former  is  generally  straight  and  rounded; 
in  the  wavy,  undulated  and  somewhat  flattened ;  in  the  curly  and  woolly 
hairs,  it  is  twisted  spirally  and  quite  flat  or 
slightly  ribbed.  The  root  is  always  straight, 
tolerably  cylindrical,  and  softer  and  thicker 
than  the  shaft,  at  least  in  its  lower  part ; 
in  living  hairs  it  ends  in  a  still  softer  knob- 
like  enlargement,  1|-  to  3  times  thicker 
than  the  shaft, — the  "  bulb  of  the  hair"  (<?), 
which  is  placed,  cap-like,  upon  a  papillary 
process  of  the  sac,  the  "  hair-papilla"  (less 
properly  termed  pulpa  or  blastema  pili, 
hair-germ),  or  in  other  words  receives  the 
papilla  in  an  excavation  in  its  base. 


4 


§  54.  Disposition  and  Size  of  the  Hairs. 
— The  hairs  are  distributed  over  almost  the 
whole  surface  of  the  body,*  but  exhibit  very 
considerable  differences  in  size  and  number, 
according  to  their  situation,  to  individual 
peculiarity,  age,  sex,  and  race.    As  regards 
the  former,  three  varieties  may  be  admitted, 
besides  many  .transitional  forms:  (1)  long 
soft  hairs,  of  1-3  feet  and  more  in  length, 
0-02-0-05  of  a  line  in  thickness;  (2)  short 
stiff  thick  hairs,  of  J-J  of  an  inch  in  length, 
and  0-03-0-07  of  a  line  in  thickness ;  (3) 
short,  excessively-fine  hairs,  down  (lanugo), 
of  1-6  lines  in  length,  and  0-006-0-01  of  a  line  in  thickness.      The  dis- 
tribution of  the  first  form  is  well  known;  to  the  second  belong  the  hairs 
at  the  entrance   of  the   nostrils   (vibrissce),   in  the  external  auditory 
passage,  the  eyelashes  (cilia),  and  eyebrows;  to  the  third,  finally,  must  , 
be  referred  the  hairs  on  the  face,  trunk,  and  extremities,  also  those  of 

FIG.  63. — Hair  and  hair  sacs  of  middling  size;  magnified  50  diameters:  a,  hair  shaft;  b, 
root  of  the  hair;  c,  bulb  of  the  hair;  d,  epidermis  of  the  hair;  e,  inner  root-sheath;  /,  outer 
root-sheath ;  g,  structureless  membrane  of  the  hair  sac ;  h,  transversely  and  longitudinal 
fibrous  layer  thereof;  t,  papilla  of  the  hair;  k,  excretory  ducts  of  the  sebaceous  glands,  with 
epithelium  and  layers  of  fibres  ;  I,  cutis  at  the  aperture  of  the  hair  sac ;  m,  stratum  mucosum  ; 
n,  horny  layer  of  the  epidermis,  the  latter  somewhat  retracted  into  the  sac;  o,  end  of  the 
inner  root- sheath. 

*  [No  hairs  exist  upon  the  upper  eyelids,  the  lips,  the  palm  of  the  hand,  and  sole  of  the 
foot ;  nor  on  the  dorsum  of  the  last  joints  of  the  fingers  and  toes,  the  inner  surface  of  the 
prepuce,  and  the  glans  penis.— TRS.] 


172  SPECIAL    HISTOLOGY. 

the  caruncula  lachrymalis,  and  those  (frequently  absent)  of  the  labia 
minora  (Henle). 

The  number  of  hairs  upon  a  given  extent  of  surface  varies  very  much, 
depending  especially  upon  age,  sex,  and  the  color  of  the  hairs.  Accord- 
ing to  Withof,  on  a  surface  of  J  of  a  square  inch  there  were  found  147 
black,  162  brown,  182  fair  hairs.  In  a  moderately  hairy  man,  he  found 
on  J  of  a  square  inch,  293  upon  the  scalp,  39  on  the  chin,  34  on  the 
pubis,  23  on  the  fore  arm,  19  upon  the  outer  margin  of  the  back  of  the 
hand,  13  on  the  anterior  surface  of  the  leg.  In  men,  closely  set  hairs 
occur  not  unfrequently  upon  the  chests,  shoulders,  and  extremities. 

The  hairs  are  placed  either  singly,  or  in  twos  and  threes,  even  four  and 
five  together.  The  latter  is  the  rule  in  the  foetus,  but  the  same  disposi- 
tion obtains  also  in  adults,  especially  in  the  lanugo.  As  Osiander  and 
especially  Eschricht,  have  shown,  the  direction  of  the  hairs  and  hair-sacs 
is  rarely  straight,  but  oblique,  and  in  different  degrees  in  different  parts 
of  the  body,  as  may  be  demonstrated  with  ease  in  the  hairs  of  embryos, 
and,  though  less  obviously,  in  adults  also.  The  regularity  depends  on  this, 
that  the  hairs  being  arranged  in  curved  lines,  which  converge  towards 
either  certain  points  or  certain  lines,  or  diverge  from  them  in  two  or  more 
directions;  there  result  a  multitude  of  figures,  which  may  with  Eschricht 
be  denominated  "  streams,"  "  whorls,"  and  "crosses."  Streams  with 
converging  hairs  are  found,  for  example,  in  the  median  line  of  the  back, 
chest,  arid  abdomen,  in  the  line  which  answers  to  the  ridge  of  the  tibia, 
&c.  &c. ;  streams  with  diverging  hairs  occur  on  the  line  between  the 
thorax  and  abdomen,  on  the  one  hand,  and  the  back  on  the  other,  &c. ; 
whorls  and  crosses  with  diverging  hairs  are  found  in  the  axilla,  on  the 
scalp,  at  the  internal  angle  of  the  eye  ;  with  converging  hairs,  on  the 
elbow.  For  further  details  I  must  refer  to  Eschricht's  figures  and 
descriptions,  concerning  which,  however,  it  is  to  be  remarked,  that  many 
variations  occur  with  regard  to  these  points,  and  Eschricht's  figures  re- 
present only  some  of  them. 

§  55.  External  peculiarities  and  chemical  composition  of  the  Hairs. — 
In  embryos,  the  hairs  are  generally  quite  colorless  and  clear ;  they  very 
slowly  become  colored,  so  that  in  youth  they  are,  in  general,  paler  than 
in  middle  age.  In  the  adult  the  downy  hairs,  which  have  remained  in 
a  foetal  condition  as  it  were,  are  invariably  the  palest ;  the  longer  ones 
are  always  darker,  and  the  darkest  are  those  of  the  head,  beard,  and 
pubis. 

The  hairs  are  very  elastic  ;  according  to  Weber,  they  stretch  without 
breaking  to  nearly  a  third  more  than  their  length,  and  if  they  be 
stretched  only  a  fifth,  they  contract  again  so  perfectly,  that  they  remain 
permanently  only  -^th  longer.  They  readily  imbibe  water,  and  as 
readily  give  it  out  again;  they  are  therefore  sometimes  dry  and  brittle, 
sometimes  moist  and  soft,  according  as  the  skin  or  the  atmosphere  con- 


OF    THE    HAIRS.  173 

tains  much  or  little  moisture.  They  become  longer  or  shorter,  accord- 
ing to  the  amount  of  moisture  which  they  contain,  whence  their  use  in 
Hygrometry.  In  spite  of  their  extensibility,  their  strength  is  consider- 
able, and  hairs  of  the  head  will  bear  at  least  6  ounces  without  breaking. 
The  chemical  composition  of  the0  hairs  is  not  yet  sufficiently  under- 
stood, but  they  are  chiefly  composed  of  a  nitrogenous  substance,  soluble 
in  alkalies  with  the  evolution  of  ammonia,  and  insoluble  in  boiling  acetic 
acid.  Scherer  and  Von  Laer  consider  it  to  be  a  combination  of  protein 
with  sulphur,  and  the  latter  supposes,  in  addition,  the  existence  of  a 
small  quantity  of  a  substance  similar  to  gelatine,  whilst  Scherer  regards 
a  second  nitrogenous  matter  which  he  found,  to  be  a  product  of  decom- 
position. Mulder  considers  the  substance  of  the  hairs  to  be  a  protein 
compound  combined  with  sulphamid,  of  which  he  finds  10  per  cent. 
Besides  their  nitrogenous  constituents,  the  hairs,  as  even  the  earlier 
investigations  showed,  contain  a  considerable  quantity  of  dark  or  clear 
fatty  matter,  which  may  be  extracted  by  boiling  in  ether  and  alcohol. 
From  horn  and  epidermis,  the  substance  of  the  hair  is  distinguished, 
according  to  Mulder,  especially  by  its  insolubility  in  acetic  acid  and  by 
the  same  test,  from  albumen  and  fibrin.  The  hairs  withstand  putrefac- 
tion better  than  any  other  part  of  the  body,  so  that  even  mummy  hairs 
are  found  to  be  quite  unchanged;  in  water  they  are  not  dissolved,  except 
in  Papin's  digester.  Metallic  oxides  color  the  hair  just  as  they  do  the 
epidermis;  thus,  for  example,  they  are  blackened  by  the  salts  of  silver 
and  manganese,  sulphurets  of  these  metals  being  produced.  Chlorine 
bleaches  them.  The  ash  amounts  to  about  1-2  per  cent.,  and  contains 
oxide  of  iron  (more  in  dark  hair) ;  oxide  of  manganese  ;  silica  (traces) ; 
phosphate  of  magnesia  and  sulphate  of  alumina  were  found  by  Jahn  in 
white  hairs;  and  according  to  Laugin,  copper  occurs  in  the  greenish 
hairs  of  those  who  work  in  copper  and  brass. 

§  56.  With  regard  to  their  more  intimate  structure,  two  substances 
may  be  distinguished  in  all  hairs  without  exception,  and  in  many  there 
are  three :  1,  the  cortical  substance,  or  better,  fibrous  substance,  which 
constitutes  by  far  the  most  considerable  portion  of  the  hair  and  deter- 
mines its  form ;  2,  the  cuticle,  a  delicate  external  investment  of  the 
fibrous  substance ;  3,  lastly,  the  central  medullary  substance,  which  is 
often  absent. 

The  cortical  or  fibrous  substance  is  longitudinally  striated,  very  often 
presents  dark  dots,  is  streaked  or  spotted  and  except  in  white  hairs,  in 
which  it  is  transparent,  is  more  or  less  deeply  colored ;  the  color  is 
sometimes  distributed  through  the  whole  substance  with  tolerable  regu- 
larity, sometimes  more  concentrated  in  certain  elongated,  granular  spots. 
The  more  intimate  structure  of  the  cortex  of  the  hair,  and  the  significa- 
tion of  its  spots  and  striae,  cannot  be  properly  understood  without  the 
use  of  acids  and  alkalies  (which  afford  important  aid  in  the  investigation 


174 


SPECIAL    HISTOLOGY. 


of  the  hairs  in  general)  and  other  manipulations.  If  a  hair  be  treated 
with  concentrated  sulphuric  acid  at  a  warm  temperature,  its  fibrous 
substance  is  much  more  readily  broken  up  than  before,  into  flat  elon- 
gated fibres  of  various  breadths  (commonly  0 '002-0 '005  of  a  line),  which 
are  characterized  particularly  by  their  rigidity  and  brittleness,  and  by 
their  irregular,  even  notched,  margins  and  ends :  in  pale  hairs  they  are 
clear,  and  in  dark  ones  have  a  dark  tinge.  These  so-called  hair-fibres 
Fig. 64.  are  not,  however,  the  ultimate  ele- 

ments of  the  fibrous  substance  ;  each 
of  them,  in  fact,  consisting  of  an 
aggregation  of  flat,  moderately-long 
fibre-cells  or  plates,  which  may  be 
found  isolated  among  the  fibres  after 
the  thorough  action  of  sulphuric  acid. 
These  (Fig.-  64),  which  may  best  be 
named  the  plates  of  the  fibrous  sub- 
stance, or  ihe  fibre- cells  of  the  cortex, 
are  flat  and  generally  fusiform,  0-024 
-0-033  of  a  line  long,  0-002-0-004, 
or  even  0-005  of  a  line  broad,  0-0012 
-0-0016  of  a  line  thick,  with  uneven 
surfaces  and  irregular  edges ;  they 
do  not  swell  up  into  vesicles  on  the 
addition  of  caustic  alkalies,  and  they 
very  frequently  exhibit  a  darker 
streak  in  their  interior,  of  which  we 
shall  speak  immediately ;  under  cer- 
tain circumstances  they  also  contain 
granular  pigment;  for  the  rest  they 
are  homogeneous,  and  present  no 
minuter  elements,  such  as  fibrillse  or 
the  like.  They  appear  to  be  more 
strongly  united  longitudinally,  than 
in  the  direction  of  their  breadth, 
whence  it  arises  that  the  cortical  sub- 
stance easily  breaks  up  into  the  long 
fibres  above  mentioned.  The  fibres  themselves  (which  I  should  not  be 
inclined  to  consider  as  compound  elements  of  the  cortical  substance, 
since  their  constituents  are  separable,  and  they  themselves  are  far  too 
irregular),  without  constituting  distinct  lamellae,  like  the  plates  of  the 
nail  and  of  the  epidermis,  form  a  compact  fibrous  bundle,  and  in  this 

FiG.  64. — Plates  or  fibre-cells  of  the  cortical  substance  of  a  hair  treated  with  acetic  acid ; 
magnified  350  diameters  :  ./#,  isolated  plates,  1,  from  the  surface  (3  single,  2  united)  ;  2,  from 
the  side.  B,  a  lamella  composed  of  many  such  plates. 


OP    THE    HAIKS. 


175 


manner  the  cortical  substance,  which  constitutes  the  principal  bulk  of 
the  hair,  is  produced. 

The  dark  spots,  dots,  and  streaks  of  the  cortex,  are  very  various  in 
their  nature,  and  are  principally  :  1,  granular  pigment ;  2,  cavities 
filled  with  air  or  fluid;  and  3,  nuclei.  The  action  of  caustic  potass  and 
soda,  which  soften  and  swell  up  the  cortical'  substance  without  attack- 
ing the  spots  (Fig.  67),  shows  that  they  are  in  great  measure  nothing 
but  aggregations  of  pigment  granules,  which  are  deposited  in  the  plates 
of  the  hair,  are  especially  frequent  in  dark  hairs,  and  vary  very  much 
in  respect  to  their  size  and  form.  Dark  spots  of  a  second  kind  are  very 
similar  to  the  pigment  deposits,  but  turn  out  on  examination  to  be  little 
cavities  filled  with  air.  They  are  best  studied  in  white  hairs,  where  they 
cannot  possibly  be  confounded  with  pigment.  Here  we  see  dispersed 
through  the  whole  cortical  substance  round  dots  of  0-0004--0008  of  a 
line,  or  longish  streaks  of  0-004  of  a  line  in  length,  0-0004-0-0008  of  a 
line  in  breadth,  which,  sometimes  more  scattered,  sometimes  more 
numerous,  and  arranged  in  irregular  lines,  run  parallel  with  the  axis  of 
the  hair.  The  dark  contours  and  somewhat  clear  centre  of  these,  attract 
attention  at  once,  and  call  to  mind  fat  granules,  which,  in  fact,  for  a 
long  time  I  held  them  to  be  ;  but  they  are  nothing  but  excessively  minute 
cavities  filled  with  air,  which  occur  very  frequently  also  in  fair,  bright- 
brown,  and  bright-red  hairs,  often  in  very  great  numbers,  while  they 
are  wanting  in  very  dark  hairs,  and 
in  the  lower  half  of  the  root  of  all 
hairs.  Thirdly,  there  occur  in  the 
cortex,  other  tolerably  dark  striae 
or  lines,  which  in  dark  hairs  are 
commonly  connected  with  the  pig- 
ment-spots in  such  a  manner  that 
the  striae  form  the  ends  of  the  spots, 
or  pass  through  them  axially ;  in 
white  and  pale  hairs  they  appear  not 
unfrequently  as  prolongations  of  the 
air  cavities,  but  in  both  kinds  of 
hairs  they  often  occur  independently, 
in  various  numbers  and  degrees  of 
distinctness.  I  hold  these  streaks, 
which  are  commonly  most  distinct  in 
pale  or  bright-brown  hairs  without 
any  medulla,  to  be  sometimes  the  ex- 
pression of  the  composition  of  the  hairs  by  the  above  described  fibre- 

FIG.  65. — A,  a  piece  of  a  white  hair  after  treatment  with  caustic  soda;  magnified  350 
diameters:  a,  nucleated  cells  of  the  medulla  without  air;  6,  cortical  substance  with  a  fine 
fibrillation  and  prominent  linear  nuclei ;  c,  epidermis  with  its  plates  projecting  more  than 
usual ;  B,  three  isolated  linear  nuclei  from  the  cortex. 


176  SPECIAL    HISTOLOGY. 

cells ;  in  other  words,  to  be  the  boundary  lines  of  the  separate  elements 
of  the  cortex,  and  sometimes  I  consider  them  to  be  their  nuclei.  For, 
even  in  the  shaft  of  the  hair,  the  cortical  plates  all  contain  fusiform 
nuclei  0-01-0-016  of  a  line  long,  0-0005-0-0012  of  a  line  broad,  which 
may,  in  fact,  be  isolated  by  rubbing  down  white  hairs  which  have  been 
boiled  in  caustic  soda.  Besides  these,  there  appear  in  the  cortical  sub- 
stance, and  with  especial  distinctness  in  a  whitish  place  immediately 
above  the  bulb,  certain  fine  striae,  which  are  produced  by  inequalities  in 
the  surface  of  the  cortical  plates,  and  which  do  not  readily  disappear, 
even  after  the  continued  action  of  alkalies,  but  eventually  give  place  to 
a  finely  fibrous  appearance ;  they  cannot  be  isolated,  but  are  visible  in 
those  portions  of  the  cortex  which  have  been  separated  by  sulphuric 
acid,  and  sometimes  even  are  very  distinct  (Fig.  66). 

The  description  of  the  cortex,  which  has  just  been  given,  holds  good 
especially  for  the  hair-shaft.  In  the  root  of  the  hair,  so  long  as  it  is  still 
solid  and  brittle,  we  find  essentially  the  same  conditions ;  and  it  is  only 
in  its  lower  half,  where  it  becomes  gradually  softer,  at  first  finely  fibrous 
and  then  granular,  that  the  structure  of  the  cortex  undergoes  a  progres- 
sive change.  Here,  in  fact,  the  above  described  plates  .are  less  rigid, 
and  take  on  more  and  more  distinctly  the  form  of  elongated  cells  (Fig. 
66)  of  0-020-0-024  of  a  line  in  length,  and  0-009-0-011  of  a  line  in 
breadth,  whose  cylindrical,  straight,  or  serpentine  nuclei  of  0-008-0-01 
of  a  line,  are  very  easily  rendered  visible  by  the  action  of  acetic  acid,  and 
may  also  be  readily  isolated.  The  soft  and  shortened  plates  then  pass 
pio>  fifi  into  elongated,  rounded  cells,  with  short  nuclei,  the 
fibrous  structure  becoming  more  and  more  obliterated, 
and  these  are  finally  continued  without  interruption  into 
the  elements  of  the  lowest  and  thickest  part  of  the  hair, 
the  bulb.  They  (Fig.  67)  are  nothing  more  than  round 
cells  of  0-003-0-006  of  a  line,  which  lie  closely  pressed 
together  ;  and  like  the  cells  of  the  mucous  layer  of  the  epidermis 
sometimes  contain  only  colorless  granules,  sometimes  are  so 
full  of  dark  pigment-granules,  that  they  become  true  pigment- 
cells.  It  must  be  added,  that  the  chemical  relations  of  the 
cortex  are  altered  in  the  lower  half  of  the  root,  its  elements  becoming 
more  sensitive  to  the  action  of  acetic  acid,  which  does  not  affect  the 
plates  of  the  shaft  at  all ;  they  swell  up  and  dissolve  in  alkalies  also, 
much  more  quickly  than  those  of  the  shaft.* 

FiG.  66. — Two  cells  from  the  cortex  of  the  root  of  the  hair  (the  finely-striated  part  of  it 
immediately  above  the  root),  with  distinct  nuclei  and  a  striated  appearance;  magnified 
350  diameters. 

FiG.  67. — Cells  from  the  deepest  part  of  the  bulb  of  the  hair;  magnified  350  diameters: 
a,  from  a  colored  bulb,  with  pigment-granules  and  somewhat  hidden  nucleus;  b,  from  a 
white  hair  with  a  distinct  nucleus  and  few  granules. 

*[Reichert  ("Bericht"'  for  1850,  Mull.  "  Archiv,"  1851)  asserts  that  the  cortical  substance 


OF    THE    HAIRS. 


177 


The  color  of  the  cortical  substance  arises  partly  from  spots  of  pigment, 
to  some  extent  from  air  cavities,  and  partly  from  a  coloring  matter  dif- 
fused through  and  combined  with  the  substance  of  the  cortical  plates. 
The  first  or  the  granular  pigment,  exhibits  all  shades  from  clear  yellow, 
through  red  and  brown,  to  black;  the  diffused  pigment  is  quite  absent  in 
white  hairs,  and  is  scanty  in  clear,  fair  hairs ;  it  is  most  abundant  in  the 
more  opaque  fair  hairs,  and  in  red  as  well  as  in  dark  hairs,  in  which  it 
may  by  itself  give  rise  to  an  intense  red  or  brown  color.  The  color  of 
the  cortex  depends  especially  upon  that  of  these  two  pigments,  but 
sometimes  the  one,  sometimes  the  other  predominates,  and  it  is  only  in 
the  very  light  and  in  the  very  dark  hairs  that  they  are  developed  in  about 
equal  proportions. 


Fig.  68. 


S 


. 


§  57.  The  medullary  substance  is  a  streak  or  cord  which  extends  in 
the  axis  of  the  hair,  from  the 
neighborhood  of  the  bulb 
nearly  to  the  point  (Figs.  65, 
68).  It  is  generally  absent 
in  the  lanugo  and  colored 
hairs  of  the  head,  but  if 
usually  present  in  the  thick, 
short  hairs,  and  in  the 
stronger  long  ones,  as  well 
as  in  the  white  hairs  of  the 
head.  If  white  hairs  be 
boiled  with  caustic  soda  until 
they  swell  and  coil  up,  we 
can  often,  by  the  use  of 
simple  pressure,  demonstrate 
without  further  trouble,  the 
cellular  structure  of  the 
medullary  cylinder,  which  is 
then  transparent  for  trans- 

FiG.  68. — A  portion  of  the  root  of  a  dark  hair  slightly  acted  upon  by  caustic  soda ;  a, 
medulla,  still  containing  air,  and  with  cells,  which  appear  pretty  distinct;  6,  cortex  with 
pigment  spots;  c,  inner  layer  of  the  epidermis;  d,  outer  layer  of  it ;  e,  inner  layer  of  the  inner 
root-sheath  (Huxley's  layer)  ;/,  outer  fenestrated  layer  (Henle's  layer).  Magnified  250  diameters. 


of  the  hair  is  composed  of  superimposed  lamina?,  and  recommends,  in  order  to  demonstrate 
the  fact,  that  a  hair  should  be  treated  with  a  solution  of  caustic  potass  of  10  per  cent,  and 
then  submitted  to  pressure.  Under  these  circumstances,  u  beautiful  lamellae  appear.  The 
separate  layers  exhibit  no  trace  of  being  composed  of  fut-ifmm  cells;  they  appear  finely 
striated,  and  in  places,  hyaline;  sometimes  elongated  spots  appear,  of  which  it  cannot  be 
determined  with  certainty  whether  they  are  nuclei  or  perforations  in  the  membrane."  In 
some,  there  was  no  trace  of  these  to  be  seen.  Reichert  considers  the  fibres  of  the  cortex  to 
be  artificial  products,  and  was  unable  to  convince  himself  of  the  existence  of  nuclei  in  this 
part  of  the  hair. — TRS.] 

12 


178  SPECIAL    HISTOLOGY. 

mitted  light  (Fig.  65  a).  If  a  hair  thus  treated  be  carefully  teased 
out,  it  is  easy  to  isolate  the  medullary  cells,  either  in  aggregate  masses, 
Fig.  69.  or  even  completely  separate  (Fig.  69).  They  are  rectangular 
or  quadrangular,  rarely  rounded  or  fusiform  of  0-007 — 0-01 
of  a  line  in  diameter,  occasionally  containing  dark,  fat-like 
granules,  and  often  when  the  alkali  has  not  acted  too  strongly, 
a  rounded  clear  spot  of  0-0016-0-002  of  a  line,  which  is  plainly 
the  rudiment  of  a  nucleus,  and  which  also  seems  to  swell  up  somewhat 
in  soda. 

In  fresh  hairs,  the  medulla  in  the  shaft  is  silvery  white  or  dark,  an 
appearance  which,  as  many  more  favorable  objects  show,  arises  from 
rounded- angular,  granular  corpuscles,  black  (opaque)  or  of  a  brilliant 
white,  according  to  the  illumination,  tolerably  uniform  in  size,  but  varying 
according  to  the  hairs,  from  0'0002-0'002  of  a  line  and  occupying  the 
medullary  cells  in  great  quantity  (Fig.  68).  These  granules  are  not  fat 
or  pigment,  as  has  been  hitherto  universally  supposed,  but  air-vesicles, 
as  may  be  readily  demonstrated  by  boiling  a  white  hair  in  ether  or  oil 
of  turpentine,  in  both  of  which  cases  the  medulla  becomes  quite  clear 
and  transparent.  If  such  a  hair,  treated  ^vith  water,  be  dried  between 
the  fingers,  it  soon,  often  quite  suddenly  and  visibly  to  the  naked  eye, 
assumes  its  previous  white  color,  and  if  immediately  after  drying,  it  be 
placed  under  the  microscope,  without  fluid,  or  with  fluid  at  one  end  only, 
nothing  is  easier  than  to  see  the  re-entrance  of  the  air  and  the  conse- 
quent darkening  of  the  medulla.  Not  only  in  white  hairs,  but  in  dark 
ones  also,  the  medulla  contains  air  in  the  fresh  state,  only  in  this  case 
it  does  not  appear  of  a  pure  silvery  white,  but  with  a  blonde,  red  or  brown 
tinge  ;  this  does  not  arise  from  any  special  pigment,  which  is  only  found 
occasionally  in  the  medulla  of  dark  hairs,  but  proceeds  from  its  being 
seen  through  the  colored  cortical  substance.  A  more  careful  investi- 
gation of  the  medullary  cells  shows,  that  while  fresh  they  contain  many 
small  cavities  in  a  viscid  substance ;  in  these  lie  the  air  vesicles,  which 
communicate  to  them  the  granular  appearance  above  described.  If  we 
observe  the  air  which  has  been  expelled  refilling  the  medulla  of  a  dried 
hair,  it  seems  as  if  all  the  cavities  of  one  and  the  same  cell  communicated 
with  one  another,  at  least  the  air  frequently  passes  in  continuous  winding 
streams  from  one  cavity  into  the  other  ;  indeed  from  the  sudden  manner 
in  which  the  air  sometimes  fills  the  medulla,  it  might  almost  be  believed 
that  the  cavities  of  contiguous  cells  were  connected  together.  However 
this  may  be  in  certain  cases,  it  is  conceivable,  that  even  if  the  cavities 
of  the  different  cells  are  quite  closed,  and  only  separated  from  one 
another  by  delicate  partitions,  the  air  still  may  quickly  fill  the  medulla 
under  the  appearances  we  have  noted.  For  the  rest,  the  vacuities  of 

FIG.  69. — Eight  medullary  cells,  with  pale  nuclei,  and  fatty  granules,  from  a  hair  treated 
with  soda  ;  magnified  350  diameters. 


OF    THE    HAIRS.  179 

the  medullary  cells,  whether  they  are  quite  closed  or  not,  are  of  different 
sizes,  the  aeriferous  medulla  appearing  sometimes  coarsely,  sometimes 
finely  granular.  I  have  also  seen  cases  in  which  the  medullary  cells 
obviously  contained  only  a  single  large  air-vesicle,  and  appeared  almost 
like  small  fat-cells.  Very  frequently  single  larger  or  smaller  spots  may  be 
observed  in  the  medulla,  which  contain  no  air,  and  are  thence  pale,  and 
this  is  constantly  the  case  in  the  lowermost  part  of  the  medulla,  close 
above  the  bulb. 

The  medulla  and  the  cortex  are  widely  different  if  we  compare  the 
extreme  forms  of  their  elements ;  in  the  one  case  we  have  rigid  homo- 
geneous elongated  plates,  almost  without  contents,  in  the  other  rounded 
vesicles  filled  with  fluid  or  air.  If,  however,  we  take  into  account  all 
their  conditions,  we  shall  find  that  the  limits  are  not  so  marked,  and  in 
fact  are  often  hardly  distinguishable.  On  the  one  hand,  for  instance, 
the  medullary  cells  are  not  unfrequently  of  an  elongated  or  short  fusi- 
form figure,  whilst  on  the  other  the  plates  of  the  cortex  present  a  con- 
siderable cavity  containing  pigment.  If  such  plates  contain,  instead  of 
pigment  or  the  smaller  air-vesicles,  air  in  a  larger  cavity,  as  occurs 
sometimes  though  not  frequently,  it  is  still  more  difficult  to  distinguish 
the  two  kinds  of  elements  from  one  another,  and  the  more  so  if,  as  in  red 
hairs,  the  medulla  and  cortex  are  in  places,  or  for  considerable  distances, 
not  distinctly  defined  from  one  another,  the  superficial  cells  of  the 
medulla  being  scattered  and  passing  quite  gradually  into  the  plates  of 
the  cortex,  which  lie  very  close  together  and  contain  much  air.  It  is 
not  intended  to  imply,  by  this,  that  the  medulla  and  the  cortex  are 
identical,  but  only  that  transitions  exist,  and  that  the  differences  which 
occur  are  less  marked  than  is  commonly  supposed. 

The  diameter  of  the  medulla  is  generally,  in  proportion  to  that  of  the 
hair  itself,  as  1 :  3-5 ;  relatively  and  absolutely,  it  is  thickest  in  short 
thick  hairs,  thickest  in  the  down  and  hairs  of  the  head.  In  a  transverse 
section  it  presents  a  round  or  flattened  figure,  and  the  cells  which  com- 
prise it  are  disposed  in  1-5  or  even  more  longitudinal  series. 

The  medullary  substance,  the  cells  in  which  were  first  accurately  de- 
scribed by  G.  H.  Meyer,  varies  most  of  all  the  constituents  of  the  hair. 
In  the  down  of  the  hairs  of  the  head,  it  has  been  stated,  by  some,  that 
it  is  wholly  absent,  which  is  to  be  corrected  thus  far,  that  it  is  certainly 
generally  absent  in  the  former,  and  frequently  in  the  latter,  perhaps 
more  frequently,  in  certain  individuals.  In  white  hairs,  even  those  of 
the  head,  of  a  tolerable  length  and  thickness,  I  have  never  failed  to  find 
it  always  beautifully  distinct.  In  rare  cases  the  medullary  tract  is 
double  throughout  (Bruns,  figure  in  Hassall),  more  frequently  divided  in 
places  into  two  tracts,  which  soon  unite  again.  In  the  lower  part  of 
the  root,  the  medulla,  which  is  here  clear,  is  often  thicker,  and  exhibits 


180  SPECIAL    HISTOLOGY. 

the  nuclei  of  its  cells  very  distinctly,  especially  after  the  addition  of 
acetic  acid.  Steinlin  and  Eylandt  assert  of  the  medullary  substance, 
that  it  does  not  belong  to  the  proper  hair,  but  to  its  papilla,  and  origi- 
nally represents  a  prolongation  of  this  into  the  free  part  of  the  hair, 
which  then  dries  up.  This  is  incorrect.  The  papilla  or  germ  of  the 
hair  is  a  part  of  the  cutis,  and  has  the  same  structure  as  the  papillae,  of 
the  latter,  whilst  the  medulla  of  the  hair  is  composed  of  isolated  cells, 
which  by  their  resistance  to  alkalies,  are  in  all  respects  allied  to  those 
of  the  epidermis.  On  the  other  hand,  in  animals,  as  has  long  been 
known,  and  as  lately  Brocker  has  especially  shown,  the  papilla  often 
projects  far,  even  to  the  point  of  the  hairs,  bristles  or  spines,  subse- 
quently drying  up  ;  but  in  these  instances,  according  to  Brocker,  it 
never,  even  after  the  action  of  potass,  exhibits  a  cellular  texture,  whilst 
this  is  always  obvious  in  the  medullary  substance,  which  is  often  present 
at  the  same  time.  Such  an  elongation  of  the  papillae  may  occasionally 
be  noticed  even  in  man,  to  a  certain  extent ;  thus  Henle  found  it  a  few 
times  prolonged  into  a  short  point.  But  any  prolongation  of  this  kind 
must  be  distinguished  as  decidedly  from  the  cellular  medullary  substance, 
as  in  animals. 

§  58.  The  cuticle  of  the  Hair  (cuticula\  is  a  very  thin,  transparent 
pellicle,  which  completely  invests  the  hair,  and  is  very  closely  united 
with  the  cortical  substance.  In  its  normal  position,  and  observed  in  an 
unaltered  hair,  it  is  evidenced  by  hardly  anything  more  than  by  nume- 
rous dark,  reticulated,  irregular  or  even  jagged  lines,  which  surround 
the  hair  at  intervals  0*002— 0*006  of  a  line  from  one  another,  and  occa- 
sionally also  by  small  serrations  at  its  apparent  edge  (Fig.  70  A) ;  if, 
on  the  other  hand,  a  hair  be  treated  with  alkalies,  the  cuticle  is  raised 
in  smaller  or  larger  lamellae  from  the  fibrous  substance,  and  is  even 
separated  into  its  elements.  These  are  quadrangular  or  rectangular 
flat  plates  without  nuclei,  generally  pale  and  transparent  (Fig.  70  B\ 

which  do  not  swell  up  into  vesi- 
cles by  the  action  of  any  re- 
agent, and  disposed  in  an  im- 
bricated manner,  form  a  simple 
membrane  which  completely 
surrounds  the  cortex  of  the  hair 
in  such  a  way,  that  the  deeper 
or  lower  cells  cover  the  upper 
ones.  By  sulphuric  acid  also 
the  structure  of  the  epidermis  is  readily  made  out ;  the  hair  is,  as  it  were, 

Fia.  70. — A,  surface  of  the  shaft  of  a  white  hair  ;  magnified  1GO  diameters.  The  curved 
lines  mark  the  free  edges  of  the  epidermic  plates:  J5,  epidermic  plates  from  the  surface, 
isolated  by  the  action  of  caustic  soda  ;  magnified  350  diameters.  One  or  both  of  their  longer 
edges  are  bent  round,  and  so  appear  dark. 


OF    THE    HAIRS.  181 

bristled  at  the  edges  with  the  erected  plates  and  by  scraping  or  rubbing, 
the  cuticle  is  less  easily  obtained  in  large  lamellae,  but  is  readily  enough 
reduced  to  its  elementary  parts. 

On  the  shaft  of  the  hair  the  cuticle  consists  only  of  a  single  layer  of 
plates  0-002-0-003  of  a  line  thick,  which  measure  0-024-0-028  of  a 
line  in  the  transverse  direction  of  the  hair ;  0-016-0-02  in  that  of  its 
length  ;  and  are  hardly  more  than  0-0005  of  a  line  in  thickness.  The 
same  structure  exists  also  in  the  upper  part  of  the  root  of  th^  hair; 
of  its  lower  part,  on  the  other  hand,  so  far  as  the  inner  root-sheath  ex- 
tends, two  layers  of  the  epidermis  constantly  occur.  The  outer  (Fig. 
(68  d  is  rendered  especially  obvious  by  the  action  of  soda  or  potassa,  and 
with  a  little  pressure  frequently  comes  away  from  the  hair  with  the  inner 
root-sheath,  whilst  the  inner  layer  becoming  undulated,  remains  lying 
upon  the  cortical  substance,  and  may  be  easily  studied,  as  well  in  the 
side  view  as  upon  its  surface.  In  hairs  that  are  torn  out,  this  layer  is 
found  only  where  they  are  covered  by  the  inner  root-sheath,  otherwise 
it  remains  behind  in  the  hair-sac.  Its  elements  also,  are  broad  cells 
without  nuclei,  covering  one  another  like  tiles,  which  do  not  swell  up  in 
alkalies,  ^and  are  soluble  with  great  difficulty ;  they  are  thicker  than 
those  of  the  other  layer,  and  measure  only  0-002—0-004  of  a  line  in  the 
direction  of  the  length  of  the  hair.  The  whole  outer  layer  measures 
0-0016-0-002  of  a  line,  whilst  the  inner  layer  upon  the  root  has  a  thick- 
ness of  0-0025-0-0035  of  a  line.  Upon  the  bulb  of  the  hair,  the 
two  layers  of  cuticular  plates  pass  with  ja,  tolerably  defined  margin 
into  soft  nucleated  cells,  which  are  broad  in  the  transverse  direction  of 
the  bulb,  very  short  longitudinally,  and  somewhat  longer  in  their  third 
diameter,  which  stands  perpendicularly  or  obliquely  to  the  longitudinal 
axis  of  the  hair.  They  are  readily  attacked  by  alkalies,  or  even  by 
acetic  acid,  possess  without  exception  transverse  and  longish  nuclei,  and 
finally  pass,  on  the  bulb,  into  the  already  described,  round  cells  of  which 
it  is  formed.* 

*  [We  cannot  agree  with  Professor  Kdlliker  that  the  cuticle  of  the  hair  passes  into  the 
outer  cells  of  the  bulb.  It  may  be  worth  devoting  a  little  space  to  this  matter,  as  the  whole 
question  of  the  homology  of  the  hair  essentially  turns  upon  it.  So  far  from  being  able  to 
trace  the  two  layers  of  the  cuticle  into  the  round  cells  of  the  bulb,  we  find  that  they  cease 
somewhat  suddenly  when  the  shaft  begins  to  expand,  while  its  substance  is  fibrous-looking 
and  contains  only  much  elongated  nuclei.  Below  this  point,  as  Henle  has  correctly,  figured 
in  his  "  Allgemeine  Anatomic,"  PI.  I.  Fig.  14,  the  transverse  striations  of  the  cuticle  are 
absent ;  and  if  the  cuticular  layer  be  viewed  in  section,  it  will  be  seen  to  be  composed  of  a 
more  transparent  substance,  which  gradually  becomes  thinner  until  it  is  hardly  distin- 
guishable as  a  distinct  layer,  and  at  the  same  time  loses  the  oblique  lamination,  which  it 
has  above,  where  it  is  continuous  with  the  two  layers  of  the  cuticle  proper.  The  careful 
addition  of  caustic  ammonia  is  particularly  fitted  to  demonstrate  the  structure  of  this  part. 
In  the  first  place,  it  raises  up  the  outer  layer  of  the  cuticle  from  the  inner,  and  shows  that 
the  former,  at  any  rate,  is  not  continuous  with  any  cells;  and  secondly,  it  dissolves  and 
forces  out  the  substance  of  the  lower  soft  portion  of  the  bulb,  so  that  the  lower  part  of  the 
cuticle  may  be  obtained  as  a  transparent,  colorless,  and  independent  sheath,  even  from 


182  SPECIAL    HISTOLOGY. 

§  59.  The  hair-sacs,  folliculi  pilorum,  are  flask-like  follicles  1-3 
lines  long,  which  embrace  the  roots  of  the  hair  tolerably  closely,  and,  in 
the  lanugo,  are  lodged  in  the  substance  of  the  upper  layers  of  the  corium, 
while  in  the  stronger  or  long  hairs,  they  generally  project  into  its  deeper 
portion,  and  even  extend  for  a  greater  or  less  distance  into  the  subcu- 
taneous cellular  tissue.  These  follicles  are  simply  to  be  regarded  as  invo- 
lutions of  the  skin,  with  its  two  constituents,  the  corium  and  the  epi- 
dermis^ and  there  may  be  distinguished,  therefore,  in  each  of  them,  an 
external  fibrous,  vascular  part,  the  proper  hair-sac,  and  a  non-vascular 
cellular  investment  lining  this, — the  epidermis  of  the  hair-sac  ;  or, 
since  it  immediately  surrounds  the  root  of  the  hair, — the  "root-sheath" 
(vagina  pili). 

§  60.  The  proper  hair-sac  consists  of  two  fibrous  investments,  an  ex- 
ternal and  an  internal,  and  of  a  structureless  membrane ;  it  is  on  an 
average  0-015-0-022  of  a  line  thick,  and  contains  in  its  lower  part  a 
peculiar  structure,  the  papilla  of  the  hair. 

The  external  fibrous  membrane  (Fig.  63  A),  the  thickest  of  the  three 
layers  of  the  hair-sac,  determines  its  external  form,  and  by  its  innermost 
layer  is  very  closely  connected  with  the  corium.  It  consists  of  common 
connective  tissue  with  longitudinal  fibres,  without  any  intermixture  of 
elastic  fibres,  but  with  a  considerable  number  of  long  fusiform  nuclei ; 
it  contains  a  tolerably  close  plexus  of  capillaries,  and  exhibits  also  a 
few  nervous  fibrils  with  occasional  divisions. 

The  internal  fibrous  membrane  (Fig.  71  a)  is  much  more  delicate  than 
the  external ;  bounded  by  smooth  surfaces,  and  everywhere  of  equal 
thickness,  it  extends  from  the  bottom  of  the  hair-sac  as  far  only  as  the 
entrance  of  the  sebaceous  glands.  To  all  appearance,  it  contains  neither 
vessels  nor  nerves,  and  is  composed  solely  of  a  simple  layer  of  transverse 
fibres,  with  a  long  narrow  nuclei,  which  may  be  seen  particularly  well 
in  the  empty  hair-sacs  of  both  coarse  and  fine  hairs,  with  or  without  the 

the  very  darkest  hairs ;  lastly,  under  favorable  circumstances,  this  reagent  raises  up  a  definite 
basement  membrane  from  the  outer  surface  of  the  lowest  part  of  the  bulb,  in  immediate 
contact  with  the  rounded  "  nuclei"  of  this  part,  and  this  basement  membrane  may  be  traced 
upwards  into  direct  continuity  with  the  homogeneous  portion  of  the  cuticle  above-described. 
(In  the  "  Edinburgh  Monthly  Journal  of  Medical  Science/'  for  March,  1853,  Mr.  Dalzell 
states  that  the  papilla  of  the  hair  has  a  basement  membrane.  Is  it  this  structure  to  which 
he  refers  ?)  In  all  cases  in  which,  in  man  or  in  animals,  we  have  isolated  the  hair-bulb 
from  its  sac,  it  seemed  to  have  a  definite  limiting  outer  line  down  to  the  narrow  neck  by 
which  it  passes  into  the  hair-sac,  though  it  was  not  often  easy  to  obtain  evidence  that  this 
limiting  line  was  the  expression  of  a  distinct  basement  membrane.  However,  the  same 
difficulty  would  occur  with  any  dermic  papilla ;  and  it  seems  to  us  that  there  is  sufficient 
evidence  to  show  that  the  cuticle  of  the  hair  is  not  the  product  of  any  direct  metamorphosis 
of  cells,  but  represents  a  modified  basement  membrane  with  a  subjacent  layer  of  peculiarly 
altered  blastema,  corresponding  precisely  with  the  "  Nasmyth's  membrane"  and  the  enamel 
of  the  teeth.  Vide  infra,  §  on  Teeth.— TES.] 


OF    THE    HAIRS. 


183 


Fig.  71. 


addition  of  acetic  acid.  They  resemble  smooth  muscular  fibres,  although 
they  cannot  be  completely  isolated  and  actually  recognized  as  true  fusi- 
form fibres  with  a  single  nucleus ;  on  which  account,  and  especially  as 
no  contractions  of  the  hair-sacs  have 
in  general  been  observed,  I  must  for 
the  present  refrain  from  positively 
deciding  upon  their  nature. 

The  third  layer,  lastly  (Fig.  71  6), 
is  a  transparent  structureless  mem- 
brane, which,  when  the  hairs  are  torn 
out,  invariably  remains  behind  in  the 
hair-sac,  and  extends  from  its  base, 
though,  as  it  would  seem,  without 
covering  the  papilla,  as  far  as  the 
inner  root-sheath,  and  perhaps  higher. 
In  the  uninjured  hair-sac  it  appears 
only  as  a  pale  streak  0-001-0-0015, 
rarely  0-002  of  a  line  thick,  between 
the  outer  root-sheath  and  the  trans- 
versely fibrous  layer  of  the  hair-sac ; 
by  preparing  an  empty  hair-sac,  how- 
ever, it  can  readily  be  obtained  in 
large  shreds,  and  then  appears  smooth 
externally ;  internally  it  is  covered 
with  very  delicate,  transverse,  often  anastomosing  lines,  which,  like  the 
membrane  itself,  remain  unchanged  in  acids  and  alkalies.  Neither  acids 
nor  alkalies  bring  out  cells  or  nuclei  in  this  membrane,  and  it  therefore 
probably  belongs  to  the  category  of  true  structureless  membranes. 

The  papilla  of  the  hair  (Fig.  63  i)  also,  less  properly  termed  the  hair- 
germ,  pulpapili,  belongs  to  the  sac,  and  corresponds  with  a  papilla  of 
the  cutis.  It  is  generally  seen  but  indistinctly,  especially  in  dark  hairs 
with  a  colored  bulb,  either  appearing,  only  as  a  clear,  indistinctly  defined 
spot,  or  after  the  tearing  out  of  the  hair,  remaining  so  covered  by  the 
cells  of  the  bulb  that  nothing  can  be  made  out  of  it.  It  is  only  in  the 
hair-sacs  of  white  hairs,  that  its  outlines  can  be  more  frequently  distin- 
guished without  wholly  isolating  it,  especially  by  the  help  of  a  little 
pressure.  Reagents,  on  the  other  hand,  avail  nothing,  for  they  attack 
the  papilla  to  about  the  same  extent  as  the  bulb,  with  the  sole  exception 
of  a  weak  solution  of  caustic  soda,  in  which  it  retains  its  outlines,  for  a 

Fio.71. — A  piece  of  the  transverse  fibrous  layer,  and  of  the  structureless  membrane 
(vitreous  membrane)  of  a  human  hair-sac,  treated  with  acetic  acid  ;  magnified  300  diame- 
ters: a,  transversely  fibrous  layer  with  elongated  transverse  nuclei ;  6,  vitreous  membrane 
in  apparent  section;  c,  its  edges,  where  the  sheath  which  it  forms  is  torn;  d,  fine  transverse 
partly  anastomosing  lines  (fibres)  on  their  inner  surface. 


184  SPECIAL    HISTOLOGY. 

time  at  any  rate,  whilst  the  cells  of  the  bulb  are  freed,  and  may  be 
pressed  out  of  the  sac.  The  papilla  is  ovate  or  fungiform,  J-^o  of  a 
line  long,  tT-sV  of  a  line  broad,  and  is  connected  with  the  layer  of  con- 
nective tissue  of  the  sac,  by  a  pedicle ;  it  has  sharp  contours  and  a  per- 
fectly smooth  surface,  and  in  its  structure  completely  agrees  with  the 
papillae  of  the  cutis,  consisting  of  an  indistinctly  fibrous  connective 
tissue  with  scattered  nuclei  and  fat  granules,  but  not  of  cells.  I  have 
taken  every  pains  to  discover  vessels  and  nerves  in  the  isolated  papilla, 
but  in  vain ;  even  acetic  acid  and  dilute  solution  of  caustic  soda,  which 
in  general  do  such  excellent  service  in  these  cases,  have  failed,  and 
Hassall  and  Gunther  met  with  the  same  results.  It  must  not  hence 
be  concluded,  that  ihepapilla  contains  no  vessels  or  nerves,  for  we  know 
that  in  other  places,  where  vessels  do  certainly  exist,  they  often  com- 
pletely escape  the  eye ;  as,  for  example,  in  the  dermal  papilla?  and  in 
the  villi;  and  with  respect  to  the  nerves,  in  the  papillae  of  the  cutis. 
In  some  animals  the  vessels  may  very  readily  be  seen. 

§  61.  The  root- sheath,  or  the  epidermic  investment  of  the  hair-sac,  is 
continuous  with  the  epidermis  around  the  aperture  of  the  follicle,  and 
may  be  divided  into  an  external  and  an  internal  layer,  which  are  dis- 
tinctly defined  from  one  another. 

The  external  root-sheath  is  the  continuation  of  the  stratum  Malpigliii 
of  the  epidermis,  and  lines  the  whole  hair-sac,  resting  for  its  lower  half 
on  the  transparent  membrane  above  described;  higher  up,  when  this 
and  the  transverse  fibres  are  absent,  it  lies  directly  upon  the  longitudi- 
nally fibrous  layer.  Its  structure  corresponds  exactly  with  that  of  the 
stratum  Malpighii,  even  in  the  having  the  outermost  cells,  which  in  the 
negro,  according  to  Krause,  are  always  brown,  and  in  whites  are  so,  at 
least  in  the  hairs  of  the  lalia  majora,  towards  the  upper  part,  arranged 
perpendicularly.  At  the  bottom  of  the  hair-sac,  the  outer  root-sheath, 
its  cells  becoming  gradually  rounded,  passes  continuously,  and  without 
any  sharp  line  of  demarcation,  into  the  round  cells  of  the  hair-bulb  which 
cover  the  papilla.  The  outer  root-sheath  is  generally  about  3-5  times 
as  thick  as  the  inner ;  but  not  unfrequently  it  becomes  thinned  towards 
its  upper  part,  and  below  invariably  passes  into  a  very  thin  lamella.  In 
the  coarse  hairs  it  measures  in  the  middle  of  the  root  0-018-0-03  of  a 
line,  and  presents  5-12  layers  of  cells. 

The  inner  root-sheath  (Fig.  68-e.  g.)  is  a  transparent  membrane 
which  extends  from  almost  the  very  bottom  of  the  hair-sac,  over  more 
than  two-thirds  of  it,  and  then  suddenly  ceases.  It  is  closely  connected 
externally  with  the  outer  root-sheath,  internally  with  the  cuticle  of  the 
hair  (its  outer  layer),  so  that  normally  there  is  no  space  between  it  arid 
the  hair;  further  it  is  distinguished  by  its  great  density  and  elasticity, 
and  it  consists  in  all  but  its  lowermost  part,  of  two  or  even  three  layers 


OF    THE    HAT  US. 


185 


of  polygonal,  elongated,  transparent,  and  somewhat  yellowish  cells,  all 
of  which  have  their  longitudinal  axes  parallel  to  that  of  the  hair  (Fig.  68). 
The  outermost  layer  (Fig.  72,  A\  which  alone  was  formerly  known,  the 
inner  root-sheath  of  Henle  is  formed  of  elongated  cells  without  nuclei, 
0-016-0-02  of  a  line  in  length,  and  0-004-0-006  of  a  line  in  breadth, 
which  are  intimately  connected,  and  in  the  ordinary  mode  of  investiga- 
tion, after  the  addition  of  acetic  acid,  caustic  soda,  or  potassa,  which 
swell  up  the  hair,  or  after  the  hair  has  been  teased  out,  present  elon- 
gated fissures  between  them,  whence  they  appear  like  a  fenestrated  mem- 
brane. In  quite  recent  hairs,  however,  if  all  reagents  and  mechanical 
injury  have  been  avoided,  we  see  hardly  any  trace  of  apertures  in  the 
upper  half  of  the  layer  in  question,  and  in  the  lowerh&lf  (from  the  finely 
fibrous  part  of  the  cortex  upwards),  at  most  mere  indications  of  them,  in 
the  form  of  striae,  clear  or  dark,  according  as  they  are  in  or  out  of  focus, 
and  similar  to  those  of  the  cortex  of  the  shaft.  We  can  hardly  avoid 
supposing,  therefore,  that  the  openings  as  they  are  commonly  seen 
(0-005-0-008  of  a  line  in  length,  and  0-001-0-03  of  a  line  in  breadth), 
are  produced  artificially  by  the  teasing  out  of  the  membrane.  Secondly, 
cells  also  occur  in  the  root-sheath,  between  which  gaps  are  never  visible. 
These  (Fig.  72,  B\  which  form  a  simple  or  a  double  layer  (Huxley's 

Fig.  72. 


layer),  are  constantly  situated  internal  to  the  common,  and  as  far  as  I 
have  seen,  always  single,  fenestrated  layer  of  cells ;  they  are  shorter  and 

FIG.  72. — Elements  of  the  inner  root-sheath  ;  magnified  350  diameters.  ^?,  from  the  outer 
layer,  1,  its  isolated  plates;  2,  the  same  in  connection,  from  the 'uppermost  parts  of  the  layer 
in  question,  after  treatment  with  caustic  soda:  a,  apertures  between  the  cells,  b;  7>,  cells  of 
the  inner  not-perforated  layer, with  elongated  and  slightly  notched  nuclei;  C,  nucleated  cells 
of  the  lowest  part  (single  layer)  of  the  inner  sheath. 


186  SPECIAL    HISTOLOGY. 

broader  than  the  cells  which  have  already  been  described  (0-014  to 
0-018  of  a  line  long,  0-006  to  0-009  of  a  line  broad),  but  are  also  poly- 
gonal, and  always  possess,  at  least  in  the  lower  half  of  the  root-sheath, 
distinct  elongated  nuclei,  often  prolonged  into  points  of  0-004-0-006  of 
line.  The  diameter  of  the  whole  inner  root-sheath  is,  upon  the  average, 
0-006-0-015  of  a  line,  whence  it  follows  that  its  cells,  of  which  there  are 
never  more  than  three  layers,  are  at  least  0-002-0-005  of  a  line  thick. 
They  are  recognizable  at  once  in  their  natural  position,  and  by  the  teasing 
out  of  the  root-sheath,  and  are  readily  isolated  by  the  use  of  soda  and 
potassa  (Fig.  72),  but  without  swelling  up,  a  character  which  no  less  than 
their  great  resistance  to  alkalies  altogether,  distinguishes  their  cells,  in 
common  with  the  epidermic  scales  of  the  hairs,  from  all  others. 

At  the  bottom  of  the  hair-sac,  the  inner  root-sheath  consists  only  of 
a  single  layer  of  beautiful,  large,  polygonal,  nucleated  cells,  without  any 
intermediate  openings  (Fig.  72,  (7),  which  becoming  at  last  soft,  delicate, 
and  rounded,  pass  without  defined  limits  into  the  outer  layers  of  the 
round  cells  of  the  hair-bulb.  Superiorly,  this  membrane  not  unfrequently 
becomes  somewhat  separated  from  the  hair,  and  ends,  not  far  from  the 
apertures  of  the  sebaceous  glands  in  a  sharp,  notched  edge,  formed  by 
its  separate  more  or  less  projecting  cells.  Thence  upwards,  it  is  re- 
placed by  a  layer  of  cells,  in  some  cases  at  first  nucleated,  but  at  other 
times  not,  which  gradually  approximates  more  and  more,  as  it  is  traced 
higher  up,  to  the  horny  layer  of  the  epidermis,  into  which  it  passes  con- 
tinuously ;  it  is  not,  however,  any  direct  continuation  of  the  inner  root- 
sheath. 

§  62.  Development  of  the  Hairs. — The  first  rudiments  of  the  hairs  are 
flask-shaped,  solid  processes  of  the  mucous  layer  of  the  epidermis  formed 
by  its  growth  inwards,  in  which  the  internal  and  external  cells  subse- 
quently become  differentiated  in  such  a  manner,  that  the  former,  a 
gradual  conversion  into  horn  going  on,  are,  in  the  axis  of  the  rudiment, 
metamorphosed,  in  the  first  place  into  a  small  delicate  hair,  and  secondly, 
around  this  into  its  internal  sheath ;  while  the  latter,  undergoing  less 
alteration  and  remaining  soft,  constitute  the  outer  root-sheath  and  the 
soft  cells  of  the  hair-bulb.  Hence  the  hairs  and  their  sheaths  arise  at 
once  in  their  totality.  The  former,  as  minute  hairs  with  root,  shaft, 
and  point,  and  are  therefore  not  developed  point  first,  as  the  teeth  are, 
with  their  crown  first,  and  still  less  as  Simon  has  supposed,  from  their 
root  first.  The  elements  of  the  youngest  hairs  are  nothing  but  elongated 
cells  similar  to  those  of  the  cortex  of  the  later  hairs,  which  are  deve- 
loped by  the  lengthening  and  chemical  alteration  of  the  innermost  cells 
of  the  rudiments  of  the  hairs.  Medullary  cells  are  entirely  wanting, 
but  the  cuticle  is  clearly  visible.  The  inner  sheath  is  striated,  presents 
no  openings,  and  consists  of  elongated  cells,  which  have  been  developed 


OF    THE    HAIRS.  187 

from  those  lying  between  the  hair  and  the  outer  sheath.  The  proper 
hair-sac  is  formed,  in  its  fibrous  layers,  essentially  in  loco,  out  of  the 
formative  cells  which  surround  the  rudiment  of  the  hair ;  possibly,  how- 
ever, they  may  be  considered  as  an  involution  of  the  cutis,  produced  by 
the  ingrowing  process  of  the  epidermis.  Its  structureless  membrane, 
which  appears  very  early,  is,  not  improbably,  closely  related  to  the  ex- 
ternal cells  of  the  rudiment  of  the  hair,  answering  to  the  outer  hair- 
sheath,  and  formed  by  an  excretion  from  them  like  the  membranes  pro- 
price  of  the  glands ;  as  to  the  papilla,  it  is  hardly  possible  to  consider  it 
as  anything  but  an  outgrowth  of  the  fibrous  layer  of  the  hair-sac, 
analogous  to  the  papillae  of  the  cutis  in  general ;  though  the  circumstance 
that  it  appears  at  a  time  when  the  hair-sac  is  hardly  demonstrable  as  a 
whole,  and  that  it  may  always  be  pulled  out  together  with  the  rudiments 
of  the  hair  and  root-sheath,  is  apparently  opposed  to  this  view. 

The  first  rudiments  of  the  downy  hairs  and  of  their  sheaths,  are  found 
in  the  human  embryo  at  the  end  of  the  third  or  at  the  beginning  of  the 
fourth  month,  upon  the  forehead  and  eyebrows.  They  consist  of  papilli- 
form  masses  of  cells  0*02  of  a  line  in  diameter  (Fig.  73)  which  are 
visible,  even  to  the  naked  eye,  as  minute  whitish  spots  separated  by 
regular  intervals.  They  are  continuously  connected  with  the  rete  Mal- 
pighii  of  the  epidermis,  and  are  nothing  more  than  perfectly  solid  pro- 
cesses of  it,  which  penetrate  obliquely  Fig.  73. 
into  the  corium,  and  here  lie  in  the 
meshes  of  a  delicate  capillary  network. 
These  cells  are  spherical,  0-003-0-004 
of  a  line  in  diameter,  and  consist  of  a 
clear  granular  substance  and  round 
nuclei  of  0-002-0-003  of  a  line. 
Nothing  was  to  be  seen  of  any  dermic  rf* 
investment  of  these  rudiments  ;  in  other  words,  the  foundation  of  what 
I  have  described  as  the  proper  hair-sac  was  not  laid.  In  the  fifteenth 
week  the  processes  were  already  larger  (0-025-0-03  of  a  line  long, 
0-013-0-02  of  a  line  broad),  flask-shaped,  and  surrounded  by  a  thin 
structureless  investment,  which  was  continued  into  a  delicate  membrane 
lying  between  the  cutis  and  the  rete  Malpighii,  but  united  more  closely 
with  the  latter.  Besides  this  investment,  which  is,  probably,  only  the 
structureless  membrane  which  I  have  discovered  in  the  perfect  hair  (see 
§  60),  another  external  layer  of  cells  occurs  on  the  hair-sacs,  which  can 

FIG.  73. — Rudiment  of  the  hair  from  the  brow  of  a  human  embryo,  sixteen  weeks  old; 
magnified  350  diameters:  a,  horny  layer  of  the  epidermis  ;  b,  its  mucous  layer;  t,  structure- 
less membrane  surrounding  the  rudiment  of  the  hair  and  continued  between  the  mucous 
layer  and  the  corium ;  m,  roundish,  partly-elongated  cells,  which  especially  compose  the 
rudiment  of  the  hair. 


188  SPECIAL    HISTOLOGY. 

generally  be  separated  only  in  shreds  with  it,  from  the  cutis,  rarely  al- 
together :  this  I  regard  as  the  first  indication  of  the  fibrous  layers  of 
the  hair-sacs.  In  the  sixteenth  and  seventeenth  weeks,  the  processes  of 
the  mucous  layer,  which  I  will  henceforward  simply  call  "  hair-rudi- 
ments," increase  in  size  up  to  -004-0-06  of  a  line  in  length,  and  0-03- 
0-04  of  a  line  in  breadth,  and  acquire  thicker  coverings,  but  as  yet  ex- 
hibit no  trace  of  a  hair.  In  the  eighteenth  week  these  first  appear  in 
the  eyebrows,  as  hair-rudiments  of  0-1-0-2  of  a  line,  their  central  cells 
becoming  somewhat  elongated,  and  arranging  themselves  with  their  lon- 
gitudinal axes  parallel  to  that  of  the  rudiment,  whilst  the  peripheral 
cells  are  disposed  with  their  now  longer  diameter  transversely.  A  variety 
of  shade  in  the  hitherto  homogeneous  hair-rudiment  arises  in  this 
manner,  and  a  central  substance,  broad  below,  running  above  into  a 
sharp  point,  becomes  marked  off  from  an  outer  portion,  which  is  narrow 
below  and  thick  above.  When  the  rudiment  has  attained  a  length  of 
0-22  of  a  line,  this  marking  off  is  still  more  distinct,  the  rather  longer 
and  especially  broader,  inner  cone  having  a  somewhat  clearer  appear- 
ance (Fig.  74).  Finally,  in  rudiments  of  hair  of  0'28  of  a  line,  the 
inner  cone  is  divided  into  two  structures,  a  central  portion  somewhat 
darker,  and  an  external,  perfectly  transparent  and  glassy, — the  hair 
and  the  inner  root-sheath, — whilst  the  peripheral  cells  which  have  re- 
mained opaque,  constitute  unmistakably  the  outer  root-sheath  (Fig. 
75  A).  At  the  same  time  the  papilla,  which  was  even  before  (Fig.  74) 
just  traceable,  becomes  more  distinct,  and  the  proper  hair-sac  also  more 
recognizable,  as  the  cells  which  lie  external  to  its  structureless  membrane 
begin  to  pass  into  fibres  which  may,  even  at  this  time,  be  known  by  their 
decussation.  The  hair-sacs  and  hairs  arise,  in  other  places,  exactly  in 
the  same  manner  as  in  the  eyebrows,  except  that  their  development  takes 
place  somewhat  later.  In  the  fifteenth  week,  no  rudiments  of  hairs  are 
visible,  except  on  the  forehead  and  eyebrows  ;  in  the  sixteenth  and 
seventeenth  week  they  appear  all  over  the  head,  back,  chest,  and  ab- 
domen ;  and  not  till  the  twentieth  week  on  the  extremities.  The  hairs 
themselves  never  make  their  appearance  earlier  than  3—5  weeks  after 
that  of  the  rudiments ;  in  the  nineteenth  week,  for  example,  the  com- 
mencement of  hairs  is  nowhere  to  be  seen,  except  on  the  forehead  and 
eyebrows ;  and  in  the  twenty-fourth  week  they  are  still  absent  upon  the 
hand  and  foot,  and  partly  on  the  forearm  and  leg. 

Once  formed,  the  hairs  and  hair-sacs  continue  to  grow.  The  former 
sometimes  penetrate  the  epidermis  immediately  (eyebrows,  eyelashes, 
Fig.  75),  sometimes  their  points  are  insinuated  between  the  horny  layer 
and  the  stratum  Malpighii,  or  among  the  elements  of  the  horny  layer 
itself,  and  grow  for  a  time  covered  by  the  epidermis  (chest,  abdomen, 
back,  extremities  [?]),  through  which  they  eventually  make  their  pas- 
sage. Involutions  of  the  skin  growing  towards  the  hairs  as  they  pass 


OF    THE    HAIRS. 


189 


out,  never  exist,  and  the  supposition  that  they  do,  rests  upon  a  wholly 
subjective  foundation. 

Fig.  75. 


Fig.  74. 


The  downy  hairs,  lanugo,  the  eruption  of  which  is  completed  in  the 
23-25th  week,  are  short  fine  hairs,  whose  peculiar  arrangement  has  been 
noted  above.  They  measure  on  the  bulb  0-01,  on  the  shaft  0-006,  at 
the  point  0-0012-0-002  of  a  line;  are  pale,  or  almost  .colorless,  and 
consist  only  of  cortical  substance  and  a  cuticle.  In  man,  the  bulb  is 
usually  colorless,  and  often  rests  upon  a  very  distinct  papilla,  arising 
in  the  ordinary  manner  from  the  bottom  of  the  hair-sac.  It  has  the 
same  three  layers  as  in  the  adult,  and  possesses  a  very  well-developed 
epidermic  investment,  consisting  of  an  external  root-sheath  of  0*004— 
0-012,  and  an  inner  sheath  of  0-006-0-008  of  a  line,  without  openings. 

After  their  eruption,  the  downy  hairs  grow  slowly  to  a  length  of  J-J 
of  a  line,  and  in  fact  to  a  greater  length  in  the  head  than  elsewhere. 
Generally  they  remain  to  the  end  of  foetal  life,  gradually  acquiring  a 
darker  color,  becoming  in  many  cases,  as  on  the  head,  even  blackish ; 
another  small  portion  falls  off  into  the  liquor  amnii,  is  swallowed  with 

FIG.  74. — Rudiment  of  a  hair  from  the  eyebrow  (O22  of  a  line  in  length),  its  inner  cells 
forming  a  distinct  cone,  as  yet  without  any  hair,  but  with  the  papilla  indicated :  a,  horny 
layer  of  the  epidermis;  6,  mucous  layer;  c,  outer  root-sheath  of  the  subsequent  sac;  i,  struc- 
tureless membrane  upon  its  outer  side ;  A,  papilla  of  the  hair. — Magnified  50  diameters. 

FIG.  75. — jl,  rudimental  hair  from  the  eyebrows,  with  just  developed  but  not  yet  erupted 
hair,  of  O28  of  a  line  in  length.  The  inner  root-sheath  projects  beyond  the  point  of  the  hair 
somewhat  at  the  upper  part,  and  laterally  at  the  neck  of  the  sac;  the  first  rudiments  of  the 
sebaceous  glands  appear  in  the  form  of  two  papillary  outgrowths  from  the  outer  root-sheath. 
JB,  hair-sac  from  the  same,  with  its  hair  just  erupted ;  the  inner  root-sheath  projects  through 
the  aperture  of  the  hair-sac;  the  rudiments  of  sebaceous  glands  are  as  yet  not  developed; 
a.  6,  c, /*, i,  have  the  same  signification  as  in  Fig.  74  :  e,  hair-bulb;  /,  hair-shaft;  g,  hair-point; 
n,  rudiments  of  the  sebaceous  glands. 


190  SPECIAL    HISTOLOGY. 

this  by  the  foetus,  and  may  afterwards  be  found  in  the  meconium.  A 
proper  shedding  of  the  hair  does  not  take  place  at  all  in  the  foetus,  so 
far  as  I  can  see,  infants  being  born  with  the  lanugo  ;  as  little  does  any 
trace  of  a  further  formation  of  hair  appear  after  its  complete  eruption. 
The  question  whether  the  point  of  the  hair  is  first  formed,  or  whether 
the  latter  is  developed  at  once  as  a  whole,  is  readily  solved.  Hairs 
which  are  just  formed,  have  a  bulb  with  soft  cells,  a  horny  point  and  an 
intermediate  portion,  in  which  the  cells  are  converted  into  horn,  and 
are  partly  found  passing  into  the  cells  of  the  root,  whence  there  can  be 
no  doubt  that  we  have  here  a  whole  hair.  That  the  horny  part  of  this 
hair  subsequently  forms  the  point  of  a  larger  hair,  is  of  no  importance; 
and  as  little  as  the  hairs  of  the  head  of  a  newly-born  infant  can  be 
called  points  of  hairs,  because  they  subsequently  become  the  points  of 
larger  hairs,  can  we  so  denominate  these.  Nor  can  it  be  said  that  the 
first  foetal  hair  subsequently  becomes,  in  totality,  the  point  of  a  larger 
hair,  since  the  hairs  do  not  grow  by  the  simple  apposition  of  new  ele- 
ments, like  the  bones,  but  by  the  multiplication  of  their  lowest  soft  cells, 
some  of  which  are  always  retained  as  a  reserve  for  cells  to  be  newly 
developed,  whilst  the  others  are  converted  into  horn ;  whence  also  it 
happens,  that  the  cells  even  of  a  complete  hair-bulb  are  to  be  regarded 
as  the  successors  of  those  of  the  foetal  hair.* 

*  [From  what  has  been  said  above  (see  note  on  the  Cuticle)  it  is  clear  we  do  not  share 
Professor  Kolliker's  view  that  the  hair  is  an  epidermic  production.  Reichert's  view,  on  the 
other  hand,  that  the  hair  results  from  the  cornification  of  a  dermic  papilla  or  matrix,  which 
drying  up  and  becoming  filled  with  air,  remains  as  the  medullary  portion,  seems  to  us  to  be 
nearer  the  truth.  There  can  be  no  doubt  of  these  two  facts:  1,  that  no  line  of  demarcation 
can  be  traced  between  the  papilla  of  the  hair  and  its  shaft;  and  2,  that  in  many  animals 
the  papilla  is  vascular  and  nervous  for  a  considerable  distance  into  the  shaft,  and,  therefore, 
is  certainly  a  dermic  structure. 

Whether  Reichert's  somewhat  mechanical  notion  of  the  "  drying  up"  of  the  matrix  to  form 
the  medulla  is  correct,  is  not  of  much  importance,  so  long  as  we  keep  in  view  the  unques- 
tionable continuity  of  tissue  and  homological  identity,  of  the  medulla  and  cortex  with  the 
dermic  papilla. 

For  us,  in  fact,  the  Hair  is  homologous  in  all  its  parts  with  the  Tooth.  The  substance  of 
the  shaft  corresponds  with  the  dentine,  offering  even  rudimentary  tubes  in  its  aeriferous 
cavities ;  the  inner  layer  of  the  cuticle  answers  to  the  enamel,  the  outer  to  Nasmyth's  mem- 
brane ;  and  whoever  will  compare  these  structures  will  be  struck  by  the  similarity  even  in 
their  appearance.  The  sac  answers  to  the  dental  capsule ;  the  outer  root-sheath  to  the  layer 
of  epithelium  (enamel  organ)  next  the  capsule ;  the  fenestrated  membrane  to  the  stellate 
tissue ;  and  what  Professor  Kolliker  calls  "  Huxley's  layer,"  to  the  columnar  epithelial  layer 
of  the  organon  adamantines.  The  comparison  may  seem  startling  at  first,  but  the  examina- 
tion of  the  development  of  the  teeth  of  an  osseous  fish,  for  example,  will  suffice,  we  believe, 
to  afford  full  justification  of  it. 

With  respect  to  the  not  very  important  question,  as  to  the  nature  of  the  first  rudiment  of 
the  hair-shaft,  i.  e.  whether  it  is  the  point  of  a  hair  or  a  whole  hair,  we  must  confess  that  we 
should  be  tempted  to  arrive  at  the  opposite  conclusion  to  our  author.  Inasmuch  as  the  por- 
tion of  the  hair  which  first  appears  becomes  the  point  of  the  fully-grown  hair,  we  should 
say  that  the  hairs  are  formed  like  the  teeth,  point  first. 

A  hair,  like  a  tooth,  has  a  definite  form  to  attain.     As  the  latter  has  a  peculiarly  con- 


OF    THE    HAIRS. 


191 


§  63.  Shedding  of  the  Hair. — After  birth,  a  total  shedding  of  the 
hairs  takes  place  in  consequence  of  the  development  of  new  hairs  within 
the  hair-sacs  of  the  lanugo,  which  gradually  force  out  the  old  ones.  This 
shedding  of  the  hairs,  which  I  discovered  in  the  eyelashes  of  a  child  of 
one  year  old,  commences  by  an  outgrowth  of  the  soft  round  cells  of  the 
bulb  and  of  the  neighboring  outer  root-sheath,  from  the  bottoms  of  the 
sacs  of  the  lanugo,  into  long  processes  composed  of  cells,  by  which  the 

Fig.  76. 


hair  is  raised  from  its  papilla,  whilst  at  the  same  time  it 
becomes  converted  into  horn  even  in  its  lowermost  por- 
tion. When  these  processes  have  attained  a  length  of 
0*25  of  a  line,  a  differentiation  of  their  outer  and  inner 
cells  takes  place,  similar  to  that  which  has  been  already 

FIG.  76. — The  eyelashes  of  a  child  of  one  year  old  pulled  out;  magnified  20  diameters: 
Jl,  one  with  a  process  of  the  bulb  or  of  the  outer  root-sheath,  of  0'25  of  a  line,  in  which  the 
central  cells  are  elongated  (their  pigment  is  not  represented),  and  are  clearly  defined  as  a 
cone  from  the  external  ones;  '.B,  eyelash  in  whose  process,  of  0'3  of  a  line,  the  inner  cone  is 
metamorphosed  into  a  hair  and  an  inner  root-sheath ;  the  old  hair  is  pushed  up.  and  like  A 
and  Fig.  75,  possesses  no  inner  root-sheath  :  a,  outer;  b,  inner  root-sheath  of  the  young  hair; 
c,  pit  for  the  papilla  of  the  hair;  c?,  bulb;  e,  the  shaft  of  the  old  hair;  /,  bulb;  g,  shaft;  A, 
point  of  the  young  hair;  t,  sebaceous  glands;  7c,  three  sudoriparous  canals,  which  in  A  open 
into  the  upper  part  of  the  hair-sac;  I,  transition  of  the  outer  root-sheath  into  the  rete  mucosum 
of  the  epidermis. 

FIG.  77. — An  eyelash  with  the  root-sheaths  from  a  child  one  year  old,  with  an  old  and  a 
growing  young  hair,  magnified  20  diameters :  the  young  hair  is  wholly  extruded,  and  now 
two  hairs  appear  at  one  aperture.  A  sudoriparous  canal  opens  into  the  hair-sac.  The 
letters  have  the  same  signification  as  in  Fig.  76. 


structed  and  narrowed  root  when  complete,  so  has  the  hair  when  it  has  attained  its  full 
growth  a  peculiarly  constructed  bulb ;  and  it  is  not  a  perfect  hair  until  this  peculiar  bulb  is 
developed.  Until  it  has  attained  this  form  it  goes  on  growing;  but  once  having  reached  it, 
it  grows  no  more,  but  falls  out  and  is  replaced  by  a  new  hair  (see  following  §). — Tus.] 


192  SPECIAL    HISTOLOGY. 

described  as  occurring  in  those  processes  of  the  stratum  Malpighii,  in 
which  the  hairs  of  the  lanugo  are  developed.  The  outer  cells,  in  fact, 
remaining  round  and  colorless,  as  they  were  before,  the  inner  ones  begin 
to  develop  pigment  in  their  interior  and  to  elongate,  becoming  distin- 
guished at  the  same  time  from  the  former,  as  a  conical  substance  with 
its  point  directed  upwards.  At  first  (Fig.  76  A\  this  central  substance 
is  quite  soft,  and  like  the  layers  of  cells  which  surround  it  externally, 
dissolves  readily  in  solution  of  caustic  soda ;  subsequently,  however, 
when,  together  with  the  process  which  incloses  it,  it  has  elongated,  its 
elements  harden,  and  separate  into  two  portions,  an  enternal  dark  pig- 
mented,  and  an  external  clear  part,  which  are  nothing  else  than  a  young 
hair,  together  with  its  inner  sheath  (Fig.  76  B).  The  young  hair, 
whose  point  at  first  does  not  project  beyond  its  inner  root-sheath,  now 
grows  gradually,  forcing  its  point  through  the  aperture  of  the  old  sac, 
while  at  the  same  time  its  root-sheath  elongates,  and  thrusts  upwards 
the  bulb  of  the  old  hair,  until  at  last  it  passes  completely  out,  and  makes 
its  appearance  at  the  same  opening  with  the  old  one,  which  is  more 
and  more  pushed  up.  When  the  development  of  the  hair  has  gone 
thus  far,  the  last  stage  may  be  readily  understood.  The  old  hair,  which 
has  for  a  long  time  ceased. to  grow,  and  to  be  connected  with  the  bottom 
of  the  sac,  being  thus  extruded,  falls  out,  while  the  young  hair  becomes 
larger  and  stronger,  and  fills  the  gap  left  by  the  old  one.  The  primary 
cause  of  the  dying  away  and  casting  off  of  the  old  hair,  I  consider  to 
be  the  development  of  the  processes  of  the  hair-bulb  and  outer  sheath 
from  the  bottom  of  the  sac,  which  has  been  described.  As  the  sacs  do 
not  elongate  to  a  corresponding  extent,  they  push  upwards  all  those 
parts  which  lie  above  them,  and  cause  a  continually  increasing  space  to 
exist  between  the  papilla  and  the  proper  hair,  or  the  point  at  which  the 
round  cells  of  the  bulb  begin  to  elongate  and  undergo  conversion  into 
horny  matter. 

The  hair  thus  becomes  in  a  manner  detached  from  the  source  of  its 
nourishment;  it  receives  less  and  less  blastema,  at  last  ceasing  to  grow, 
and  becoming  converted  into  horn  in  its  lowest  part.  The  cells  of  the 
processes,  on  the  other  hand,  which  are  connected  with  the  papilla,  are 
incessantly  supplied  from  it  with  new  formative  material,  which  for  the 
time  they  apply  not  to  the  formation  of  horny  matter,  but  to  their  own 
growth.  In  this  manner  the  processes  continue  to  grow,  and  mechani- 
cally elevate  the  cornified  root  of  the  old  hair  with  its  sheaths,  to  the 
aperture  of  the  sebaceous  glands,  where  to  all  appearance  a  partial  so- 
lution of  the  old  sheaths  takes  place  :  this  may  be  observed  with  cer- 
tainty in  the  inner  sheath,  and  must  be  assumed  to  occur  in  the  outer. 

All  that  has  been  said,  holds  good  only  with  respect  to  the  eyelashes. 
The  hairs  of  the  head,  and  the  other  hairs  of  the  body  of  the  child  (al- 
most a  year  old)  in  question,  never  contained  more  than  one  hair,  though 


Of    THE    HAIRS.  193 

their  bulbs  presented  processes  without  hairs  like  those  which  precede 
the  shedding  of  the  eyelashes  ;  such  processes,  in  fact,  being  of  very 
common  occurrence  in  the  hairs  of  children  within  the  first  year.  I  be- 
lieve I  am  not  wrong,  if  from  the  presence  of  these  processes  I  deduce 
the  universal  occurrence  of  a  shedding  of  the  hairs,  particularly  as  it  is 
certain  that  in  many  children  within  the  first  2-6  months  after  birth, 
the  hairs  of  the  head  fall  out  and  are  replaced  by  new  ones.  How- 
ever, further  observation  is  necessary  to  determine  what  period  is  occu- 
pied by  this  first  shedding  of  the  hair,  in  what  hairs  it  occurs,  and 
whether  perhaps  the  process  is  subsequently  repeated. 

If  we  compare  the  shedding  of  the  hairs  with  their  first  develop- 
ment, we  find  a  great  resemblance  between  the  two  processes.  In  both, 
elongated  projections,  wholly  formed  of  round  soft  cells,  shoot  like  buds 
from  the  stratum  Malpighii^  in  the  one  case  of  the  skin  itself,  in  the  other 
of  the  hair-sacs  and  hairs.  In  both,  a  separation  of  the  inner  from  the  outer 
cells  next  takes  place ;  and  while  the  latter  are  metamorphosed  into  the 
outer  root-sheath,  the  former  become  the  inner  root-sheath  and  the  hair. 
The  latter  arises,  as  is  still  more  clear  in  the  shedding  of  the  hairs  than  in 
their  first  development,  like  the  nail,  with  all  its  parts  at  once,  as  a  small 
hair  provided  with  point,  shaft,  and  root,  and  which  only  subsequently 
begins  to  grow,  in  consequence  of  which  it  enlarges  in  all  its  parts, 
and  finally  reaches  the  surface.  The  differences  between  the  two  modes 
of  development  are  very  inconsiderable,  and  chiefly  depend  upon  the 
rudimentary  hair-processes,  in  the  one  case  proceeding  from  the  hairs 
themselves,  but  not  in  the  other;  and  upon  the  circumstance  that  the 
young  hairs,  although  in  both  cases  they  lie  at  first  in  a  closed  space, 
reach  the  surface  more  readily  in  the  one  case,  than  in  the  other. 

In  the  periodical  shedding  of  the  hair  of  animals,  the  observations 
of  Heusinger  and  Kohlrausch,  and  lately  those  of  Langer,  Gegenbaur, 
and  Steinlin,  show  that  the  new  hairs  are  also  developed  in  the  sacs  of 
the  old  ones;  although,  according  to  the  last  author,  with  whom  how- 
ever Langer  is  not  quite  in  accord,  the  process  does  not  appear  to  be 
exactly  the  same  as  in  man. 

§  64.  Physiological  Observations. — The  hairs  have  a  definite  length, 
dependent  upon  locality  and  'Sex,  but  if  they  are  cut  they  grow  again, 
and  consequently  exhibit  the  same  conditions  as  the  other  horny  textures. 
The  place  from  whence  the  growth  of  the  hair  proceeds  is  unquestionably 
the  bottom  of  the  hair-sac.  Here  there  arise  around  the  papillae  with 
the  co-operation  of  a  blastema  formed  out  of  its  vessels  or  those  of  the 
hair-sac,  new  elements,  by  the  continual  multiplication  of  the  existing 
cells,  while  those  which  are  already  present,  somewhat  higher  up  pass 
uninterruptedly,  the  middle  ones  into  medullary  cells,  the  next  into  cor- 

13 


194  SPECIAL    HISTOLOGY. 

tical  plates,  the  outermost  into  epidermic  scales,  and  thus  the  horny  part 
of  the  hair  is  continually  forced  from  below  upwards,  and  elongates. 
In  the  latter  no  formation  of  elementary  parts  takes  place,  but  at  most 
a  certain  metamorphosis  of  those  which  are  already  existent,  which  pro- 
duces a  gradual  thinning  of  the  root  from  the  bulb  upwards,  until  it 
acquires  the  thickness  of  the  shaft.  Higher  up  still,  these  changes 
of  the  elementary  parts  cease,  whence  cut  hairs,  for  example,  do  not 
produce  new  points.  The  root-sheaths  and  the  outer  layer  of  the  epi- 
dermis take  no  part  in  the  growth  of  the  cut  hairs. 

The  complete  hair,  though  non-vascular,  is  not  a  dead  substance.  Al- 
though the  processes  which  go  on  in  it  are  not  at  all  understood,  we 
may  suppose  that  fluids  are  diffused  through  it  which  subserve  its  nu- 
trition and  maintenance.  These  fluids  are  furnished  from  the  vessels  of 
the  papilla  and  sac  of  the  hair,  in  all  probability  ascend  (particularly 
from  the  bulb) ;  without  any  special  canals  through  the  cortex  upwards, 
and  thus  reach  all  parts  of  the  hair.  Having  served  for  the  nutrition 
of  the  hair,  they  evaporate  from  its  outer  surface  and  are  replaced  by  a 
fresh  supply.  Perhaps  the  hairs  also  absorb  fluids  from  without,  though 
of  course  only  in  the  condition  of  vapor,  like  a  hair  used  as  a  hygrometer  ; 
on  the  other  hand  I  cannot  believe  that,  as  many  authors  would  seem  to 
suppose,  the  secretion  of  the  sebaceous  glands  passes  from  without  into 
the  hairs,  since  the  perfectly  closed  cuticle  is  probably  impervious 
to  it.  In  the  same  way  it  seems  to  be  in  nowise  proved  that  the  hairs 
are  pervaded  by  a  peculiar  oleaginous  fluid  (Laer),  which  might  proceed 
from  the  medullary  substance  (Reichert),  and  which  keeps  it  greasy, 
for  such  a  fluid  has  not  been  demonstrated,  and  the  greasiness  of  the 
hairs  may  be  more  simply  explained  by  the  externally  adherent  sebaceous 
matter,  which  is  readily  visible.  The  existence  of  hair  in  the  medullary 
axis  and  in  the  cortex  can  only  arise  from  a  disproportion  between  the 
supply  of  fluid  from  the  hair-sac  and  the  amount  evaporated  ;  it  is  owing 
as  it  were,  to  a  drying-up  of  the  hair,  which,  however,  must  not  be  sup- 
posed to  go  so  far  that  the  hair  contains  no  fluid  in  its  aeriferous  portion. 
In  any  case,  however,  these  portions  are  the  most  inactive,  or  relatively 
dead  parts  of  the  hair ;  the  cortex,  on  the  other  hand,  which  is  also 
most  readily  altered  by  alkalies  and  acids,  notwithstanding  the  apparent 
hardness  and  density  of  its  elements,  is  the  most  rich  in  juices,  and  is 
that  in  which  the  nutritive  process  is  most  actively  going  on.  Hence 
it  follows,  that  the  hair  lives,  and  is  to  a  certain  extent  dependent  upon 
the  collective  organism,  particularly  on  the  skin,  from  whose  vessels 
(i.  e.  those  of  the  hair-sac)  it  derives  the  materials  necessary  for  its 
maintenance.  Therefore,  as  Henle  well  says,  the  condition  of  the  hair 
is  a  sort  of  index  of  that  of  the  activity  of  the  skin  ;  if  they  are  soft  and 
shining,  the  skin  is  turgescent  and  transpires ;  if  they  are  dry,  brittle, 
and  rough,  then  it  may  be  concluded  that  the  surface  of  the  body  is  in 
a  collapsed  condition. 


OF    THE     HAIRS.  195 

The  falling  out  of  the  hairs  certainly  depends,  in  many  cases, — when, 
for  example,  it  takes  place  in  the  course  of  normal  development, — on 
nothing  else  than  a  want  of  the  necessary  nutritive  material,  which  in 
the  instance  already  explained,  in  speaking  of  the  shedding  of  the  hairs, 
depends  on  the  detachment  of  the  hair  from  its  matrix  by  the  abundant 
production  of  cells  at  the  bottom  of  the  hair-sac.  In  age,  perhaps,  it 
arises  simply  from  the  obliteration  of  the  vessels  of  the  hair-sacs. 

The  whitening  of  the  hairs,  which  chiefly  depends  upon  a  decoloration 
of  the  cortex,  and  less  upon  that  of  the  almost  colorless  medulla,  should 
probably  be  here  considered,  for  its  normal  occurrence  in  old  age  gives 
it  the  significance  of  a  retrogressive  development. 

The  frequent  occurrence  of  cases,  in  which  the  hair  grows  gray  first 
at  its  point  or  in  the  middle,  and  the  well-established  instances  of  its 
rapidly  becoming  white,  are  interesting,  and  strongly  testify  to  the 
vitality  of  the  hair ;  but  it  has  not  yet  been  shown,  what  peculiar  -pro- 
cesses in  the  elements  of  the  hair  produce  the  decoloration  of  its  different 
pigments. 

As  in  youth  hairs  which  are  shed  are  replaced  by  others,  so  at  a  later 
age  something  similar  appears  to  occur.  It  is  quite  certain  that  during 
the  period  of  full  health  and  activity,  a  continual  replacement  of  the 
numerous  hairs  which  fall  out  goes  on ;  furthermore  that  new  hairs  in 
great  numbers  spring  up  at  the  time  of  puberty  in  certain  localities,  but 
the  manner  in  which  this  takes  place  is  unknown.  Inasmuch  as  even  in 
adults  we  find  hair-sacs  with  little  processes  downwards,  whose  proper 
hair  has  an  abrupt  clavate  end,  as  in  the  child ;  since  further,  in  this 
case  it  not  unfrequently  happens  that  two  hairs  come  out  of  one  aper- 
ture, and  even  exist  together  in  one  sac ;  and,  finally,  since  in  hairs 
which  have  fallen  out  spontaneously,  we  invariably  find  roots  like  those* 
which  exist  in  the  extruded  hairs  of  the  first  shedding,  it  may  be 
assumed  that  an  actual  shedding  of  the  hairs  occurs,  even  at  a  later 
period,  in  such  a  manner  that  the  old  hair-sacs  produce  new  hairs  while 
they  throw  off  the  old  ones.  I  do  not,  however,  intend  to  affirm  by 
this,  that  an  actual  new  formation  of  hairs  does  not  occur  after  birth, 
but  only  this  much,  that  in  adults  they  are  certainly  regenerated  from 
the  already  existing  hair-sacs,  especially  if  it  be  recollected  that,  accord- 

*  [Henle  ("  Allg.  Anat,"  p.  303)  gives  a  very  excellent  description  of  this  state  of  the 
hair-bulb:  "  Instead  of  the  soft  cellular  hair-bulb,  we  find  an  inconsiderable  clavate  enlarge- 
ment, which  is  solid  and  fibrous,  like  the  substance  of  the  shaft,  only  more  clear.  From  its 
outer  surface,  short  and  irregular  processes  project  downwards,  which  are  probably  the 
notched  lower  edges  of  the  outermost  layers  of  the  cortical  substance ;  they  look  like  fibres 
connecting  the  hair  with  the  inner  wall  of  the  sac.  This  kind  of  root  is  found  in  hairs 
which  have  fallen  out  spontaneously,  and  it  is,  therefore,  probable  that  it  belongs  to  a  later 
stage  of  development  of  the  hair,  or  rather  marks  the  conclusion  of  its  development.  When 
the  connection  with  the  sac  has  ceased,  which  is  the  case  in  these  clavate  roots,  the  hair 
grows  no  longer  5  probably  it  is  no  longer  nourished,  but  falls  out." — 


196  SPECIAL    HISTOLOGY. 

ing  to  Heusinger's  observations,  the  whiskers  of  dogs,  when  pulled  out, 
are  produced  from  the  same  sacs  in  a  few  days,  and  also  that  during  the 
shedding  of  the  hair  in  adult  animals,  according  to  Kohlrausch,  the 
young  hairs  are  produced  from  the  old  sacs.  Also,  when  the  hairs 
which  have  fallen  out  after  a  severe  illness,  are  replaced,  it  is  more 
probable,  since,  according  to  E.  H.  Weber,  the  sacs  of  lost  hairs  remain 
for  a  long  time,  that  they  arise  in  the  old  sacs,  than  that  new  ones  are 
developed.* 

The  multiplication  of  the  cells  of  the  bulb  of  the  hair  during  its 
growth  takes  place  unquestionably,  not  by  free  cell-development,  since 
no  trace  of  anything  of  the  kind  is  to  be  seen  in  any  bulb,  but  either 
by  endogenous  cell-development  round  portions  of  contents,  or  by  divi- 
sion. I  do  not  think  that  all  those  hairs  which  possess  a  sharply-defined 
clav'ate  bulb  are  on  that  account  dead  and  ready  to  fall  out.  It  is  cer- 
tainly thus  in  many  cases  ;  but  in  others  this  condition  indicates  nothing 
more  than  the  normal  termination  of  growth,  whence  of  course,  it  does 
not  follow  that  the  nutrition  also  has  ceased.  In  proof  of  the  occurrence 
of  a  continual  development  of  the  hairs  independently  of  the  old  hair- 
sacs,  the  hairs  which  lie  spirally  curled  up  under  the  epidermis  and 
subsequently  break  through  it,  upon  the  forearm,  leg,  &c.,  are  frequently 
cited.  But  I  do  not  know  that  it  would  not  be  more  correct  to  consider 
this,  with  many  pathologists,  rather  as  an  abnormal  process.  In  the 
first  place  this  formation  of  the  hairs  by  no  means  occurs  in  all  per- 
sons ;  and  secondly,  where  it  does,  there  are  found  together  with  those 
coiled-up  hairs,  which  are  apparently  normally  developed,  others  which 
are  evidently  abnormal,  in  great  quantities.  These,  often  in  consider- 
able number  (up  to  9),  with  thick  sheaths,  lie  in  one  sac  and  have 
rounded  points,  with  irregular  bulbs.  With  respect  to  their  relations, 
it  might  for  the  present  be  wiser,  so  long  as  an  actual,  normal  new 
development  of  hairs  has  not  been  demonstrated,  not  to  assume  it,  and 
to  consider  that,  even  at  a  later  period,  the  development  of  new  hairs 
within  the  old  sacs  is  the  normal  mode,  especially  since  Dr.  Langer  has 
actually  observed  it  to  take  place  in  many  instances  in  the  very  same 
manner  as  that  which  I  have  described  in  children.  The  reason  why 
the  hairs  grow  continually,  if  they  are  cut,  but  not  otherwise,  is  the 
same  as  I  have  already  adduced,  to  account  for  the  same  occurrence  in  the 

*  [Berthold  (Mull  "  Archiv,  "  1850)  has  communicated  some  curious  statistics  relative  to 
the  growth  of  Hairs.  The  hairs  of  the  head  of  a  female  of  from  16  to  24  years  of  age,  grow 
at  the  rate  of  7  lines  a  month.  The  growth  of  the  hairs  of  the  beard  is  quicker  the  oftener 
they  are  cut;  shaved  every  12  hours  they  would  attain  a  length  of  from  5^-12  inches  per 
annum  ;  every  24  hours,  from  5—7^  inches;  every  36  hours,  from  4-6^  inches.  They  grow 
faster  by  A  during  the  day  than  during  the  night;  and  in  18  days  of  summer,  0026  more 
than  in  18  days  of  winter. — TBS.] 


OF    THE    HAIRS.  197 

nails.  The  vessels  of  the  papilla  excrete  a  certain  quantity  of  nutritive 
fluid,  just  so  much  as  is  sufficient  to  keep  the  whole  hair  continually 
moist  and  in  a  state  of  vitality.  If  the  hair  be  cut,  more  nutritive  fluid 
is  supplied  than  the  hair  can  use,  and  therefore  it  grows  by  the  aid  of 
the  superfluity  until  it  has  attained  its  typical  length  again,  or.  if  it  be 
continually  cut,  it  as  continually  grows. 

Dzondi,  Tieflfenbach  ("Nonnullade  regeneratione  ettransplantatione," 
Herbip,  182*2)  and  Wiesemann  (De  coalitu  partium,  Lips.  1824)  have 
succeeded  in  transplanting  the  hairs  with  their  sacs.  Hairs  are  deve- 
loped also  in  abnormal  places,  e.  g.  on  mucous  membranes,  in  encysted 
tumors,  ovarian  cysts,  and  in  all  these  cases,  even  in  the  lungs  (Mohr's 
case),  possess  sacs,  root-sheaths,  and  an  otherwise  normal  structure. 
No  hairs  are  developed  upon  cicatrices  of  the  skin.  No  satisfactory 
reason  can  be  given  for  the  excessive  growth  of  the  hairs,  nor  for  their 
morbid  universal  falling  out,  together  with  their  frequent  reproduction 
in  the  same  way ;  probably  the  principal  causes  are  to  be  found  in 
increased  or  diminished  exudations  from  the  vessels  of  the  papilla  and 
of  the  hair-sac,  and  more  remotely  in  the  state  of  the  skin  and  the 
organism  in  general.  In  other  cases  vegetable  productions  (fungi]  in  the 
interior  of  the  hair  itself  (in  Herpes  tonsurans,  the  "  Teigne  tondante," 
Mahon),  according  to  Gruby  ["  Gaz.  M£d.,"  1844,  No.  14],  and  Malmsten, 
(Mull.  "Arch.,"  1848,  1),  or  under  the  epidermis  of  the  hair  and  around 
it  (in  the  Porrigo  decalvans  of  Willan  according  to  Gruby),  are  con- 
cerned in  the  production  of  baldness,  which  then  is  limited  (Alopecia 
cir  cum  script  a).  The  process  of  becoming  gray  is  also  obscure,  although 
grief,  excessive  intellectual  activity,  and  nervous  influences  are  sometimes 
evidently  concerned  in  it.  It  is  not  until  physiology  and  chemistry 
have  approached  these  latter  processes,  that  we  can  hope  for  a  scientific 
pathology  and  treatment  of  the  hair.  Plica  polonica,  which,  according 
to  Bidder  (1.  c.),  is  a  disease  of  the  shaft  of  the  hair,  is  said  by  Guens- 
burg  and  Walther  (Miiller's  "  Archiv,"  1844,  p.  411,  and  1845,  p.  34), 
to  arise  from  a  fungus  which  is  developed  in  the  hairs  (bulb,  shaft),  and 
partly  destroys  them  ;  whilst  Munter  (ibid.,  1845,  p.  42)  could  find  no 
such  fungus.  This  disease,  as  well  as  peculiar  yellowish-white  rings 
upon  the  human  hairs,  consisting  of  epithelial  cells  without  nuclei 
(Svitzer,  in  u  Fror.  Notizen,"  1848,  No.  101),  which  appear  to  consist 
of  an  altered  secretion  of  the  sebaceous  glands,  are  less  interesting 
from  a  histological  point  of  view,  and  therefore  are  but  shortly  adverted 
to  here. 

For  microscopic  investigation,  a  white  hair  with  its  sac  should  be 
chosen  in  the  first  instance,  subsequently  colored  ones.  Transverse 
sections  may  be  obtained,  either  by  shaving  twice  at  short  intervals 
(Henle)  or  by  cutting  hair  on  a  glass  (H.  Meyer),  or  in  a  bundle  be- 
tween two  cards  (Bowman),  or  fixed  in  a  cork  (Hartin);  longitudinal 


198  SPECIAL    HISTOLOGY. 

sections,  by  splicing  a  finer  or  splitting  a  coarser  hair.  The  hair-sacs 
may  be  examined,  both  isolated  and  with  the  hair  ;  their  different  layers 
may  be  separated  by  preparations,  and  the  nuclei  of  the  external  ones 
may  be  demonstrated  by  acetic  acid.  Concerning  the  papillae ^  all  that 
is  necessary  has  been  said  above;  the  whole  upper  part  of  the  root-sheath 
generally  follows  the  hair  when  it  is  torn  out,  and  in  the  macerated  skin 
it  comes  out  very  readily  with  the  hair ;  its  cells  may  be  made  out  with- 
out addition,  or  by  a  little  acetic  acid  or  caustic  soda.  The  inner  root- 
sheath  is  often  to  be  found  entire  in  torn  out  hairs,  and  may  without 
further  preparation,  or  by  stripping  off  the  outer  sheath,  be  readily  re- 
cognized in  all  its  parts.  Caustic  soda  and  potassa  acting  for  a  short 
time,  make  it  still  more  distinct.  The  cuticle  must  particularly  be  exa- 
mined with  alkalies  and  sulphuric  acid,  like  the  hair  itself.  The  most 
important  details  upon  this  point  have  already  been  given,  and  more 
may  be  found  in  Bonders  (I.  c.).  I  will  only  add  that  in  this  case  also, 
the  application  of  a  high  temperature  (see  above,  in  the  section  on  the 
nails)  saves  much  time.  In  investigating  foetal  hairs,  in  the  very  young 
state  it  is  sufficient  to  tear  off  the  epidermis,  attached  to  which  the  rudi- 
ments of  the  hairs  will  be  found.  In  older  embryos,  fine  sections  of  the 
skin  must  be  made ;  or  the  epidermis  and  the  corium  may  be  stripped 
off  together,  in  which  case  caustic  soda  is  of  assistance. 

Literature. — Eble,  "  Die  Lehre  von  den  Haaren  in  der  gesammten 
organischen  Natur.,"  2  Bde.,  Wein,  1831 ;  Eschricht,  "  Ueber  die 
Richtung  der  Haare  am  menschlichen  Korper,"  in  Mull.  "Arch.,"  1837, 
p.  37  ;  V.  Laer,  "  De  structura,  capill.  hum.  observationibus  microscopicis 
illustr.,"  "Dissert,  inaug.,"  Traject.  ad  Rhenurn,  1841,  und  "  Annelin 
der  Chemie  u.  Pharmacie,"  Bd.  45,  No.  147  ;  G.  Simon,  "  Zur  Entwick- 
lungsgeschchite  der  Haare,"  Miill.  "Arch.,"  1841,  p.  361 ;  Krause,  article 
"  Haut.,"  in  Wagner's  "  Handworterbuch  d.  Phys."  1844,  Bd.  ii.  p.  124  ; 
Kohlrausch,  "  Ueber  innere  Wurzelscheide  und  Epithelium  des  Haares," 
Miill.  "  Arch.,"  1846,  p.  300 ;  Jasche,  "  De  telis  epithelialibus  in  genere 
et  de  iis  vasorum  in  specie,"  Dorpat,  1847  ;  Kb'lliker,  "  Ueber  den  Bau 
der  Haarbalge  und  Haare,"  in  the  "  Mitthiel  d.  ziirich.,  naturf.,"  Ges., 
1847,  p.  177;  Hessling,  "  Vom  Haare  und  seinen  Scheiden  in  Froriep 
neue  Notizen,"  1848,  No.  113;  Langer,  "  Ueber  den  Haarwechsel,  bei 
Thieren  und  beim  Menschen,"  in  den  "  Denkschr.  d.  Wien,"  Akad., 
1850,  Bd.  i.  The  comparative  anatomy  of  the  hairs  is  treated  of  by 
Heusinger  in  Meckel's  "Arch,"  1822,  1823,  und  "System  der  Histio- 
logie ;"  Erdl,  in  "  Abh.  d.  Munch.,"  Akad.,  Bd.  III.  ii. ;  Gegenbaur,  in 
"  Verhund  d.  phys.  med.  Gesellschaft  zu  Wurzburg,"  1850;  Steinlin,  in 
"  Zeitschrift,  fiir  rationellen  Medizin,"  Bd.  IX.  The  allied  horny  tis- 
sues are  described  in  the  "Dorpat.  dissertations,"  by  Brocker,  "  De 
textura  et  formatione  spinarum,"  1849  ;  Hehn,  "De  text,  et  form, 
barbie  Balsense,"  1849;  Schrenk,  "De  formatione  pennre,"  1849. 


OF  THE  GLANDS  OF  THE  SKIN. 


199 


IV.  OF  THE  GLANDS  OF  THE  SKIN. 


Fig.  78. 


A.  OF  THE  SUDORIPAROUS  GLANDS. 

§  65.  The  Sudoriparous  Crlands  consist  of  a  single  delicate,  more  or 
less  convoluted  tube,  which  secretes  the  sweat.  They  are  formed  over 
the  whole  surface  of  the  skin,  with  the  exception  of  the  concave  side  of 
the  concha  of  the  ear,  of  the  external  auditory  meatus,  the  glans  penis, 
one  lamella  of  the  prepuce,  and  a  few  other  localities  ;  and  open  upon 
it  by  numerous  fine  apertures. 

§  66.  In  every  sudoriparous  gland  (Fig.  45,  Fig.  78),  we  may  distin- 
guish, the  glandular  coil  (Fig.  78  a,  Fig.  75  g),  or  the  proper  gland, 
from  the  excretory  duct  or 
sudoriparous  canal  (Fig.  45 
h,  Fig.  78  b).  The  former  is 
a  rounded  or  elongated  corpus- 
cle of  a  yellowish  or  transpa- 
rent yellowish-red  color,  which 
in  general  measures  ^—\  of  a 
line ;  but  on  the  eyelids,  the 
integument  of  the  penis,  scro- 
tum, nose,  convex  side  of  the 
concha  of  the  ear,  on  the 
other  hand,  not  more  than 
iV-tjz  of  a  line  ;  whilst  on 
the  areola  of  the  nipple  and 
in  its  neighborhood,  at  the 
root  of  the  penis,  and  between 
the  scrotum  and  perinseum,  it  attains  as  much  as  J  a  line,  and  in  the 
hairy  parts  of  the  axilla  reaches  as  much  as  J-1-1J  line  in  thickness, 
and  1—3  lines  in  breadth. 

The  sudoriparous  glands,  in  most  cases,  are  lodged  in  the  meshes  of 
the  pars  reticularis  of  the  corium,  sometimes  more  superficially,  some- 
times deeper,  surrounded  by  fat  and  loose  connective  tissue,  together 
with  or  among  hair-sacs.  They  occur  more  rarely  in  the  subcuta- 
neous connective  tissue,  or  at  its  boundaries,  as  for  example  in  the 
axilla,  to  some  extent  in  the  areola  mammce,  in  the  eyelids,  penis,  and 
scrotum,  the  palm  of  the  hand  and  sole  of  the  foot.  In  the  two  last- 
named  localities,  they  are  disposed  in  rows  under  the  ridges  of  the  cutis, 

FIG.  78. — A  sudoriparous  coil  and  its  vessels;  magnified  35  diameters:  a,  glandular  coil; 
6,  excretory  duct  or  sweat  duct ;  c,  vessels  of  a  glandular  coil,  according  to  Todd  and  Bow- 
man. 


C.    " 


200  SPECIAL     HISTOLOGY. 

and  at  tolerably  equal  distances  apart ;  in  other  places  they  are  met 
with,  usually  in  a  regular  manner,  singly  or  in  pairs,  in  each  mesh  of 
the  corium,  although,  according  to  Krause,  spaces  of  J-J  a  line  exist, 
where  they  are  totally  absent,  or  occur  in  groups  of  three  or  four 
close  together.  In  the  axilla,  the  glands  form  a  connective  layer  under 
the  corium. 

According  to  Krause,  there  occur  on  a  square  inch  of  the  skin  be- 
tween  400  and  600  glands  on  the  back  of  the  trunk,  the  cheeks,  and  the  two 
superior  segments  of  the  lower  extremities  ;  924-1090  on  the  anterior 
part  of  the  trunk,  on  the  neck,  brow,  the  forearm,  back  of  the  hand 
and  foot ;  2685  on  the  sole  of  the  foot ;  and  2736  on  the  palm  of 
the  hand.  The  total  number  of  the  sudoriparous  glands,  without  reck- 
oning those  of  the  axilla,  is  estimated  (somewhat  too  highly)  by  Krause 
at  2,381,248,  and  their  collective  volume  (with  those  of  the  axilla)  at 
39,653  cubic  inches. 

The  vessels  of  the  sudoriparous  glands  are  particularly  well  seen  in 
those  of  the  axilla  (Fig.  78) ;  in  others,  the  vessels  may  also  be  seen 
here  and  there  (best  in  the  penis,  where,  for  example,  glands  of  0-36  of 
a  line  are  supplied  by  the  most  delicate  ramifications  of  an  artery  of 
0-06  of  a  line,  in  their  interior);  and  in  successful  injections  of  the 
skin,  the  glands  appear  as  reddish  corpuscles.  Nerves  have  not  hitherto 
been  found  in  them. 

§  67.  Intimate  Structure  of  the  Glandular  Coil. — The  sudoriparous 
glands,  in  general,  consist  of  a  single  much  convoluted  canal  (in  one 
case,  according  to  Krause,  }  of  a  line  long),  twined  into  a  coil, 
which  retains  pretty  nearly  the  same  diameter  throughout  its  length, 
and  terminates,  either  upon  the  surface  of  the  coil,  or  in  its  interior,  in 
a  slightly  enlarged  blind  extremity.  In  the  large  glands  of  the  axilla 
alone,  the  canal  is  usually  divided,  dichotomously,  into  branches,  which 
subdivide,  and  sometimes,  though  rarely,  anastomose  ;  and  after  giving 
off  small  caecal  processes,  each  separate  branch  finally  terminates  in  a 
blind  extremity.  The  glandular  canals  have  either  thin  or  thick  walls 
(Fig.  79).  The  former  (Fig.  79  A)  possess  an  external  fibrous  invest- 
ment, consisting  of  indistinctly  fibrous  connective  tissue,  with  scattered 
elongated  nuclei ;  internally  this  is  sharply  limited,  perhaps  by  a  mem- 
brana  propria,  and  is  covered  by  a  single,  double,  or  multiple  layer  of 
polygonal  cells  of  0-005-0-007  of  a  line,  which  in  their  chemical  rela- 
tions, and  otherwise,  correspond  perfectly  with  the  deep  cells  of  pave- 
ment-epithelium, except  that  they  almost  invariably  contain  a  few  fatty 
granules,  and  still  more  frequently  a  small  quantity  of  yellowish  or 
brownish  pigment-granules. 

The  thick-coated  sudoriparous  glandular  canals  (Fig.  79  B]  possess, 
besides  the  two  layers  just  described,  a  middle  layer  of  smooth  muscles 


OP    THE    GLANDS    OF    THE    SKIN. 


201 


running  longitudinally,  whose  elements  are  easily  separable,  as  muscu- 
lar fibre-cells  of  0-015-0-04  of  a  line  long,  0-002-0-005,  or  even  0-008 
of  a  line  broad,  occasionally  with  a  few  pigment-granules,  and  each  con- 
taining a  roundish  elongated  nucleus.  Whenever  the  glandular  tubes  con- 


rig.  79. 


tain  only  fluid,  the  epithelium  is  a  single  very  distinct  layer  of  polygo- 
nal cells  of  0-006-0-015  of  a  line ;  in  the  opposite  case  it  can  be  seen 
only  with  difficulty  or  not  at  all.  With  respect  to  the  occurrence  of 
these  two  forms  of  glandular  canals,  the  thick  muscular  walls  are  found, 
especially  in  the  large  glands  of  the  axilla,  whose  cells  all  possess  mus- 
cular walls,  and  thence  acquire  a  very  peculiar  striated  appearance.  I 
have  noticed  a  precisely  similar  structure  only  in  the  large  glands  of  the 
root  of  the  penis  and  of  the  nipple,  although  it  is  true  that  there  is 
occasionally  a  muscular  development,  but  slighter  and  only  partial,  in  the 
glands  of  the  palm,  whose  wide  canals  are  distinguished  by  the  thickness 
of  their  walls,  and  exhibit  a  muscular  structure  distinctly  enough,  though 
thinner  than  elsewhere.  The  same  description  applies  to  certain  glands 
of  the  scrotum,  and  even  of  the  back,  of  the  labia  majora,  of  the  mons 
veneris,  and  of  the  neighborhood  of  the  anus  ;  yet  with  this  limitation, 
that  often  only  a  small  part  of  the  glandular  tube,  perhaps  merely  its 
caecal  extremity,  is  provided  with  a  muscular  coat.  The  glands  of  the 
leg,  of  the  penis,  of  the  thorax  (the  areola  excepted),  of  the  eyelids,  and 
the  majority  of  those  of  the  back  and  thigh,  of  the  chest  and  abdomen, 
as  well  as  of  the  two  prominent  segments  of  the  upper  extremity,  are 
delicate  and  without  muscles. 

The  diameter  of  the  glandular  canals  varies,  in  the  smaller  glands  from 
0-022-0-04  of  a  line,  and  is  about  0-03  of  a  line  on  the  average ;  the 

FIG.  79. — Sweat  ducts  ;  magnified  350  diameters.  A,  one  with  thin  walls  and  a  central  cavity 
without  a  muscular  coat,  from  the  hand  :  a,  connective  investment ;  6,  epithelium  ;  r,  cavity. 
JB,  a  portion  of  a  canal  without  a  cavity,  and  with  a  delicate  muscular  layer,  from  the  scro- 
tum :  a,  connective  tissue;  6,  muscular  layer;  c,  cells  which  fill  the  glandular  canal  with 
yellow  granules  among  their  contents. 


202  SPECIAL    HISTOLOGY. 

thickness  of  the  walls,  0-002-0-003 ;  of  the  epithelium,  0-006 ;  of  the 
cavity,  0'004— 0-01  of  a  line.  Among  the  axillary  glands  some  have 
canals  of  0-07-0-1,  even  0-15  of  a  line,  with  walls  0-006  of  a  line  in 
thickness,  without  the  epithelium,  and  half  of  which  is  formed  by  the 
muscular  layer  ;  others  and  in  fact  the  largest  glands,  possess  canals  of 
0*03—0-06,  with  walls  of  0*004  of  a  line  ;  in  the  areola  and  the  genitalia 
also,  the  dimensions  of  the  larger  glands  vary,  though  within  narrower 
limits. 

All  the  coils  of  the  sudoriparous  glands  are  penetrated  by  connec- 
tive tissue,  interspersed  with  fat-cells,  which  supports  the  vessels  and 
unites  the  separate  convolutions  of  the  tubes  with  one  another  ;  some  of 
them  have  an  external  fibrous  covering  investing  the  whole  coil  (of  com- 
mon connective  tissue  with  fusiform  nuclei),  which  is  particularly  well 
developed  in  those  more  isolated  coils  which  are  lodged  in  the  subcuta- 
neous cellular  tissue  (penis,  axilla,  &c.) 

§  68.  Secretion  of  the  Sudoriparous  Glands. — All  the  smaller  sudori- 
parous glands  contain,  as  soon  as  any  cavity  is  apparent  in  their  canals, 
which,  however,  is  by  no  means  always  the  case,  nothing  but  a  clear, 
bright  fluid,  without  any  formed  contents.  In  the  axillary  glands,  on 
the  other  hand,  the  contents  abound  in  formed  particles,  and  appear 
either  as  a  grayish,  transparent,  semi-fluid  substance,  with  innumerable 
fine,  pale  granules,  and  often  with  solitary  nuclei ;  or  as  a  whitish-yellow 
tolerably  viscid  matter,  with  a  varying  quantity  of  larger,  opaque, 
colorless,  or  yellow  granules,  nuclei  and  cells,  similar  to  the  epithelial 
cells  above  described.  That  these  cell  contents,  which,  as  I  have  found, 
contain  much  protein  and  fat,  differ  considerably  from  the  common 
sweat,  which  is  fluid  and  presents  no  formed  elements,  and  probably 
rather  approximate  to  the  sebaceous  secretion  of  the  skin,  is  evident,  on 
which  account  we  might  be  induced  to  remove  the  glands  of  the  axilla 
from  the  class  of  sudoriparous  glands,  and  to  regard  their  secretion  as 
of  a  peculiar  kind.  These  glands,  however,  sometimes  afford  a  secre- 
tion containing  but  few  granules,  or  even  nothing  but  fluid  ;  and  among 
the  larger  axillary  glands  smaller  ones  occur,  which,  so  far  as  regards 
their  contents,  exhibit  many  transitions,  on  the  one  hand  into  the  large, 
and  on  the  other  into  common  small  glands.*  If  we  further  consider 

*  [However  true  it  may  be  that  this  secretion  is  sometimes  fluid,  and  similar  to  that  of 
sudoriparous  glands  in  other  situations,  this  is  the  exception,  and  by  no  means  the  rule. 
But  it  is  not  on  account  of  their  secretion,  but  mainly  of  their  different  structure,  that  these 
glands  have  been  separated  from  the  common  sudoriparous  glands.  They  differ  from  them 
by  being  united'  into  groups,  and  by  their  yellowish  color.  In  size,  too,  they  vary.  Many 
are  5  or  6  times  larger:  some  attain  the  size  of  2  lines  in  diameter.  The  groups  can  be 
readily  seen  with  the  unassisted  eye,  if  the  adipose  tissue  adhering  to  a  flap  of  skin  from  the 
axilla  be  removed.  They  then  appear  as  small  granulations  of  a  reddish  or  rosy  tint,  and 
are  soft  and  pulpy.  The  excretory  ducts  are  not  spirally  wound  as  in  the  ordinary  sudori- 
parous glands. 

In  the  Negro  these  axillary  glands  as  first  pointed  out  by  Prof.  Horner  (American  Journal 


OF    THE    GLANDS     OF    THE    SKIN.  203 

that,  occasionally,  the  sudoriparous  glands  in  other  situations,  as,  for 
instance,  in  the  areola  of  the  nipple,  contain  a  fluid  abounding  in  granules, 
it  is  clear  that  it  is  unadvisable  to  distinguish  the  large  axillary  glands 
from  the  common  kind,  on  account  of  the  difference  in  their  secretion  ; 
and  the  more  so,  indeed,  because  we  by  no  means  know  whether  the 
latter,  under  certain  circumstances,  may  not  contain  granules. 

As  respects  the  origin  of  the  granular  contents,  they  must  be  referred 
to  the  cells  which  are  developed  in  the  glandular  tubes.  For  we  fre- 
quently meet  in  these  with  cells  containing  the  same  granules,  which 
also  occur  free  within  the  glandular  canals  ;  and  frequently  may  be  said 
to  constitute  their  whole  contents.  It  sometimes  happens,  also,  that  in 
one  and  the  same  gland  the  ends  of  the  glandular  tubes  contain  nothing 
but  cells,  while  the  excretory  duct  exhibits  hardly  any  trace  of  them, 
presenting  merely  granules  and  scattered  free  nuclei ;  and  in  this  case 
we  can  easily  see  that  the  cells,  as  they  pass  further  upwards,  become 
broken  up  to  a  greater  and  greater  extent,  thus  setting  free  their  nuclei 
and  the  granules  in  their  interior.  These  cells  plainly  proceed  from 
the  epithelial  cells  lining  the  canal  of  the  sudoriparous  coil ;  for,  in  the 
first  place,  the  cells  of  the  contents  of  the  epithelium  resemble  one  an- 
other in  all  respects  ;  and  secondly,  where  cellular  or  granular  contents 
are  found  in  the  glands  themselves,  the  epithelium  is  for  the  most  part 
completely  absent,  so  that  the  former  rests  immediately  upon  the  muscu- 
lar membrane.  Now,  since  on  the  other  hand,  in  those  glands  which 
contain  only  a  clear  fluid,  the  epithelium  is  always  easily  seen,  and 
often  presents  many  dark  (even  golden  yellow)  pigment  granules  in  its 
cells,  it  may  perhaps  be  assumed,  that  the  cells  in  the  contents  are 
nothing  but  detached  epithelium,  and  that  the  secretion  mainly  depends 
upon  a  growth  and  continual  casting  off  of  the  epithelial  cells. 

The  examination  of  the  secretion  of  the  sudoriparous  glands  is  neither 
chemically  nor  microscopically  complete.  As  regards  the  former,  the 
fact  that  the  axillary  glands  secrete  fat  and  a  nitrogenous  substance 
in  large  quantities,  appear  to  me  interesting,  since  from  the  obvious 
similarity  in  structure  between  these  and  the  other  sudoriparous  glands, 
we  may  perhaps  draw  some  conclusions  as  to  the  secretion  of  the  latter. 
We  already  know  that  the  ordinary  perspiration  contains  nitrogenous 
matters  (extractive)  ;  and  as  Krause  (1.  c.,  p.  146)  has  clearly  shown, 
fat,  also ;  and  it  may  be  asked  whether  these  substances  do  not  perhaps 
in  certain  situations  (e.  g.  hand,  foot)  occur  more  abundantly,  or  under 
certain  conditions  (local,  adhesive,  peculiarly  odorous  perspiration) 
increase  in  quantity.  The  so-called  sweat-corpuscles  of  Henle  (1.  c., 
pp.  915  and  939),  that  is,  structures  similar  to  the  mucus-corpuscles,  I 

of  Med.  Science,  184G),  are  much  larger  than  in  the  White.  To  the  secretion  of  these  large 
glands  indeed,  the  peculiar  smell  of  Negroes  is  attributed. 

In  the  groin  sudoriparous  glands  very  similar  in  their  structure  to  these  axillary  glands  are 
met  with. — DaC.] 


204 


SPECIAL    HISTOLOGY. 


Fig.  80. 


have  hitherto  found  neither  in  the  sweat  of  man  nor  in  the  smaller 
glands  ;  but  I  may  remark  that  almost  constantly,  even  in  the  smaller 
sudoriparous  glands,  certain  canals  exist  which  present  no  cavity,  but 
are  wholly  filled  with  epithelial  cells.  These  appeared  to  me  always 
to  be  near  the  blind  end  (Fig.  79,  B\  whilst  those  which  are  nearer  the 
excretory  duct,  almost  invariably  exhibit  a  cavity  0*004— 0*1  of  a  line 
in  diameter,  I  consider  it  therefore  to  be  not  impossible,  that  in  the 
common  sudoriparous  glands,  a  cellular  secretion  is  at  times  formed  and 
excreted  in  the  same  manner  as  in  the  axillary  glands  ;  for  from  what 
we  see  in  the  canals  of  the  latter,  it  can  hardly  be  doubted  that  granules, 
nuclei,  and  perhaps  also  remains  of  cells,  occur  in  the  sweat  of  the 
axilla.  Whether  the  sweat  in  different  individuals  and  races  of  men 
present  notable  differences  is  unknown,  for  it  is  not  ascertained  that 
the  different  odor  of  the  cutaneous  exhalation  in  the  European  and  the 
Negro,  for  instance,  depends  on  the  sweat  or  the  material  of  the  per- 
spiration ;  nor  have  its  pathological  relations  been  investigated,  at  all 
events  not  microscopically. 

§  69.  Sweat-Ducts.— The  excretory  ducts  of  the  sudoriparous  glands, 
the  sweat-ducts,  or  spiral  canals  (Figs.  45,  80),  commence  at  the  upper 

end  of  the  glandular  coil  as  simple 
canals,  ascend  with  slight  undulations 
vertically  through  the  corium,  and  then 
penetrate  between  the  papillce  (never 
through  their  points),  into  the  epider- 
mis. Here  they  begin  to  twist,  and 
according  to  the  thickness  of  the  cuticle 
they  perform  from  2-16  closer,  or 
more  distant  spiral  turns,  until  even- 
tually they  terminate  by  small,  round, 
often  funnel-shaped  apertures,  the  so- 
called  stveat-pores  on  the  free  surface 
of  the  epidermis. 

The  length  of  the  sweat-ducts  de- 
pends on  the  situation  of  the  glands 
and  the  thickness  of  the  skin.  The 
commencement  of  the  duct  is  invaria- 
bly narrower  than  the  canal  in  the 
coil  itself,  measuring  0-009-0-012  of 
a  line  ;  it  continues  narrow  up  to  its 
entrance  into  the  stratum  Malpighii 

FIG.  80. — Perpendicular  section  through  the  epidermis  and  outer  surface  of  the  corium  of 
the  bulb  of  the  thumb,  transversely  through  two  ridges,  treated  with  acetic  acid;  a,  horny 
layer  of  the  epidermis;  6,  mucous  layer;  c,  cutis;  d,  simple  papilla;  e,  compound  papilla;  /, 
epithelium  of  a  sweat-duct  passing  into  the  mucous  layer;  g,  cavity  of  it  in  the  cutis;  h,  in 
the  horny  layer  ;  t,  sweat-pore. — Magnified  00  diameters. 


OF    THE    GLANDS     OF    THE    SKIN.  205 

where  it  dilates  to  about  double  the  size,  i.  e.,  to  0-024-0-28  of  a  line 
(Fig.  80);  retaining  this  breadth,  it  traverses  the  epidermis,  and  ter- 
minates in  an  aperture  of  513—^  of  a  line.  In  the  axillary  glands,  the 
excretory  duct  measured  in  one  case  at  the  level  of  the  sebaceous 
glands  0'06-0*09  of  a  line,  immediately  under  the  epidermis  0*03,  in  the 
epidermis  itself  0'06  of  a  line.  In  the  corium  the  sweat-ducts  have 
always  a  distinct  cavity,  an  external  investment  of  connective  tissue, 
with  elongated  nuclei  (in  the  glands  of  the  axilla,  muscles  also), 
at  all  events,  inferiorly,  and  an  epithelium  composed  of  at  least 
two  layers  of  polygonal,  nucleated  cells  without  pigment  granules. 
Where  the  ducts  enter  the  epidermis,  they  lose  their  investment  of 
connective  tissue,  which  coalesces  with  the  outermost  layer  of  the  corium, 
and  henceforward  they  are  bounded  by  nothing  but  layers  of  cells, 
which  in  the  stratum  Malpighii  are  nucleated,  but  in  the  horny  layer 
are  without  nuclei.  Chemically  and  morphologically  they  completely 
resemble  the  epidermic  cells,  with  the  sole  exception  that  they  are  dis- 
posed more  perpendicularly,  particularly  in  the  horny  layer.  The  duct 
has  often  a  distinct  cavity  in  the  epidermis,  at  other  times  there  is  a 
granular  streak  in  the  place  of  it,  which  is  probably  either  a  secretion 
or  a  deposit  from  the  secretion.  The  sweat-pores,  whose  disposition, 
corresponding  wTith  that  of  the  glands,  is  sometimes  very  regular,  at 
others  more  irregular,  are  distinguishable,  even  with  the  naked  eye,  in 
the  palm  of  the  hand  and  sole  of  the  foot.  In  other  localities  they  are 
visible  only  writh  the  aid  of  the  microscope ;  occasionally  the  excretory 
ducts  of  two  glands  unite  into  a  single  canal  (Krause). 

§  70.  Development  of  the  Sudoriparous  Glands. — The  sudoriparous 
glands  first  appear  in  the  fifth  month  of  embryonic  life,  and  are  originally 
perfectly  solid,  slightly  flask-shaped,  processes  of  the  stratum  Malpighii  of 
the  epidermis,  and  are  very  similar  to  the  first  rudiments  of  the  hair- 
sacs.  In  the  earliest  condition  which  I  have  observed,  the  processes 
measured  in  the  sole  of  the  foot  0-03— 0*09  of  a  line  in  length,  and  0-01 
of  a  line  in  breadth  at  the  neck,  at  the  bottom  0-018-0-02  of  a  line, 
and  even  the  very  longest  did  not  penetrate  more  than  half  through  the 
cutis,  which  was  0-25  of  a  line  thick.  They  were  entirely  composed  of 
round  cells,  perfectly  similar  to  those  of  the  stratum  Malpighii  of  the 
epidermis ;  besides  which,  each  process  had  a  delicate  investment,  which 
was  continuous  with  the  boundary  of  the  inner  surface  of  the  epidermis. 
No  trace  of  sweat-pores  or  ducts  was  visible.  At  the  beginning  of  the 
sixth  month,  the  glands  in  the  sole  of  the  foot  and  palm  of  the  hand 
extend  as  far  as  the  middle  and  inner  fourth  of  the  cutis,  measure  at 
the  clavate  extremity  0-028-0-04  of  a  line,  and  0-016-0-02  of  a  line  in 
the  duct  which  arises  from  them,  are  already  slightly  serpentine,  and 
present  a  cavity,  at  all  events  partially  in  their  narrow  portion;  they 
do  not,  however,  penetrate  the  cuticle,  or  in  any  way  open  on  the 


206  SPECIAL    HISTOLOGY. 

surface.     It  was  not  before  the  seventh  month  that  I  perceived,  in  the 
same  situations,  the  first  indications  of  the  sweat-pores  and  ducts  in  the 


Fig.  81. 

-  mm 
i.-.i 


epidermis,  though  as  yet  very  indistinct,  and  the  latter  forming  only 
half  a  spiral  turn  (Fig.  82,  A) ;  at  the  same  time  the  part  of  the  gland 
which  projected  into  the  corium  was  more  considerably  developed, 
reached  as  far  as  the  innermost  portion  of  that  structure,  and  at  its 
csecal  extremity  was  bent  into  a  hook  or  even  slightly  convoluted,  so  as 
to  afford  the  first  indication  of  a  glandular  coil  of  about  0-04  to  0-06  of 
a  line.  The  canal  arising  from  it  usually  presented  several  marked 
undulations,  and  measured  in  total  thickness  0-015-0-022  of  a  line,  with 
a  cavity  of  0-003-0-004  of  a  line,  which  frequently  extended  even  to 
the  terminal  coil :  like  the  latter  it  was  composed  of  the  original  though 
thickened  membrane  continuous  with  the  surface  of  the  corium,  and  of 
an  epithelium  consisting  of  many  layers  of  pale,  polygonal,  or  rounded 
cells.  The  glands  of  the  rest  of  the  body  about  this  period,  appeared 
to  me  to  be  similarly  constituted.  I  can  say  nothing  as  to  their 
earlier  condition,  but  even  those  of  the  axilla  were  in  no  wise  distin- 
guished from  the  rest.  From  this  time  the  development  goes  on  very 
rapidly ;  the  end  of  the  gland  elongates  more  and  more,  and  coils  itself 
up  (Fig.  82  B\  so  that  it  assumes  an  appearance  hardly  different  from 
that  which  it  presents  in  the  adult.  In  the  new-born  infant,  the  glan- 
dular coils  in  the  heel  measure  0-06-0-07  of  a  line  (in  a  child  of  four 
months  0-06-0-1  of  a  line  on  the  heel,  in  the  hand  0-12  of  a  line),  present 

FIG.  81. — Rudiment  of  a  sudoriparous  gland  of  a  human  embryo  at  five  months;  magni- 
fied 3.50  diameters:  a,  horny  layer  of  the  epidermis;  5,  mucous  layer;  c,  corium;  d,  rudimen- 
tary glands,  as  yet  without  any  cavity,  and  consisting  of  small  round  cells. 

FIG.  82. — ^,  rudiment  of  a  sudoriparous  gland  from  a  seven  months' foetus ;  magnified 
50  diameters.  The  letters  a,  6,  c?,  as  in  Fig.  81.  The  cavity  e  is  present  throughout,  only  it 
does  not  extend  quite  so  far  as  the  end  of  the  thicker  part  of  the  rudiment  of  the  gland, 
which  becomes  converted  into  the  glandular  coils.  The  continuation  of  the  canals  into  the 
epidermis  and  the  sweat-pores,/,  are  present.  J2,  a  coil  of  a  sudoriparous  gland,  from  a 
fcetus  at  the  eighth  month. 


OF    THE    GLANDS    OF    THE    SKIN.      f  207 

much  convoluted  canals  of  0-015-0-022  of  a  line,  and  traverse  the  epi- 
dermis with  their  already  twisted  ducts  (in  the  corium  of  0-008,  in  the 
rete  MalpigUi  of  0-022  of  a  line). 

It  results  from  these  facts  that  the  sudoriparous  glands  are  nothing 
else  than  involutions  of  the  skin,  and  do  not  begin  as  hollow  structures, 
but  are  at  first  a  simple  development  of  the  stratum  mucosum.  By  a 
continual  process  of  cell-multiplication,  the  original  rudiments  grow 
deeper  and  deeper  into  the  skin,  acquire  their  peculiar  spiral  windings, 
and  divide  into  the  glandular  coil  and  the  sweat-duct ;  while  at  the  same 
time,  either  by  liquefaction  of  their  central  part,  which  would  thus,  as 
it  were,  represent  a  first  secretion,  or  by  the  excretion  of  a  fluid  between 
their  cells,  a  cavity  is  produced.  How  the  sweat-duct  in  the  epidermis 
and  the  pore  are  formed  is  doubtful ;  probably  by  a  formative  process 
in  the  epidermis  itself.  According  to  a  few  measurements  which  I  have 
instituted  ("  Mikroscop.  Anat.,"  II.  i.  171),  a  development  of  sudoripa- 
rous glands  appears  to  take  place  even  after  the  fifth  month,  whilst 
the  whole  number  appears  to  exist  at  birth. 

Little  is  known  as  to  the  pathological  conditions  of  the  sweat-glands. 
Kohlrausch  (Muller's  "  Archiv,"  1843,  p.  866), -has  found  them  of  con- 
siderable size  (J  a  line)  in  an  ovarian  cyst,  together  with  hairs  and 
sebaceous  follicles.  In  Elephantiasis  graecorum,  G.  Simon  and  Brii eke 
(Simon,  "  Hautkrank.,"  p.  268),  noticed  an  increase  in  size  of  the  sudo- 
riparous glands,  and  V.  Barensprung  observed  the  same  thing  in  a  kind 
of  wart  (1.  c.,  p.  81) ;  the  latter  also  found  that  these  glands  were  atro- 
phied in  corns,  and  that  the  duct  in  the  outer  layers  of  the  epidermis 
had  disappeared.  The  condition  of  the  several  glands  in  old  age,  in 
cases  where  the  secretion  of  sweat  is  altogether  wanting,  and  in  ab- 
normal perspirations,  is  not  known.  In  a  remarkable  case  of  Ichtliyosis 
congenita  (very  similar  to  that  mentioned  by  Steinhausen,  only  more 
marked)  in  a  new-born  infant,  which  was  examined  by  Dr.  H.  Muller 
and  myself,  the  sudoriparous  glands  were  present ;  their  excretory  ducts, 
so  far  as  regards  their  course  through  the  epidermis,  which  was  thickened 
to  2  lines,  were  partly  disposed  as  usual,  partly  they  were  placed,  as 
in  the  sole  of  the  foot,  with  their  outer  portions  almost  completely  hori- 
zontal, and  ran  in  some  places  for  as  much  as  1J  line  in  this  manner, 
so  that  in  superficial  sections  of  the  epidermis  they  appeared  as  parallel, 
at  first  sight  altogether  abnormal  canals,  with  a  cavity  of  0-0025-0-003 
of  a  line.  The  contents  of  the  ducts  were  very  peculiar,  consisting  in- 
variably of -a  multitude  of  white  oil  drops.  I  observed  sudoriparous 
glands  also  in  the  case  described  by  Mohr,  of  a  great  cavity  containing 
hairs  in  the  lung  (a  Berlin  Med.,  Central-zeitung,"  1839,  No.  13),  they 
were  about  0-24  of  a  line  in  diameter,  and  were  contained  in- a  panni- 
culus  adiposuSj  with  common  fat-cells ;  and  it  may  be  remarked  that  the 


208  %  SPECIAL    HISTOLOGY. 

wall  of  the  cavity  besides  the  panniculus  also  presented  a  corium  with 
papillae,  and  an  epidermis  like  the  external  integument. 

Method  of  Investigation. — To  examine  the  position  of  the  sudoriparous 
glands  and  their  excretory  ducts,  fine  sections  of  fresh  or  slightly-dried 
skin  of  the  palm  or  sole  should  be  prepared,  and  made  transparent  by 
acetic  acid  or  caustic  soda.  Gurlt  used  for  this  purpose  skin  hardened 
and  rendered  transparent  in  a  solution  of  carbonate  of  potassa  (liquor 
kali  carbonici).  Giraldes  macerates  the  skin  for  twenty-four  hours  in 
dilute  nitric  acid  (1  part  acid,  2  parts  water),  and  for  twenty-four  hours 
in  water, — a  process  which,  according  to  Krause,  is  very  useful,  as  the 
glands  become  yellow,  and  are  readily  distinguished.  In  macerated 
pieces  of  the  skin,  the  cellular  lining  of  the  sweat-ducts  may  be  drawn 
out  of  the  corium,  in  the  form  of  long  tubes,  with  the  epidermis  ;  in 
delicate  parts  of  the  skin  I  have,  not  unfrequently,  succeeded  in  doing 
this  after  treatment  with  concentrated  acetic  acid.  The  investigation 
of  the  glandular  coils  themselves  is  very  easy  in  the  axillary  glands ;  in 
the  others  the  skin  must  be  prepared  from  within,  and  the  glands  sought 
for  partly  upon  the  inner  surface  of  the  cuts,  partly  in  its  meshes, — a 
method  which  readily  succeeds,  with  a  little  attention,  particularly  in 
the  hand,  foot,  and  nipple.  The  large  glands  of  the  ball  of  the  foot  of 
the  Dog,  described  by  Gurlt,  are  particularly  well-fitted  for  demonstra- 
tion, and  still  more  those  of  the  prepuce  and  of  the  integuments  of  the 
udder  of  the  Horse,  which  lie  quite  loose  in  the  subcutaneous  tissue.  If 
it  be  desired  to  count  the  glands,  their  apertures  may  be  sought  for,  or 
a  piece  of  skin  of  determinate  size  may  be  treated  according  to  Giraldes' 
method,  and  examined  portion  by  portion  (Krause).  For  the  study  of 
the  development  of  the  glands,  sections  of  the  fresh  and  dried  skin  of 
the  heel  and  palm  of  embryos,  may  be  made  with  the  double  knife  or 
razor.  In  embryos  preserved  in  spirit,  if  the  sections  be  fine,  the  glands 
may  also  be  very  well  seen,  especially  in  the  first  moments  of  the  action 
of  caustic  soda. 

Literature. — Breschet  et  Roussel  de  Vauzeme,  "Recherches  ana- 
tomiques  et  physiologiques  sur  les  appareils  tegumentaires  des  animaux," 
in  the  "  Annales  des  Sciences  Nat.,"  1834,  pp.  167  and  321  (discovery 
of  the  sudoriparous  glands) ;  Gurlt,  "  Vergleichende  Untersuchungen 
iiber  die  Haut  des  Menschen  und  der  Haussaugethiere,  besonders  in 
Bezug  auf  die  Absonderungsorgarie  des  Hauttalges  und  des  Schweisses," 
in  Muller's  "  Archiv,"  1835,  p.  399  (first  good  figures  of  the  glands 
themselves).  [Robin,  "  Note  sur  une  espece  particuliere  des  glandes  de  la 
peau  de  1'homme,"  in  the  "Annales  des  Sciences  Nat.,"  1845;  Homer, 
"  On  the  Odoriferous  Glands  of  the  Negro,"  in  American  Journal  of 
Med.  Sciences,  1846.]  Besides  these,  compare  especially  the  general 
works  of  Todd  and  Bowman,  Henle,  Valentin,  Hassall,  and  myself;  the 
above-cited  treatises  of  Krause,  myself,  Simon,  Von  Biirensprung,  and 
Wilson ;  further  the  figures  of  Berres,  tab.  XXIV. ;  R.  Wagner,  "Icon. 


OF    THE    GLANDS    OF    THE     SKIN.  209 

Phys.,"  tab.  XVI.,  fig.  9 ;  F.  Arnold,  "Icon.    Org.   Sens.,"  tab.   XL, 
and  my  own  "  Mikr.  Anat.,"  tab.  I. 

B.  OF  THE  CERUMINOUS  GLANDS. 

§  71.  The  ceruminous  glands  of  the  Ear  are  brownish  simple  glands, 
in  external  appearance  precisely'similar  to  the  sudoriparous  glands,  which 
do  not  exist  in  the  whole  external  auditory  meatus,  but  only  in  its  car- 
tilaginous portion,  where  they  are  situated  between  the  lining  membrane 
of  the  passage  and  the  cartilage,  or  the  fibrous  substance  which  supplies 
its  place,  in  a  tough  subcutaneous  tissue,  containing  little  fat.  They 
form  a  connected  yellowish-brown  layer,  visible  enough  to  the  naked 
eye,  which  is  thickest  in  the  inner  half  of  the  cartilaginous  meatus,  and 
becomes  gradually  thinner  and  more  lax  externally,  extending,  however, 
quite  as  far  as  the  cartilaginous  meatus  itself.  Each  ceruminous  gland 
consists  of  a  glandular  coil  and  an  excretory  duct.  The  former  (Fig. 
83  d),  T\)-J-i  °f  a  line  in  gize>  is  formed  by  the  multitudinous  convolu- 
tions of  a  single  canal  of  0-03— Of06  on  the  average  0-04-0*05  of  a  line  in 
thickness,  which  occasionally,  although  not  constantly,  throws  out  little 
diverticula,  and  terminates  in  a  blind  slightly  enlarged  end.  From  the 
coil  a  short  straight  excretory  duct,  0*017— 0-024  of  a  line  thick,  passes 
perpendicularly  upwards,  penetrates  the  corium  and  epidermis  of  the 
auditory  meatus,  and  usually  opens  independently  in  a  circular  pore  of 
0*044  of  a  line,  or  else  into  the  upper  part  of  a  hair-sac. 

The  following  is  the  intimate  structure  of  the  ceruminous  glands. 
The  canals  of  the  coil  present  a  fibrous  coat,  and  an  epithelium,  the 
former  being  0-004-0-005,  the  latter  0-004  of  a  line  in  thickness.  The 
fibrous  covering  presents  exactly  the  same  conditions  as  in  the  larger 
sudoriparous  glands,  that  is,  it  consists  of  an  internal  longitudinal  layer  of 
smooth  muscles,  0-0023-0-0026  of  a  line  in  diameter,  and  an  external  layer 
of  connective  tissue,  with  scattered  nuclei,  and  occasionally  very  fine  trans- 
verse nucleus-fibres.  The  epithelium  rests  immediately  upon  the  mus- 
cular layer,  and  consists  of  polygonal  cells  of  0-006-0*01  of  a  line  in  a 
single  layer,  which  contain  a  greater  or  smaller  number  of  yellowish- 
brown  pigment-granules,  of  immeasurable  minuteness,  insoluble  in  acids 
and  alkalies  in  the  cold,  or  whitish  fat-globules  up  to  0-001  of  a  line  in 
size,  and  which  are  so  disposed  that  the  whole  lengths  of  a  gland  con- 
tain generally  only  one  and  the  same  kind  of  granules ;  whence  it  arises 
that  they  appear  either  uniformly  brownish  or  opaque  (by  reflected  light 
whitish).  The  contents  of  the  glandular  canals  are  sometimes  a  clear 
fluid,  sometimes  a  granular  substance  composed  principally  of  cells  ana- 
logous to  those  of  the  epithelium,  whence  it  would  seem  that  the  same 
kind  and  mode  of  secretion  occurs  in  them  as  in  the  sudoriparous  glands. 
The  excretory  ducts  possess  a  coat  of  connective  tissue,  and  an  epi- 
thelium consisting  of  several  layers,  and  constituted  of  small  nucleated 

14 


210 


SPECIAL    HISTOLOGY. 


cells,  without  fat  or  pigment-granules.  In  their  cavity,  which  is,  how- 
ever, riot  always  distinct,  they  sometimes  contain  a  clear  fluid;  some- 
times a  small  quantity  of  finely-granulated  substance. 


Fig.  83. 


Ai. 


§  72.  The  Cerumen  of  the  ear  is  commonly  considered  to  be  the 
secretion  of  these  glands,  though  this  is  only  partially  correct.  If  we 
examine  the  yellow  or  brownish,  soft  or  more  solid,  viscid  substance 
which  is  formed  within  the  cartilaginous  meatus,  it  is  found  to  contain 
various  constituents :  independently  of  a  few  hairs,  occasionally  an 
Acarus  folliculorum^  and  epidermic  cells  in  various  numbers,  there 
occur, — 1.  Very  many  cells  completely  filled  with  pale  fatty  matter  of 
0'009— 0*02  of  a  line,  usually  of  an  oval,  flattened,  irregular  shape  ;  in 
which,  on  the  addition  of  water,  or  still  better  of  caustic  soda,  the  fat 
is  separated  in  isolated,  round,  or  irregular  dark  drops.  2.  Much  free 
fatty  matter  in  the  form  of  pale,  small  yellowish  round  drops,  which,  on  the 
addition  of  water,  appear  as  dark  spherical  granules,  from  an  immeasurable 
minuteness  up  to  0-002  of  a  line  and  more ;  and  it  is  only  upon  this  addition 
that  they  become  quite  distinct,  but  at  the  same  time  are  decolorized. 

FIG.  83. — Perpendicular  section  through  the  skin  of  the  external  auditory  meatus  ; 
a,  corium ;  6,  stratum  Mulpighii;  c,  horny  layer  of  the  epidermis;  d,  coil  of  the  ceruminons 
glands;  c,  their  excretory  ducts  ;  /,  their  apertures;  g,  hair-sacs  ;  A,  sebaceous  glands  of  the 
meatus ;  i,  masses  of  fat. — Magnified  20  diameters. 


OF  THE  GLANDS  OF  THE  SKIN.  211 

3.  Yellow  or  brownish  granules,  and  masses  of  granules,  free  or  rarely  in 
cells,  few  upon  the  whole.  4.  Lastly,  when  the  secretion  is  more  fluid,  also 
a  small  quantity  of  a  clear  liquid.  I  consider  that  the  first-named  cells 
belong  to  the  sebaceous  secretion  of  the  external  meatus ;  but  that  the 
remainder  is  the  secretion  of  the  ceruminous  glands,  which  would,  there- 
fore, eliminate  oily  fluid  with  scattered  brown  granules.  This  being  the 
case,  the  analysis  by  Berzelius  of  the  common  ear-wax,  a  mixture  of  the 
sebaceous  and  proper  ceruminous  secretion,  must  only  be  admitted  with 
caution.  In  my  opinion,  the  brownish-yellow  bitter  substance,  soluble 
in  alcohol  and  water,  found  by  him,  and  the  pale  yellow  strong-tasted 
extractive  matter,  hardly  soluble  in  water,  and  not  at  all  in  alcohol, 
must  be  attributed  to  the  ceruminous  glands ;  the  remaining  fat,  the  horny 
matter,  and  probably  also  most  of  the  albumen,  to  the  sebaceous  glands  ; 
whilst  the  relations  of  the  salts  must,  of  course,  be  left  undetermined. 

The  vessels  of  the  ceruminous  glands  are  disposed  like  those  of  the 
sudoriparous ;  in  one  case  I  noticed,  in  addition,  a  fine  nervous  fibre  of 
0-003  of  a  line  in  the  midst  of  a  gland.  As  to  the  development  of  these 
glands  I  can  only  say,  that  in  a  foetus  of  five  months  they  had  the  form 
of  straight,  pale  processes  of  the  stratum  Malpighii  of  the  epidermis  of 
the  external  auditory  meatus,  were  entirely  composed  of  nucleated  cells, 
and  ended  by  a  slightly  enlarged  termination  somewhat  twisted  upon  its 
axis,  in  which  the  first  indication  of  a  glandular  coil  was  presented.  In 
other  words,  these  rudimentary  glands  exactly  resembled  the  sudoripa- 
rous glands  at  the  same  period ;  and  considering  the  great  anatomical 
resemblance  between  the  two  structures,  I  do  not  doubt  for  a  moment 
that  the  ceruminous  glands,  both  in  their  first  commencement  and  sub- 
sequently, go  through  the  same  phases  as  the  former. 

According  to  all  that  I  have  seen  of  the  ceruminous  glands,  I  must 
consider  them  to  be  mere  modifications  of  the  sudoriparous.  In  speak- 
ing of  these  it  has  already  been  remarked,  that  their  secretions  are 
certainly  not  everywhere  identical,  being  in  one  locality  more  aqueous, 
in  another  fatty  and  albuminous,  with  peculiar  odorous  ingredients. 
Even  although  the  cerumen  may,  to  some  extent,  contain  peculiar  sub- 
stances, e.  #.,  the  yellow  bitter  substance,  which,  however,  according  to 
Lehmann,  is  not  bilin,  nevertheless,  taking  into  account  the  other  cor- 
respondences (consider  the  almost  constant  and  often  very  abundant 
yellow  granules  in  the  sudoriparous  glands,  which  are  also  insoluble  in 
acids  and  alkalies),  we  may  associate  the  ceruminous  glands  with  the 
sudoriparous,  especially  with  the  larger  among  the  latter,  which  are 
both  anatomically  and  physiologically  most  closely  allied  to  them ;  in 
fact,  I  am  inclined,  for  my  own  part,  to  think,  that  the  smallest  pale 
ceruminous  glands  at  the  commencement  of  the  meatus  are  hardly  dis- 
tinguishable from  common  sudoriparous  glands.  Nothing  is  known  of 
the  pathological  conditions  of  the  ceruminous  glands — of  the  cerumen 


212  SPECIAL    HISTOLOGY. 

itself  we  know  that  it  is  often  quite  solid,  at  other  times  fluid,  puriform, 
and  pale  colored.  In  the  latter  case,  which  is  seen  in  congested  condi- 
tions of  the  external  meatus,  it  contains  far  more  fluid  and  free  fat  than 
usual,  and  very  beautiful  cells  containing  fat.*  With  regard  to  the 
mode  of  examining  the  ceruminous  glands,  I  must  refer  to  the  sudori- 
parous glands,  with  which  they  wholly  agree  in  position,  chemical  rela- 
tion to  acids,  alkalies,  &c.  &c. 

Literature. — R.  Wagner,  "  Icones  Phys.,"  tab.  xvi.  fig.  11,  A,  B ; 
Krause  and  Kohlrausch,  in  Muller's  "  Archiv,"  1839,  p.  cxvi. ;  Pappen- 
heim,  "  Beitrage  zur  Kentniss  der  Structur  des  gesunden  Ohres,"  in 
Froriep's  "Neue  Notizen,"  1838,  No.  141,  p.  131,  and  Specielle  Gebe- 
lehre  d.  Gehororgans  (Breslau,  1840);  Henle,  "Allg.  Anat."  pp.  915, 
916,  934,  941 ;  Huschke  "Eingeweidelehre,"  p.  819;  Hassall,  "Microsc. 
Anatomy,"  &c.,  p.  427,  pi.  Ivii. ;  Valentin,  article  "  Gewebe,"  in  Wagner's 
"Handw.  d.  Phys.,"  i.  p.  755. 

C.     OF  THE  SEBACEOUS  GLANDS. 

§  73.  The  Sebaceous  Grlands  are  small  whitish  glands,  which  exist  in 
almost  every  part  of  the  skin,  and  which  afford  the  cutaneous  sebaceous 
or  fatty  secretion. 

In  form  they  vary  very  considerably ;  the  simplest  (Fig.  84,  A)  are 
short  follicles  of  an  elongated  or  pyriform  shape ;  in  others — the  simple 
racemose  glands — two,  three,  or  even  more  follicles  or  vesicles  are 
united  with  a  shorter  or  longer  peduncle ;  whilst  in  others,  lastly  (Figs. 
84  B,  85),  two,  three,  or  more  simple  clusters  of  follicles  communicate 
with  a  common  duct,  constituting  an  elegant  compound  racemose  gland. 
Besides  these  three  forms,  which  represent  only  the  chief  varieties,  there 
are  a  good  many  intermediate  ones,  which  do  not  require  any  detailed 
description. 

The  sebaceous  glands  occur  principally  in  the  hairy  parts  of  the  body, 
opening,  in  common  with  the  hair-sacs,  upon  the  surface,  whence  they 
have  also  been  termed  the  glands  of  the  hair-sacs. 

In  all  the  coarser  hairs,  the  glands  appear  to  be  lateral  appendages 
of  the  hair-sacs,  and  open  by  narrow  excretory  ducts  into  them  (Figs. 

*  [There  is  an  occasional  ingredient  in  the  so-called  cerumen  which  is  worthy  of  notice, 
viz.  a  mucedinous  fungus.  Attention  has  been  recently  called  to  its  occurrence  by  Dr. 
Inman  ("  Quarterly  Journal  of  Micros.  Science,"  January,  1853),  who  states  that  a  pellet  of 
ear-wax  which  he  examined  was  composed  of  nothing  but  this  fungus,  with  a  minute  por- 
tion of  epithelium.  However,  Professor  Mayer,  of  Bonn,  so  long  ago  as  1844  ("Beobach- 
tung  Von  Cysten  mit  Fadenpilzen  aus  dem  aussern  Gehorgange,"  &c.,  Muller's  "Archiv," 
1844,  p.  404),  described  at  length  the  structure  of  certain  sacs  containing  fungi,  which  were 
extracted  from  the  external  auditory  meatus  of  a  girl  eight  years  old, — in  whom  they  appear 
to  have  been  at  first  accompanied  by  considerable  deafness  and  irritation.  The  sacs  were 
as  large  as  a  pea,  and  open  atone  end;  externally  they  were  composed  of  layers  of  epithe- 
lium scales,  from  which  mucedinous  threads,  terminated  by  globular  sporangia,  projected  into 
the  cavity  of  the  sac.  These  sacs  appear  to  have  been  repeatedly  formed  and  discharged, 
to  a  very  considerable  number. — TRS  ] 


OF    THE    GLANDS    OF    THE    SKIN. 


213 


75,  76,  77,  83),  whilst  in  the  lanugo  the  ducts  and  the  hair-sacs  are 
often  of  about  the  same  diameter  (Fig.  84  _#),  and  open  into  a  common 
canal,  which  may  be  regarded  as  a  continuation  of  the  one  as  much  as 
of  the  other ;  or  the  ducts  may  even  be  the  larger  (Fig.  85),  the  hairs 
bearing  a  subordinate  relation  to  them,  so  that  their  sacs  open  into  the 
glands,  and  the  hairs  come  out  through  the  glandular  opening  itself.  In 
the  hairless  parts  of  the  surface,  sebaceous  glands  occur  only  in  the 
labia  minora  (vide  §  54),  and  in  the  glans  penis  and  prepuce,  whilst 
they  do  not  exist  in  the  glans  and  prepuce  of  the  clitoris.  In  general, 
the  glands  are  situated  close  to  the  hair-sacs  in  the  superficial  layer  of 
the  corium,  and  are  larger  in  the  finer  hairs  than  in  the  coarser ;  in 

Fiff.  84.  Fig.  85. 


particular  cases,  however,  they  present  many 
differences.  With  respect  to  the  glands  of  the 
larger  hair-sacs,  they  are  usually  of  the  simple 
racemose  kind,  having  an  average  size  of  JQ- 
T3^  of  a  line,  and  are  disposed  around  the  sac  to 
the  number  of  from  2  to  5.  The  smallest,  of 
0-1-0*16  of  a  line,  occur  in  pairs,  attached  to 

FIG.  84. — Sebaceous  glands  from  the  nose;  magnified  50  diameters.  A,  simple  tubular 
gland  without  any  hair ;  _B,  compound  gland,  which  has  a  common  opening,  with  a  hair- 
sac  :  a,  glandular  epithelium,  connected  with  6,  the  stratum  Malpighii  of  the  epidermis  •  c, 
contents  of  the  glands,  sebaceous  cells,  and  free  fat;  d,  the  separate  racemes  of  the  compound 
gland ;  e,  hair-sacs  (root-sheath),  with  the  hair,  /. 

FIG.  85. — A  large  gland  from  the  nose,  with  a  little  hair-sac  opening  into  it ;  magnified 
50  diameters.  The  letters  a-/ as  in  Fig.  84. 


214  SPECIAL    HISTOLOGY. 

each  hair  of  the  scalp;  they  are  somewhat  larger,  0-16-0-24  of  a  line 
in  the  hairs  of  the  beard,  and  the  longer  hairs  of  the  chest  and  axilla, 
in  which  situations  several  glands  are  usually  disposed  around  the  hair 
follicle ;  the  largest  of  all  exist  on  the  mons  veneris,  the  labia  majora, 
and  the  scrotum,  where,  at  all  events  in  the  last-mentioned  locality,  they 
are  found  at  the  deepest  boundary  of  the  corium,  and  the  glands,  from 
four  to  eight  being  connected  together,  represent  beautiful  rosettes  J-J 
-1  line  broad.  Attached  to  the  sacs  of  the  smaller  coarse  hairs,  I  find 
smaller  sebaceous  glands  of  0-06-0-24  of  a  line,  mostly  in  pairs;  and 
also  in  the  eyebrows,  eyelids,  and  the  hairs  at  the  entrance  of  the  nos- 
trils. The  lanuginous  hairs  have  generally  larger  glands,  or  aggrega- 
tions of  glands  of  £-1  of  a  line ;  these  are  best  displayed  in  the  nose, 
the  ear  (concha,  fossa  scaplioidea\  the  penis  (anterior  half),  and  the 
areola  mammae,  especially  in  the  first  of  these  situations,  where  the 
glands  often  attain  a  colossal  size,  and  altogether  peculiar  forms  (Fig. 
85) ;  the  glands  generally  have  a  diameter  of  -*-J  of  a  line  on  the 
caruncula  lachrymalis,  the  lips,  brow,  thorax,  and  abdomen ;  they  are 
somewhat  smaller,  -*-• J  of  a  line,  but  almost  always  larger  than  in  the 
hairs  of  the  scalp,  in  the  eyelids,  cheeks,  neck,  back,  and  extremities. 
Of  the  glands  which  are  not  connected  with  hair-sacs,  only  a  portion  of 
those  of  the  labia  minora  are  of  large  size  (0'14— 0*5  of  a  line)  and 
rosette-shaped,  with  an  aperture  of  0-083  of  a  line ;  the  others  are  for  the 
most  part  simply  tubular,  and  at  most  0-12-0-16  of  a  line  long,  0-04- 
0-06  of  a  line  broad.  The  glandular  vesicles  of  the  sebaceous  glands 
are  either  round,  or  pyriform  and  flask-shaped,  or  even  elongated  or 
tubular.  Their  size  varies  exceedingly,  from  0-06—0-16  of  a  line  in 
length,  0-02-0-1  of  a  line  in  breadth,  and  is  in  the  mean  0-04  of  a  line  in 
the  round  ones  ;  0-08  in  length,  and  0-03  of  a  line  in  breadth  in  the  others. 
The  excretory  ducts  also  have  very  different  dimensions,  sometimes  long, 
sometimes  short,  broad  or  narrow ;  the  principal  excretory  ducts  measure 
in  the  nose  and  labia  minora  up  to  J  of  a  line  in  length,  y5-J  of  a  line 
in  breadth,  and  have  an  epithelium  0-015-0-03  of  a  line  thick. 

The  sebaceous  glands  on  the  glans  penis,  and  on  the  inner  lamella  of 
the  prepuce  or  "  Tyson's  glands,"  are  very  inconstant,  occurring  some- 
times only  in  a  very  small  number,  sometimes  in  hundreds.  They  are 
ordinary  sebaceous  glands,  which  are  distinguished  from  those  of  other 
regions  by  their  not  being  connected  with  hair-sacs,  and  by  their  open- 
ing independently  on  the  surface  of  the  skin.  They  may,  generally,  be 
perceived  by  the  naked  eye  as  small  whitish  points,  which  do  not  project 
above  the  skin ;  and  in  sections  of  the  skin  treated  with  caustic  soda  or 
acetic  acid,  their  peculiarities  may  be  readily  studied  with  the  micro- 
scope. They  appear  to  be  sometimes  tubular,  at  others,  simply  racemose ; 
the  former  present  a  round  or  pyriform  follicle  of  0-048-0-12  of  a  line 
in  diameter,  and  a  straight  excretory  duct  of  -^  of  a  line  in  length,  and 


OF    THE    GLANDS    OF    THE    SKIN. 


215 


Fig.  86. 


0-024-0-035  of  a  line  in  breadth  ;  the  latter  have  two  to  three,  or  at  most 
five,  terminal  vesicles,  and  measure  0-08—0-18  of  aline  altogether.  The 
apertures  of  both  kinds  of  glands, 
\vhich  have  a  diameter  of  0-02-0-06 
of  a  line,  are  easily  seen.  With  re- 
gard to  the  position  of  the  glands, 
I  would  remark  that  I  have  never 
failed  in  finding  them,  10-50  and 
more,  in  number,  on  the  inner  la- 
mella of  the  prepuce,  especially  in 
the  neighborhood  of  the  frcenulum, 
and  its  anterior  part ;  while  on  the 
glans  itself  and  its  neck,  they  are 
sometimes  totally  absent,  sometimes 
they  occur  on  its  anterior  surface, 
and  then  generally  in  great  numbers 

(up  to  100).  On  the  prepuce,  the  glands  are  for  the  most  part  racemose, 
in  the  penis  more  simple.  Their  contents  exactly  resemble  those  of  the 
sebaceous  glands,  viz.  cells  containing  fat,  of  which  more  will  be  said 
below. 

The  sebaceous  glands  of  the  external  sexual  organs  in  the  female,  are 
found,  generally  in  great  numbers,  on  the  inner  and  outer  surface  of  the 
labia  minor  a,  and  some  of  them  are  as  large  as  those  belonging  to  the 
fine  hairs  on  the  labia  majora,  while  some  are  smaller.  I  have  never 
found  sebaceous  glands  in  the  glans  and  inner -lamella  of  the  prceputium 
clitoridis,  although  Burkhardt  speaks  of  such  in  the  corona  clitoridis, 
but,  in  a  few  instances,  I  have  met  with  them  about  the  urethra  and  the 
entrance  of  the  vagina.  Resembling  the  sebaceous  glands  in  all  essential 
points,  except  their  larger  size,  are  the  Meibomian  glands  in  the  eyelids, 
of  which  a  more  particular  description  will  be  given  when  we  treat  of 
the  eye. 

According  to  E.  H.  Weber  (Froriep,  "Notiz.,"  Marz,  1849),  the 
smegma  prceputii  of  the  Beaver,  the  "  Castor"  is  not,  in  the  main,  a 
glandular  secretion,  since  only  a  small  portion  of  the  pouch  in  which  it 
is  secreted  is  furnished  with  very  simple,  rounded,  lenticular  glandules, 
the  largest  measuring  ^d  of  a  line.  The  secretion,  in  individuals  of 
both  sexes,  may  rather  be  described  as  a  laminated  substance  lining  the 
entire  "  castor  pouch,"  and  consisting  merely  of  epidermic  cells  and 
minute  fatty  globules.  Leydig  ("Zeitsch.  f.  w.  Zool.,"  Bd.  II.,  pp.  22, 
31,  et  seq.),  finds  no  glands  at  all  in  the  "  castor-pouch  ;"  and  according 

FIG.  86. — Two  sebaceous  glands;  the  larger,  1,  from  the  inner  lamella  of  the  prepuce; 
the  smaller,  2,  from  the  glans  penis:  a,  glandular  epithelium  continued  into  the  stratum 
Malpighii  of  the  skin;  6,  c,  contents  of  the  gland,  with  scattered  larger  fat  drops;  g,  horny 
layer  of  the  epidermis,  projecting  somewhat  into  the  duct. — Magnified  50  diameters. 


216 


SPECIAL    HISTOLOGY. 


Fig.  87. 


to  him,  the  same  is  the  case  in  the  prseputial  sac  of  the  Weasel,  whilst 
in  the  Rat  and  Mouse,  the  prepuce  contains  true  sebaceous  glands  of  a 
complicated  structure. 

§  74.  The  minute  structure  of  the  sebaceous  glands  may  be  described 
as  follows  : — Each  gland  possesses  an  external  delicate  coat  of  connective 
tissue,  continued  from  the  hair-sac,  or,  in  the  case  of  free  glands,  from 
the  corium,  and  containing  masses  of  cells,  which  exhibit  different  con- 
ditions, according  to  the  part  of  the  gland.  If  we  proceed  from  the 
excretory  duct  of  one  of  them  (Fig.  88  B\  we  see,  that  not  only  the 
fibrous  coat  of  the  hair-sac,  but  a  portion  of  its  inner  root-sheath,  also, 
passes  into  the  duct,  and  lines  it  with  nucleated,  rounded,  or  polygonal 
cells,  disposed  in  several  (two  to  six)  layers.  This  cellular  layer  is  con- 
tinued, becoming  more  and  more  delicate,  into  the  remoter  parts  of  the 

gland,  and  ultimately  pene- 
trates into  the  proper  glan- 
dular vesicles,  clothing  them 
with  a  single,  rarely  a  double, 
layer.  Internally  to  these 
f  cells,  which  are  distinguished 
by  a  greater  or  smaller 
number  of  fat  granules  from 
the  epithelial  cells  above 
them,  there  immediately  suc- 
ceed, in  the  glandular  vesicles 
themselves,  others  (Fig.  8T  B  b)  containing  more  fat ;  and  these  finally  pass 
into  the  innermost  cells  of  the  glandular  vesicles,  which  are  invariably 
larger  (of  0-016-0-028  of  a  line)  than  the  middle  and  outermost  cells, 
are  rounded  or  elongated  in  their  form,  and  so  filled  with  colorless  fat 
that  they  might,  not  improperly,  be  termed  sebaceous  cells  (Fig.  87  B). 
The  fat  contained  in  them  appears  either  still  to  retain  the  form  of  dis- 
crete drops  (55),  as  in  the  outer  cells,  or,  as  is  indeed  more  frequently 
the  case,  under  that  of  larger  drops ;  and  in  many  cells  there  are  but  a 
few  of  them,  or  even  only  a  single  one,  which  quite  fills  the  cell  (d) ;  in 
consequence  of  which  these  cells  greatly  resemble  the  fat-cells  of  the 
panniculus  adiposus.  If  these  innermost  cells,  which  rarely  exhibit 
any  nucleus,  are  traced  onward  towards  the  excretory  duct,  nothing  is 

FiG.  87. — Jl,  a  glandular  vesicle  of  a  common  sebaceous  gland;  magnified  250  diameters: 
a,  epithelium  sharply  defined,  but  without  any  investing  membrana  propria,  and  passing 
continuously  into  the  fat-cells,  b  (their  contours  are  too  indistinctly  drawn),  in  the  interior  of 
the  glandular  tube. — B,  sebaceous  cells  from  the  glandular  tube,  and  the  cutaneous  sebaceous 
matter;  magnified  350  diameters:  a,  smaller  nucleated  cells,  still  more  of  an  epithelial 
character,  and  containing  but  little  fat;  b,  cells  abounding  in  fat,  without  visible  nucleus  ; 
c,  cell  in  which  the  fat  is  beginning  to  flow  into  one  mass;  d,  cell  with  one  fat-drop  ;  e,/, 
cells  from  which  the  fat  has  partially  escaped. 


OF    THE    GLANDS    OF    THE    SKIN.  217 

more  easy  to  observe  than  that  similar  cells,  applied  uninterruptedly  one 
to  the  other,  are  continued  into  this  also,  i.  e.  into  the  canal  lined  by  its 
epithelium  ;  then,  entering  the  hair-sac,  they  occupy  the  space  between 
the  hair  and  the  epidermis  of  the  hair-sac,  and  are  finally  extruded. 
These  cells  are  the  sole  sources  of  the  cutaneous  sebaceous  matter,  a 
substance  which,  when  fresh  and  at  the  common  temperature,  is  semi- 
fluid, but  in  the  dead  subject  more  consistent,  like  butter  or  soft  cheese, 
whitish  or  whitish-yellow  in  color,  sometimes  viscid,  at  others  friable. 
Its  cells,  in  the  fresh  secretion,  adhere  together  more  or  less  closely, 
and  are  thence  generally  flattened  and  irregular  in  form ;  their  mem- 
brane is  not  recognizable,  and  their  contents  are  quite  homogeneous, 
and  transparent,  with  a  yellowish  hue.  If  dilute  alkalies,  however,  be 
added,  they  swell  up  after  a  short  time  into  beautiful  round  or  elongated 
vesicles,  in  which,  in  consequence  of  the  penetration  of  the  reagent,  the 
fat  divides  into  separate  drops  of  various  sizes,  and  into  irregular 
masses ;  at  the  same  time  the  sebaceous  matter  becomes  white,  owing 
to  the  numerous  minute  fatty  particles  which  are  produced,  and  larger 
fat-drops  are  formed,  probably  in  consequence  of  the  solution  of  many 
cells.  Besides  that  in  the  cells,  the  sebaceous  matter  also  contains  free 
fat,  in  larger  or  smaller  quantity,  and  in  some  cases,  perhaps,  an  exces- 
sively minute  amount  of  a  clear  fluid. 

It  appears,  then,  that  the  cutaneous  sebaceous  matter  is  a  secretion, 
consisting,  so  to  speak,  only  of  formed  elements,  either  cells  containing 
fat  alone,  or  cells  together  with  drops  of  fat.  These  constituents  are 
formed  in  the  vesicular  ends  of  the  glands,  in  consequence  of  a  produc- 
tion of  cells,  which,  as  in  the  epidermic  tissues  in  general,  proceeds  en- 
tirely from  the  pre-existing  cells,  unaided  by  free  cell-development,  of 
which  there  is  in  this  case  no  indication.  By  endogenous  development 
round  portions  of  contents,  or  by  division,  cells  are  continually  produced 
at  the  bottom  of  the  glandular  vesicles.  These  are  at  first  pale,  and 
contain  but  few  granules,  like  the  epithelial  cells  from  which  they  arise  ; 
but  as  they  are  forced  towards  the  interior  by  cells  developed  after  them, 
they  are  very  soon  completely  filled  with  moderately  large,  round,  dark, 
fat-granules.  They  thus  proceed  towards  the  excretory  ducts  ;  and  the 
fat  drops  contained  in  them  running  more  and  more  together,  and  the 
membranes  themselves  becoming  rather  more  resistant,  they  eventually 
assume  the  form  of  the  sebaceous  cells  above  described.  The  free  fatty 
matter  in  the  sebaceous  secretion  is  formed,  in  certain  cases,  by  the 
solution  of  the  cells  whilst  still  in  the  interior  of  the  glandular  vesicles, 
for,  in  fact,  in  many  glands,  free  fat,  in  smaller  or  larger,  often  very 
considerable  drops  (Fig.  86  B\  is  met  with,  even  in  the  terminal 
vesicles ;  however,  it  is  also,  perhaps,  produced  in  consequence  of  its 
draining  from  closed  cells,  a  supposition  which  is  not  a  little  strengthened 
by  the  circumstance,  that  the  fat-containing  cells  in  the  excreted  seba- 


218  SPECIAL    HISTOLOGY. 

ceous  matter  are  seldom  filled  to  distension,  but  appear  for  the  most  part 
variously  flattened,  or  even  corrugated,  and  contain  only  a  small  quantity 
of  fat.  Understood  in  this  way,  the  formation  of  the  cutaneous  sebaceous 
matter  resembles  in  many  respects  that  of  the  cuticle.  The  young,  easily 
soluble  cells  at  the  bottom  of  the  glandular  follicles  may  be  compared 
to  the  Malpighian  cells  of  the  epidermis,  and  the  less  soluble  ones  of 
the  secretion  filled  with  fat,  to  the  horny  plates,  which  seems  the  more 
appropriate,  if  we  consider,  1,  that  the  deep  layer  of  the  epidermis  of 
the  hair-sac  is  continued  into  the  ducts  of  the  glands,  and  even  the 
outermost  cells  of  the  terminal  vesicles;  and  2,  that  the  epidermis,  in 
some  situations  being  constantly  detached,  form  secretions  (I  refer  to  the 
smegma  iwceputii  of  the  penis  and  clitoris),  substances  which  are,  more- 
over, to  all  appearance  chemically  allied  to  the  sebaceous  secretion ;  for 
the  latter,  it  may  be  remarked,  according  to  an  analysis  of  the  contents 
of  a  distended  gland  by  Esenbeck  (Gmelin's  "  Handbuch  der  Chemie," 
Bd.  ii.),  contains  principally,  fat,  24-2 ;  albumen  and  casein,  24*2 ;  ex- 
tractive matters,  24 ;  and  phosphate  of  lime,  20  per  cent. ;  substances 
which  are  found,  at  all  events  in  part,  in  the  smegma. 

Of  nerves,  I  have  seen  no  indication  in  the  sebaceous  glands,  nor  of 
vessels  distributed  upon  and  between  their  lobules ;  whilst  numerous 
minute  vessels  and  even  capillaries,  undoubtedly  exist  around  the  larger 
glands,  most  distinctly  in  the  penis  and  scrotum,  as  well  as  in  the 
ear.  I  would,  moreover,  refer  to  the  smooth  muscles  described  above, 
when  speaking  of  the  cutis,  which  are  found  in  the  neighborhood  of  the 
sebaceous  glands,  and  whose  contraction  is,  perhaps,  not  inoperative 
towards  the  emptying  of  their  contents. 

§  75.  Development  of  the  Sebaceous  Grlands. — The  first  formation  of 
the  sebaceous  glands  takes  place  at  the  end  of  the  fourth  and  in  the 
fifth  month,  and  is  intimately  connected  with  that  of  the  hair-sacs,  since 
they  make  their  appearance  simultaneously  with  the  hairs,  or  shortly 
after,  as  outgrowths  of  the  hair-sacs  ;  whence  they  are  not  all  formed 
at  once,  but  those  of  the  eyebrows,  forehead,  &c.,  first,  those  of  the  ex- 
tremities last.  The  mode  of  their  development,  more  precisely  described, 
is  as  follows :  When  the  rudiments  of  the  hair-sacs  have  attained  a 
considerable  development,  and  the  first  indication  of  the  hair  is  visible 
in  them  (Fig.  75,  A,  B],  there  are  perceptible,  on  their  outer  surface, 
small,  indistinctly-bounded  papillary  processes  (u,  v),  which  consist  of  a 
cellular  substance,  solid  throughout  and  continuous  with  the  outer  root- 
sheath,  and  of  a  delicate  investment,  which  is  continuous  with  that  of  the 
hair-sac.  These  processes  of  the  external  root-sheaths  of  the  hair-sacs, 
as  they  may  properly  be  called,  at  first  of  0-02-0-03  of  a  line  in  length, 
and  0-01-0-016  of  a  line  in  thickness,  now  begin  to  grow  in  proportion 
to  the  hair-sacs,  become  globular,  and  finally,  while  they  extend  them- 


OF  THE  GLANDS  OF  THE  SKIN.  219 

selves  and  incline  obliquely  towards  the  bottom  of  the  sac,  pyriform 
and  flask-shaped.  A  formation  of  fat  in  the  internal  cells  now  com- 
mences (Fig.  88,  A\  which,  beginning  at  the  bottom  of  the  pyriform  pro- 
cesses, is  continued,  also,  into  their  pedicles,  and  finally  includes  the 
cells  of  the  outer  root-sheath,  until  at  last  the  fat  cells  reach  as  far  as 
the  canal  of  the  hair-sac  (Fig.  88,  J9).  The  gland  and  its  contents  are 

Fig.  88. 


now  complete,  and  it  needs  only  that  the  cells  at  the  bottom  of  the 
gland,  or  the  glandular  vesicles,  should  multiply,  to  force  the  sebaceous 
cells  in  the  duct  into  the  hair-sac,  and  fully  to  establish  the  secretion. 
The  sebaceous  glands,  therefore,  like  the  sudoriparous,  are,  at  first, 
solid  outgrowths  of  the  Malpighian  layer  of  the  skin,  for  which  an  ex- 
ternal opening  is  not  developed  till  afterwards,  and  the  first  cutaneous 
sebaceous  matter  is  formed  by  a  metamorphosis  of  the  inner  cells  of  the 
rudiment  of  the  gland,  while  the  space  which  these  cells  occupied  be- 
comes the  cavity  of  the  gland,  which,  however,  never  appears  empty, 
but  is  continually  filled  by  successive  generations  of  cells. 

The  development  of  the  glands,  up  to  this  point,  proceeds  pretty 
quickly.  It  may  be  stated  generally,  that  so  long  as  the  hairs  have  not 
appeared  externally,  the  rudiments  of  the  glands  are  papillary,  measure 
scarcely  more  than  0-03  of  a  line,  and  for  the  most  part  contain  cells 
which  are  still  quite  pale ;  after  the  hairs  have  made  their  appearance 
externally,  we  find  larger  pyriform  rudiments  with  a  thicker  end,  of 
0-024-0-05  of  a  line,  the  cells  of  which  are  partly  still  pale,  partly 

FIG.  88. — To  elucidate  the  development  of  the  sebaceous  glands  in  a  six-months'  fcetus  : 
a,  hair ;  6,  inner  root-sheath,  here  more  closely  resembling  the  horny  layer  of  the  epidermis ; 
c,  outer  root-sheath  ;  c?,  rudiments  of  the  sebaceous  glands.  A,  flask-shaped  rudiment  of  the 
gland,  with  fat  developed  in  the  central  cells';  jB,  larger  rudiments;  the  development  of  fat 
has  taken  place  also  in  their  neck,  and  fatty  cells  have  been  excreted  into  the  hair-sac, 
giving  rise  to  the  glandular  cavity  and  the  secretion. — Magnified  about  250  diameters. 


220  SPECIAL    HISTOLOGY. 

contain  fat,  and  which  now  soon  open  into  the  hair-sac.  In  the  fifth 
month,  therefore,  the  secretion  has  already  begun  in  many  places,  and 
in  the  sixth  it  is  everywhere  established.  At  the  same  time,  however, 
it  is  to  be  observed  that,  together  with  the  original  glands,  which  occur, 
one  or  two  together  to  each  sac,  in  the  sixth  month,  new  rudiments  are 
produced,  which  generally  lie  deeper,  and  taking  on  the  same  course  as 
that  which  has  been  described,  soon  become  secreting  glands.  The  fatty 
cells  of  the  newly-formed  glands  invariably  contain  many  fat-globules, 
never  a  single  large  drop ;  nuclei  also  occur  in  them,  as  in  the  pale  cells 
which  surround  them. 

The  further  development  of  the  sebaceous  glands  depends  on  the  out- 
growth of  the  external  fatless  cells  of  the  originally  simple  tubular  gland, 
into  solid  processes,  which  by  degrees  become  changed  into  glandular 
vesicles,  in  the  same  way  as  the  first  rudiments.  By  repeated  budding 
of  the  primitive  or  secondary  glandular  vesicles,  the  larger  clusters  are 
formed,  and  from  them  the  most  complicated  forms  which  are  met  with. 
The  so-called  glandular  rosettes  proceed,  very  often,  from  a  single  rudi- 
ment, which,  growing  rapidly,  surrounds  the  hair-sac  on  all  sides ;  at 
other  times,  however,  from  two  or  more  primary  processes  of  the  outer 
root-sheath.  In  the  seven  months'  foetus,  most  of  the  glands  are  simple 
pedunculated  follicles  of  0-04-0-06  of  a  line  in  length,  and  0-02-0-03  of 
a  line  in  breadth,  which  are  appended,  singly  or  in  pairs,  to  the  hair- 
sacs  ;  in  the  ear  alone,  do  four  or  five  glands  of  the  simplest  kind  sur- 
round a  sac,  and  form  rosettes  of  not  more  than  0*06  of  a  line  in  dia- 
meter ;  in  the  nose,  simple  clusters  of  at  most  0*1  of  a  line  are  presented. 
In  the  new-born  infant,  instead  of  the  simple  follicles,  simple  racemose- 
glands  are  found  in  all  the  above-mentioned  situations,  one,  or  more 
rarely  two,  to  a  sac  0-1-0-12  of  a  line  in  length,  and  only  0-04-0-06  of 
a  line  in  breadth ;  on  the  chest,  the  glands  are  rosette-like,  also  on  the 
ear,  temple,  nose,  nipple,  labia  majora,  and  scrotum,  where  they  mea- 
sure 0-1,  in  the  last  four  places  even  0-4  of  a  line  and  more.  From 
these  data,  it  results,  that  after  birth  an  increase  in  size  takes  place  in 
most  of  the  glands,  and  assuredly  in  the  same  manner  as  during  the 
foetal  period,  a  view  which  is  favored  by  the  occasional  occurrence  of 
pale,  solid,  glandular  lobules,  even  in  the  adult ;  certain  glands  arise 
only  after  birth,  viz.  those  of  the  labia  minora. 

Sebaceous  glands  also  occur  in  abnormal  localities ;  thus  Kohlrausch 
(Mull.  "Arch.,"  1843,  p.  365),  observed  them  in  an  ovarian  cyst,  and 
Von  Barensprung  (1.  c.,  p.  104)  in  a  subcutaneous  cystic  tumor  of  the 
brow ;  in  both  places  they  were  connected  with  hair-sacs,  whence  it  may, 
perhaps,  be  concluded,  that  they  are  very  frequently  to  be  found  in 
cysts  which  contain  hair.  In  fact  I  met  with  very  beautiful  sebaceous 
glands,  with  a  considerable  amount  of  sebaceous  matter,  in  the  walls  of 


OF    THE    GLANDS    OF    THE    SKIN.  221 

the  cyst  containing  hair,  mentioned  above,  from  the  lung  (Mohr's  case) ; 
Von  Barensprung  has,  he  believes,  though  rarely,  observed  a  new  de- 
velopment of  sebaceous  glands  in  cicatrices  of  some  years'  standing. 
When  the  hairs  fall  out,  the  sebaceous  glands  seem  to  disappear,  at 
least  I  have  repeatedly  failed  in  finding  them  in  bald  places.  Hyper- 
trophy* of  the  sebaceous  glands  takes  place,  according  to  E.  H. 
Weber  (Meckel's  "Archiv,"  1827,  p.  207),  in  cutaneous  cancer;  ac- 
cording to  Von  Barensprung  in  akrothymion,  or  moist  warts  (1.  c., 
p.  81),  and  in  ncevus  pilosus.  The  comedones  also,  among  which  I 
place  Lichen  pilaris,  at  least  as  Simon  defines  it  (1.  c.,  p.  334), 
are  hair-sacs  and  sebaceous  glands  distended  with  sebaceous  matter, 
which  are  especially  frequent  where  the  glands  are  distinguished  by 
their  large  size,  as  on  the  nose,  the  lips,  the  chin,  the  ear,  the  areola, 
and  the  scrotum.  They  arise,  either  in  consequence  of  the  obstruc- 
tion of  the  apertures  of  the  hair-sacs  by  impurities,  or  of  the  formation 
of  a  more  viscid  and  consistent  secretion ;  and  they  contain,  besides 
one  or  many  hairs,  which  may  also  be  wanting,  fatty  cells,  like  those  of 
the  normal  cutaneous  sebaceous  matter,  epidermic  cells  proceeding  from 
the  hair-sacs,  free  fat,  often  crystals  of  cholesterin  and  the  Acarus 
folliculorum.  Milium  consists  of  small  white  spots  on  the  eyelids,  the 
root  of  the  nose,  the  scrotum,  and  ear,  which  are  formed,  as  Von  Baren- 
sprung is  certainly  right  in  supposing,  from  the  sebaceous  glands  also, 
by  their  distension  alone,  without  the  hair-sacs;  in  consequence  of 
which,  rounded  prominences  without  any  aperture  are  formed  and  raise 
up  the  skin  :  their  secretion,  similar  to  that  of  the  comedones,  may  still 
frequently  be  pressed  out  through  the  hair-sacs.  Finally,  there  can  no 
longer  be  any  doubt  that  the  sebaceous  cysts  which  lie  in  the  corium 
itself  (atheroma,  steatoma,  meliceris,  and  molluscum\  must  also  be  re- 
garded as  colossal  hair-sacs  with  sebaceous  glands.  Further  details  may 
be  found  in  the  works  cited. 

With  respect  to  a  little  parasite,  the  Acarus  folliculorum^  which 
resides  in  healthy  and  distended  hair-sacs  and  sebaceous  glands,  I  must 
refer  to  G.  Simon  (1.  c.,  p.  287).  In  the  case  of  Iclithyosis  congenita 
above  referred  to,  Dr.  H.  Muller  and  I  found  the  excretory  ducts  of 
the  sebaceous  glands  in  the  epidermis  everywhere  dilated  to  0-02-0-06 
of  a  line,  with  saccular  diverticula,  often  lying  many  together  one 
behind  another,  of  0-04-0-12  of  a  line,  and  quite  full  of  sebaceous 
matter.  Here  and  there  a  hair  was  found  in  one  of  these  ducts,  so 
that  it  appeared  at  the  same  time  to  be  a  hair-sac. 

In  investigating  the  sebaceous  glands,  they  should  either  be  prepared 
from  within,  by  cutting  them  with  the  hair-sacs  which  belong  to  them 
from  the  cutis,  or  perpendicular  sections,  not  too  fine,  may  be  made. 

*  [These  glands,  when  hypertrophied,  frequently  lose  their  glandular  structure,  and  are 
changed  into  yellowish  granular  masses. — DaC.] 


222  SPECIAL    HISTOLOGY. 

The  minuter  structure  may  be  best  studied,  at  first  in  the  glands  of  the 
scrotum  and  penis,  or  labia  minora,  as  these  can  be  isolated  without  any 
trouble ;  to  which  end  acetic  acid,  which  renders  the  surrounding  parts 
transparent,  is  very  serviceable.  With  the  others,  so  far  as  form,  posi- 
tion, and  size,  are  concerned,  the  use  of  alkalies,  especially  of  caustic 
soda,  is  most  advisable,  inasmuch  as  they  clear  all  the  other  parts,  while 
they  act  but  little  on  the  glands  on  account  of  the  quantity  of  fat  they 
contain.  If  it  be  desired  to  study,  not  so  much  the  investments,  as  the 
cells  of  the  glands,  obtaining  at  the  same  time  a  view  of  their  whole 
figure,  there  is  no  plan  better  than  maceration ;  the  hairs  with  their 
root-sheaths,  and  the  cellular  masses  of  the  sebaceous  glands,  epithelium 
and  contents,  may  then  be  drawn  out  altogether.  Where  the  epidermis 
is  thin  (on  the  scrotum,  labia  majora,  glans  penis),  the  same  end  may 
be  attained  in  a  short  time  by  the  dropping  on  it  concentrated  acetic 
acid,  and  also  by  using  caustic  soda  in  the  same  manner,  though  with 
greater  destruction  of  the  glandular  cells.  To  study  development,  the 
maceration  of  foetal  skin,  and  the  rendering  it  transparent  by  acetic 
acid,  are  of  great  use.  The  fat-cells  in  the  interior  of  the  glands  are 
isolated  with  great  ease  by  teasing  out  a  large  gland,  and  the  secretion 
may  be  examined  without  addition,  and  also  with  water  and  caustic  soda. 
Literature. — Compare  the  works  cited  above  under  the  head  of  "  Skin," 
by  Gurlt,  p.  409 ;  Krause,  p.  126 ;  G.  Simon,  p.  9 ;  Valentin,  p.  758 ; 
the  " Essay  on  the  Hairs,"  by  Eschricht,  which  has  been  mentioned; 
then  the  general  works  by  Henle,  p.  899 ;  Todd  and  Bowman,  p.  424, 
fig.  92 ;  Hassall  (pi.  liv.  should  be  liii.),  p.  401 ;  Bruns,  p.  349 ;  Gerber, 
p.  75,  figs.  40,  42,  43,  44,  45,  239 ;  Arnold,  part  II.,  the  figures  of 
Wagner,  "Icon.  Phys.,"  tab.  xvi.,  fig.  11,  c;  Arnold,  "Icon.  Anatom.," 
Ease.  II.,  tab.  xi.,  fig.  10,  and  Berres,  tab.  xxiv.,  besides  that  G.  Simon, 
"  Ueber  die  sogenannten  Tyson'schen  Dru'sen  an  der  Eichel  des  mann- 
lichen  Gliedes,"  in  Muller's  "  Archiv,"  1844,  p.  1. 


OF  THE  MUSCULAR  SYSTEM. 

§  76.  To  this  system  belong  all  the  transversely  striped  muscles, 
which,  together  with  their  accessory  appendages,  the  tendons  and 
fasciae,  serve  for  the  movements  of  the  skeleton,  of  the  proper  organs  of 
sense,  and  of  the  integuments.  These  muscles  constitute  a  system 
situated  between  the  integuments  and  the  bones,  and  between  the  bones 
themselves,  the  individual  parts  of  which  are  so  associated  and  united  by 
common  membranes,  that  they  may  conveniently  be  regarded  as  a  whole. 

§  77.  The  proper  elements  of  the  muscles  in  question,  visible  even  to 


THE     MUSCULAR     SYSTEM. 


223 


Fig.  89. 


the  naked  eye, — the  transversely  striated  (animal  or  voluntary)  muscular 
fibres,  or  primitive  fasciculi, — are  distinguished,  especially  by  their  size 
and  the  distinctness  of  their  individual  parts,  from  those  of  most  of  the 
striped  muscles  occurring  in  other  situations  (heart,  large  venous  trunks, 
pharynx,  oesophagus,  larynx,  urethra).  With  respect  to  this  latter 
characteristic,  it  is  to  be  remarked  that  the  sheath  of  the  primitive 
fasciculus,  or  the  sarcolemma,*  in  every  fasciculus  without  exception, 
especially  on  the  addition  of  water,  acetic  acid,  and  alkalies,  may  at 
once  be  recognized  as  a  perfectly  structureless,  transparent,  elastic, 
smooth  membrane,  which  in  man,  as  in  the  mam- 
malia, is  distinguished  by  its  delicacy  from  the  same 
tissue  in  the  lower  Vertebrata,  and  particularly  in 
the  naked  Amphibia.  The  muscular  or  primitive 
fibrils  may,  though  not  without  difficulty,  be  isolated, 
especially  in  muscles  that  have  undergone  slight 
maceration,  or  have  been  boiled,  or  immersed  in 
alcohol  or  chromic  acid.  In  general  they  are  vari- 
cose, that  is  to  say,  present  more  or  less  distinct 
enlargements,  at  intervals  of  O'0004-O'OOl  of  a  line ; 
in  consequence  of  which  arrangement,  and  owing  to 
the  circumstance  that  the  thicker  and  thinner  spaces, 
throughout  the  entire  thickness  of  the  fasciculus,  are 
placed  regularly  on  the  same  level,  the  latter  for  the 
most  part  appears  to  be  marked  with  delicate  trans- 
verse bands.  Occasionally,  moreover,  in  addition,  a 
fine  parallel  striation  is  evident,  or,  more  rarely, 
where  the  enlargements  on  the  fibrils  are  less  appa- 
rent or  quite  imperceptible,  simply  a  longitudinal 
striation.  In  adults,  the  fibrils  do  not  enclose  any  central  space  or 
canal  (Jacquemin,  Skey,  Valentin),  but,  with  the  addition  of  a  small 
quantity  of  a  connecting  interstitial  substance,  constitute  perfectly 
compact  fasciculi  (Fig.  90).  On  the  inner  side  of  the  sarcolemma^ 

FIG.  89. — Primitive  fibrils  from  a  primitive  fasciculus  of  the  Axolotl  (Siredon  pisciformis)  ; 
magnified  600  diameters  :  a,  a  small  fascicular  composed  of  them  ;  6,  an  isolated  fibril. 

*  [It  is  greatly  to  be  doubted  whether  the  universality  of  the  occurrence  of  this  structure 
should  be  so  strongly  affirmed.  We  have  been  unable  to  detect  it  either  in  the  muscular 
bundles  of  the  heart,  or  in  the  great  majority  of  those  of  the  tongue,  or  in  any  of  the  muscles 
of  a  seven-months'  foetus.  In  fact,  the  question  of  the  existence  of  a  sarcolemma  as  an 
independent  structure  very  much  resembles  that  of  the  existence  of  "  fibrils."  The  sarco- 
lemma must  be  considered  merely  as  the  outer  portion  of  the  transparent,  homogeneous 
matrix,  in  which  the  "  sarcous  elements"  are  imbedded  (vide  infra)]  and  the  possibility  of 
raising  it  up  by  artificial  means,  or  of  observing  its  optical  expression,  as  a  distinct  structure, 
will  depend  upon  the  amount  to  which  it  is  developed  relatively  to  the  various  elements, 
and  the  extent  of  chemical  differentiation  which  has  gone  on  it  as  compared  with  the  rest 
of  the  matrix. — TRS.] 


224 


SPECIAL    HISTOLOGY. 


numerous  nuclei  always  exist,  of  a  lenticular  or  fusiform  shape,  fre- 
quently with  nucleoli)  and  from  0-003-0-005  of  a  line  long.  These 
nuclei  are  not  placed  with  any  regularity ;  sometimes  two  or  more  at 
the  same  level,  or  in  rows,  or  alternately  one  behind  the  other.  Fatty, 
or  yellowish  pigment-granules,  also,  frequently  occur  around  the  nuclei 
and  between  the  fibrils,  chiefly,  however,  in  muscular  fibres  which  are 
not  in  a  perfectly  normal  condition. 

The  form  of  the  muscular  fasciculi  is  rounded-polygonal.  In  thick- 
ness they  vary  from  0-005-0-03  of  a  line,  or  more.  In  the  trunk  and 
extremities  they  are  invariably  thicker  (0-016-0-03  of  a  line)  than  on 
the  head,  in  which  situation,  especially  in  the  facial  muscles,  they  are 


Fig.  90. 


Fig.  91. 


distinguished  by  the  smallness  of  their  fibres  (0-005-0-016  of  a  line) ; 
but,  with  respect  to  this,  it  is  to  be  remarked  that  great  differences  not 
unfrequently  exist  in  one  and  the  same  muscle.  From  all  that  is  known, 
it  would  appear  that  there  is  no  absolute  difference  in  the  size  of  the 
muscular  fibre  in  man  and  in  woman,  or  between  weak  and  robust  indi- 
viduals. On  the  other  hand,  it  is  not  improbable  that  in  one  case  one 
extreme,  and  in  a  second  the  other,  may  prevail.  The  thickness  of  the 
primitive  fibrils,  in  man,  amounts  on  the  average  to  0*0005  of  a  line; 
their  number,  in  one  of  the  larger  fasciculi,  must  reach  several  hundreds, 
but  is  not  accurately  known.  The  distance  between  the  transverse 
striae  varies  usually  from  0-0004  to  0-001  of  a  line. 

Various  controversial  opinions  still  prevail  with  respect  to  the  consti- 
tution of  the  muscular  fibres.  Several  authors  assert,  or  at  all  events 
consider  it  probable,  that  the  primitive  fibrils  are  produced  artificially. 

FiG.  90. — Transverse  section  of  some  muscular  fibres  or  primitive  fasciculi  from  the 
gastrocnemius  of  man  ;  magnified  300  diameters :  a,  sarcolemma  and  interstitial  connective 
tissue ;  ft,  transverse  section  of  the  muscular  fibrils,  with  the  interstitial  substance. 

FIG.  91. — Portion  of  a  muscular  fibre  of  man.  treated  with  acetic  acid,  magnified  450 
diameters:  a,  sarcolemma;  ft,  a  simple  nucleus;  c,  double  nucleus,  surrounded  with  fatty 
molecules. 


THE  MUSCULAR  SYSTEM. 


225 


Fig.  92. 


This  is  the  opinion  entertained  by  Remak,  who  thinks  a  pre-existing 
division  of  the  muscular  cylinder  still  problematical ;  of  Briicke,  who 
appears  to  regard  the  contents  of  the  muscle-tubes  during  life  as  fluid ; 
of  Du  Bois-Reymond,  and,  above  all,  of  Bowman.  According  to  the 
latter,  a  division  of  the  muscular  fibres  into  "  discs"  (Fig.  92)  is  quite  as 
natural,  although  not  so  frequent,  as  that  into  fibrils, 
and  that  they  may  be  considered  as  columns  composed 
of  such  discs,  quite  as  correctly  as  bundles  of  fibrils. 
Were  a  muscular  fibre  completely  divided  in  the  direc- 
tion of  both  the  transverse  and  longitudinal  striae, 
rounded,  angular,  minute  particles  would  be  produced, 
which  may  be  termed  primitive  particles,  or  "  sarcous 
elements,"  In  the  fibre,  these  elementary  particles  are 
connected  in  both  directions,  the  same  particles  in  the 
one  case  constituting  a  "disc,"  and  in  the  other  a  seg- 
ment or  joint  of  the  fibrils.  The  division  into  discs, 
upon  which  Bowman  lays  especial  stress,  would  in  my 
opinion  have  been  of  importance  had  it  occurred  as  fre- 
quently as  that  into  fibrils,  and  also,  occasionally,  in 
recent  muscle ;  but  it  is  not  so, — for,  in  the  first  place, 
nothing  of  the  sort  can  ever  be  seen  in  recent  muscles 
of  man  and  the  higher  animals ;  and  in  the  second  place,  even  in  mace- 
rated or  otherwise  manipulated  fasciculi,  the  breaking  up  into  discs  is 
an  extremely  rare  phenomenon ;  whilst,  on  the  other  hand,  the  isolation 
and  exhibition  of  the  fibrils  may  be  obtained,  in  almost  every  instance, 
by  any  one  at  all  conversant  with  the  subject.  Moreover,  in  transverse 
sections  of  perfectly  fresh  living  muscles,  as,  for  instance,  of  the  thigh 
of  a  Frog,  made  by  means  of  the  double-bladed  knife,  the  transverse 
section  of  the  fibrils  is  just  as  evident  and  distinct  as  in  dried  muscles, 
whilst,  in  precisely  similar  longitudinal  sections,  not  a  trace  of  the 
"discs"  can  be  detected.  This  fact  at  once  sets  aside  all  those  views, 
according  to  which  the  muscular  fibres,  during  life,  consist  of  a  homo- 
geneous, solid,  or  fluid  substance,  or  of  minute  particles,  connected  in 
two  directions.  To  Bowman's  opinion,  moreover,  is  opposed  the  fact 
that  his  assumed  "elementary  particles,"  except  in  macerated  muscles, 
where  such  a  thing  readily  occurs,  can  only  with  difficulty  be  obtained 
in  an  isolated  form,  whilst,  according  to  his  view,  such  a  disintegration, 
in  cases  where  these  particles  do  not  cohere  firmly,  either  in  a  longitu- 
dinal or  transverse  direction,  would  necessarily  take  place  with  equal 

FIG.  92. — Jl,  a  primitive  fasciculus,  separating  transversely  into  discs;  magnified  350 
diameters.  It  exhibits  distinct  transverse  and  fainter  longitudinal  striae.  The  discs,  of 
which  one  more  highly  magnified  is  seen  at  B,  are  granular,  and  consist  of  the  primitive 
particles  (parcous  elements)  of  Bowman,  or  segments  of  the  fibrils  according  to  other 
authors  (after  Bowman). 

15 


226 


SPECIAL    HISTOLOGY. 


Fig.  93. 


facility  in  either ;  and  in  the  second  place,  that,  in  the  thoracic  muscles 
of  insects,  the  individual  fibrils  may  be  very  distinctly  and  beautifully 
seen  (Fig.  93)  in  the  muscles,  when  quite  fresh.  When  we  consider  the 
great  similarity  between  the  muscles  of  insects  and  of 
the  higher  animals,  in  every  essential  particular,  this 
fact  appears  to  me  to  be  of  a  striking  nature.  I  am, 
therefore,  from  this  and  the  other  reasons  assigned, 
thoroughly  convinced  of  the  existence  of  fibrils  during 
life,  and  believe  that,  where  they  do  not  so  readily 
admit  of  being  isolated,  as  in  man  and  many  animals, 
they  are  connected  by  a  homogeneous,  tenacious  (albu- 
minous), interstitial  substance,  which  is  very  evident  in 
a  transverse  section,  and  in  fact  so  firmly,  that,  under 
certain  circumstances,  transverse  rupture  of  the  fasciculi 
may  take  place,  that  is  to  say,  in  the  direction  of  the 
thinner  spaces  of  the  fibrils  ;  as  also  occurs  in  other 
fibres ;  for  instance,  in  the  elastic  tissue,  smooth  muscles, 
and  even  in  the  corneous  cells  (internal  root-sheath  and 
cortex  of  the  hair).  With  all  this,  it  must  not  be  sup- 
posed that  fibrils  exist  in  all  muscular  fibres  of  animals, 
either  themselves  striped  or  corresponding  to  the  striped  fibres  here 
described.  The  study  of  development  and  of  comparative  anatomy 
much  rather  teaches  that  the  muscular  fibre  occurs  in  various  conditions, 
and,  particularly,  that  it  frequently  exhibits  more  homogeneous  contents, 
with  or  without  transverse  striation,  and  without  fibrils.  This,  however, 
of  course,  affords  no  ground  for  the  assumption  of  such  a  condition  in 
man  and  the  mammalia  also ;  and  although  such  muscular  fibres,  in 
certain  animals,  readily  break  up  into  transverse  segments  (Leydig), 
still,  it  is  not  thereby  proved  that  in  the  higher  animals  a  similar 
division  of  the  contents  is  to  be  regarded  as  natural,  and  that  into 
fibrils  as  artificially  produced. 

The  diameter  of  the  primitive  fasciculi  varies,  not  inconsiderably,  in 
different  muscles,  or  in  one  and  the  same  muscle.  Henle  (who  is  fol- 
lowed by  Gerlach),  at  an  earlier  period,  assigned  to  them  a  diameter 
of  0-005-0-006,  and  at  most  of  0-017  of  a  line;  but  more  lately 
(Stadelmann,  "  Sectiones  transversse"),  has  declared  that  these  measure- 
ments are  not  universally  correct.  I  will  here  give  some  particulars 
upon  which  the  measurements  stated  above,  in  the  text,  are  founded. 
In  a  female,  the  fasciculi  of  the  sacro-lumbalis  measured  0 '016— 0 '028, 
the  majority  0-020-0-022  of  a  line;  in  the pectoralis  major,  0-01-0-03, 
most  of  them  0-02  of  a  line;  deltoid,  0-016-0-026,  the  majority  0-02- 
0-022  of  a  line;  in  the  masseter,  0-006-0-02,  the  majority  0-01-0-018 

FIG.  93. — Primitive  fibres  from  a  quite  recent  transverseJy-striated  muscle  of  a  Bug; 
magnified  350  diameters. 


THE    MUSCULAR    SYSTEM.  227 

of  a  line  ;  in  the  retrahens  auricula?,  0-006-0-015,  the  greater  part  0-008- 
0-01  of  a  line.  In  a  male,  their  diameter  in  the  pectoralis  amounted 
to  0-018-0-28  of  a  line,  the  greater  number  measuring  0-02-0-022  of 
a  line ;  in  the  deltoid,  0-012-0-024  for  the  largest,  and  for  the  smaller 
0-016-0-02  of  a  line  ;  in  the  olliquus  abdominis  externus,  0-16-0*024  and 
0-016-0-02  of  a  line;  in  the  orbicularis  oris,  0-008-0-016  and  0-01- 
0-012  of  a  line ;  in  the/rcwteZw,  0-006-0-014  and  0-008-0-01  of  a  line. 
In  a  second  individual,  the  pectoralis  major  contained  fibres  of  0-0068— 
0-024,  most  of  them  0-018-0-02  of  a  line;  the  pyramidalis,  some  of 
0-01-0-028,  the  majority  0-02  of  a  line. 

With  respect  to  the  nature  of  the  primitive  fibrils,  much  still  remains 
to  be  cleared  up.  In  general  they  must  be  regarded  as  solid ;  and,  in 
fact,  there  is  nothing  to  indicate  the  existence  of  a  cavity  in  them.  It 
is  fully  ascertained  that  it  is  to  them  that  the  transverse  striation  of  the 
primitive  fasciculus  is  due.  It  is  still  doubtful,  however,  whence  the 
appearance  of  transverse  striation  in  the  fibrils  themselves  arises; 
whether  from  their  being  spirally  twisted  (Arnold),  from  zigzag  curva- 
tures (Will),  or  from  varicosities.  All  that  I  have  seen  leads  me  to 
adopt  the  latter  view,  which  is  also  that  most  generally  entertained.  I 
do  not  deny  that,  in  the  examination  of  numerous  fibrils,  appearances 
are  occasionally  met  with,  favorable  to  the  other  two  views,  and  parti- 
cularly to  that  of  Will ;  but  it  is  much  more  usual  to  find  simple  nodular 
enlargements.  The  large  fibrils  in  the  perennibranchiate  Amphibia 
(Siren,  Proteus,  Menopoma),  (Fig.  89),  are  above  all  others  adapted  for 
this  investigation.  In  these  animals,  when  they  have  been  preserved 
in  spirit,  the  fibrils  become  isolated  in  considerable  numbers,  and  may 
be  examined  on  all  sides.  It  is  the  same  with  the  muscles  of  the  thorax 
in  Insects. 

Quite  lately  Dr.  Barry  has  propounded  the  view  that  each  muscular 
fibril  is  constituted  of  two  spirally  convoluted  filaments  running  in  the 
same  direction.  I  have  seen  nothing  of  the  kind,  and  do  not  hesitate 
to  describe  the  whole  of  Dr.  Barry's  exposition  as  nothing  but  a  myth, 
and  his  figures  as  fantastical  images. 

As  regards  the  notion  adopted  by  Bowman,  Dobie,  and  others,  that 
the  fibrils  &re  constituted  of  still  more  minute  particles  (sarcous  ele- 
ments), it  may  perhaps  be  stated,  as  the  study  of  development  shows,  that 
the  fibrils  do,  in  fact,  at  first  appear  to  consist  of  separate  particles. 
But  the  question  is  whether  in  the  adult  such  elementary  particles  con-* 
tinue  to  be  evident,  and  this,  at  present,  I  am  inclined  to  deny. 

The  nuclei  of  the  muscular  fibres,  in  man,  are  situated,  as  I  agree 
with  Schwann  in  stating,  only  on  the  inner  surface  of  the  sarcolemma, 
and  not  within  the  fibrils ;  that  they  are  not  placed  externally  on  the 
fasciculi,  as  was  formerly  stated  by  Henle  and  Stadelmann,  and  more 
lately  by  Gerlach,  is  readily  perceived,  when  the  muscles  are  treated 


228  SPECIAL    HISTOLOGY. 

with  alkalies.  Under  these  circumstances  the  partially-swollen  nuclei 
escape,  together  with  the  fibrils,  in  a  state  of  solution,  from  the  sheaths, 
which  remain  behind,  and  before  they  are  dissolved  may  be  easily  exa- 
mined in  an  isolated  state.  In  many  muscles,  even  when  there  are  no 
granules  between  the  fibrils,  larger  or  smaller  fatty  molecules  occur 
around  the  nuclei.* 

*  [With  regard  to  the  vexed  question  of  the  ultimate  structure  of  striped  muscle,  we  ques- 
tion if  any  real  improvements  have  been  made  upon  the  description  originally  given  by  Mr. 
Bowman  ("  Phil.  Trans.,"  1840),  viz.,  that  it  consists  of  minute,  dark,  subangular  particles, 
the  "sarcous  elements,"  imbedded  in  a  more  transparent  connecting  substance  or  matrix; 
that  neither  discs  nor  fibrils  can  be  said  to  exist  in  the  normal  state, — the  breaking  up  of  the 
muscular  bundle  into  either  of  these  elements,  resulting  simply  from  the  manner  in  which 
the  lines  of  greatest  cohesion  are  disposed,  at  the  time  when  mechanical  violence  is  applied 
to  it.  The  assertion  in  the  text  that  the  fresh  muscle  of  man  and  the  mammalia  does  not 
break  up  into  discs,  is  decidedly  erroneous — as  we  have  seen  it  occur  repeatedly. 

Nor  can  we  grant  the  invisibility  of  the  discs  in  longitudinal  sections  of  muscle :  what 
may  be  the  case  in  such  sections  made  with  the  double  knife,  we  do  not  know, — but  in  those 
accidental  longitudinal  fractures  of  the  muscular  bundles  of  man,  mammals,  and  insects, 
which  constantly  occur,  the  edges  of  the  discs  are  most  distinct.  Again,  without  making 
any  section  at  all,  the  discs  may,  especially  in  insects,  be  traced,  by  altering  the  focus  of  the 
microscope,  through  the  entire  thickness  of  the  bundles.  The  argument  in  the  text,  in  fact, 
proves  too  much ;  for  if  the  fibrils  are  visible  over  the  whole  transverse  section,  their  dark 
parts  (discs)  alternating  with  the  light  ones,  must  be  as  visible  in  a  section,  made  in  any 
longitudinal  plane,  as  they  are  on  the  surface.  However,  that  the  appearance  of  discs  should 
be  absent  in  any  longitudinal  section  of  striped  muscle  is,  to  us,  simply  incomprehensible. 

With  regard  to  the  thoracic  muscles  of  insects,  it  is  to  be  observed,  in  the  first  place,  that 
they  do  not  represent  ultimate  fibrils,  but  non-fibrillatcd  primitive  bundles.  Dr.  Auber,  in  a  valu- 
able paper  in  "  Siebold  and  Kolliker's  Zeitschrift"  (H.  3  and  4,  1853),  has  already  shown 
that  there  is  no  defined  line  of  demarcation  to  be  drawn  between  these  and  the  ordinary 
muscles  of  insects,  the  two  forms  passing  into  one  another  by  the  peculiar  flat  bundles  of 
the  Libellulidae,  though  he  still  considers  the  thoracic  muscles  to  represent  ultimate  fibrils. 
His  sole  argument,  however,  is  their  resemblance  to  the  ultimate  fibrils  of  the  higher  animals, 
which  we  think  loses  all  force,  when  we  consider  a  fact  that  he  has  overlooked,  namely, 
that  the  muscles  of  the  legs,  &c.,  present  a  very  beautiful,  though  very  delicate  fibrillation — 
the  fibrils  being  not  more  than  JJJ^Q^  —  Ffijjfjs^1  °f  an  ^nc^  in  diameter;  that  is,  not  more 
than  from  one-third  to  one-sixth  the  diameter  of  the  thoracic  muscles.  Examined  carefully 
with  a  high  power  (600),  with  a  good  definition,  the  edges  of  the  discs,  which  under  a 
lower  power  appeared  very  sharp  and  even,  are  seen  to  be  distinctly  granular,  and  to  be 
composed  of  minute,  somewhat  fusiform  or  rounded  particles,  not  more  than  ^oAuutn  °^ an 
inch  in  diameter,  distinct  from  one  another,  and  imbedded  in  the  general  transparent  matrix, 
which  is  marked  by  fine  longitudinal  lines  running  between  the  rows  of  particles.  Occa- 
sionally, the  broad,  dark  discs  appear  to  be  separated  by  a  delicate  line,  and  this  line,  if  carefully 
examined,  is  found  to  be  composed  of  similar,  but  far  more  minute  and  paler  particles.  How- 
ever, this  appearance,  though  very  common,  is  not  to  be  met  with  in  all  the  bundles.  Acetic  acid 
swells  the  muscle  up,  and  renders  the  sarcous  elements  still  more  distinct,  though  the  whole 
becomes  very  pale.  If  dilute  ammonia  be  added  to  such  a  bundle,  so  as  to  neutralize  the 
acid,  it  resumes  its  original  dimensions,  and  almost  its  original  appearance,  except  that  the 
sarcous  elements  have  often  a  wonderful  sharpness  of  outline. 

The  thoracic  fibres,  treated  with  acetic  acid,  become  exceedingly  pale,  and  the  distance 
between  the  discs  is  much  increased.  The  latter  often  assume  a  granular  appearance,  but 
not  so  distinctly  as  in  the  former  case;  nor  have  we  been  able  to  detect  any  fibrillation  of 
the  intermediate  substance,  nor  any  minute  sarcous  elements,  in  them.  They  share  the 
former  character,  however,  no  less  than  the  latter,  with  multitudes  of  unquestionable  mus- 
cular bundles — so  that  taking  into  consideration  the  existence  of  fibrils  very  much  minuter 


THE    MUSCULAR    SYSTEM.  229 

§  78.  The  muscular  fibres  in  the  trunk  and  extremities  are,  in  general, 
so  associated,  without  the  existence  of  any  divisions,  reticular  connec- 
tion, or  termination  in  the  interior  of  the  muscles,  as  to  constitute  con- 
tiguous prismatic  bundles  extending  the  entire  length  of  the  muscle. 

than  the  thoracic  fibres  in  the  muscles  of  insects,  and  the  gradual  transition  of  the  latter  into 
undoubted  bundles,  we  do  not  hesitate  to  regard  these  thoracic  fibres  as  homologous,  not  with 
primitive  fibrils,  but  with  primitive  bundles;  and  therefore  to  neglect  any  argument  which 
may  be  drawn  from  their  existence,  to  that  of  primitive  fibrils  during  life  in  the  higher 
animals. 

The  answer  to  the  question,  whether  primitive  fibrils  exist  during  life  or  not,  in  fact,  de- 
pends very  much  upon  the  meaning  of  the  words.  If  it  be  meant  that  the  muscular  bundle 
is  like  a  rope,  the  fibrils  being  the  separate  strands,  united  by  "  a  homogeneous,  tenacious 
substance," — we  should  say  that  nothing  of  the  kind  exists  during  life.  If,  on  the  other 
hand,  it  be  meant  only  that  the  molecules  of  the  muscle  are  so  arranged  as  to  break  up  more 
readily  and  more  frequently  in  the  longitudinal  direction  than  any  other  (just  as  a  bar  of 
wrought  iron  would  tear  into  longitudinal  fibres  rather  than  in  any  other  way,  though  it 
could  by  no  means  be  said  that  it  was  composed  of  longitudinal  fibres),  why,  there  can  be 
no  question  that  such  is  the  fact.  The  behavior  of  a  muscular  fasciculus,  under  the  alter- 
nate action  of  acetic  acid  and  ammonia,  is  as  instructive  with  regard  to  this  point,  as  that  of 
bundles  of  connective  tissue. 

The  existence  of  varicosities  of  the  fibrils  must  depend  very  much  upon  their  state  of  ex- 
tension. Normally,  they  do  not  exist,  unless,  perhaps,  the  fibril  has  been  split  off  from  the 
very  edge  of  a  bundle,  where  the  sarcous  elements  often  project  strongly.  When  very  much 
stretched  again,  since  the  sarcous  elements  are  more  solid  and  resisting  than  the  matrix,  they 
will  form  knots,  and  the  fibrils  will  appear  more  or  less  varicose.  The  great  majority  of  in- 
stances in  which  the  fibrils  appear  varicose,  however,  depend  on  imperfect  definition — and 
the  same  may  be  said  of  supposed  zigzag  bendings;  while  the  spiral  fancies,  on  the  other 
hand,  are  more  probably  connected  with  an  imperfect  judgment. 

Recently,  Drs.  Sharpey  ("  Quain's  Elements")  and  Carpenter  ("  Manual  of  Physiology") 
have  advocated  a  view,  the  former,  however,  with  some  doubts  (to  which  Professor  Kolliker 
does  not  refer),  founded  upon  an  examination  of  the  preparations  of  muscular  fibrils,  made 
by  Mr.  Lealand.  They  distinguish  quadrilateral  dark  spaces  in  the  fibrillae,  each  of  which 
is  set,  as  it  were,  in  a  transparent  frame  of  the  same  shape;  these  joined  together  constitute 
the  fibril,  the  lines  of  junction  of  the  frames,  or  "cells"  being  indicated  by  a  dark  line.  We 
have  repeatedly  seen  the  appearances  which  are  thus  described;  but  so  far  as  we  have 
been  able  to  discover,  they  invariably  arise  from  that  peculiar  interposition  of  rows  of  mi- 
nute paler  sarcous  elements,  between  the  ordinary  broad  dark  ones,  to  which  we  have  re- 
ferred above  in  describing  the  muscles  of  insects. 

Very  often,  the  finer  sarcous  elements  are  completely  wanting,  as  in  the  thoracic  muscles 
of  Insects,  in  the  muscles  of  the  Frog,  and  in  many  of  the  bundles  in  Mammals;  and  in 
these  cases  there  is,  of  course,  no  evidence  at  all  of  the  existence  of  any  such  "cells." 

In  conclusion,  we  may  state  the  view  which  we  are  led  to  take  of  the  structure  of  striped 
muscle,  in  a  few  words.  In  a  homogeneous,  transparent  matrix,  definite  particles  are  im- 
bedded— the  sarcous  elements, — which  are  arranged  side  by  side,  in  even  transverse  rows. 
In  some  cases  the  sarcous  elements  are  all  of  one  size;  in  others,  they  are  alternately  larger 
and  smaller.  The  reason  of  this  difference  does  not  at  present  appear,  but'it  is  very  pos- 
sibly connected  with  the  nutrition  of  the  muscle.  The  matrix  usually  tends  to  break  up 
into  longitudinal  bands — the  "  fibrils," — which  have  the  diameter  either  of  a  single  sarcous 
element,  or  of  some  multiple  thereof;  it  likewise  tends  to  break  up  in  the  transverse  direc- 
tion, giving  way  between  the  pairs  of  rows  (discs)  of  sarcous  elements ;  but  these  cleavage 
lines  are  no  indication  of  the  existence  of  discs  or  fibrils,  as  such  in  the  unaltered  muscle. 
The  sarcolernma  is  simply  the  outer  portion  of  the  matrix,  and  its  demonstrability  as  a  sepa- 
rate structure  depends  upon  the  extent  to  which  it  is  developed,  and  the  amount  of  chemical 
change  which  it  may  have  undergone  relatively  to  the  inner  portion. — TBS.] 


230  SPECIAL    HISTOLOGY. 

These  secondary  muscular  fasciculi,  as  they  are  termed,  are,  each  of 
them,  enclosed  by  a  special  envelop  of  connective  tissue,  and,  several 
together,  united  by  stronger  membranes  into  tertiary  fasciculi,  which, 
lastly,  in  a  greater  or  less  number,  unite  and  constitute  the  separate 
bellies  of  the  muscle,  or  muscles  themselves.  If  the  muscular  fasciculi 
are  placed  in  the  same  plane,  they  constitute  the  membranous  or  flat 
muscles  ;  and  when  disposed  in  a  thick  bundle,  the  elongated  or  columnar 
muscles.  The  muscles  consequently  are  aggregations  of  numerous, 

larger  and  smaller  secondary 
and  tertiary  fasciculi,  the 
sheaths  or  perimysium  of 
which  constitute  a  connected 
system,  in  which  that  por- 
tion which  surrounds  the  en- 
tire muscle,  as  the  perimy- 
sium externum  or  muscular 
sheath  (vagina  muscularis), 
is  to  be  distinguished  from 
the  more  internal  elements 
immediately  surrounding  the 
larger  and  smaller  fasciculi  and  the  muscular  fibres — the  perimysium 
internum.  The  thickness  of  the  secondary  fasciculi  varies  from  J  to  i 
a  line ;  that  of  the  tertiary  and  still  larger  bundles,  which  are  most 
evident  in  muscles  with  coarse  fibres  (glutceus  maximus,  deltoideus],  is 
so  various,  and  the  division  of  the  muscle  in  these  more  remote  constitu- 
ents is  so  arbitrary,  that  there  is  nothing  specially  to  be  said  with  re- 
spect to  them. 

The  muscular  sheaths  or  envelops,  perimysium,  composed  of  con- 
nective tissue,  which  are  for  the  double  purpose  of  conveying  the  vessels 
and  nerves  of  the  muscles,  and  of  connecting  the  muscular  fibres  and 
supporting  them  when  in  action,  vary  in  thickness  according  to  the 
greater  or  less  size  of  the  groups  of  fasciculi  surrounded  by  them. 
They  are  always,  however,  delicate,  dull-white,  non-glistening  tunics, 
consisting  of  common  connective  tissue,  and  minute,  isolated  or  anasto- 
mosing elastic  fibres,  of  at  most  O001  of  a  line  in  thickness^  the  latter 
occurring  in  greater  number,  especially  in  the  perimysium  externum, 
which  may,  consequently,  very  properly  and  conveniently,  be  regarded 
as  a  semi-elastic  membrane,  and  its  function  estimated  in  accordance 
with  this  structure.  In  all  muscles,  especially  in  those  of  a  more  lax 
construction,  a  certain  number  of  adipose  cells  of  the  usual  kind  (fre- 

FiO.  94. — Transverse  section  from  the  redus  capitis  anticus  major  of  Man,  magnified  350 
diameters:  a,  external  perimysium;  6,  perimysium  internum;  c,  primitive  fasciculus  and 
secondary  muscular  fasciculus. 


THE    MUSCULAR    SYSTEM.  231 

quently  containing  beautiful  fat-crystals)  occur,  and  in  fat  persons  they 
are  found  quite  in  the  interior. 

[It  was  formerly  supposed  that  the  primitive  muscular  fasciculi  ran 
in  a  perfectly  straight  direction  towards  their  insertions,  without  dividing 
or  anastomosing ;  but  this  is  not  correct.  Recent  investigations,  made 
partly  alone,  partly  with  the  assistance  of  Dr.  Corti,  have  demonstrated 
the  anastomosis  of  the  fasciculi  of  striped  muscles  in  the  hearts  probably 
of  all  Mammalia.  We  observed  anastomosing  fasciculi  in  Man,  in  the 
Rabbit,  Dog,  Cat,  Calf,  Frog,  Heron,  andLeydig  has  seen  them  in  the  Ruff. 
In  the  Mammalia,  and  in  Man,  they  are  frequent,  and  extremely  delicate, 
and  the  anastomosis  occurs  by  means  of  short  transverse  or  oblique  branches 
extending  between  parallel  fasciculi.  In  the  larynx,  oesophagus,  pharynx, 
and  the  tongue  of  the  Rabbit,  nothing  similar  to  this  was  met  with,  but  we 
found  in  the  tongue  of  the  Frog,  immediately  under  the  mucous  membrane 
(which  is  readily  removed  in  boiled  preparations),  the  most  delicate  divi- 
sions, although  no  anastomoses.  Fasciculi  of  0*03  of  a  line  or  more,  could 
be  observed  to  form,  by  successively  dividing  at  acute  angles,  large 
bundles  of  fine  branches  (the  finest,  0-0012  to  0-0016  of  a  line),  which 
were  inserted  into  the  mucous  membrane  of  the  tongue  between  its 
glands.  I  have  seen,  also,  in  the  lymph-heart  of  frogs,  an  anastomosis 
of  the  striped  muscles  similar  to  that  occurring  in  the  heart,  and  Dr. 
Leydig  (Zeitschrift  fur  Wissenschaftliche  Zoologie,  Bd.  I.  Heft  2,  3), 
has  observed  anastomoses  in  the  muscles  of  Paludina  virspara,  which 
genetically  correspond  to  the  striped  muscles.  In  the  muscles  of  the 
trunk  and  extremities  in  Man  and  in  the  Mammalia,  I  have  never  been 
able  to  discover  even  the  trace  of  an  anastomosis,  although  it  occa- 
sionally appeared  to  me,  as  if  some  fasciculi  before  or  at  their  connec- 
tion with  tendons,  divided  within  a  short  space  two  or  three  times.  I 
have  certainly  seen  this  division  in  the  tails  of  batrachian-larvse,  where 
single  fibres  at  their  insertion  into  tendons  separated  into  from  three  to 
five  conical  branches.  (From  Kolliker's  Micr.  Anat.,  1. 1,  p.  210.) — DaC.] 

§  79.  Connection  of  the  Muscles  with  other  parts. — The  muscular 
fibres  are  connected  with  the  movable  parts,  the  bones,  cartilages,  arti- 
cular capsules,  the  skin,  &c.,  partly  in  a  direct  manner,  partly  with  the 
intervention  of  fibrous  elements,  the  tendons,  fascice,  certain  forms  of 
muscular  ligaments  and  membranes  (lig.  interossece,  membrance,  obtura- 
torice).  Those  muscles  which  are  attached  either  wholly,  or  at  one  or 
the  other  end  without  the  intervention  of  tendons,  constitute  on  the 
whole  the  smaller  number.  Where  the  muscular  fibres  arise  directly 
from  bone  (obliqut,  iliacus,  psoas,  glutsei,  &c.)  and  cartilage  (transversus 
abdominis,  diaphragm),  or  rest  immediately  upon  those  structures  (ser- 
rati,  omohyoideus,  sterno-hyoideus,  aural  muscles),  they  never  extend 


232  SPECIAL    HISTOLOGY. 

further  than  to  the  periosteum  or  pericliondrium,  terminating  abruptly 
on  those  membranes,  with  the  fibres  of  which  they  are  not,  in  any  way, 
continuous,  nor  do  they  come  into  immediate  contact  with  the  bone  or 
cartilage.  Where  the  muscles  extend  to  the  skin,  they  either  expand 
immediately  beneath,  and  without  any  connection  with  it,  or  radiate  in 
it,  in  the  form  of  larger  or  smaller  divergent  fasciculi  (facial  muscles) ; 
in  which  case  they  appear  to  be  inserted,  at  all  events  occasionally,  at 
once  into  the  filamentary  processes  of  connective  tissue.*  But  the  pre- 
cise mode  of  connection  of  these  tissues  has  not  yet  been  ascertained. 

§  80.  The  sinews,  tendons,  are  brilliant,  white  or  yellowish  structures, 
composed  almost  entirely  of  connective  tissue.  They  are  subdivided, 
according  to  their  figure,  into  the  rounded,  cord-like,  true  tendons,  and 
into  membranous  aponeuroses  (centrum  tendineum,  galea,  tendons  of 
the  abdominal  muscles,  latissimus  dor  si,  cucullaris,  &c.).  The  two 
forms,  either  in  their  external  configuration  or  internal  constitution,  do 
not  admit  of  definite  distinction ;  they  consist  of  connective  tissue, 
which  is  characterized  by  the  parallelism  of  its  elementary  fibres,  its 
consistence,  and  its  poverty  in  elastic  filaments.  The  elements  of  the 
connective  tissue,  the  fibrillce,  may  be  readily  perceived,  in  fresh  tendon, 
to  be,  as  they  are  everywhere,  extremely  minute.  In  the  cord-like 
tendons,  they  are  slightly  wavy  in  their  course,  all  perfectly  uniform  in 
size,  parallel  to  the  long  axis  of  the  tendon,  and  in  the  recent  state  so 
closely  approximated,  that  the  demonstration  of  the  existence  of  primi- 
tive fasciculi  is  not  easy.  Such  fasciculi,  however,  do  exist,  having  a 
breadth  of  0*006— 0*008  of  a  line,  and  a  rounded  polygonal  figure,  as 
may  be  seen,  especially  in  transverse  sections  of  dried  tendons,  particu- 
larly on  the  addition  of  alkalies.  But  in  the  natural  state  they  are  so 
firmly  united  that  they  cannot  be  isolated. 

On  the  other  hand,  in  true  tendons,  in  the  recent  state,  secondary 
and  tertiary  fasciculi  are  very  evident  (Fig.  95).  Delicate  dissepiments, 
in  fact,  of  loose  connective  tissue,  penetrate  the  substance  of  the  tendon, 

*  [The  insertion  of  muscles  without  the  intermediation  of  tendons,  directly  into  the  con- 
nective tissue  of  the  skin  and  mucous  membranes,  is  seen  very  beautifully  in  the  tongue  and 
in  the  facial  muscles  of  Mammals.  The  former  case  has  been  well-described  by  Dr.  Salter 
(Todd's  "  Cyclopaedia,"  article  "  Tongue") ;  the  latter  may  be  examined  with  great  ease  in 
the  levator  labii  superioris  of  the  Rat.  Here  the  muscular  bundles  run  in  the  subcutaneous 
connective  tissue,  keeping  a  pretty  even  diameter  until  they  nearly  reach  their  insertions. 
They  then  divide  into  many  branches,  each  of  which  either  tapers  off  to  a  conical  extremity, 
or  divides  into  a  number  of  delicate  pointed  processes.  In  either  case,  the  ends  of  the  mus- 
cular fibre  gradually  or  suddenly  lose  their  striation,  and  pass  directly  into  the  irregular 
nucleated  bands  of  the  connective  tissue.  No  sarcolemma  can  be  demonstrated  in  the 
branched  ends  of  the  muscles,  and  the  bands  of  the  connective  tissue  are  directly  continuous 
with  the  matrix  of  the  muscle;  the  change,  from  the  one  to  the  other,  being  evidenced 
merely  by  the  appearance  of  the  sarcous  elements.  Nothing  can  afford  a  more  complete 
proof  of  the  homology  between  the  pseudo-fibril lated  tissue  of  muscle  and  that  of  connective 
tissue,  than  what  we  find  here. — TRS.] 


THE    MUSCULAR    SYSTEM. 


233 


Fig.  95. 


and  by  their  mutual  connection  form  a  continuous  system  of  parallel 
tubes,  thus  dividing  the  tendinous  fibrils  or  primitive  fasciculi  into 
numerous  larger  or  smaller 
groups.  Secondary  fasciculi, 
mostly  of  a  polygonal,  or  per- 
haps rounded  or  elongated 
figure,  and  having  a  diameter 
of  0-03-0-06  of  a  line,  may  be 
very  readily  distinguished  ;  and 
tertiary  fasciculi,  with  poly- 
gonal contours,  of  0-1-0-05  of 
a  line,  and  more  in  diameter, 
and  bounded  by  rather  stronger 
dissepiments ;  there  are,  also, 
generally  apparent,  still  larger 
subdivisions,  composed  of  nume- 
rous tertiary  fasciculi,  and 
which,  being  closely  united  in 
very  various  numbers  and 
groups,  by  a  common  envelop 
of  lax  connective  tissue,  constitute  the  tendon  itself.  The  aponeuroses 
are  constituted  either  in  the  same  way  as  the  true  tendons,  and  consist 
of  several  layers  of  parallel,  secondary  fasciculi,  disposed  contiguously 
in  the  same  plane,  or  more  resemble  the  fibrous  membranes,  and  present 
primary  and  secondary  fasciculi  decussating  in  two  or  more  directions 
(abdominal  muscles,  diaphragm). 

Fine  elastic  fibres  (the  so-termed  nuclear  fibres)  occur  in  the  secondary 
fasciculi  of  all  tendons,  in  various  conditions  of  development :  sometimes 
as  a  series  of  slender  fusiform  cells  connected  by  delicate  processes ; 
sometimes  as  fully-formed  fibres  of  uniform  thickness,  or  as  isolated 
fusiform  cells.  The  arrangement  of  these  elastic  elements  is  uniform 
throughout,  and  they  run  at  regular  distances,  parallel  to,  and  among 
the  fasciculi  of  connective  tissue.  -  Consequently,  in  the  transverse 
section  of  a  tendon,  the  dark  ends  of  the  elastic  fibres  are  apparent, 
distributed,  at  constant  distances  of  0-007-0-008  of  a  line  apart,  over 
the  whole  section.  But,  besides  these  stronger  elastic  filaments,  mea- 
suring from  0-0005— 0-001  of  a  line,  there  exist  in  most,  perhaps  in  all 
tendons,  extremely  delicate  fibrils  of  0-0002-0-0004  of  a  line,  connecting 
the  former  in  various  directions,  so  that  in  reality  there  is,  in  every  ten- 
don, an  elastic  network,  penetrating  and  entwining  the  fasciculi  of  con- 

FIG.  95. — Transverse  section  of  a  tendon  of  the  calf,  magnified  20  diameters:  a,  secondary 
fasciculus;  6,  tertiary ;  c,  nuclear  fibres  not  quite  in  transverse  section,  but  appearing  as 
little  streaks  in  the  former ;  d,  interstitial  connective  tissue. 


234 


SPECIAL    HISTOLOGY. 


nective  tissue.     These  fibrils  may  also  be  distinguished  on  a  transverse 

section,  as  minute  dark  points,  or  as  lines 
radiating  from  the  coarser  points  exhibited 
in  the  section  (Fig.  96) ;  and  they  are  still 
more  evident  in  longitudinal  sections,  in 
which,  more  especially,  the  whole  of  the 
fibrous  system  just  described  comes  very 
readily  into  view.  In  such  sections,  also, 
it  is  evident  that,  in  every  case  in  which 
the  formative  cells  of  which  the  fibres  are 
constituted  still  retain  a  certain  degree  of 
independence,  very  distinct  elongated  nu- 
clei exist  in  them.  Besides  these  elastic 
fibres,  the  tendons,  in  certain  situations, 
contain  cartilage-cells  (vid.  infra),  as  well  as  common  fat-cells,  particu- 
larly in  the  more  lax  tendons,  as  in  the  tendinous  fibres  of  the  in- 
tercostal muscles,  of  the  triangularis  sterni,  masseter,  &c. 

The  transversely  banded  aspect  of  the  tendons,  to  which  their  glisten- 
ing appearance  is  due,  depends  simply  upon  the  numerous  curves  of 
their  fibrils,  which  correspond  with  each  other  throughout  the  fasciculus  ; 
this  appearance  is  destroyed  when  the  tendon  is  forcibly  stretched,  and 
merely  indicates  its  innate  elasticity,  which  comes  into  play  in  the 
relaxed  condition. 


The  primary  tendinous  fasciculi,  according  to  Bonders  and  Mole- 
schott,  are  seen  in  transverse  sections  treated  with  potass.  This  reagent, 
according  to  them,  separates  the  secondary  fasciculi  into  smaller  ones, 
each  of  which  consists  of  from  5  to  10  primitive  fasciculi.  In  moistened 
transverse  sections  of  dried  tendon  of  man  and  the  mammalia,  I  can 
very  distinctly  recognize  the  primitive  fasciculi,  although  they  have 
extremely  delicate  outlines.  The  appearance  thus  obtained  affords  an 
indistinct  image  of  that  presented  in  a  transverse  section  of  muscle. 
Even  the  very  fibrils  are,  in  this  way,  rendered  distinct,  a  circumstance 
which  appears  to  me  of  the  greatest  importance.  When  a  transverse, 
not  a  longitudinal,  section  of  tendon  moistened  with  water  or  acetic  acid 
is  examined,  there  will  be  observed  in  all  the  secondary  fasciculi,  or  in 
the  primary  when  they  can  be  distinguished,  if  not  in  all,  yet  in  most 
cases,  an  extremely  regular  and  minute  punctation,  nearly  like  that  of 
the  muscular  fasciculi  (Fig.  90),  only  not  quite  so  distinct.  The  appa- 
rent granules  are  pale,  round,  of  the  same  diameter  as  the  tendinous 
fibrils  which  are  obtained  in  other  ways,  and  can  be  explained  in  no 
other  manner  than  as  being  the  transverse  sections  of  such  fibrils. 


FIG.  96. — Tendon  of  the  tibialis posticus  (Man),  magnified  60  diameters:  a,  secondary  fas- 
ciculi ;  6,  thicker  nuclear  fibres ;  c,  interstitial  connective  tissue. 


THE    MUSCULAR    SYSTEM. 


235 


These  facts,  better  than  any  other,  contradict  Reichert's  view,  according 
to  which  the  tendinous  tissue  is  composed  of  a  homogeneous  substance. 
( Vid.  §  24,  note.) 

§  81.  Connections  of  the  Tendons  with  other  parts. — The  tendons  are 
connected  on  the  one  side  with  the  muscles,  and  on  the  other  with  the 
various  parts  moved  by  the  muscles.  Even  by  the  naked  eye,  it  may 
be  seen  that  the  former  connection  is  effected  in  the  one  case  in  such 
a  way  that  the  tendon  and  muscle  are  continued  into  each  other  recti- 
linearly,  and  in  the  other  so  that  the  muscular  fibres,  with  rounded 
extremities,  join  the  borders  and  surfaces  of  the  tendons  and  aponeuroses 
at  an  acute  angle,  as  in  the  instance  of  the  penniform  muscles.  The 
microscopic  conditions  in  these  two  cases  are  widely  different.  In  the 
former,  the  muscular  fasciculi  pass  immediately  into  those  of  the  tendon, 
in  such  a  way  that  no  sharply-defined  limit  exists  between  the  two  tissues, 

Fig.  97. 


and  the  entire  fasciculus  of  muscular  fibrils  is  con- 
tinuous with  a  nearly  equal-sized  bundle  of  tendinous 
fibrils  (Fig.  97).  Extraordinary  as  it  may  sound,  I 
must  say — in  order  to  describe  the  impression  that 
this  sort  of  conjunction  of  muscle  and  tendon  gives 
me — that  it  is  that  of  a  continuous  connection  of  the 
muscular  and  tendinous  fibrils.  Where  the  muscular 
fasciculi  join  the  tendons  and  aponeuroses  at  an  acute 
angle,  we  find,  in  complete  contrast  with  the  condition 
just  described,  an  abrupt  limit  between  the  muscle 
and  tendon  (Fig.  98).  For,  in  this  case,  the  fibres  of 
the  muscle  really  end,  for  the  most  part,  obliquely 
truncated,  with  a  slightly  conical  projecting  terminal 

FIG.  97. — A  primitive  fasciculus :  a,  from  one  of  the  internal  intercostal  muscles  of  Man, 
continuous  into  a  tendinous  fasciculus,  6,  into  which  it  passes  without  any  defined  limit. — 
Magnified  350  diameters. 

FIG.  98. — Disposition  of  the  muscular  fibres  at  their  oblique  insertion  into  the  tendon  of 
the  gastrocnemius  (Man):  a,  a  portion  of  the  tendon  cut  longitudinally;  6,  muscular  fibres 
with  slightly  conical  or  truncated  extremities,  affixed  in  small  depressions  on  the  inner 
aspect  of  the  tendon,  to  the  border  of  which  the  perimysium  internum,  c,  is  connected. — Mag- 
nified 350  diameters. 


236  SPECIAL    HISTOLOGY. 

surface,  or,  more  rarely,  perceptibly  attenuated,  though  always  rounded, 
and  are  attached  at  a  more  or  less  acute  angle  to  the  surfaces  of  the 
tendons  and  aponeuroses,  and  on  the  borders  of  the  former.  Notwith- 
standing this,  however,  the  connection  between  the  two  tissues  is  of  the 
most  intimate  kind.  The  extremities  of  the  primitive  fasciculi  are  in- 
serted into  minute  pits  in  the  surface  of  the  tendon,  whilst,  at  the  same 
time,  the  connective  tissue  between  them,  the  perimysium  internum,  is 
continuous  with  that  on  the  surface  of  the  tendon.  These  relations  are 
best  observed  in  muscles  which  have  lain  a  long  time  in  spirit,  or  been 
boiled ;  in  which,  also,  the  sacciform  blind  extremity  of  the  sarcolemma 
may  occasionally  be  clearly  seen.  The  last-described  condition  occurs 
whenever  muscular  fibres  and  tendons  meet  obliquely,  consequently  in  all 
semiperiniform  and  penniform  muscles  ;  in  those  whose  tendons  of  inser- 
tion commence  as  membranous  expansions  (soleus,  gastrocnemius,  &c.), 
and  which  arise  from  the  surfaces  of  fasciae,  bones,  and  cartilages. 
Where,  on  the  other  hand,  aponeuroses  or  tendons,  with  their  elemen- 
tary tissues,  join  muscles  in  a  straight  line,  a  real  transition,  for  the 
most  part,  takes  place  between  the  tendinous  fasciculi  and  muscular 
fibres,  but  not  always,  for,  even  in  such  apparently  rectilinear  transition 
of  muscles  into  tendons,  there  is  frequently  an  oblique  insertion  of  the 
former,  with  free  extremities,  though  at  very  acute  angles ;  in  such 
cases,  for  instance,  as  where  tendons  penetrate  deeply  into  the  substance 
of  a  muscle,  and  there  divide  into  separate  fasciculi.  From  what  I  have 
hitherto  observed,  there  are  many  muscles  in  which  all  the  fasciculi 
connected  with  tendons  begin  or  terminate  free,  and  indeed  scarcely 
one  in  which  this  is  not  the  case,  with  a  greater  or  less  number  of  fas- 
ciculi ;  whence  it  may  be  deduced,  as  a  general  rule,  that  the  tendons 
have  for  the  most  part  a  less  diameter  than  the  muscles. 

Besides  muscles,  tendons  are  connected  with  bones,  cartilages,  fibrous 
membranes  (sclerotica,  sheath  of  the  optic  nerve,  tendinous  fasciae), 
ligaments,  and  synovial  membranes  (subcruralis,  &c.).  With  the  first- 
named  textures,  the  connection  is  either  indirect,  with  the  intervention 
of  the  periosteum  and  perichondrium,  into  the  similarly  constituted 
elements  of  which  the  tendinous  fibres,  for  the  most  part,  are  continuous, 
or  to  the  thickness  of  which  they  appear  to  add  or  direct.  In  the  latter 
case  (tendo  Achillis,  tendons  of  the  quadriceps,  pectoralis  major,  del- 
toideus,  latissimus  dor  si,  ilio-psoas,  glutcei,  &c.),  the  tendinous  fasciculi 
rest,  at  an  acute  or  right  angle,  on  the  surface  of  the  bones,  and  become 
attached,  without  the  intervention  of  the  periosteum,  which  is  wholly 
wanting  in  these  situations,  to  all  the  elevations  and  depressions  of  the 
surface  (Fig.  99).  Close  to  the  bones,  the  tendons  frequently  contain, 
throughout  a  certain  extent,  delicate,  isolated  cartilage  cells,  which 
are  sometimes,  however,  contiguous  and  disposed  in  small  rows.  In 
exceptional  cases,  I  have  also  seen  the  tendinous  fibrils,  at  their  extre- 


THE    MUSCULAR    SYSTEM. 


23T 


mities  next  the  bctae,  entirely  incrusted  with  calcareous  salts,  in  the 
form  of  granules  (ossified).     In  fibrous  membranes,  the  tendons  cease 


Fig.  99. 


quite  imperceptibly,  and  without  any  interruption  of  continuity  (tensor 
fascice,  biceps  humeri). 

In  man,  I  must  positively  deny  that  the  tendinous  fasciculi  are  ever 
connected  merely  with  the  sarcolemma  (Reichert).  Nor  could  I  satisfy 
myself  that  this  is  the  case  in  the  River-crab,  in  which  the  tendons,  it 
may  be  remarked,  consist  of  chitine.  Whilst  other  animals  have  afforded 
indubitable  evidence  of  the  existence  of  the  same  conditions  as  in  man, 
the  Frog,  in  particular,  presents  evidence  of  this  fact ;  in  the  tadpole 
of  which,  owing  to  the  sparing  development  of  pigment  in  the  tail,  the 
transition  of  the  extremities  of  the  muscular  fibres,  which  are  frequently 
divided  into  three  and  five  serrations,  into  the  same  number  of  minute 
tendons,  may  be  very  distinctly  seen.  In  the  caudal  muscles,  also,  of 
the  Cod,  I  noticed,  very  distinctly,  the  continuous  connection  of  the 
tendons  and  muscles  ;  in  this  case,  owing  to  the  shortness  of  the  muscles, 
many  muscular  fibres  were  even  seen  in  their  entire  length,  together 
with  the  tendinous  fasciculi  at  each  end.* 

FIG.  99. — Insertion  of  the  tendo  JLchillis  into  the  calcaneum  of  a  Man  sixty  years  old :  •#, 
bone  with  lacunse,  a;  canalli  and  fat-cells,  6;  J3,  tendon  with  tendinous  fibrils  and  cartilage 
cells,  c. — Magnified  300  diameters. 

*  [There  can  be  no  doubt  that  both  the  modes  of  connection  between  muscles  and  their 
tendons,  described  above,  exist.  Is  it  not  possible  that  the  gradual  transition  or  the  sharp 


238  SPECIAL    HISTOLOGY. 

§  82.  Accessory  organs  of  the  Muscles  and  Tendons. — A.  The  mus- 
cular envelops  or  fascia?  are  fibrous  membranes  surrounding  single 
muscles  or  entire  groups  of  muscles,  together  with  their  tendons.  They 
differ  in  structure  according  to  the  degree  in  which  they  partake  of  the 
character  of  tendons  and  ligaments,  or  of  simple  muscular  sheaths;  in 
the  one  case  presenting  that  of  tendons,  and  in  the  other  of  membranes 
composed  of  connective  tissue  and  elastic  fibres.  In  the  former  case 
they  'are  white  and  glistening,  and  exhibit,  in  all  respects,  the  structure 
of  tendons  and  aponeuroses ;  in  the  latter  they  frequently  contain  a 
larger  quantity  of  fine  elastic  fibres  in  their  connective  tissue,  and  in 
some  places  may  even  assume  the  structure  and  dull-yellow  aspect  of 
the  elastic  membranes  (via1.  Fig.  49),  and  contain  a  close  elastic  network 
of  the  strongest  kind.  The  fascia?  are  always  of  the  tendinous  character, 
where  for  some  mechanical  purpose  a  tough  unyielding  structure  is 
requisite.  They  are  of  this  kind,  therefore: — 1.  At  their  origin  from 
bones.  2.  Where  muscles  arise  from  them,  and  they  are  of  the  nature 
of  aponeuroses.  3.  Where  tendons  radiate  into  them,  and  they  them- 
selves act  as  terminal  tendons.  4.  Where  thickened  portions  of  them 
supply  the  place  of  ligaments.  On  the  other  hand,  they  are  more  or 
less  elastic  where  they  constitute  a  firm  envelop  to  the  muscles,  but,  at 
the  same  time,  one  which  does  not  impede  their  changes  in  form.  This 
is  their  character,  especially  in  the  middle  of  the  limbs. 

[The  membranes  interosseoe  (forearm,  leg,  foramen  ovale\  which  are 
not  usually  reckoned  among  the  fasciae,  are  not  apparently  of  the  nature 
of  ligaments  of  the  bones,  but  rather  of  intermuscular  ligaments.  The 
plantar  and  palmar  aponeuroses  serve,  in  part,  as  tendons  for  the  smaller 
muscles  of  the  hand  and  foot,  but  chiefly  as  ligaments  for  the  retention 
of  the  flexor  tendons,  in  which  respect  they  are  analogous  to  the  lig.  cruci- 
atum  carpi  dorsale,  &c.  In  them,  even  in  the  adult,  the  entire  course  of 
development  of  the  nuclear  fibres  (minute  elastic  fibres),  may  be  studied. 
Between  the  fasciculi  of  connective  tissue,  straight  series  of  10  to  20  and 
more,  thickly  placed,  elliptical  cells  of  0-006  to  0-012  of  aline,  with  round 

line  of  demarcation  between  the  muscle  and  its  tendon  may  have  some  connection  with  the 
age  and  completeness  of  the  particular  bundle  examined?  In  the  Frog,  we  have  noticed 
that,  among  neighboring  bundles,  some  exhibit  transitions  between  the  proper  muscular 
tissue  and  the  tendon,  while  others  have  the  former  very  sharply  defined ;  and  the  exami- 
nation of  the  insertion  of  the  triceps  extensor  cubiti  of  a  seven-months'  foetus  has  afforded  us 
the  most  evident  transitions  from  tendon  into  muscle,  although  the  insertion  of  the  bundles 
is  here  very  oblique.  The  best  way  of  expressing  the  mode  of  connection  of  muscles  with 
their  tendons,  perhaps,  would  be  to  say  that  the  matrix  of  the  muscle  and  the  matrix  of  the 
connective  tissue,  into  which  it  is  inserted,  whether  in  the  form  of  tendon  or  otherwise,  are 
invariably  continuous;  the  appearance  of  continuity  or  of  discontinuity  of  the  two  tissues, 
arising  solely  from  the  sudden  or  gradual  cessation  of  the  deposit  of  the  sarcous  elements  at 
their  point  of  junction. 

The  nature  of  the  corpuscles  which  are  to  be  found  at  the  junction  of  tendons  with  bones 
and  cartilages — Professor  Kolliker's  "cartilage-corpuscles" — has  been  adverted  to  in  the 
note  at  p.  97. — TRS.] 


THE    MUSCULAR    SYSTEM.  239 

nuclei,  and  2  to  6  minute  opaque  fat-granules,  occasionally  occur  ;  the 
cells  afterwards  disappear,  and  the  nuclei,  which,  on  the  addition  of 
acetic  acid,  appear  a  little  yellowish,  become  more  and  more  elongated, 
and  transformed  into  long,  slender,  straight,  or  slightly-curved  fibres, 
which  are,  finally,  conjoined  into  long  nuclear  fibres;  these  fibres,  how- 
ever, upon  the  whole  are  rare.  The  elongated  nuclei  are  not  always 
placed  in  a  straight  line,  one  behind  the  other,  but  frequently  in  an  ob- 
lique, and  in  various  other  directions.  In  this  way  are  produced  serpen- 
tine nuclear  fibres,  which,  even  when  fully  formed,  are  still  surrounded 
with  isolated  fat-granules,  and  lie  as  it  were  in  vacant  spaces  in  the  con- 
nective, tissue.  In  this  case,  consequently,  the  nuclear  fibres  are  not 
formed  from  the  nuclei  of  the  cells,  from  which  the  connective  tissue  is 
formed,  but  from  special  cells  of  a  temporary  nature;  which  circum- 
stance, were  the  fact  of  general  application,  would  make  it  intelligible, 
that  nuclear  fibres  may  both  surround  the  secondary  fasciculi  of  connec- 
tive tissue,  and  also  exist  without  any  such  tissue  (membranous  reticular 
expansions  of  nuclear  fibres,  "Micr.  Anat.,"  II.  1,  p.  226)]. 

B.  Ligaments  of  the  tendons. — The  tendons  are  retained  in  their  posi- 
tions by  various  ligaments.  Independently  of  certain  ligamentous  por- 
tions of  the  fasciae,  which,  being  attached  to  the  bones,  form  tubular 
processes  around  tendons,  or  otherwise  confine  them,  there  are  the  so- 
called  tendinous  sheaths  (lig.  vaginalia  tendinum),  as  for  instance  on  the 
flexor  tendons  of  the  fingers  and  toes,  where  they  are  formed  of  nume- 
rous successive  narrow  bands,  which  in  these  situations  serve  to  strengthen 
the  mucous  sheaths.  Other  ligaments  to  be  referred  to  this  class,  are 
the  lig.  carpi  proprium,  the  trochlea,  and  the  retinacula  tendinum. 

0.  Mucous  bursce  and  sheaths, — bursar  mucosce  et  vaginae  synoviales. — 
Where  muscles  or  tendons,  in  their  movements,  rub  upon  hard  parts 
(bones,  cartilages),  or  on  other  muscles,  tendons,  and  ligaments,  there 
are  found,  between  the  parts  in  question,  spaces  filled  with  a  slightly 
viscid  fluid,  which,  according  to  Virchow  (Wurzb.  "Verb."  II.  281), 
contain  not  mucus,  but  a  material  very  similar  to  colloid  matter,  and 
which  anatomists  have  been  used  to  regard  as  lined  with  a  special  mem- 
brane, a  synovial  membrane.  These  spaces  are  said  to  constitute  closed 
sacs  of  a  rounded  or  elongated  form,  which  either  simply  invest  the 
opposed  surfaces  of  bones  and  tendons,  bones  and  muscles,  &c., — bursce 
mucosce;  or  in  the  form  of  double,  although  connected  tubes,  cover  at 
the  same  time  the  surface  of  the  tendons,  and  of  the  parts  between 
which  the  tendons  play, — vagince  synoviales.  The  truth  of  the  matter 
is  this,  that  it  is  only  the  smallest  of  these  spaces  which  are  lined  with 
a  continuous  membrane;  most  of  them  are  in  many  situations  without 
such  a  lining.  With  respect  to  the  mucous  bursse,  those  appertaining  to 
the  muscles  (psoas,  iliacus,  deltoid,  &c.),  are,  eminently,  to  be  consi- 
dered as  continuous  sacculi,  whilst  in  those  belonging  to  the  tendons,  a 


240  SPECIAL    HISTOLOGY. 

membrane  can  only  be  detached  in  parts,  and  is  found  to  be  almost 
wholly  wanting  exactly  at  the  points  where  the  mutually  gliding  parts 
are  in  contact.  Precisely  the  same  thing  obtains  in  the  synovial  sheaths, 
among  which  the  common  sheaths  of  the  flexor  tendons  of  the  fingers 
and  toes,  only  in  a  certain  measure,  retain  the  form  of  a  so-termed 
serous  sac,  although,  even  in  this  case,  many  parts  of  the  surface  of  the 
tendons  are  without  any  such  membranous  lining.  Whence  it  would 
appear,  that  in  this  case,  as  in  many  others,  the  old  doctrine  of  the  ex- 
istence of  continuous  serous  sacs  requires  thorough  emendation.  In 
most  of  the  synovial  sheaths,  and  in  many  mucous  bursse,  are  found 
occasionally,  particularly  in  the  retinacula,  smaller  or  larger,  reddish 
fimbriated  processes,  exactly  resembling  those  of  the  joints,  and  which, 
in  like  manner,  are  nothing  but  vascular  processes  of  the  synovial  mem- 
brane. 

D.  Fibro-cartilages  and  sesamoid  bones. — The  tendons  of  some  muscles 
(tibialis  posticus,  peronceus  longus],  in  those  portions  which  run  in  the 
tendinous  sheaths,  contain,  imbedded  in  their  substance,  dense  semi-carti- 
laginous bodies,  which  are  known  under  the  name  of  sesamoid  cartilages 
(fibro-eartilagines  sesamoidece\  and  when,  as  occasionally  happens,  they 
become  ossified,  of  sesamoid  bones  (ossa  sesamoidea) ;  the  latter  occur 
normally,  imbedded  in  the  flexor  tendons  of  the  fingers  and  toes,  pre- 
senting one  surface  towards  an  articulation. 

Respecting  the  more  intimate  structure  of  the  last-mentioned  parts, 
the  following  is  to  be  remarked.  The  sesamoid  bones  consist  of  common, 
finely  cancellated  osseous  substance,  are  on  one  side  closely  surrounded 
by  tendinous  or  ligamentous  tissue,  and  on  the  other,  which  is  invested 
with  a  thin  layer  of  cartilaginous  substance,  project  into  an  articulation. 
The  ligaments  of  tendons,  in  correspondence  with  their  function,  possess 
exactly  the  same  firm  structure  as  that  of  the  tendinous  portions  of  the 
fasciae  and  of  the  tendons  themselves,  and  exhibit  occasionally  fine  elas- 
tic fibres  in  process  of  development,  or  the  round  formative  cells  of  such 
fibres  disposed  in  rows.  The  retinacula  tendinum  have  a  more  delicate 
structure ;  their  function  being  rather  to  convey  vessels  to  the  tendons, 
they  consequently  contain  chiefly  a  more  lax  connective  tissue,  with  fine 
elastic  fibres,  and  also  fat-cells.  The  mucous  bursse,  which  are  invariably 
thin-walled,  consist,  in  as  far  as  they  possess  a  distinct  membrane,  of 
fasciculi  of  connective  tissue,  crossing  each  other  in  the  most  various 
directions,  loosely  connected,  and  in  many  places  anastomosing,  toge- 
ther with  some  fine  elastic  fibres.  The  mucous  sheaths,  on  the  other 
hand,  in  agreement  with  their  double  function,  which  in  one  respect  is 
that  of  a  mucous  bursa,  and  in  another  that  of  ligaments  confining  the 
tendon  or  of  tendinous  sheaths,  present  in  their  thinner  parts  the  struc- 
ture of  bursce  mucosce,  and  in  the  thicker,  an  unmixed,  dense  connective 
tissue,  frequently  with  cells  disposed  in  rows,  which  pass  into  elastic 


THE    MUSCULAR    SYSTEM.  241 

fibres.  Both  of  these  kinds  of  sacs  are  lined,  on  the  inner  surface,  to- 
gether with  the  parts  contained  in  or  otherwise  bounding  them,  but  only 
in  places,  with  an  epithelium,  consisting  for  the  most  part  of  a  simple  layer 
of  nucleated  polygonal  cells  0-004-0-007  of  a  line  in  diameter.  The  parts 
which  are  bare  of  epithelium,  are : — many  portions  of  the  mucous  sheaths, 
and  the  tendons  lying  in  them,  and  certain  spots  of  the  bursce  mucosce 
themselves,  which  are  distinguishable  by  their  dull  lustre  and  yellowish 
aspect,  and  which  occur  especially  in  those  situations  where  the  tendons 
and  parts  surrounding  them  are  exposed  to  a  greater  degree  of  pressure. 
The  common  flexor  sheath  of  the  fingers  is  lined  throughout  with  epi- 
thelium; and  the  same  may  be  said  of  the  mucous  bursse,  in  which  it  is 
only  certain  loop-like  ligaments,  which  beyond  the  limits  of  the  bursae 
still  surround  the  tendons,  that  do  not  present  any  cellular  covering,  as 
is  the  case,  occasionally,  in  the  subscapularis  poplitceus,  &c. 

All  these  bare  places,  which  are  uncovered  by  epithelium,  invariably 
exhibit,  almost  throughout,  the  nature  of  fibre-cartilages,  the  dense  con- 
nective tissue  of  which  they  are  composed,  and  which  for  the  most  part 
is  furnished  with  but  few  elastic  elements,  containing  a  greater  or  less, 
often  a  very  considerable  number  of  cartilage-cells"  (Fig.  99),  amongst 
which,  the  most  frequent  are  rounded 
cells,  with  a  dark  contour,  although  by 
no  means  with  thick  walls,  measuring 
0-006-0-012  of  a  line,  with  a  roundish 
nucleus  of  0-003  of  a  line,  and  clear  fluid, 
with  or  without  some  minute,  opaque  fatty  granules.  Besides  these, 
there  are,  moreover,  elongated  cells,  with  one  or  two  nuclei ;  round, 
thin-walled  cells,  containing  1,  2-20  secondary  cells,  with  thick  walls, 
and  dark  contours  ;  the  mother-cells  measuring  as  much  as  0-02-0-03  of 
a  line ;  and  lastly,  elongated  cells,  with  concentric  deposits,  inclosing  a 
nucleus,  or  nucleated  secondary  cell.  In  the  tendons,  the  simpler  forms 
of  cells  almost  exclusively  occur,  and  the  cells,  although  frequently  ex- 
tremely numerous,  are  for  the  most  part  isolated,  or,  at  most,  disposed 
in  rows  or  groups  of  2-6,  which  are  contained  in  the  connective  tissue, 
both  superficially  and  more  deeply.  In  most  cases,  the  common  con- 
nective tissue  alternates  with  one  more  resembling  fibro-cartilage,  so 
that  the  tendon,  on  a  transverse  section,  presents  a  speckled,  white  and 
yellowish  aspect;  or  it  maybe, that  the  outer  surface  only  of  the  tendon 
contains  cartilage,  the  deeper  portions  retaining  their  usual  condition. 
Where  the  deposition  of  the  cartilage  cells  is  most  abundant,  the  tendons 
become  thickened,  or  even  studded,  as  it  were,  with  distinct,  fibro-carti- 
laginous  masses  (peroneus  longus,  tib.  posticus).  In  the  mucous  bursse 
and  the  other  parts  above  named,  the  cartilage  cells  are  placed,  not  un- 

FIG.  100. — Cartilage-cells  from  the  vaginal  ligaments  surrounding  the  tendons  of  the 
poplit&us,  magnified  350  diameters:  a,  cell  with  one;  6,  with  two  nuclei;  c,  cell  with  one; 
rf,  with  two  secondary  cells,  both  of  which  have  rather  thick  contents. 

16 


212  SPECIAL    HISTOLOGY. 

frequently,  in  closer  aggregation,  or  in  longer  rows  of  5-10  cells  or 
more,  in  which  rows  the  terminal  cells  are  invariably  the  smallest,  and 
the  middle  ones  the  largest.  On  the  cuboid  bone,  where  the  tendon  of 
the  peroneus  longus  passes  over  it,  there  is  a  layer  of  true  cartilage 
J-J  a  line  thick. 

The  vascular  processes  of  the  tendinous  sheaths  and  mucous  bursse, 
correspond  with  those  of  the  articulations,  only  that  they  are  for  the 
most  part  of  smaller  size. 

The  synovial  sacs  of  the  muscular  system  are  not  mere  meshes  of 
connective  tissue,  like  the  subcutaneous  mucous  bursse,  since  they  have, 
invariably,  an  epithelial  lining  in  certain  places  ;  they  bear  just  as  little 
resemblance,  however,  to  the  proper  serous  sacs  (pleura,  peritonaeum,  &c.), 
because,  with  a  few  exceptions,  their  epithelium  is  never  complete,  and 
also  because  the  cellular  coat  of  the  serous  membrane  is  almost  uni- 
versally wanting  entirely  in  some  spots.  The  synovial  sacs  of  the  mus- 
cular system,  on  the  other  hand,  and  the  synovial  capsules,  which  also 
never  possess  a  complete  epithelium,  and  frequently  communicate  with 
mucous  bursse  (quadriceps  femoris,  popliteus,  subscapularis,  &c.),  belong 
to  one  and  the  same  category,  and  diifer  in  some  points  from  the  serous 
sacs ;  with  respect  to  which,  however,  it  must  not  be  forgotten  that  transi- 
tionary  forms  between  these  two  kinds  of  sacs  exist. 

No  one  seems  to  have  remarked  upon  the  occurrence  of  cartilage  cells 
in  the  various  textures  which  go  to  the  construction  of  the  synovial  sacs 
of  the  muscular  system  (except  in  the  fibro-cartilages  of  the  tendons); 
and  the  more  so,  because  even  Henle  refers  the  fibro-cartilage  of  the 
tendinous  sheaths  to  his  interarticular  cartilages  (bandscheiben).  It  is 
quite  true  that  the  cartilage  cells,  while  often  occurring  isolated  in  the 
connective  tissue,  or  more  frequently  only  in  certain  spots  aggregated 
together,  are  not  always  readily  seen ;  they  may,  however,  be  recognized 
in  sufficiently  thin  sections,  and  very  distinctly  on  the  addition  of  acetic 
acid.  The  cell-membranes  are  not  in  this  case  utterly  destroyed,  any 
more  than  they  are  in  the  cartilage  cells  of  the  interarticular 
ligaments,  &c.,  and  no  doubt  can  be  entertained  as  to  their  being 
true  cartilage  cells,  W7hich,  Almost  without  exception,  exist,  not  as  a 
tissue,  but  rather  dispersed  in  the  connective  tissue.  Those  spots 
in  which  they  exist  in  great  quantity  may  be  described  as  fibro-car- 
tilaginous  places;  but  the  distinction  between  these  fibro-cartilages 
and  those  of  true  fibres  not  of  the  nature  of  cellular  tissue  (epiglottis, 
ossifying  bones),  must  not  be  lost  sight  of.  Genuine  cartilage,  as  on 
the  cuboid  bone,  I  have  never  as  yet  met  with  in  any  other  tendinous 
sheath;  not  even  in  the  sulcus  malleoli  externi  et  interni ;  in  the  sulcus 
of  the  heel ;  nor  in  the  sheath  of  the  peronceus  on  the  longus  calcaneum  ; 
in  which  situations,  cartilage  cells  are,  indeed,  everywhere  to  be  seen, 
but  only  scattered  in  the  connective  tissue. 


THE    MUSCULAR    SYSTEM. 


243 


With  respect  to  the  rows  of  cells  which  are  met  with  in  ligaments  of 
the  tendons,  and  in  the  tendinous  sheaths,  the  nuclei  of  which,  after  the 
disappearance  of  the  cell,  continue  to  grow  and  arrange  themselves 
together  in  the  form  of  nuclear  fibres,  I  cannot  avoid  remarking  upon 
their  close  resemblance  to  the  more  simple  cartilage  cells  of  the  ten- 
dinous sheaths  and  tendons,  a  resemblance  so  close,  that  I  should  almost 
be  inclined  to  indicate  it  as  marking  their  identity,  if  it  did  not  sound 
altogether  strange,  to  speak  of  a  transition  of  the  nuclei  of  cartilage  cells 
into  nuclear  fibres.  If  not  as  identical,  still  they  may  be  regarded  as 
analogous  formations  ;  and  the  rather  so,  because  in  almost  every  case 
where  cartilage  cells  occur  in  the  connective  tissue,  rows  of  cells  of  this 
kind,  and  their  relation  to  elastic  fibres  may  be  shown  to  exist,  as  well 
as  in  the  interarticular  cartilages,  or  ligamentous  discs  of  Henle,  as  they 
are  termed,  afterwards  to  be  described.  On  the  other  hand,  it  is  true, 
similar  rows  of  cells  are  to  be  found  in  the  palmar  fascia,  tendons  and 
ligaments,  although  those  structures  possess  no  indubitable  cartilage-cells. 

§  83.    Vessels  of  the  Muscles  and  their  accessory  Organs.     A.  Blood- 
vessels.— The  ramifications  of  the  larger  vessels  present  little  that  is 
peculiar.     The  trunks  reach  the  muscles  in  an  oblique  or  transverse 
direction  and  then  subdivide,  running 
in  the  perimymum  internum,  in  an 
arborescent  manner,  and  at  acute  or 
obtuse  angles,  so  that  every  part  of 
the  muscle  is  supplied  by  them.    The 
minutest  arteries   and   veins   usually      a. 
run  parallel  with  the  muscular  fibres, 
between  which  they  constitute  a  vas- 
cular  plexus,  so  characteristic   that, 
once  seen,  it   can  never  be  mistaken. 
The  interstices  of  the  plexus  are  rec- 
tangular, with  the  longer  sides  parallel 
to  the  longitudinal  axis  of  the  muscle, 
and  it  is  of  course  composed  of  two      ^ 
sets  of  vessels,  one  longitudinal,  which, 
as  is  shown  most  conclusively  in  trans- 
verse sections  of  injected  muscle,  lie 
in  the  fissures  between  two  muscular 
fasciculi,  or  in   the  irregular  spaces 
left  between  several  of  them,  and  the 
other  transverse,  which  -anastomosing 
in  various  ways  with  the  former,  surround  the  muscular  fibres. 


Fig.  101. 


Thus 


FIG.  101.— Capillary  vessels  in  muscle,  magnified  350  diameters:  a,  artery;    6,  vein; 
c,  capillary  plexus. 


244  SPECIAL    HISTOLOGY. 

each  separate  primitive  fasciculus  is  lodged,  to  a  certain  extent,  in  a 
plexus  of  capillaries,  and  being  surrounded  on  all  sides  by  them,  is 
very  abundantly  supplied  with  blood.  The  capillaries  of  muscle  are 
among  the  most  minute  in  the  human  body,  their  diameter  being  often 
less  than  that  of  the  blood-corpuscles  themselves.  In  one  of  Hyrtl's 
preparations,  they  measure  0-0025-0-003  of  a  line;  in  the  pectoralis 
major,  when  filled  with  blood,  0-002-0-003,  and  when  empty  0-0016- 
0-0020  of  aline. 

The  tendons  may  be  reckoned  amongst  those  parts  of  the  body  which 
are  the  most  scantily  supplied  with  blood-vessels.  The  smaller  tendons, 
in  the  interior,  present  no  trace  of  vessels,  whilst  externally,  in  the  more 
lax  connective  tissue  by  which  they  are  surrounded,  there  exists  a  wide- 
meshed  capillary  plexus.  In  the  larger  tendons,  a  few  vessels  occur  in 
the  superficial  layers,  and  in  the  largest,  by  means  of  the  microscope 
and  injection,  a  scanty  vascular  network  may  also  be  rendered  evident 
in  the  deeper  layers ;  but  even  in  this  case  the  innermost  portions  of  the 
tendon  are  entirely  without  vessels.  The  tendon-ligaments  present  the 
same  conditions  as  the  tendons,  only,  that  in  them  even  still  fewer  ves- 
sels can  be  perceived.  The  thinner  fascias,  also,  are  altogether  non- 
vascular  ;  sparing  ramifications,  exclusive  of  those  in  the  lax  connective 
tissue,  amply  supplied  with  blood-vessels,  which  covers  their  surface, 
are  found  in  the  thicker  fasciae,  such  as  the  fascia  lata.  The  synovial 
membranes  of  the  muscular  system,  on  the  other  hand,  are  very  vascular, 
and  especially  their  processes  ;*  with  respect  to  these  synovial  mem- 
branes, however,  since  they  agree  in  all  respects  with  the  synovial  capsules 
of  the  osseous  system,  nothing  further  need  be  remarked  in  this  place. 

B.  The  muscles  are  very  scantily  supplied  with  lymphatics  ;  the 
smaller  muscles,  in  fact,  such  as  the  omohyoid,  subcrural,  &c.,  have  none 
at  all,  either  in  their  substance  or  on  the  surface  ;  and  among  the  largest 
muscles,  it  is  only  in  some,  that  solitary  lymphatics,  measuring  J  and  J 
of  a  line  are  seen  accompanying  the  blood-vessels.  The  deep  or  mus- 
cular blood-vessels  in  the  extremities,  it  is  true,  are  accompanied  by 
lymphatics,  but  these  are  few  in  number  ;  and  from  the  latter  two  circum- 
stances, it  may  be  concluded,  that  even  the  larger  muscles  are  but  poorly 
supplied  with  these  vessels.  If  they  had  not  actually  been  observed  in 
the  fasciculi  in  certain  cases,  it  might  have  been  a  question,  whether 
muscles  in  general  did  possess  lymphatics  at  all ;  the  occurrence  of 
the  deep  lymphatic  vessels  proves  nothing  towards  this,  it  being  quite 
possible  that  the  contents  of  these  vessels,  scanty  as  they  are,  might  be 
derived  from  the  skin  (vola  manus,  planta  pedis,  &c.),  from  the  joints, 
or  perhaps  from  the  bones.  It  may  also  be  concluded,  that  if  a  few 

*  [The  vessels  generally  form  loops,  which  communicate  with  each  other  by  means  of 
delicate  branches,  and  which  can  readily  be  traced  to  the  extremity  of  each  process. — DaC.] 


THE    MUSCULAR    SYSTEM.  245 

lymphatics  really  exist  in  the  larger  muscles,  they  do  not  run  among  the 
secondary  fasciculi,  but  only  in  the  more  vascular  perimysium  between 
the  larger  and  more  lax  subdivisions,  and  especially  where  the  latter 
contains  adipose  tissue,  and  is  consequently  soft,  as,  for  instance,  in  the 
glutceus,  and  in  the  superficial  layers  of  the  muscles. 

Lymphatic  vessels  have  never  yet  been  noticed  in  tendons,  fasciae, 
and  the  synovial  capsules  of  the  muscular  system.  At  the  same  time, 
it  cannot  be  said,  at  all  events  in  the  latter  instance,  that  lymphatics 
may  not,  as  in  other  serous  membranes,  be  contained  in  the  sub-serous 
connective  tissue. 

§  84.  Nerves  of  Muscles. — The  distribution  of  the  muscular  nerves, 
with  respect  even  to  their  coarser  relations,  presents  considerable  pecu- 
liarity, it  being  evident,  in  most  muscles,  that  the  nerves  come  in  con- 
tact with  their  fibres  only  at  a  few  limited  points,  and  are  by  no  means 
connected  with  them  throughout  their  entire  length.  With  respect  to 
the  ultimate  termination  of  the  nerves,  it  may  be  stated  that  in  all 
muscles  there  exist  anastomoses  of  the  smaller  branches,  forming  the  so- 
termed  "plexuses."  These  anastomoses  among  the  larger  branches 
are  seen  chiefly,  if  not  altogether,  where  the  entire  ramification  of  the 
nerves  takes  place  within  an  extremely  limited  compass  (vid.  note) ; 
elsewhere  they  rarely  occur,  or  are  wholly  absent.  Those  between  the 
smaller  and  smallest  branches  (terminal  plexuses,  Valentin),  on  the 
other  hand,  are  very  numerous  everywhere,  forming  elongated  roundish 
meshes,  which  run  for  the  most  part  parallel  with  the  longitudinal 
direction  of  the  fasciculi.  These  terminal  plexuses,  composed,  some- 
times of  smaller,  sometimes  of  larger,  meshes,  and  formed  principally 
by  the  ramules  of  one  small  branch,  though  not  altogether  isolated  one 
from  the  other,  proceed  to  form  what  are  termed  by  Valentin  the  ter- 
minal loops;  by  which  I  understand  nothing  more  than  anastomoses  of 
the  ultimate  twigs,  effected  by  means  of  one  or  a  few  primitive  fibres 
passing  from  one  twig  into  another.  It  is  consequently  unimportant 
whether  they  follow  a  straight  course,  or  are  curved  in  a  looplike  form 
(Fig.  102).  Whether,  besides  these  loops,  there  are  also  free  termina- 
tions of  the  nerve-fibres,  such  as  are  known  to  exist  in  the  lower  animals, 
and  as  I  believed  I  once  noticed  in  a  Rabbit,  is  altogether  doubtful ; 
whilst  it  is  certain  that,  even  in  man,  divisions  of  the  nerve-fibres  take 
place,  although  they  are  rare,  and  detected  with  difficulty,  and  their 
relation  to  the  loops,  it  must  be  confessed,  is  still  to  be  made  out. 

The  trunks  entering  the  muscles  are  composed  principally  of  thick 
nerve-fibres,  about  twelve  of  the  finer  ones  occurring,  on  an  average, 
among  100  of  the  larger  (Volkmann).  They  become  smaller  in  the 
interior  of  the  muscle,  so  that  the  terminal  plexus  consists  only  of 
extremely  minute  fibrils,  measuring  000-1-0-0025  of  a  line  in  diameter. 


246 


SPECIAL    HISTOLOGY. 


In  some  cases,  even,  the  gradual  attenuation  of  the  fibres  may  be 
directly  observed,  proving  that  the  diminution  in  size  does  not  take 
place,  in  this  case  at  least,  in  consequence  of  division.  Thus,  in  the 


Fig.  102. 


Fie.  103. 


omohyoid,  I  have  noticed  several  nerve-fibres  of  0-004-0-0053  of  a  line, 
derived  from  trunks  measuring  0-05-0-07  of  a  line,  become  attenuated 
(within  a  distance  of  0-15-0-2  of  a  line),  to  a  diameter  of  0-002-0-0026 
of  a  line,  and,  after  a  further  course  of  0 '.4—0*5  of  a  line,  acquire  that 
of  the  smallest  fibrils,  or  0-001  of  a  line.  Simultaneously  with  this 
change  in  size,  the  nerve-fibres  assumed  in  all  respects  the  aspect  of  the 
so-termed  sympathetic  nerves,  and  ultimately  became  pale,  with  a  simple 
contour  line,  and  disposed  to  form  varicosities ;  at  the  same  time  that 
they  appeared  to  lose  every  vestige  of  a  coat  composed  of  connective 
tissue,  they  still  retained  dark  borders,  and  consequently  were  not  non- 
medullated  fibres  (or  free  axis-cylinders),  such  as  are  seen  in  other  ter- 
minations of  nerves. 

Nervi  vasorum  (vascular  nerves),  accompanying  the  bundles  of  vessels, 
otfcur  in  all  muscles,  and,  according  to  the  size  of  the  latter,  form 
larger  or  smaller  branches.  They  are  composed  only  of  the  smallest 
fibres,  and  always  follow  the  course  of  the  large  vessels,  which  can  still 

FIG.  102. — Ultimate  expansion  of  the  nerves  in  the  omohyoid  muscle  of  Man,  magnified 
350  diameters,  and  treated  with  soda:  a,  interstices  of  the  terminal  plexus;  6,  terminal 
loops  ;  c,  muscular  fibres. 

FIG.  103. — Divisions  of  the  primitive  nerve-fibres  in  muscle,  magnified  350  diameters: 
^4,  double  division  from  the  omohyoid  muscle  in  Man;  a,  neurilemma ;  JS,  division  of  a 
nerve  from  a  facial  muscle  of  the  Rabbit  into  three  apparently  pointed  twigs. 


THE    MUSCULAR    SYSTEM.  247 

be  recognized  as  arteries  and  veins.  I  have  not  seen  how  they  termi- 
nate ;  and  this  much  only  I  know — that  they  are  never  met  with  on  the 
capillaries,  and  very  frequently,  also,  are  not  to  be  found  on  the  smallest 
arteries  and  veins.  Occasionally,  one  or  more  fibrils  from  the  terminal 
plexus  of  the  muscular  nerves  may  be  seen  to  join  these  vessels ;  a  cir- 
cumstance quite  in  accordance  with  the  demonstrable  fact  that  the  vas- 
cular nerves  in  many  parts,  for  instance  in  the  extremities,  are  derived 
from  the  spinal  nerves. 

The  smaller  tendons  contain  no  nerves,  and  the  larger,  such  as  the 
tendo  Achillis  and  the  tendon  of  the  quadriceps  femoris,  only  vascular 
nerves.  The  fascice  and  sheaths  of  tendons  are  also  without  nerves,  as 
well  as  the  synovial  capsules  of  the  muscular  system,  so  far  as  I  am  at 
present  aware. 

In  many  of  the  small  muscles,  the  extent  of  space  included  in  the 
distribution  of  the  nerve  is  extremely  limited,  as  for  instance  in  the 
superior  belly  of  the  omohyoid,  in  a  portion  of  which,  three  inches  long, 
the  space  over  which  the  nerves  are  distributed,  does  not  exceed  from 
five  to  eight  lines  in  length.  The  trunk  of  the  nerve  entering  in  the 
middle  of  the  transverse  axis,  divides  into  two  equal  primary  branches, 
one  passing  towards  the  left,  and  the  other  towards  the  right,  border  of 
the  muscle,  and  each  giving  rise  to  numerous  anastomosing  branches  of 
all  sizes,  and  thus  supplying  the  entire  thickness  of  the  muscle  from  the 
most  superficial  to  the  deepest  layers.  Whilst  this  distribution  of  the 
nerve  takes  place  at  one  point, — a  distribution  not  unlike  that  in  an 
organ  of  sense, — the  rest  of  the  muscle  presents  the  utmost  poverty,  or 
even  a  complete  deficiency,  of  nerves.  In  one  case,  which  I  examined 
closely,  I  was  unable,  besides  the  few  vascular  nerves  in  these  portions, 
to  detect  more  than  three  small  nervous  twigs  of  0-021,  0-028,  0-042  of 
a  line,  which,  though  derived  from  the  main  nerves,  differed  from  the 
other  branches  in  their  distribution.  Two  of  them  ran  directly  towards 
the  lower,  and  one  towards  the  upper,  end  of  the  belly  of  the  muscle, 
giving  off  a  few  filaments  composed  of  one  or  two  primitive  fibrils  which 
passed  through  the  muscle,  and  terminated,  a  little  before  reaching  the 
intermediate  and  terminal  tendons,  in  the  most  minute  twigs  and  single 
nerve-fibrils.  I  found  the  same  conditions  of  the  nerves  in  the  sub- 
cruralis,  and  in  one  of  the  costo-cervical  muscles  (arising  from  the  first 
rib  in  the  cervical  fascia),  as  in  the  omohyoid;  in  the  sternohyoid, 
sternothyroid,  omohyoid  (inferior  belly),  the  same  condition  in  some 
parts  was  noticed,  whilst,  in  others,  one  apparently  different  existed, 
that  is  to  say,  the  branches  of  the  nerves  frequently  did  not  all  divide 
at  the  same  level,  but  were  more  widely  spread.  It  was  easily  seen, 
however,  that  the  above-described  mode  of  division  essentially  obtained, 
also,  in  this  case, — viz. :  that  the  separate  portions  of  the  muscles  are  in 


248  SPECIAL    HISTOLOGY. 

connection  with  the  nervous  plexuses,  only  at  a  point  of  limited  extent. 
The  proof  of  the  existence  of  similar  conditions  in  other  small  muscles 
was  more  difficult,  as  in  those  of  the  orbit,  where  the  nerves  reach  the 
muscles  at  acute  angles,  follow  a  longer  course  in  them,  with  their 
primary  branches,  and  form  their  ultimate  ramifications  at  various, 
more  or  less  widely  separated  points ;  yet  even  in  this  case  it  was 
tolerably  well  made  out.  It  is  easy  to  understand  that,  in  the  larger 
muscles,  a  microscopic  examination,  in  toto,  is  impossible ;  but  it  can  be 
shown  in  other  ways,  as  by  the  preparation  and  examination  of  minute 
flat  fasciculi  taken  in  their  entire  length,  that  conditions  exist,  at  all 
events  in  some  of  them,  similar  to  those  which  appear  to  be  evidenced 
in  the  small  muscles.  It  is  thus  seen,  especially  in  muscles  of  lax 
structure,  that  each  fasciculus  presents  precisely  the  same  conditions  as 
an  entire  smaller  muscle.  How  the  distribution  of  the  nerves  is  effected 
in  muscles  with  long  fasciculi  (sartorius,  latissimus  dorsi,  &c.),  I  have 
not  examined ;  it  is  probable  that  in  this  case  each  primitive  fasciculus 
is  joined  by  the  nerves  at  several  points,  widely  apart. 

Valentin  and  Emmert,  in  the  year  1836,  simultaneously  described  the 
terminations  of  the  primitive  nerve-fibres  in  the  muscles,  to  be  in  the  form 
of  loops,  and  the  former  maintained  that  the  nerves  of  sensation  termi- 
nated in  a  similar  way.  But  Physiology  having  more  recently  shown 
that  she  does  not  well  know  what  is  to  be  done  with  these  loops,  and 
Microscopic  Anatomy  having  distinctly  demonstrated  the  existence,  in 
many  situations,  of  other  modes  of  termination  of  the  nerves  (Pacinian 
bodies,  &c.),  the  loops  have  fallen  into  such  discredit,  that  the  question 
now  is,  not  as  before,  whether,  besides  the  loops,  there  are  other  modes 
of  termination,  but  rather,  whether  loops  really  exist  anywhere  ?  With 
respect  to  the  muscles  especially,  anatomists  seem  inclined  to  deny  their 
existence  altogether,  since  divisions  and  terminations  of  nerve-fibres  have 
been  discovered  in  them ;  but  this  conclusion,  from  what  has  been  re- 
marked above,  would  be  incorrect.  Henle  also,  in  Canstatt's  Jahresb. 
f.  1847,  p.  63,  says,  that  in  his  opinion  the  loops  had  been  too  rashly 
discarded;  while  on  the  other  hand,  Wagner,  with  reference  to  this  ques- 
tion, places  the  analogy  with  what  is  seen  in  the  Frog,  &c.,  above  direct 
observation,  and  denies  the  existence  of  loops.  With  respect  to  divisions 
of  the  nerves,  Wagner  ("Gott.  Nach.,"  1852,  p.  27),  finds  them  to  be 
tolerably  frequent  in  the  muscles  of  the  Mouse.  I  would,  moreover,  re- 
mark, that  in  one  case,  I  think  I  noticed  a  minute  ganglion  with  about 
five  cells  on  a  nervous  twig  in  the  omohyoid  of  man ;  the  observation, 
however,  was  not  satisfactory,  the  muscle  having  been  previously  treated 
with  soda. 

In  the  Invertebrata,  many  observers  have  long  since  described  free 
terminations  of  the  nerve  fibrils,  and  their  insertion  with  expanded  ends 
into  the  muscular  fibres,  as  Doyere  in  the  Tardigrada,  and  Quatrefages 


THE    MUSCULAR    SYSTEM.  249 

in  Eolidina,  and  some  Rotifera  (uAnn.  d.  Sc.  K,"  1843,  p.  300,  and  pi. 
11,  fig.  12).  I  myself,  in  a  larva  of  Chironomus  (a  dipterous  insect), 
noticed  a  single  nerve-fibre,  proceeding  to  the  two  muscular  fasciculi  of 
the  simple  tarsus,  bifurcate  into  two  branches,  which  were  implanted  upon 
the  surface  of  the  muscle,  with  somewhat  expanded  terminations.  In 
the  Vertebrata,  Muller  and  Briicke  first  described  division  of  the  nerves 
in  the  orbital  muscles  of  the  Pike  (J.  Muller,  "Physiol.,"  4th  ed.  vol.  1, 
p.  524),  and  in  Amphioxus,  Quatrefages  noticed  conditions  precisely  like 
those  met  with  in  the  Invertebrata  above  mentioned.  The  observation 
is  easily  confirmed,  as  respects  the  orbital  muscles  of  the  Pike,  in  which, 
upon  the  teasing  out  of  the  fasciculus  either  of  the  fresh  muscle  as  well 
as  after  it  had  been  treated  with  corrosive  sublimate,  and  rendered  trans- 
parent by  acetic  acid,  numerous  divisions  of  the  nerves  are  apparent. 
They  are  nevertheless  not  nearly  so  frequent  in  this  case,  as  in  the  Frog, 
nor  are  the  divisions  more  than  bifid  or  trifid.  Besides  this,  I  was  espe- 
cially struck  with  the  glaring  contrast  that  was  presented,  to  what  is  seen 
in  the  Mammalia,  in  the  enormous  extent  of  space  included  in  the  dis- 
tribution of  the  nerve-fibres ;  a  distribution  so  extensive,  that  it  is  by  no 
means  easy  to  find  a  single  primitive  fasciculus  which  has  not  a  nerve- 
fibre  going  to  it;  in  many  places  even,  the  latter  were  seen  in  apposition 
with  a  fasciculus  throughout  a  great  extent,  and  surrounding  it  with 
loops,  or  with  a  variable  number  of  spiral  convolutions.  A  similar  con- 
dition was  observed  by  R.Wagner  in  the  orbital  muscles  of  the  Torpedo, 
whilst  in  other  muscles  the  nerves  were  very  scantily  supplied  ("  Gb'tt. 
Nach.,"  Oct.,  1851).  In  the  Amphibia,  divisions  and  free  terminations 
of  the  nerves  have  been  described  by  Wagner.  The  former  are  remark- 
ably beautiful  and  numerous.  They  commence  in  nerve-fibres,  measur- 
ing 0-004-0-006  of  a  line,  in  the  smaller  trunks  and  branches,  and  are 
several  times  repeated,  with  a  gradual  diminution  of  the  fibres,  until 
extremely  minute  filaments  measuring  0-001-0-0015  of  a  line  are 
formed.  The  divisions  are  for  the  most  part  di-  or  tri-chotomous,  more 
rarely  multiple;  in  one  instance,  however,  Wagner  noticed  eight  ramus- 
culi.  The  ultimate  filaments  are  pale,  and  have  a  simple  contour  line. 
They  never  penetrate  into  the  muscular  fasciculus,  but,  after  running  a 
short  distance,  are  either  applied  obliquely  or  transversely  to  it,  or  proceed 
for  some  distance  in  close  contiguity  and  parallel  with  it;  in  either  case, 
becoming  attenuated  to  a  sharp  point,  and  frequently  as  fine  as  a  fibril 
of  connective  tissue.  All  these  conditions  are  best  seen  in  the  mylohyoi- 
deus  (Wagner),  and  above  all,  in  a  delicate  cutaneous  muscle  of  the 
thorax,  as  was  pointed  out  to  me  by  Ecker,  and  in  which  the  distribu- 
tion of  the  nerves  has  recently  been  very  accurately  described  by  Reichert. 
He  observed  in  this  case,  as  I  had  done  in  man,  that  only  a  small  por- 
tion of  the  muscle  was  well  supplied  with  nerves,  which  were  but  spar- 
ingly distributed  to  the  other  portions.  The  trunk  of  the  nerve  supply- 


250 


SPECIAL    HISTOLOGY. 


ing  the  160-180  fasciculi  of  this  muscle,  contains,  according  to  Reichert, 
7-10    fibres,  and    ultimately,    by    continual   division,  forms    290-340 


Fig.  104. 


terminal  filaments,  so  that  there  is  more  than  one  for  each  muscular 
fasciculus. 

§  85.  Chemical  and  Physical  Relations  of  the  Muscles. — In  100 
parts  of  fresh  beef  there  are  contained,  according  to  Bibra,  72-56— 
74-45  parts  of  water.  The  solid  constituents  (25-55-27-44)  in  a  man 
59  years  old,  were  composed  of  a  residue  insoluble  in  boiling  water, 
alcohol,  and  ether,  16-83;  soluble  albumen  and  coloring  matter,  1-75; 
substance  affording  gelatine,  1-92;  extractive  matter  and  salts,  2-80; 
fat,  4-24.  The  fat  is  derived  chiefly  from  the  blood,  the  fat-cells  in  the 
muscles  and  their  nerves,  and  in  part  perhaps  from  the  muscular  fibres 
themselves,  in  which  microscopic  fat  granules  are,  at  all  events  occasion- 
ally, evident.  The  gelatine  is  derived  from  the  perimysium,  in  smaller 
proportion  also  from  the  vessels  and  neurilemma;  none,  on  the  contrary, 
is  afforded  by  the  sarcolemma,  which  is  still  apparent  in  muscles  com- 
pletely exhausted  by  boiling,  whence  (in  opposition  to  Reichert)  it  is 
evident  that  the  sarcolemma  should  not  be  referred  to  connective  tissue. 
The  inorganic  salts  and  the  albumen  are  principally  afforded,  probably 
by  the  muscular  fibre  itself,  as  are  also  and  above  all  the  salts  described 
by  Liebig  and  Scherer  in  the  juice  of  muscles,  of  the  lactic,  acetic,  bu- 
tyric, and  formic  acids,  the  free  lactic  acid,  the  creatin  and  creatinin, 

FIG.  104. — Divisions  of  nerve-fibres,  in  a  small  twig  from  the  cutaneous  thoracic  muscle 
of  the  Frog;  magnified  350  diameters:  a,  bifurcation;  b,  threefold  division. 


THE    MUSCULAR    SYSTEM.  251 

the  sugar  of  muscles  or  inosit,  and  the  coloring  matter,  which  substances, 
even  the  last-named,  are  lodged  partly  in  the  fibrils  themselves,  partly 
and  chiefly,  and  this  is  the  case  especially  with  the  albumen,  in  the  in- 
terstitial substance,  by  which  the  fibrils  are  connected  together.  The 
16*83  parts  of  insoluble  residue  belong  in  part  to  the  elastic  tissue  in 
the  vessels  and  perimysium,  and  to  the  smooth  muscle  in  the  vessels,  but 
principally  to  the  muscular  fibrils  themselves,  which,  as  we  have  before 
seen  (§  27),  consist  of  a  substance  allied  to  fibrin.  The  sarcolemma  is 
less  affected  by  alkalies  and  acids  than  the  fibrils,  and  approaches  in  its 
nature  more  nearly  to  the  membrana  propria  of  the  glands,  the  walls  of 
the  capillaries,  and  the  membrane  of  many  cells.  The  coloring  matter 
of  the  muscles  (and  the  muscles  themselves),  like  the  blood,  becomes 
bright  red  in  the  air,  or  still  more  in  oxygen  gas,  and  is  rendered  dark 
by  sulphuretted  hydrogen.  It  is  extracted,  and  indeed  readily,  by  water, 
but  not  by  salts,  in  which  circumstance,  that  is  to  say,  in  an  altera- 
tion in  the  degree  of  concentration  of  the  plasma  with  which  the  muscle 
is  imbued,  is  perhaps  to  be  sought  the  principal  reason  for  the  readiness 
with  which  the  color  of  the  muscles  is  altered  in  disease. 

The  muscles,  although  softer  and  more  easily  torn  than  the  tendons, 
possess,  nevertheless,  considerable  tenacity,  particularly  during  life,  and 
they  have  a  certain  degree  of  elasticity.  During  life,  as  has  been  cor- 
rectly remarked  by  E.  Weber,  even  when  not  under  the  influence  of 
the  nerves,  they  are  not  for  the  most  part  in  their  natural  form,  but 
stretched,  or  in  a  state  of  tension,  and  like  harp-strings  in  the  same 
condition,  exert  an  elastic  force.  This  is  satisfactorily  shown  when  the 
tendons  of  the  extensor  muscles  in  an  animal's  limb  which  is  strongly 
flexed,  are  cut  through,  the  nerves  having  been  previously  divided, 
whereupon  the  tendons  are  very  considerably  retracted  (E.  Weber). 
This  tension  of  the  muscles  varies  very  much,  according  to  the  position 
of  the  limbs.  It  is  very  slight  when  the  body  is  at  rest  with  the  limbs 
semiflexed,  still  less  or  even  wholly  absent  when  a  muscle  falls  into  a 
state  of  repose  after  it  has  acted  powerfully  upon  the  limb ;  greater, 
and  manifested  in  the  greatest  degree,  when  the  antagonists  of  a  muscle 
are  acting  with  all  their  force.  According  to  Weber,  the  living  muscle, 
when  in  a  state  of  inactivity,  may  be  compared  with  caoutchouc,  seeing 
that,  like  that  substance,  they  possess  a  very  great  elastic  extensibility ; 
or,  in  other  words,  a  slight  but  very  perfect  elasticity,'  as  may  be  readily 
perceived  in  the  muscles  even  of  dead  animals,  which  may  be  alternately 
stretched  and  allowed  to  retract.  Owing  to  their  elasticity,  the  muscles 
offer  scarcely  any  hindrance  to  the  movements  of  the  limbs,  arid  in  con- 
sequence of  its  perfect  nature,  they  recover  their  previous  form  and 
length  even  after  the  greatest  possible  extension.  This  is  exemplified 
in  the  stretching  of  the  abdominal  muscles  in  pregnancy  and  in  certain 
pathological  conditions.  When  the  muscles  are  in  a  state  of  activity, 


252  SPECIAL    HISTOLOGY. 

their  elasticity  alters  in  a  very  remarkable  manner :  1.  During  the  con- 
traction they  become  more  extensible  or  less  elastic,  on  which  account 
they  exert  a  much  less  force  by  their  contraction  than  would  otherwise 
be  the  case,  had  their  elasticity  remained  unchanged,  and  the  same  as 
in  the  inactive  condition.  2.  The  elasticity  of  the  active  muscle,  in  one 
and  the  same  muscle,  is  extremely  variable ;  it  continues  to  diminish  as 
long  as  it  is  in  action,  whence  arise  the  phenomena  of  fatigue  and  loss 
of  power  in  the  muscles  (E.  Weber). 

In  the  dead  muscle,  according  to  the  same  observer,  the  elasticity  is 
less  perfect;  that  is  to  say,  the  dead  muscle,  when  stretched,  does  not 
altogether  resume  its  pristine  form,  and  consequently  is  more  readily 
torn,  although  such  a  muscle  as  the  gracilis  may  still  be  capable  of  sup- 
porting a  weight  of  eighty  pounds  without  breaking.  But  at  the  same 
time  it  is  also  less  extensible,  more  rigid,  less  flexible, — or  its  elasticity 
is  greater.  The  phenomena  of  fatigue  in  the  muscles  are  consequently 
to  be  distinguished  from  those  induced  by  death.  In  the  former  state, 
the  diminution  of  elasticity  occurs  during  the  influence  of  the  nerves 
and  the  contractions  of  the  muscle  itself,  probably  in  consequence  of 
changed  conditions  in  the  molecular  nutrition  of  the  muscle,  and  is  con- 
sequently a  vital  phenomenon  ;  whilst  in  the  latter  case,  innervation, 
nutrition,  and  contraction  have  ceased,  and  the  increase  of  elasticity, 
which  produces  what  is  termed  the  rigor  mortis,  is  a  purely  physical 
phenomenon,  and  not  to  be  confounded  with  the  increased  tension,  which, 
under  the  influence  of  life,  takes  place  during  the  contraction  of  the 
muscles,  simultaneously  with  a  diminution  of  the  elasticity. 

The  tendons  are  very  firm,  and  but  slightly  elastic ;  and  contain, 
according  to  Chevreuil,  in  100  parts,  only  62§03  of  water,  considerably 
less  therefore  than  the  muscles.  They  consist  principally  of  a  substance 
affording  gelatin,  although  they  are  transformed  with  more  difficulty 
than  other  parts  into  that  principle. 

In  my  opinion  the  muscles  are  sometimes  in  a  state  of  tension,  some- 
times in  their  natural  form,  sometimes  even  compressed,  and  to  all  these 
three  conditions  vital  contraction  may  be  superadded.  If  a  muscle  in 
a  state  of  extension  contract,  so  as  not  to  assume  its  natural  form,  it 
will  still  be  in  a  state  of  tension  after  the  remission  of  the  contraction, 
arid  if  divided  will  retract.  On  the  other  hand,  if  a  muscle  in  its 
natural  form  contract,  it  will,  after  the  cessation  of  the  nervous  influence, 
immediately  become  extended  ;  as,  for  instance,  the  contracted  heart, 
or  an  isolated  muscle  excited  by  galvanism.  Consequently,  when  we 
speak  of  the  elasticity  of  muscles,  their  tension,  not  only  when  they 
are  extended,  but  also  in  the  compressed  condition,  must  be  considered ; 
and  this  appears  to  me  of  some  physiological  importance,  as  in  this  way 
the  extension  of  contracted  muscles  (heart),  and  of  muscles  whose 


THE    MUSCULAR    SYSTEM.  253 

antagonists  are  paralyzed,  becomes  intelligible.  With  respect  to  the 
cadaveric  rigidity,  the  important  facts  have  quite  recently  come  to  light, 
that  it  may  be  arrested  by  the  injection  of  blood  (Brown-Se'quard);  and 
also  that  it  takes  place  even  in  the  living  animal,  when  the  supply  of 
blood  to  a  group  of  muscles  is  entirely  cut  off  (Stannius).  In  the  latter 
case,  the  irritability  of  the  nerves  ceases  at  the  same  time,  and  on  the 
restoration  of  the  circulation  the  normal  conditions  in  both  muscles  and 
nerves  are  also  restored.  By  these  facts,  all  hypotheses  respecting  the 
occurrence  of  the  cadaveric  rigidity,  except  that  of  Weber,  are  contra- 
dicted; even  that  of  Briicke,  which  asserts  that  it  is  caused  by  the 
coagulation  of  the  fibrin  existing  in  the  muscular  fibre.  But  at  the 
same  time  the  question  also  arises,  as  to  what  is  the  proximate  cause  of 
the  change  in  the  elastic  conditions  of  the  muscles,  whether  it  be  due 
to  the  death  or  cessation  of  activity  of  the  nerves,  or  to  the  deficient 
supply  of  blood  to  the  muscles  themselves  ?  Stannius  decides  in  favor 
of  the  former  supposition,  and  is  consequently  driven  to  the  conclusion, 
that  during  life  the  motor  nerves  act  upon  the  muscles,  by  reducing, 
during  the  state  of  repose,  their  natural  amount  of  elasticity,  whilst  in 
the  contraction  of  the  muscle  the  influence  of  the  nerves  is  momentarily 
relaxed.  Thus,  according  to  Stannius,  the  rigidity  connected  with  con- 
traction, and  vital  contraction,  would  be  identical,  and  nothing  more 
than  the  condition  of  the  muscle  when  freed  from  all  nervous  influence, 
and  lasting  until  the  nerve  again  puts  the  muscle  into  a  state  of  rest, 
or  its  substance  is  decomposed.  I  must  own  that  in  this  view,  which 
moreover  had  already  been  proposed  by  Engel  ("  Zeitsch.  der  Wiener," 
Aerzte,  1849),  I  do  not  at  present  agree ;  and  in  particular  would 
remark,  that  the  circumstance  of  the  contractions  which  occur  during 
life  being  much  more  considerable  than  those  which  attend  the  rigor 
mortis,  appears  to  be  opposed  to  it. 

§  86.  Development  of  the  Muscles  and  Tendons. — The  rudiments  of 
the  muscles  consist,  originally,  of  the  same  formative  cells  as  those  of 
which  the  rest  of  the  body  of  the  embryo  is  constituted ;  and  it  is  not 
till  afterwards  that  the  muscles,  tendons,  &c.,  are  gradually  developed 
by  a  histological  differentiation.  In  man,  the  muscles  are  not  evident 
before  the  end  of  the  second  month  ;  at  first,  however,  they  cannot  be 
detected  by  the  unaided  eye  ;  they  are  soft,  pale,  gelatinous,  and  not 
to  be  distinguished  from  their  tendons.  In  the  tenth  and  twelfth  week 
they  are  more  distinct,  especially  in  specimens  preserved  in  alcohol  ; 
and  at  this  time  the  tendons  also  may  be  distinguished  as  somewhat 
clearer,  but  at  the  same  time  transparent  streaks. 

In  the  fourth  month,  both  the  muscles  and  tendons  are  still  more 
distinct,  the  former  being,  on  the  trunk,  of  a  light  reddish  color,  the 
latter  less  transparent,  and  grayish,  both  retaining  a  soft  consistence. 


254 


SPECIAL    HISTOLOGY. 


Fig.  105. 


From  this  period,  both  textures  acquire  more  and  more  of  the  configu- 
ration which  they  afterwards  retain,  so  that  at  the  maturity  of  the 
embryo, — excepting  that  the  muscles  are  still  softer  and  paler,  and  the 
tendons  more  vascular  and  less  white, — they  no  longer  present  any 
difference  worth  notice. 

With  respect  to  their  intimate  conditions,  the  primitive  fasciculi,  in 
the  embryo,  at  the  end  of  the  second  month,  present  the  aspect  of  elon- 
gated bands  (Fig.  105)  0-001  of  a  line  broad,  with  nodular  enlargements 
at  different  points,  at  which  places  are  situated  elongated  nuclei ;  the 
bands  exhibit  either  a  homogeneous  or  finely  granular  aspect,  and  but 
rarely  an  extremely  faint  indication  of  transverse  striation.  In  their 
further  development,  these  primitive  muscular  fasciculi,  which,  as  com- 
parative histology  teaches,  originate  in  cells  arranged  in  a  linear  series, 
continue  to  increase  in  breadth  and  length,  and  their  contents,  the 
original  cell-contents,  are  developed  into  the  muscular  fibrils.  In  the 
fourth  month  (Fig.  106)  they  measure  for  the  most  part  0-0028—0-005, 
some  even  0-006  of  a  line,  whilst  others  do  not  exceed  0-0016,  and 
0-002  of  a  line.  The  larger  ones  are,  still,  always  flattened,  but  of 
uniform  width,  and  also  considerably  thicker  than  before,  mostly  with 
evident  longitudinal  and  transverse  striae,  and  even  with  fibrils,  which 
admit  of  being  isolated.  It  is  partially  evident,  even  in  a  longitudinal 

Fig.  106.  view,  but  still  better  in  a  trans- 

verse section,  that  in  many 
cases,  the  fibrils  do  not  occupy 
the  entire  thickness  of  the  pri- 
mitive tube,  but  that  they  are 
deposited  around  its  periphery, 
the  interior  being  as  yet  filled 
with  a  homogeneous  substance 
as  at  first,  and  which  now  ap- 
pears like  a  canal  within  the 
fibrils.  All  the  primitive  tu- 
bules possess  a  sarcolemma  (6), 
which  on  the  application  of 
acetic  acid  or  soda,  appears  as 
a  very  delicate  membrane,  which 
by  the  imbibition  of  water,  may 
occasionally  be  raised  from  the 
fibrils.  The  tubes,  moreover, 

FiG.  105. — Primitive  fasciculi  of  an  eight  to  nine  weeks'  human  embryo ;  magnified  350 
diameters:  1,  two  fibres  without  transverse  strise;  2,  fibres  presenting  the  first  indications 
of  transverse  striation  ;  a,  nuclei. 

FiG.  106. — Primitive  fibres  of  a  four  months'  human  embryo;  magnified  350  diameters: 
1,  a  fasciculus,  with  a  clear,  as  yet,  non-fibrillated  substance  in  the  interior:  2,  fasciculus 
without  such  contents,  with  an  indication  of  transverse  striation  ;  a,  nuclei ;  b,  sarcolemma. 


THE    MUSCULAR    SYSTEM.  255 

as  at  first,  present  nuclei  lying  close  upon  the  sarcolerama,  and  which 
frequently  cause  rounded  elevations  on  the  surface  of  the  tube,  and  may 
be  observed  actively  engaged  in  the  process  of  multiplication.  They 
are  all  vesicular,  roundish  or  elongated,  with  very  distinct,  simple  or 
double  nucleoli  measuring  0-0004-0*0008  of  a  line,  and  frequently  with 
two  secondary  cells  in  the  interior.  They  are  much  more  numerous 
than  previously,  and  most  frequently  disposed  in  pairs  closely  approxi- 
mated ;  but  often,  also,  in  groups  of  three  or  four  or  even  six,  either 
contiguous  or  arranged  serially.  From  this  period  to  that  of  birth,  no 
further  important  change  takes  place  in  the  muscular  fasciculi,  except 
an  increase  in  their  size.  In  the  new-born  infant  they  measure  0*0056 
-0-0063  of  a  line,  are  solid,  rounded,  polygonal,  longitudinally  or 
transversely  striated,  according  to  circumstances,  as  in  the  adult,  with 
very  readily  isolated  fibrils,  and  no  longer  any  appearance  of  nuclei. 

From  what  has  been  remarked,  it  is  clear  that  the  sarcolemma  repre- 
sents the  sum  of  the  membranes  of  the  coalesced  cells,  and  that  the  nuclei 
of  the  youngest  fasciculi  are  the  original  cell-nuclei,  whose  descendants 
are  represented  in  the  nuclei  of  the  older  fibres,  which  have  multiplied 
by  an  endogenous  process.  The  muscular  fibrils  are  the  altered  contents 
of  the  original  tubes,  become  solid ;  they  appear,  demonstrably  in  many 
instances,  to  be  formed  on  the  inner  surface  of  the  sarcolemma,  from 
without  to  within,  but  in  other  cases  probably  in  the  whole  of  the  tube 
at  once. 

The  growth  of  the  entire  muscle  is  chiefly  to  be  referred  to  the  in- 
crease, both  longitudinal  and  in  thickness,  of  the  primitive  fasciculi ; 
and  the  rudiments  of  all  the  future  primitive  fasciculi  appear  to  be  formed, 
probably  even  as  early  as  the  original  rudiments  of  the  muscle  itself — 
in  every  case  at  the  middle  period  of  foetal  life.  In  the  embryo,  at  the 
fourth  or  fifth  month,  they  are  perhaps  five  times  as  thick  as  in  one  at 
two  months ;  in  the  new-born  infant  they  measure  for  the  most  part 
twice,  occasionally  even  three  and  four  times  as  much  as  in  the  fourth 
and  fifth  month,  and  in  the  adult  their  size  is  perhaps  five  times  greater 
than  in  the  new-born  child.  The  number  of  fibrils  must  necessarily  in- 
crease in  proportion  to  the  size  of  the  fasciculus,  because,  according  to 
Harting,  they  are  but  little  thicker  in  the  adult  than  in  the  foetus.  The 
perimysium  is  developed,  as  I  find  in  agreement  with  Valentin  and 
Schwann,  after  the  type  of  the  common  connective  tissue,  from  fusiform, 
coalesced  formative  cells. 

The  elementary  parts  of  the  tendons  are,  in  no  case,  formed  earlier 
than  those  of  the  muscles ;  for,  in  embryos  from  the  eighth  to  the  ninth 
week,  I  have  never  been  able  to  detect  a  trace  of  them,  although  at  this 
time  the  muscular  fibres  are  'quite  distinct.  It  is  not  till  the  third  or 
fourth  month,  when,  moreover,  they  become  distinctly  visible  to  the 
naked  eye,  that  their  elementary  constituents  can  be  made  out,  at  this 
time  presenting  the  appearance  of  long  parallel  bands  with  elongated 


256 


SPECIAL    HISTOLOGY. 


nuclei,  which,  as  the  observations  of  Schwann  and  myself  (§  24)  on  very 
young  animals  show,  are  formed  by  the  coalescence  of  fusiform  cells. 
As  early  as  the  fourth  month  they  may  be  distinctly  recognized  as  primi- 
tive fasciculi,  which  are  wavy,  and  present,  at  intervals,  elongated  nuclei 
0-0035-0-006  of  a  line  long,  and  0-0016  of  a  line  broad,  but  are  as  yet 
without  distinct  fibrils,  and  not  more  than  0-0012-0-0016  of  a  line  wide. 
Fig.  107.  From  this  period  up  to  the  end  of  foetal  life,  the  fasci- 

culi gradually  increase  in  width,  so  that  in  the  new- 
born infant  they  measure  0-002-0-0025  of  a  line;  at 
the  same  time  their  fibrils  are  developed,  as  are  also 
fine  elastic  filaments  among  the  fasciculi,  from  special 
fusiform  formative  cells  (vide  §  23).  If  these  fasciculi 
be  compared  with  those  of  the  adult,  measuring  0-006 
-0-008  of  a  line,  it  is  obvious,  that  the  fasciculi  of  the 
tendons  are  continually  acquiring  an  increase  in  thick- 
ness from  their  first  origin,  so  that  their  proportional 
sizes  in  the  four  months'  foetus,  the  new-born  child,  and 
the  adult,  are  about  as  1  :  1,  8  :  6 ;  and,  also,  that  in 
every  case  the  growth  of  the  tendons  must  in  a  great 
measure  be  referred  to  the  increased  thickness  and 
elongation  of  their  fasciculi.  It  would,  moreover,  appear,  that  subse- 
quent to  the  primary  rudiments  of  the  tendons,  new  fasciculi  continue 
to  be  added  during  foetal  life. 

Some  controversial  opinions  are  still  entertained  with  respect  to  the 
development  of  the  muscular  fibres.  Reichert  and  Hoist  maintain  that 
each  fibril  is  the  product  of  a  single  cell,  and  regard  it  as  the  equivalent 
of  the  smooth  muscular  fibre,  or  contractile  fibre-cell.  This  view  is  er- 
roneous, as  is  readily  shown  by  the  examination  of  the  mammalian  and 
human  embryo.  Leydig's  declaration,  quite  recently,  in  its  favor 
(Beitr.  p.  78),  is  explained  by  his  having  confounded  the  peculiar  secon- 
dary muscular  fasciculi  in  the  plagiostomous  fishes  with  the  primitive 
fasciculi  of  the  higher  Vertebrata.  In  the  Batrachia,  according  to 
Lebert  and  Remak,  in  the  development  of  the  muscles,  elongated  simple 
cells,  with  self-multiplying  nuclei,  are  found,  the  contents  of  which  cells 
undergo  a  metamorphosis  similar  to  that  occurring  in  the  elongated 
muscular  tubules  formed  of  numerous  cells,  which,  according  to  my  ob- 
servations, also  exist  in  these  animals.  The  contractile  part  of  the  mus- 
cular fibre,  whether  it  be  transversely  striped  or  not,  and  whether  it 
presents  fibrils  or  not,  is  generally  developed  from  without  to  within,  in 
the  sarcolernma,  forming  a  sort  of  tube  w.hich  does  not  become  solid  till 
afterwards ;  less  frequently  it  appears  as  a  more  solid  cord  on  one  side 

FIG.  107. — From  the  tendo  ^chillis  of  a  new-born  child,  magnified  250  diameters,  and 
treated  with  acetic  acid,  in  order  to  show  the  formation  of  fine  elastic  fibres. 


THE    MUSCULAR    SYSTEM.  257 

•within  the  muscular  fibre.  In  the  former  case,  the  nuclei  and  the  original 
contents  of  the  formative  cells,  which  often  contain  a  large  quantity  of 
fatty  matter,  are  situated  in  the  interior  of  the  embryonic  muscular 
tubule,  or  between  it  and  the  sarcolemma ;  in  the  latter  always  close 
upon  the  sarcolemma. 

With  respect  to  the  pathological  relations  of  these  tissues,  the  follow- 
ing remarks  may  be  offered :  The  substance  of  the  striated  muscles  is 
not  regenerated,  and  wounds  of  muscles  heal  simply  with  a  tendinous 
callus.  A  new  formation  of  them  has  been  noticed  by  Rokitansky 
("Zeitsch.  der  Wiener,"  Aerzte,  1849,  p.  331),  in  a  case  of  tumor  of 
the  testis  in  an  individual  18  years  old,  and  by  Virchow  ("  Verh.  der 
Wurzb.,"  Ges.,  I.)  in  an  ovarian  tumor.  In  the  latter  case,  which  came 
under  my  own  observation,  there  were  elongated,  fusiform,  transversely 
striated  cells,  each  with  a  nucleus,  similar  to  those  described  by  Remak 
in  the  Tadpole.  The  state  of  the  elementary  parts  in  hypertrophy  of 
the  muscles  is  uncertain.*  This  condition,  however,  except  in  the  tongue, 
heart,  and  certain  respiratory  muscles  (Bardeleben),  does  not  perhaps 
occur  at  all ;  it  is  at  all  events  extremely  rare  in  the  striped  muscles. 
(Romberg,  "Nervenkr.,"  p.  291,  asserts,  that  such  a  condition  ensues 
upon  long-continued  cramps,  though  it  appears  to  me  that  this  point  is 
not  yet  sufficiently  established.)  Equally  uncertain,  also,  is  the  intimate 
condition  of  the  muscular  elements  in  the  increased  development  caused 
by  exercise,  and  whether  this  depend  upon  the  growth  of  the  pre-exist- 
ing muscular  fasciculi,  or  on  the  introduction  of  new  ones — the  latter  of 
which  supposition  may  perhaps  be  affirmed  without  much  chance  of  error, 
in  the  case  of  the  extreme  degrees  of  pathological  hypertrophy.  Atrophy 
of  the  muscles  is  very  frequent,  as  in  old  age,  paralysis,  particularly  of 
the  tongue,  and  in  cases  of  lead-poisoning,  and  in  the  development  of 
cancer,  fibrous  tumors  (consequent  on  inflammation),  and  of  fat,  &c., 
in  the  substance  of  the  muscles.  The  processes,  however,  which  are  set 
up  in  these  cases,  have  as  yet  been  but  little  investigated.  In  extreme 
old  age  I  find  the  fasciculi  small,  presenting  occasionally  a  diameter  of 
not  more  than  0-004-0-008  of  a  line,  easily  broken  up,  mostly  without 
transverse  stripes,  and  with  the  fibrils  indistinct,  whilst  they  frequently 
contain  yellowish  or  brown  granules,  as  much  as  0-001  of  a  line  in  size, 
often  in  large  quantity,  and  very  many  vesicular  nuclei  with  nucleoli. 

*  [Wedl  has  observed  longitudinal  rows  of  yellow  or  brownish  granules  in  hypertro- 
phied  as  well  as  in  atrophied  muscle.  These  granules  are  not  dissolved  by  acetic  acid  or 
alkalies;  and  seem  deposited  around  the  nuclei  of  the  sarcolemma.  In  hypertrophied 
muscle,  a  peculiar  gelatinous  substance  in  the  interstitial  tissue  is  sometimes  met  with. 
This  causes  the  primitive  fasciculi  to  adhere  to  each  other,  and  generally  results  in  a  com- 
plete softening  and  destruction  of  the  sarcolemma,  in  the  place  of  which  we  find  a  fine 
granular  mass. 

The  interstitial  substance  is  sometimes  found  in  an  hypertrophied  state.  If  this  occur  to 
any  extent  it  produces  an  atrophy  of  the  muscular  fibre. — DaC.] 

17 


258  SPECIAL    HISTOLOGY. 

The  nuclei  often  form  continuous  rows,  or  are  accumulated  on  the  inner 
surface  of  the  sarcolemma,  exhibiting  in  a  peculiar  manner  the  same 
distinct  indications  of  an  energetic  multiplication  by  endogenous  forma- 
tion, as  are  presented  in  the  embryo  (vide  this  §,  supra).  In  fatty  de- 
generation^ the  muscular  fasciculi  are,  by  degrees,  replaced  by  connective 
tissue  and  fat  cells  which  are  developed  between  them ;  whilst,  at  the 
same  time,  minute  fatty  molecules  are  developed  in  great  number  within 
them,  in  place  of  the  fibrils,  which  gradually  disappear. 

Paralyzed  muscles  were  found  by  Reid  ("  On  the  relation  between 
Muscular  Contractility  and  the  Nervous  System,"  "Edinburgh  Monthly 
Journal  of  Med.,"  1841)  to  be  thinner,  softer,  and  paler;  and  Valentin 
("Phys.,"  2  ed.  2  Th.,  p.  62)  noticed  in  such  cases  that  the  transverse 
stripes  were  indistinct,  or  had  disappeared,  and  could  no  longer  be  pro- 
duced by  water,  alcohol,  &c. ;  the  longitudinal  stripes  existed,  but  did 
not  present  their  usual  aspect,  more  resembling  those  of  macerated 
muscle.  Subsequently  the  altered  fasciculi  disappeared  in  part,  and 
were  to  some  extent  replaced  by  fat.  In  a  case  of  atrophy  of  the  pec- 
toralis  major  caused  by  cancer,  I  noticed  conditions  similar  to  those  I 
had  observed  in  old  age,  viz.  :  destruction  of  the  fibrils,  the  develop- 
ment of  brownish  granules,  and  the  presence  of  numerous  nuclei,  to- 
gether with  a  clear  fluid  in  the  persistent  sarcolemma ;  and  lastly  a 
diminution  of  the  fasciculi,  which  did  not  measure  more  than  0-002- 
0*004  of  a  line  in  width.  I  also  believe,  that  I  noticed  in  many  fasci- 
culi the  development  of  larger,  serially  disposed  cells,  with  very 
large  and  distinct  nuclei,  exactly  like  the  so-termed  cancer-cells. 
The  condition  of  the  muscles  in  emaciation  is  unknown.  In  an  ema- 
ciated Frog,  which  had  fasted  for  eight  months,  Bonders  observed 
that  the  fasciculi  were  more  slender,  which  he  attributed  chiefly  to  the 
removal  of  the  interstitial  substance  between  the  fibrils.  Paleness  of 
the  muscles  is  very  common  in  dropsy,  chlorosis,  paralysis,  lead-poison- 
ing, old  age,  &c.  ;  in  which  cases,  probably  the  numerous  brown  or 
yellow  granules  are  formed  from  a  portion  of  the  coloring  matter. 
This  condition  is  generally  associated  with  softening,  in  which  the  fas- 
ciculi no  longer  exhibit  any  distinct  transverse  striae  or  fibrils,  and 
readily  break  up  into  numerous  particles,  or  even  into  a  pultaceous 
matter.  In  tetanus,  in  which  rupture  of  a  muscle  frequently  occurs, 
Bowman  ("Phil.  Transact.,"  1841,  p.  69)  observed  on  the  fasciculi 
numerous  nodular  enlargements,  in  which  the  transverse  strise  were  very 
closely  approximated,  and  between  them  either  actual  rupture  of  the 
fibrils,  or  at  all  events  a  considerable  stretching  and  disorganization  of 
them,  both  of  which  states  are  clearly  to  be  referred  to  a  powerful  and 
irregular  contraction.  The  muscles  sometimes  contain  concretions, 
particularly  as  the  result  of  the  cretification  of  pus,  tubercles,  and  cys- 
ticercus-vesicles ;  sometimes  also  true  bones,  such  as  are  produced  after 
prolonged  exercise  in  the  deltoid  and  other  muscles  (Exercirknochen). 


THE    MUSCULAR   SYSTEM. 


259 


Of  parasites  are  to  be  noticed  the  not  unfrequent  Cysticercus  cellulose? 
and  Trichina  spiralis  ;  and,  besides  these,  in  the  Eel  a  nematoid  worm, 
observed  by  Bowman  ("  Cyclop,  of  Anat."  II.  p.  512)  alive,  in  the  al- 
most empty  sarcolemma.  I  met  with  something  analogous  to  the  latter, 
some  years  ago,  in  the  abdominal  muscles  of  the  Rat  (as  have  V.  Sie- 
bold  and  Miescher  also  in  the  Mouse) ;  that  is  to  say  white  streaks  4-7 
lines  long,  and  0*09— O'Ol  of  a  line  wide,  which,  on  microscopic  exa- 
mination, proved  to  be  hollow  primitive  fasciculi,  entirely  filled  with 
elliptical,  slightly  curved  corpuscles,  O004-0-005  of  a  line  long,  by 
0*0019  of  a  line  wide,  and  manifestly  ova.  The  portions  of  the  fas- 
ciculi thus  transformed  into  pouches,  had  walls  0-009-0-01  of  a  line 
thick,  with  transverse  stripes,  and  were  continuous  at  either  end  with 
the  perfectly  normal  fibre. 

§  87.  Physiological  Remarks. — The  most  remarkable  peculiarity 
of  the  muscles  is  their  contractility.  In  each  contraction,  the  primitive 
fasciculi  shorten  themselves  in  a  rectilinear  direction,  and  at  the  same 
time  become  thicker ;  they  do  not,  however,  undergo  any  considerable 
condensation.  It  is  probable,  that  the  contractions  generally  take 
place  simultaneously  in  every  part  of  a  fasciculus,  although  at  the  same 
time  it  is  not,  of  course,  intended  to  be  said  that  the  contraction  does 
not  commence  at  the  points  where  the  terminations  of  the  nerves  occur, 
and  that  this  contraction  does  not  precede,  though  by  a  space  of  time 
immeasurably  short,  or  at  all  events  inappreciable  by  the  eye,  that  of 
the  other  portions  of  the  fasciculus.  Under  certain  conditions,  how- 
ever, successive,  progressive,  and  partial  contractions  are 
observed.  If  during  the  contraction  of  a  muscle,  its 
longitudinal  and  transverse  striae  are  noticed,  it  is  diffi- 
cult to  show  that  where  the  former  exist,  they  disappear 
during  the  contraction,  and  give  place  to  transverse 
markings ;  and  that  the  latter,  where  they  were  already 
present,  become  more  distinct,  and  more  closely  approxi- 
mated. Moreover,  in  the  easily  isolated  fibrils  of  the 
thoracic  muscles  of  insects,  it  is  easy  to  perceive  that 
they  exhibit  very  variable  conditions  in  different  ani- 
mals, and  vary  frequently  in  one  and  the  same  indivi- 
dual. Sometimes  they  are  almost  without  transverse 
markings,  and  very  pale ;  sometimes  darker,  and  with 
distinct  transverse  lines;  sometimes,  again,  very  dis- 
tinctly ringed ;  and  together  with  these  varying  condi- 
tions, does  the  thickness  of  the  fibrils  and  the  distance 
between  the  transverse  striae,  vary  also ;  so  that  the 

Fig.  108.  Primitive  fibres  from  the  alar  muscles  of  the  "  Dung-Fly :"  a,  slender  fibril, 
with  very  distant  delicate  transverse  striae ;  6,  thicker  fibre,  with  closer,  alternately  stronger  and 
fainter  striae;  c,  still  thicker  fibril,  with  the  striae  more  closely  approximated;  rf,  fibril  with 
lateral,  alternate  elevations  (they  have  come  out  too  dark). — Magnified  350  diameters. 


Fig.  108. 


260  SPECIAL    HISTOLOGY. 

fibrils  which  exhibit  the  most  distinct  striation,  are  almost  as  thick  again 
as  the  others,  and  their  transverse  striae  are  placed  almost  twice 
as  closely  together.  It  may  thence,  perhaps,  be  allowable  to  con- 
clude, that  in  the  act  of  contraction  the  principal  phenomenon  con- 
sists in  the  shortening  and  thickening  of  the  fibrils,  and  also,  that 
the  changes  in  the  fasciculus  above  noticed  depend  upon  these  changes 
in  the  fibrils.  The  further  question  now  arises:  how  is  this  shortening 
of  the  fibrils  effected  ?  and  whence  does  the  transverse  striation  arise  ? 
Is  the  latter  connected  with  the  vital  conditions  of  the  muscle,  or  is  it 
produced  independently  of  these  ?  It  is  unnecessary  to  answer  the  latter 
query  in  the  affirmative,  for  dead  muscles  exhibit  transverse  striae,  and 
indeed,  under  the  same  conditions  as  the  living.  This  is  best  shown  in 
muscles  successively  subjected  to  various  degrees  of  tension;  and  con- 
sequently, all  notion  of  a  merely  partial  contraction  of  the  fibril,  which 
arises  on  the  first  observation  of  these  conditions,  must  be  relinquished. 
The  transverse  striation  is  manifestly  merely  a  physical,  not  a  vital 
phenomenon.  It  arises,  either  because  the  fibrils  are  not  homogeneous 
throughout  their  whole  length,  but  divided  into  numerous  small  seg- 
ments^ some  of  which  are  possessed  of  greater  elasticity  than  the  others ; 
or,  in  the  opposite  case,  it  may  depend  upon  the  circumstance,  that  the 
fibrils  are  soft  filaments,  which,  in  shortening,  become  curved  in  a  zig- 
zag or  wavy  manner,  or  varicose.  Which  of  these  two  views  is  the 
correct  one,  cannot  at  present  be  determined ;  and  this  much  only  can 
be  said,  that  in  favor  of  the  former  supposition,  the  fact  can  be  adduced, 
that  fibrils,  after  maceration,  readily  break  up  into  minute  particles 
(sarcous  elements,  Bowman),  and  possibly  consist  of  a  series  of  such 
elements  connected  by  a  heterogeneous  interstitial  substance ;  whilst  in 
favor  of  the  second,  are  the  conditions  presented  in  the  fibrils  of  con- 
nective tissue,  which  are  undoubtedly  homogeneous  throughout,  and  yet 
when  made  to  contract  by  the  application  of  acetic  acid,  exhibit  extreme- 
ly delicate  transverse  markings,  in  consequence  of  which,  the  fasciculi 
composed  of  them  frequently  offer  a  deceptive  resemblance  to  those  of 
striped  muscle.  It  is  difficult  to  say  whether  the  sarcolemma  partici- 
pates actively  in  the  shortening  of  the  fibrils,  although,  especially  from 
the  consideration  of  its  chemical  and  physical  properties,  which  ap- 
proach those  of  elastic  tissue,  I  am  rather  inclined  to  the  opinion,  that 
its  function,  in  the  contraction  of  the  fibre,  is  merely  passive.  The 
same  may  with  greater  certainty  be  affirmed  of  the  albuminous  fluid 
uniting  the  individual  fibrils.  Consequently,  it  is  not  the  muscular 
fasciculus,  in  toto,  but  only  the  fibrils,  which  are  to  be  regarded  as  the 
contractile  elements  ;  a  position  which  is  not  shaken  by  the  circum- 
stance, that  other  conditions  occur  in  the  smooth  muscles,  and  in  many 
muscles  in  the  Invertebrata  (those  that  exhibit  no  fibrils). 

This  is  not  the  place  to  dilate  upon  the  causes  to  which  the  contrac- 


THE  MUSCULAR  SYSTEM.  261 

tions  of  the  muscles  are  due,  and  by  which  they  are  necessarily  produced, 
and  I  will  merely  offer  the  following  remarks.  There  can  be  no  doubt 
that  the  contractility  of  the  muscular  substance  is  a  proper  and  inherent 
attribute,  and  only  called  into  manifest  action  to  a  certain  extent  through 
the  nerves;  whilst  it  is  equally  certain,  that  there  are  no  facts  which 
conclusively  demonstrate,  that  the  striped  muscles  contract  indepen- 
dently of  a  previous  nervous  influence.  What  the  processes  are  which 
take  place  in  the  fibrils  during  the  contraction  is  wholly  doubtful;  but 
it  is  to  be  hoped  that  the  further  investigation  of  the  laws  of  the  electric 
currents  in  the  muscles,  prosecuted  in  the  way  so  successfully  pursued 
by  Du  Bois  Reymond  ("  Untersuchungen  tiber  thier.  Electricitat,"  Ber- 
lin, 1848-49),*  will  throw  some  light  upon  this,  as  yet,  obscure  subject. 
It  would  be  more  than  bold  to  hazard  an  assertion  with  respect  to  the 
nature  and  mode  of  action  of  the  nerves  upon  the  muscles,  since  we  are 
quite  as  much  in  the  dark  as  to  the  processes  which  take  place  in  the 
nerves,  as  we  are  with  regard  to  those  occurring  in  the  muscles  them- 
selves. From  the  anatomical  facts,  which  prove,  that  in  many  animals 
the  motor  nerve-fibres  come  in  contact  with  each  primitive  muscular 
fasciculus  only  at  a  few  points,  and  never  penetrate  into  its  interior,  it 
is,  however,  rendered  evident,  that  in  the  contraction  of  a  muscle,  the 
nervous  influence  must  act  from  a  certain  distance. 

The  muscles  also  possess  sensibility,  though  of  a  rather  peculiar  kind, 
because  punctures,  burns,  and  incisions  into  their  substance,  excite 
scarcely  any  sensations  worth  naming,  whilst  every  muscle,  after  long- 
continued  activity,  as  well  as  when  affected  with  cramps  or  spasms,  be- 
comes painful  and  very  sensitive  to  pressure.  They  are  also  endowed 
with  an  extremely  delicate  sense  of  feeling  for  their  own  state  of  con- 
traction, so  that  they  are  capable  of  estimating  very  minute  variations 
in  the  force  with  which  they  act.  The  apparent  contradiction  between 
these  facts  is  easily  accounted  for,  by  the  consideration  that  the  muscu- 
lar nerves  contain  but  very  few  sensitive  fibres,  as  is  readily  shown  in 
the  nerves  of  the  orbital  muscles,  &c.  These  fibres,  to  which  probably 
belong  the  few  filaments  above  described,  which  are  distributed  over  the 
whole  muscle,  though  too  scanty  to  render  a  muscle  sensible  to  local  im- 
pressions, nevertheless  suffice,  when  implicated  in  the  contraction  of  the 
entire  muscular  substance,  to  convey  to  the  sensorium  the  degree  of 
pressure  to  which  they  are  subjected,  and,  when  the  organs  are  over- 
exerted, to  induce  pain,  in  consequence  of  the  frequently-repeated  irri- 
tation which  they  have  undergone,  or  of  the  compression  they  endure 
from  the  rigidity  of  the  muscle. 

The  mechanical  relations  of  the  muscles  have  been  excellently  treated 
of  in  the  article  by  E.  Weber  (1.  c.),  from  which  the  following  conclusions 
may  be  drawn.  The  extent  of  the  shortening  of  the  muscles  amounts, 

*  Translated  by  Dr.  Jones,  London,  1853. 


262  SPECIAL    HISTOLOGY. 

in  experiments  upon  animals,  on  the  average  to  fths,  or  in  powerful 
muscles  even  to  fths.  The  contractile  force  of  a  muscle  does  not  de- 
pend, cceteris  paribus,  upon  its  length,  but  solely  on  its  transverse  sec- 
tional area;  that  is  to  say,  on  that  of  all  its  primitive  fasciculi,  so  that 
a  longer  and  a  shorter  muscle  exert  the  same  force,  when  the  sum  of  the 
transverse  sections  of  all  the  fasciculi  is  the  same  in  both.  According 
to  the  observations  of  Schwann  and  Weber,  the  elasticity  of  the  muscles 
diminishes  at  each  contraction,  and  consequently  the  molecular  motions, 
called  into  play  in  them  under  the  nervous  influence,  must  be  connected 
with  a  change  in  their  substance  of  an  altogether  peculiar  kind,  which, 
however,  can  certainly  only  be  regarded  as  a  secondary  effect.  The 
degree  of  contraction  differs  according  to  the  amount  of  antagonism 
with  which  it  meets ;  if  the  latter  be  sufficiently  powerful,  no  true  move- 
ment of  the  limb  takes  place,  that  is  to  say,  the  points  of  origin  and 
insertion  of  a  flexor  muscle  (for  instance)  do  not  approximate ;  never- 
theless, the  fibres  themselves  contract  to  a  certain  extent,  in  consequence 
of  which  the  whole  muscle  becomes  tense.  This  tension  must  be  care- 
fully distinguished  from  that  dependent  upon  the  muscular  elasticity, 
which  is  generally  much  less  considerable.  What  has  been  termed  the 
"tone" — tonus — of  muscles,  does  not  in  most  cases  depend  upon  con- 
traction, but  is  an  elastic  tension ;  I  therefore  hold,  that  the  posture  of 
the  body  and  the  occlusion  of  the  transversely  striated  sphincters  during 
sleep,  has  nothing  to  do  with  a  contraction  of  the  muscles,  although  such 
contraction  is  indubitably  requisite  to  bring  the  body  into  this  posture. 
In  my  opinion,  during  sleep,  all  the  muscles  (of  course,  with  the  excep- 
tion of  the  respiratory)  are  at  rest,  being  held  in  a  state  of  tension,  and 
of  antagonism  to  their  opponents  merely  by  their  elastic  force,  and  are 
consequently  in  the  condition  of  a  muscle  when  supported,  in  a  person 
in  the  waking  state.  As  for  instance,  a  biceps,  when  the  arm  is  bent, 
may  immediately  lose  its  tension  if  the  arm  be  supported,  so  in  the  same 
way  may  all  other  voluntary  muscles;  only  it  must  not  be  forgotten, 
that  such  a  condition  of  muscular  rest  may  ensue  upon  all  conceivable 
degrees  of  contraction.  Even  the  orbicularis  oris,  when  contracted,  may 
be  at  rest  and  lose  its  vital  tension.  The  mouth,  nevertheless,  will  re- 
main closed,  for  this  reason,  that  although  the  elastic  force,  as  always 
after  a  contraction,  will  not  fail  to  exert  a  certain  degree  of  extension 
upon  it,  it  is  unable  to  open  the  mouth,  owing  to  its  limited  amount  and 
inability  to  overcome  the  weight  of  the  lips.  I  do  not  believe  in  any 
muscular  "tone,"  if  under  that  term  be  understood  a  long-continued 
involuntary  contraction  (though  at  first  excited  by  the  will) ;  but  am  of 
opinion,  that  what  has  been  mosj;  generally  described  under  this  name, 
is  merely  an  elastic  tension,  which  has  been  confounded  with  the  con- 
traction upon  which  it  has  ensued.  Prom  all  we  know,  the  nerves  are 
incapable  of  exciting  a  long  persistent  contraction  in  the  striped  muscles, 


THE    MUSCULAR    SYSTEM.  263 

but  very  capable  of  producing  great  effects,  when  the  states  of  contrac- 
tion and  of  rest  are  duly  alternated^  as  for  instance  in  walking,  running, 
&c.,  and  in  the  heart  and  respiratory  muscles. 

The  importance  of  this  view  of  the  nature  of  the  muscular  "tone," 
as  regards  the  physiology  of  the  nerves,  is  sufficiently  obvious ;  but  in 
pathology  also,  it  may  be  employed,  in  explanation  of  the  retraction  of 
divided  muscles,  and  the  shortening  which  takes  place  in  muscles  whose 
antagonists  are  paralyzed.  The  former,  as  correctly  pointed  out  by  E. 
Weber,  depends  upon  the  elastic  force,  and  takes  place,  as  far  as  I  know, 
only  in  extended,  tense  muscles,  but  not  in  those  which  are  in  a  state  of 
contraction,  which,  on  the  contrary,  when  cut  across,  immediately  be- 
come lengthened,  as  may  be  readily  observed  in  the  Frog.  It  is  quite 
true,  that  contractions  also  take  place  in  divided  muscles,  in  conse- 
quence of  nervous  influence ;  but  these  are  never  more  than  local,  and 
cease  without  the  production  of  any  important  effect  on  the  form  of  the 
wound  in  the  muscle. 

The  shortening  which  occurs  in  the  antagonists  of  paralyzed  muscles, 
is  not  referable  either  to  the  elastic  force  of  the  non-paralyzed  muscles, 
which  is  much  too  slight  to  influence  the  position  of  a  limb,  or  to  their 
persistent  "tone,"  but  depends  simply  upon  the  voluntary  innervation 
of  the  muscles,  which  are  still  in  an  active  condition,  and  which,  no 
longer  meeting  with  any  opposition  from  their  antagonists,  draw  the  limb 
in  their  own  direction.  The  persistence  of  the  oblique  position  which 
now  ensues,  may  be  readily  explained  without  our  necessarily  assuming 
the  existence  of  a  permanent  contraction,  when  it  is  considered  that 
muscles,  the  antagonists  of  which  are  paralyzed,  never  again  become 
elastically  tense.  In  lead-palsy,  for  instance,  when  the  first  contraction 
of  the  flexors,  consequent  upon  the  paralysis  of  the  extensors,  ceases, 
the  former,  even  under  the  most  favorable  circumstances,  become  ex- 
tended only  so  far  as  to  assume  their  natural  form,  a  condition  from 
which  necessarily  results  the  semiflexed  position  of  the  part  affected. 
In  accordance  with  this  view,  I  regard  the  permanent  condition  of  the 
unaffected  side  of  the  face,  in  one-sided  paralysis  of  the  facial  nerve,  and 
that  of  the  upper  eyelids  in  blepharoptosis,  as  produced,  not  by  a  per- 
sistent contraction,  but  as  indicative  of  a  state  of  perfect  rest  in  the 
muscles,  except  when  voluntary  movements  take  place.  The  falling  of 
the  upper  eyelid  is  explained  by  the  paralysis  of  the  levator,  and  the 
inability  of  the  orbicularis,  by  its  extension  after  a  previous  closure,  to 
raise  the  eyelid  beyond  a  certain  point.  In  the  same  way  the  distortion 
of  the  face  is  produced,  at  first  by  the  voluntary  contraction  consequent 
on  the  paralysis,  upon  the  cessation  of  which  it  is  impossible  that  the 
previous  symmetry  of  the  features  should  be  restored,  because  the  anta- 
gonist muscles  on  the  opposite  side  are  paralyzed,  and  their  slight  elastic 
force  during  life  is  insufficient,  simply  upon  the  cessation  of  the  contrac- 


264 


SPECIAL    HISTOLOGY. 


tion,  to  restore  the  pristine  position  of  the  lips,  angle  of  the  mouth,  &c. 
An  actual  distortion,  therefore,  dependent  upon  persistent  muscular 
contraction,  can  only  take  place  in  consequence  of  morbid  conditions  of 
the  central  organs. 

In  the  investigation  of  the  muscles  it  is  necessary  that  they  should  be 
studied  in  the  fresh  state,  and  with  the  aid  of  various  reagents.  The 
primitive  fasciculi  are  most  easily  isolated  in  muscles  which  have  been 
boiled  or  immersed  in  spirit,  in  which  also,  the  transverse  strise  are  for 
the  most  part  very  well  displayed,  as  is  also  the  case  after  treatment 
with  corrosive  sublimate  or  chromic  acid.  In  the  study  of  the  transverse 
strise,  it  is  above  all  indispensable  that  the  muscles  should  be  viewed  in 
various  degrees  of  extension  and  contraction  (Fig.  109).  The  former 
conditions,  which  are  well  worth  observation,  are 
readily  viewed,  if  long  slender  muscles,  such  as 
the  hyoglossi  of  the  Frog,  &c.,  are  examined  on  a 
wooden  stage  having  a  central  opening  filled  in 
with  glass.  It  will  then  be  seen,  when  no  exten- 
sion whatever  is  employed,  that  the  transverse 
strise  are  narrow  (about  0-0004  of  a  line)  and  very 
closely  approximated,  and  that  the  fasciculus  itself 
is  broad;  whilst,  when  it  is  extended  to  the  utmost, 
the  stripes  are  0-0008  of  a  line  wide,  and  placed 
at  the  same  distance  apart,  and  that  the  fasciculus  is  narrower.  The 
contractions  must  be  observed  either  in  fresh  muscles  still  quivering,  and 
kept  moist  with  serum,  albumen,  or  vitreous  humor;  or  in  the  way  pro- 
posed by  E.  Weber, — and  which  consists  in  the  galvanizing,  by  means 
of  the  rotation  apparatus,  of  the  muscle  to  be  examined,  such,  for  in- 
stance, as  the  abdominal  muscles  and  slender  muscles  of  the  extremities 
in  the  Frog,  the  diaphragm  and  cutaneous  muscles  of  the  smaller  Mam- 
malia, &c.  For  this  purpose  the  muscle  must  be  placed  upon  a  piece  of 
looking-glass,  from  a  small  space  in  the  middle  of  which  the  metallic 
coating  has  been  removed.  One  of  the  conducting  wires  is  brought 
through  an  opening  in  the  stage,  or  else  affixed  to  it  so  as  to  be  im- 
movably in  contact  with  one  of  the  portions  of  tinfoil.  If  the  muscle 
now  be  viewed  under  a  magnifying  power  of  100  linear,  whilst  the  second 
conducting  wire  is  brought  in  contact  with  the  other  portion  of  tinfoil, 
the  moment  the  circuit  is  completed,  its  fibres  will  be  seen  to  contract  in 
a  rectilinear  direction,  and  at  the  same  time  to  become  thicker,  whilst 
the  transverse  striae  are  more  closely  approximated  (vide  Fig.  109,  which 
represents  both  a  contracted  and  an  extended  muscle).  The  muscular 
fibres  remain  in  this  condition  so  long  as  the  galvanic  influence  is  kept 

FIG.  109. — A  primitive  fasciculus  of  a  Frog's  muscle  in  different  degrees  of  extension : 
Jl,  the  fasciculus,  stretched  and  slender,  with  broad  distant  transverse  strice;  J5,  the  same  not 
extended,  broader,  and  with  narrower,  closely  approximated  strise — Magnified  350  diameters. 


THE    MUSCULAR    SYSTEM.  265 

up,  whilst  when  the  circuit  is  broken  they  elongate  themselves  as  rapidly 
as  they  contracted,  and  present  zigzag  flexures,  when  the  muscle  is  lying 
free,  but  not  when  it  is  stretched  by  small  weights  attached  to  it  by 
threads.  From  this  it  is  evident,  that  if  zigzag  flexures  take  place 
during  life,  which  is  not  yet  known  to  occur,  they  can  only  arise  when 
muscles  in  the  quiescent  condition  are  not  in  a  state  of  tension ;  as,  for 
instance,  in  the  case  of  a  flexor  muscle,  which  has  come  into  a  state  of 
rest  after  it  has  produced  its  full  effect  upon  the  limb.  The  sarcolemma 
is  readily  seen  in  the  muscles  of  Amphibia  and  Fishes,  especially  in 
specimens  preserved  in  spirit,  in  which  it  frequently,  but  for  the  most 
part  in  places,  appears  at  a  distance  from  the  fibrils.  In  the  higher 
animals  and  in  man,  it  is  occasionally  seen  when  the  fasciculi  are  teased 
out ;  and  also  in  macerated  and  boiled  muscles,  and  on  the  addition  of 
acetic  acid  or  alkalies.  For  this  purpose  I  would  especially  recommend 
caustic  soda,  which  in  many  cases  renders  the  contents  of  the  muscular 
tubules  so  fluid,  that  they  escape  in  a  continuous  stream  together  with 
the  nuclei,  when  the  sheaths  come  very  clearly  into  view.  In  no  case, 
however,  is  the  sarcolemma,  in  man,  more  beautifully  exhibited  than  it  is 
in  softened,  atrophied  muscles  which  have  undergone  fatty  or  other  de- 
generations ;  and,  in  fact,  the  greater  the  degree  of  degeneration,  the 
more  distinctly  is  this  structure  exhibited.  The  muscular  fibrils,  in  fresh 
muscles,  are  constantly  visible  only  in  a  transverse  section,  and  in  the 
thoracic  muscles  of  insects,  elsewhere  it  is  true  they  are  occasionally 
seen,  but  more  by  chance  than  otherwise.  They  are  easily  isolated 
artificially  in  preparations  preserved  in  spirit,  particularly  in  the  peren- 
nibranchiate  Reptiles  (Siredon,  Proteus,  &c.),  by  treatment  with  chromic 
acid  (Hannover),  by  maceration  for  from  8  to  21  days,  at  a  temperature 
of  1—8°  R.  in  water,  to  which,  for  the  prevention  of  putrefaction,  some 
corrosive  sublimate  has  been  added  (Schwann) ;  maceration  also  in  the 
fluids  of  the  mouth  (Henle)  allows  of  their  being  readily  exhibited ; 
whilst,  according  to  Frerichs  (Wagner,  "  Handworterb.,"  III.  I.  p.  814), 
in  the  stomach,  the  fasciculi  break  up  into  Bowman's  discs.  The  nuclei 
of  the  fasciculi  are  best  studied  under  the  application  of  acetic  acid ;  by 
soda  (vide  supra)  they  may  be  isolated,  and  by  potassa  be  made  to  swell 
considerably  (Donders).  On  the  subject  of  the  effect  of  various  reagents 
on  the  elementary  tissues  of  muscle,  the  treatises  of  Donders  (Holland. 
"Beitrage")  and  Paulsen  ("  Observ.  michrochem.,"  Dorpat,  1849)  may 
be  consulted.  The  vessels  of  muscle  are  studied  in  fresh,  thin  muscles, 
and  in  injected  preparations;  the  nerves  in  the  smallest  human  muscles, 
in  the  muscles  of  the  smaller  Mammalia,  in  the  cutaneous  muscle  on  the 
thorax  of  the  Frog,  with  or  without  the  addition  of  soda.  The  perimysium, 
and  the  form  and  position  of  the  muscular  fibres,  are  very  well  shown 
in  transverse  sections  of  half-dried  muscles;  and  the  same  observation 
holds  good  with  respect  to  the  elementary  tissues  of  the  tendons.  The 


266  SPECIAL    HISTOLOGY. 

insertions  of  the  latter  into  the  bones,  and  their  cartilage-cells  in  those 
situations  are  readily  seen  ;  in  the  tendo  Achillis,  for  instance,  in  vertical 
sections  of  dried  preparations;  with  respect  to  their  relation  to  the 
muscular  fasciculi,  vide  supra,  §  81.  In  order  to  examine  the  cartilage- 
cells  in  tendons,  thin  horizontal  sections  are  taken  from  the  surface, 
which  are  treated  with  acetic  acid,  or  a  very  dilute  solution  of  soda.  For 
the  study  of  the  development  of  muscle,  the  naked  Amphibia  must  be 
placed  in  the  first  rank,  and  the  Mammalia  only  in  the  second. 

Literature. — Besides  the  memoirs,  cited  in  §  27,  there  are  to  be  men- 
tioned: G.  Valentin,  article  "  Muscles,"  in  the  "  Encyclopaedic  Dictionary 
of  the  Medical  Sciences,"  vol.  xxiv.  pp.  203-220,  Berlin,  1840  ;  H.  R. 
Ficinus,  "De  fibrse  muscularis  form&  et  structure  Diss.  inaug.,"  Lips., 
1836,  4,  cum  tab. ;  F.  Will,  some  remarks  upon  the  origin  of  the  trans- 
verse stripes  of  muscles,  in  Muller's  "Archiv,"  1843,  p.  358  ;  R.  Remak, 
on  the  "  Development  of  the  Primitive  muscular  Fasciculi,"  in  Froriep's 
"N.  Notiz.,"  1845,  Nr.  768  ;  Ed.  Weber,  art.  "Muscular  Motion,"  in 
R.  Wagner's  "Manual  of  Physiology,"  vol.  iii.  2d  division,  1846  ;  Kol- 
liker,  in  "Ann.  d.  Sc.  Nat.,"  1846  ;  Dobie,  "  Observations  on  the  Minute 
Structure  and  Mode  of  Contraction  of  Voluntary  muscular  Fibre,"  in 
"Ann.  Nat.  Hist.,"  N.  Ser.  III.  1849;  Lebert,  "  Recherches  sur  la  For- 
mation des  Muscles  dans  les  Animaux  vertebras,  in  Ann.  d.  Sc.  N.," 
1850,  p.  205. 


OF  THE  OSSEOUS  SYSTEM. 

§  88.  The  Osseous  System  consists  of  a  great  number  of  hard  organs, 
the  Bones,  of  a  peculiar,  uniform  structure,  which  are  united  either 
immediately  or  by  means  of  other  tissues,  such  as  cartilage,  ligaments, 
or  articular  capsules,  into  a  connected  whole — the  skeleton. 

The  osseous  tissue,  in  man,  presents  two  principal  forms — the  compact 
and  spongy.  The  perfect  solidity  of  the  former,  however,  is  only  appa- 
rent, as,  even  to  the  naked  eye,  it  is  seen  to  be  penetrated  by  narrow 
channels  which  run  in  various  directions,  and  by  a  still  greater  number 
of  similar  but  smaller  canals,  which  are  brought  into  view  by  the  micro- 
scope. These  vascular  or  Haversian  canals  (medullary  canals  of  authors), 
may  be  said  to  be  almost  entirely  absent  in  the  spongy  substance,  in 
which  they  are  represented  by  wider,  rounded,  or  elongated  spaces, 
visible  to  the  unassisted  eye,  which  are  filled  with  marrow,  in  some 
bones  occupied  by  veins  or  nerves  (cochlea),  and  termed  the  medullary 
spaces  or  cells  (cancelli,  cellules  medullares).  These  spaces  all  anasto- 
mose together,  and  are  formed  by  the  reticular  arrangement  of  the  small 
quantity  of  osseous  tissue,  which  is  disposed  in  the  form  of  fibres,  larninse, 
and  small  rods.  When  the  spaces  are  of  a  larger  size,  the  substance  is 


THE    OSSEOUS    SYSTEM.  267 

termed  subst.  cellularis,  and  when  smaller,  subst.  reticularis.  The  latter, 
in  some  situations  where  the  cavities  are  smaller,  and  the  osseous  parti- 
tions stronger,  approaches  in  character  the  compact  substance,  although 
it  does  not  actually  become  such ;  and  in  others  it  passes  without  any 
defined  limit,  into  compact  tissue.  This  does  not,  however,  prove  that 
the  two  substances  are  identical,  but  as  we  learn  from  observation  of 
their  development,  depends  simply  upon  the  circumstance  that  the 
spongy  substance  very  frequently  arises  in  a  partial  expansion  of  the 
compact.  The  share  taken  by  the  two  substances  in  the  formation  of 
the  different  bones,  and  parts  of  bones,  varies  very  considerably.  It  is 
only  in  a  few  situations  that  the  compact  substance  is  met  with  by  itself 
without  vascular  canals — as  in  the  lamina  papyracea  of  the  ethmoid 
bone,  some  portions  of  the  lachrymal  and  palate  bones,  &c.  It  occurs 
more  frequently,  however,  with  vascular  canals,  and  without  spongy 
substance  as  in  many  individuals  in  the  thinnest  portion  of  the  scapula, 
ilium,  acetabulum,  cranial  bones  (ala  magna,  parva  of  the  sphenoid,  the 
orbital  process  of  the  frontal  bone,  &c.)  Spongy  substance  with  a  thin 
compact  cortex,  without  vascular  canals,  exists  in  the  auditory  bones,  on 
the  surfaces  covered  with  cartilage  of  all  bones,  probably  also  in  the 
smaller  spongy  bones.  In  all  other  cases,  and  consequently  in  most 
situations,  the  two  substances  are  conjoined,  but  in  such  a  way,  that 
sometimes  the  spongy  substance  predominates  (spongy  bones  and  parts 
of  bones),  as  in  the  vertebra?,  carpal  and  tarsal  bones  ;  sometimes  the 
compact,  as  in  the  diaphyses  of  the  long  bones ;  or  the  two  are  in  equal 
proportions,  as  in  the  flat  bones. 

§  89.  Intimate  Structure  of  the  Osseous*  Tissue. — The  osseous  tissue 
consists  of  a  dense,  for  the  most  part  indistinctly  lamellar  fundamental 
substance  or  matrix,  penetrated  by  vascular  canals  and  numerous  minute 
microscopic  spaces — the  bone-cells,  or  lacuna?  (bone-corpuscles  of  authors), 
having  very  minute  hollow  processes,  the  lone-canaliculi. 

The  vascular  canals  of  the  bones,  or  the  Haversian  canals  (canaliculi 
medullares),  are  minute  tubules,  having  an  average  diameter  of  0 -QI- 
C-OS of  a  line,  and  in  the  extremes  one  varying  from  0*004  to  0-18  of  a 
line,  and  which,  except  in  the  thinner  parts  of  the  facial  bones,  as  above 
mentioned,  exist  universally  in  the  compact  substance,  forming  in  it  a 
wide  network  similar  to  that  of  the  capillaries.  In  the  long  bones,  and 
also  in  the  ribs,  clavicle,  pubis,  iscJiium,  and  lower  jaw,  they  run  chiefly 
in  a  direction  parallel  to  the  long  axis  of  the  bone,  and,  as  shown  in 
longitudinal  sections,  either  parallel  to  the  surface  or  perpendicular  to 
it,  at  distances  varying  from  0*06  to  0'14  of  a  line  apart.  They  are 
connected  by  transverse  or  oblique  branches,  which  run  in  the  direction 
both  of  the  radius  and  of  the  tangents  of  a  transverse  section  of  the 
bone.  Consequently,  under  a  low  magnifying  power,  in  longitudinal 


268 


SPECIAL    HISTOLOGY. 


sections  of  one  of  those  bones,  either  parallel  to  the  surface  or  perpen- 
dicular  to  it,  closely  approximated  canals  running   parallel  to  each 


Ficr.  110. 


Fisr.  111. 


other,  chiefly  in  a  longitudinal  direction,  are  seen,  here  and  there  with 
connecting  branches,  and  thus  forming  a  network,  consisting  of  elon- 
gated, and  most  generally  rectangular  meshes  (Fig.  111).  And  in  a 

transverse  section — transverse  sections 
of  the  canals,  placed  at  tolerably  defi- 
nite but  small  distances  apart,  are  prin- 
cipally apparent  (Fig.  112);  which, 
more  especially  in  younger  bones,  are 
occasionally  connected  by  a  tangential 
branch,  and  some  anastomoses  in  the 
direction  of  the  radius.  In  transverse 
sections  of  festal  and  undeveloped  bone 
(in  man  even  at  the  age  of  eighteen), 
scarcely  any  transverse  canals  occur, 
but  chiefly  those  running  horizontally 

FlG.  110. — Segment  of  a  transverse  section  from  the  shaft  of  the  femur  of  an  individual  18 
years  old:  a,  Haversian  canals;  6,  their  openings  internally;  c,  externally ;  d,  osseous  sub- 
stance with  lacunae.  In  this  figure  transverse  sections  of  vascular  canals  and  fundamental 
lamellae  are  not  shown. — Magnified  350  diameters. 

FlG.  111. — Haversian  canals  from  the  superficial  lamellae  of  the  femur  of  an  individual  18 
years  old,  treated  with  hydrochloric  acid :  a,  canals ;  6,  osseous  substance  with  lacunae. — 
Magnified  60  diameters. 


THE    OSSEOUS    SYSTEM.  269 

in  the  direction  of  the  tangents  and  radius  (Fig.  110),  so  that  the  bones 
appear  to  consist  entirely  of  short  thick  lamellae,  each  of  which,  upon 
closer  examination,  is  seen  to  belong  to  two  canals,  and  exhibits  a  pale 
central  line,  indicating  the  division  between  the  two  constituent  portions 
of  which  it  is  formed. 

In  the  jto  bones,  the  greater  number  of  the  canals  do  not  run  in  the 
direction  of  the  thickness  of  the  bone,  but  almost  all,  parallel  with  its 
surface,  and  indeed  in  lines  which  may  be  conceived  as  radiating  from 
one  point  (tuber  pariet  ale,  front  ale,  upper  and  anterior  angle  of  the 
scapula,  articular  portion  of  the  ilium)  in  a  penicillar  or  stellate  manner 
towards  one  or  several  sides ;  or  less  frequently,  as  in  the  sternum,  are 
all  parallel  to  each  other.  In  the  short  bones,  lastly,  there  is  most 
usually  one  predominant  direction  in  which  the  canals  run,  as  the  ver- 
tical in  the  vertebrae, — that  of  the  long  axis  of  the  extremity  in  the 
carpal  and  tarsal  bones,  &c. ;  it  must  be  remarked,  however,  that  the 
larger  processes  of  these  bones,  as,  for  instance,  the  spinous  processes 
of  the  vertebrae,  differ  in  this  respect  from  the  rest  of  the  bone,  and,  like 
those  of  other  bones,  such  as  the  coracoid  and  styloid  processes,  exhibit 
the  same  disposition  of  the  canals  as  that  which  exists  in  one  of  the 
shorter  cylindrical  bones.  The  lamellae,  fibres,  and  bars  of  the  spongy 
substance,  occasionally  present  a  few  vascular  canals,  but  only  when 
they  are  of  some  thickness. 

As  the  Haversian  canals  are  vascular  channels,  they  open  in  certain 
situations :  1,  externally,  on  the  outer  surface  of  the  bone ;  and,  2, 
internally,  on  the  walls  of  the  medullary  cavities  and  spaces.  In  both 
situations,  excessively  fine  and  coarser  pores  may  be  everywhere  per- 
ceived, partly  visible  to*  the  naked  eye,  and  which  are  more  numerous 
in  proportion  to  the  thickness  of  the  cortex  of  the  bone.  But  the  rela- 
tion of  the  vascular  canals  in  the  compact  substance  to  these  canals 
thus  proceeding  from  within  and  without,  only  partially  resembles  that 
between  the  branches  and  trunks  of  vessels,  and  only  in  the  outermost 
and  innermost  lamellae  of  the  cortical  substance.  In  the  interior  of  the 
cortical  portion  of  a  bone  the  canals  are  independent,  and  morphologi- 
cally may  be  most  aptly  compared  to  a  capillary  network,  which*  at  its 
borders  is  in  connection  at  many  points  with  larger  canals.  Where  the 
cortical  substance  rests  upon  the  spongy  substance,  as  in  the  interior  of 
the  ends  of  the  diaphyses,  and  in  the  lateral  periphery  of  the  apopliyses, 
the  vascular  canals  are  continuous,  sometimes  abruptly,  sometimes  quite 
gradually,  expanding  in  an  infundibuliform  manner,  and  frequently 
anastomosing,  with  smaller  or  larger  medullary  spaces,  so  that,  very 
often,  no  definite  limit  is  perceptible  between  them.  I  have  never  yet 
noticed  caecal  terminations  of  the  vascular  canals  ;  it  is,  however,  certain 
that  in  many  situations  on  the  surface  they  must  constitute,  over  exten- 
sive spaces,  closed  networks,  especially  where  very  few  or  no  vessels 


270  SPECIAL    HISTOLOGY. 

enter  the  compact  substance,  as  at  the  points  of  insertion  of  many 
tendons  and  ligaments,  and  beneath  several  muscles  (temporal).* 

§  90.  The  matrix  of  bone  is  lamellar,  and  the  lamellae  (Fig.  112)  are 
apparent  in  thin  sections,  but  are  still  better  shown  in  bones  from  which 
the  earthy  matter  has  been  removed,  or  which  have  been  exposed  to  the 
weather  or  calcined,  in  which  cases  the  lamellae  exfoliate,  and,  in  the 
cartilage  of  decalcified  bones,  may  even  be  raised  with  the  forceps.  In 
the  middle  portions  of  the  cylindrical  bones  they  constitute  two  systems  : 
— one  general,  in  which  the  lamellae  are  parallel  with  the  external  and 
internal  surfaces  of  the  bone,  and  numerous  special  ones,  around  the 
separate  Haversian  canals.  These  two  systems  are  in  some  places  in 
immediate  connection,  but,  in  most,  merely  in  apposition,  and  on  that 
account  they  may  conveniently  be  regarded  as  of  two  kinds ;  a  view 
with  respect  to  them  which  is  in  some  degree  supported  by  the  pheno- 
mena presented  in  their  development. 

The  lamellce  of  the  Haversian  canals  (Fig.  112  c,  113  5)  surround 
those  canals  concentrically,  in  greater  or  less  number.  They  consti- 
tute, as  it  were,  the  walls  of  the  canal,  and  are  intimately  united  to  each 

*  [A  most  valuable  contribution  to  our  knowledge  of  the  structure  and  development  of 
Bone  has  lately  been  made  by  Messrs.  Tomes  and  De  Morgan,  in  their  "  Observations  on 
the  Structure  of  Bone,"  read  before  the  Royal  Society  in  June,  1852,  but  not  yet  published. 
We  are  enabled,  however,  by  the  kindness  of  those  gentlemen  in  allowing  us  to  inspect 
many  of  their  preparations,  and  in  furnishing  us  with  the  proofs  of  their  paper,  to  make 
some  very  important  additions  and  corrections  to  the  text.  We  may  add,  that  although  we 
do  not  always  agree  with  Messrs.  Tomes  and  De  Morgan  in  the  interpretation  of  the  facts, 
differences  which  we  shall  duly  note,  our  own  investigations  have  led  us  to  believe  that 
their  paper  is  by  far  the  most  accurate  account  of  the  process-of  ossification  which  has  yet 
appeared. 

These  writers  have  pointed  out  the  important  fact,  that,  besides  the  well-known  Haver- 
sian canals,  other  cavities  exist  in  bone,  which  they  denominate  Haversian  spaces.  These 
have  irregular  outlines  similar  to  that  of  the  surface  of  exfoliations,  while  the  boundaries  of 
the  Haversian  canals  are  always  more  smooth  and  rounded.  Again,  in  the  latter,  the 
laminae  are  more  or  less  conformable  with  the  canal ;  while  the  walls  of  the  spaces  are 
formed  by  the  unconformable  edges  and  surfaces  of  the  laminae  of  the  adjacent  Haversian 
canals,  which  have,  as  it  were,  been  eaten  away  to  form  the  space.  In  fact,  bone,  so  far 
from  being  a  permanent  or  stationary  structure,  is  continually  being  deposited,  and  as  con- 
stantly re-absorbed.  The  Haversian  spaces  are  the  result  of  the  absorption  of  previously- 
existing  osseous  tissue ;  but  when  this  process  has  gone  on  to  a  certain  extent,  deposition 
commences  in  the  spaces,  and  they  are  converted  into  Haversian  canals.  The  calibre  of 
these  canals  now  becomes  narrowed  up  to  a  certain  point  by  the  continual  laminar  deposi- 
tion of  ossific  matter,  which,  after  a  while,  is  traversed  by  new  absorptive  tunnels,  or 
Haversian  spaces,  and  is  removed  in  its  turn. 

The  spaces  are  very  numerous  arid  large  in  newly-formed  bone  situated  near  ossifying 
cartilage;  while,  in  older  bone,  they  are  far  less  frequent  and  generally  smaller.  They  are, 
however,  never  absent ;  being  found  even  in  old  subjects.  They  may  be  observed  in  various 
conditions  in  a  series  of  sections.  In  one  place  the  space  will  have  attained  a  large  size, 
while,  in  another  part  of  the  same  section,  its  commencement  will  be  seen  extending  from 
one  side  of  an  Haversian  canal.  One  side  of  a  space  may  be  becoming  the  seat  of  a  new 
system,  while  the  opposite  is  undergoing  further  enlargement. — TRS.] 


THE    OSSEOUS    SYSTEM. 


271 


other,  much  in  the  same  way  that  the  laminae  of  the  walls  of  the  larger 
vessels  are  continuous  with  each  other.     The  number  of  lamellae  belong- 


Fiff.  112. 


Fig.  113. 


ing  to  a  canal,  and  the  collective  thickness  of  the  system  formed  by 
them  varies  not  inconsiderably,  and  bears  no  constant  relation  to  the 
size  of  the  canal,  as  is  the  case  to  some  extent  in  the  vessels ;  small 
canals,  therefore,  are  not  unfrequently  surrounded  by  numerous  lamellae, 
and  larger  ones  by  but  few.*  In  general,  it  may  be  said  that  the  largest 

FIG.  112. — Segment  of  a  transverse  section  of  a  human  metacarpal  bone,  treated  with  oil 
of  turpentine :  a,  external  surface  of  the  bone,  with  the  exterior  fundamental  lamellae ;  6, 
internal  surface  towards  the  medullary  cavity,  with  the  inner  lamellae;  c,  Haversian  canals 
in  transverse  section  with  their  lamellar  systems;  d,  interstitial  lamellae ;  e,  lacunse  and 
processes. — Magnified  90  diameters. 

FIG.  113. — Portion  of  a  transverse  section  of  the  shaft  of  the  humerus,  magnified  350  dia- 
meters, treated  with  oil  of  turpentine :  a,  Haversian  canals ;  6,  their  lamellar  systems,  each 
lamella  presenting  a  more  transparent  and  more  opaque  portion,  with  radiating  striae  in  the 
latter;  e,  darker  lines,  which  probably  indicate  greater  intermissions  in  the  deposition  of  the 
osseous  substance ;  d,  lacunae  without  visible  rays.  From  a  preparation  by  Dr.  H.  Miiller. 

*  [The  "interstitial  laminae"  are  the  remains  of  Haversian  systems,  the  larger  parts  of 
which  have  been  removed  by  absorption  to  form  new  spaces.  The  irregular  outline  of  the 


272  SPECIAL    HISTOLOGY. 

canals  have  thin  walls,  those  of  a  middle  size  thick  ones,  and  the  most 
minute,  again,  walls  of  little  thickness.  The  thinnest  walls  I  have 
commonly  noticed  measure  0-008-0-02,  and  the  thickest,  0*08-0*1  of 
a  line.  The  thickness  of  the  lamellae  varies  between  0-002  and  0-005 
of  a  line,  being  on  the  average  0*003  to  0*004  of  a  line ;  in  number 
there  are  usually  from  eight  to  fifteen  ;  sometimes,  however,  no  more 
than  four  or  five,  and  occasionally  as  many  as  from  eighteen  to  twenty- 
two. 

The  lamellae  of  the  Haversian  canals,  together  with  their  canals, 
extend  to  the  internal  and  external  surfaces  of  the  diaphyses,  where 
they  are  connected  with  the  general  lamellae  above  mentioned, — the 
fundamental  lamellce  (Fig.  111).  The  latter  constitute  an  external  and 
an  internal  layer,  and  penetrate  also  into  the  substance  of  the  diapliysis, 
where  they  are  interposed  between  the  separate  lamellar  systems  and 
the  medullary  canals.  The  two  former  layers,  or  the  external  and  in- 
ternal fundamental  lamellce,  are  parallel  to  the  external  and  internal 
surfaces  of  the  bone,  and  vary  in  thickness  apparently  without  any 
definite  rule,  from  0*02  to  0*3,  or  even  0*4  of  a  line.  The  latter,  or 
interstitial  fundamental  lamellce,  are  seen  most  clearly  where  the  super- 
ficial fundamental  laminae  are  developed,  in  partial  connection  and 
parallel  with  which  they  extend  from  without  inwards,  and  from  within 
outwards,  some  distance  into  the  substance  of  the  diapJiyses,  where  they 
are  interposed,  in  masses  varying  in  thickness  from  0*02  to  0*12  of  a 
line,  between  the  other  lamellae  (Fig.  112  d).  In  the  interior  of  the 
compact  substance,  on  the  other  hand,  in  man,  the  Haversian  systems 
are  so  closely  crowded  that  there  can  be  no  question  as  to  the  non-exis- 
tence of  lamellar  groups  between  them,  and  it  is  evident  that  those 
lamellae,  which  in  a  transverse  section  appear  in  man  to  be  parallel 
with  the  surface,  almost  all  belong  to  horizontal  canals ;  and  it  is  but 
rarely  that  distinct  interstitial  masses  are  seen,  as  is  usually  the  case  in 
other  mammalia.  The  thickness  of  the  separate  lamellae  just  described 
is  much  the  same  as  that  of  the  lamellae  of  the  Haversian  canals,  and 
their  number  varies  from  10  to  100. 

We  have  hitherto  considered  only  the  diapliyses  of  the  long  bones. 
In  their  apophyses,  the  thin  cortical  layer  of  compact  substance  natu- 
rally presents  only  a  few  systems  of  Haversian  canals,  which,  however, 
are  constituted  as  elsewhere.  The  exterior  fundamental  lamellae  are 
few  in  number,  and  internally,  owing  to  the  existence  there  of  the  spongy 
substance,  they  are  wholly  wanting.  In  the  latter  substance,  the  very 
few  Haversian  canals  present  lamellar  systems  as  usual,  except  that 
they  are  thin,  and  the  remainder,  according  to  the  condition  of  the 
osseous  network,  consists  of  a  lamellated  and  fibrous  tissue,  which  in 

outermost  of  the  lamina  of  an  Haversian^canal  (see  Fig.  113)  results  from  its  being  the  first 
deposition  within  the  pre-formed  irregular  Haversian  space.  (Tomes  and  De  Morgan,  1.  c., 
p.  5.)— TRS.] 


THE    OSSEOUS    SYSTEM.  273 

general  follows  the  contour  of  the  medullary  spaces  and  cells.  The 
flat  and  short  bones  present  a  similar  arrangement  internally,  whilst  the 
cortical  substance  of  these  bones  diifers  from  that  of  the  cylindrical, 
only  in  the  circumstance,  that  the  fundamental  lamellae,  in  the  flat  bones, 
form  layers  parallel  with  both  surfaces  of  the  bone.  The  thickness  of 
the  fundamental  lamellae  in  the  cranial  bones  (parietal),  is  sometimes 
the  same  in  both  aspects,  and  varies  from  0'08  to  0-16  of  a  line,  some- 
times they  are  wanting  in  vascular  situations,  and  in  places,  wholly  so, 
on  the  external  aspect  of  the  bone,  in  which  case  the  Haversian  lamellae 
reach  almost  to  the  surface. 

With  respect  to  the  intimate  structure  of  the  osseous  lamellae,  which 
is  best  studied  in  transverse  sections,  dried,  polished,  and  sufficiently 
thin,  there  is  usually  evident,  besides  the  bone-cells  and  canaliculi,  in 
the  generally  not  very  distinct  lamellae,  an  extremely  fine  though  very 
distinct  punctuated  appearance,  so  that  the  whole  osseous  tissue  appears 
granular,  and  to  be  composed  as  it  were  of  separate,  densely  crowded, 
pale  granules,  measuring  0-0002  of  a  line  (Fig.  114).  If  water  or 
weak  syrup,  or  albumen,  be  applied  to  a  slice  of  bone,  it  assumes  a 
condition  probably  similar 
to  that  which  it  possesses  Flg 

during  life.  The  lamellae, 
for  the  most  part  (both  in 
transverse  and  perpen- 
dicular sections),  become 
clearly  visible,  and  their 
granular  aspect  is  quite  dis- 
tinct, although  not  so  de- 
fined as  before  the  bone  was 
thus  treated.  For  in  the  first  place,  together  with  the  granules,  there  is 
exhibited  a  close,  pale  striation,  referable  to  the  canaliculi,  which  are  filled 
with  fluid  and  which,  extending  in  various  directions  through  the  tissue, 
renders  its  delineation  more  complex ;  there  are  also  apparent  in  each 
lamella,  as  it  were,  two  layers,  one  pale  and  more  homogeneous,  the 
other  darker  and  granular,  which  latter  chiefly  is  striated.  When  this 
condition  is  clearly  displayed,  an  extremely  delicate  marking  is  produced, 
resembling  that  seen  in  transverse  sections  of  certain  urinary  calculi 
(Fig.  113).  When  once  seen  in  moistened  sections,  indications  of  this 
arrangement  will  occasionally  be  observed  in  dried  preparations.  In 
bone  treated  with  hydrochloric  acid,  the  granules  and  striae  (dependent 
on  the  canaliculi),  in  sections  both  transverse  and  perpendicular  to  the 

FIG.  114.  Portion  of  a  perpendicular  section  of  a  parietal  bone,  magnified  300  diame- 
ters:  a,  lacunae,  with  pale,  only  partially-visible  prolongations,  filled  with  fluid  as  in  the 
natural  state  :  b,  granular  matrix.  The  striated  places  indicate  the  boundaries  of  the 
lamellae. 

18 


274  SPECIAL    HISTOLOGY. 

surface,  are  less  distinctly  apparent,  whilst  the  lamellar  structure  is  very 
manifest,  and  most  generally  two  layers  may  be  noticed  in  each  lamella, 
though  by  no  means  so  clearly  as  shown  in  Fig.  113.*  In  sections 
parallel  to  the  surface,  the  bone,  in  many  situations,  appears  almost 
homogeneous  throughout,  presenting  no  trace  of  a  granular  structure, 
whilst  in  others  a  structure  of  that  kind  is  obscurely  visible,  together 
with  minute  points  (Deutsch),  and  besides  these  a  longitudinal  striation  ; 
which  last  gives  the  whole  a  fibrous  aspect.  From  this  circumstance, 
many  authors  appear  to  have  been  led  to  describe  the  bone  as  composed 
of  fibres,  but  quite  incorrectly,  for  although  the  study  of  their  develop- 
ment shows,  that  the  ossifying  parts  are,  to  a  certain  extent,  very  dis- 
tinctly fibrous,  it  is  impossible  to  demonstrate  anything  of  the  sort  in 
perfect  bone.  On  the  other  hand,  there  is  no  doubt  that  a  coarsely 
fibrous  appearance  exists,  and  especially  in  the  bone-cartilage  of  the 
compact  substance,  as  has  already  been  remarked  by  others,  and  which 
is  probably  due  to  the  fibrous  fasciculi  of  the  original  blastema;  care 
however  should  be  taken  not  to  look  upon  longitudinal  sections  of 
lamellae  as  such  fibres. f  When  bone  is  burnt  and  the  fragments  crushed, 

*  [According  to  Tomes  and  De  Morgan,  the  laminae,  when  well  developed,  are  always 
constituted  of  two  portions, — an  outer,  highly  granular,,  often  composed  of  a  single  line  of 
large  granules,  and  an  inner,  which  is  singularly  clear  and  transparent,  and  to  all  appear- 
ance without  granulation  or  any  recognizable  structure.  This  distinct  separation  into  two 
layers,  however,  does  not  always  exist;  and  in  a  complete  Haversian  canal,  the  innermost 
lamina  of  all  is  frequently  clear,  glassy,  and  structureless. 

The  circumferential  laminae  are  not  so  constantly  present  as  is  generally  supposed,  and 
they  rarely  entirely  surround  the  shaft  of  a  long  bone,  still  more  rarely  the  flat  bones.  In 
the  fast-growing  bones  of  young  animals  they  are  absent,  while  in  adults  they  are  usually 
well  developed  in  some  parts ;  so  that  their  presence  seems  to  indicate  that  the  bone  is 
nearly  stationary  in  its  growth.  In  young,  rapidly  growing  bone,  the  circumferential  laminae 
are  replaced  by  a  series  which  may  be  called  the  undulating  lamina.  The  surface  of  the 
bone  sends  off  processes,  formed  of  reduplicated  lamina?,  which  eventually  arch  over  and 
enclose  those  vessels  of  the  periosteum  which  lie  nearest  them.  The  spaces  thus  formed 
become  the  seat  of  Haversian  systems.  Young  growing  bone,  therefore,  may  be  distinguished 
from  that  of  adult  animals,  by  its  being  composed  of  Haversian  systems  with  intervening 
undulating  laminae.  (Tomes  and  De  Morgan,  b.  c.,  pp.  4-6.) — TRS.] 

t  [Messrs.  Tomes  and  De  Morgan  (1.  c.,  pp.  13,  14)  adduce  very  good  reasons  for  believ- 
ing that  the  fibrous  appearance  which  may  often  be  detected  in  the  laminaB  of  bone  arises 
from  imperfect  illumination  and  definition,  and  express  their  belief  that  bone  substance  "  is 
composed  of  granules  or  granular  cells,  imbedded  in  a  more  or  less  clear,  homogeneous  or 
subgranular  matrix."  They  go  on  to  say,  "  Thus  as  regards  the  basement,  homogeneous 
tissue,  it  will  be  found  that  where  lamination  is  highly  developed,  the  laminaB  have  a  trans- 
parent and  structureless,  and  a  more  opaque  and  granular  part,  to  which  the  former  appears 
to  be  the  matrix.  The  peripheral  lamina  of  the  Haversian  systems  is  generally  clear  and 
free  from  granularity,  and  the  internal  lamina  sometimes  presents  a  similar  structureless 
appearance.  The  matter  which  fills  up  the  Haversian  systems  in  the  full-grown  antlers  of 
the  Cervidae  affords  another  and  a  very  striking  example  of  transparent  structureless  osseous 
tissue,  which  in  this  instance  is  the  more  distinct,  from  the  absence  of  canaliculi  in  its  sub- 
stance. Then,  again,  we  have  another  instance  in  the  clear  tissue  which  is  sometimes  found 
between  the  superficial  Haversian  systems  of  ordinary  bone.  It  has  already  been  described 
as  a  non-laminated  element  found  on  the  surface  of  certain  bones.  In  the  instances  already 
cited,  and  no  doubt  in  many  others  which  may  be  found  in  the  skeletons  of  the  lower  ver- 


THE  OSSEOUS  SYSTEM.  275 


it  affords,  according  to  Tomes,  minute  angular  granules,  from  -Jth  to 
the  diameter  of  the  human  blood  corpuscle,  and  measuring,  according 
to  Todd  and  Bowman,  gouoth-niosth  of  an  inch,  and  which  are  also 
rendered  evident  when  bone  is  boiled  in  a  Papins'  digester.  From  these 
particulars,  and  from  the  granular  aspect  of  fresh  bone,  which  has  also 
been  noticed  by  Tomes  and  by  Todd  and  Bowman,  and  moreover  from 
the  pretty  nearly  equal  size  of  the  granules  visible  in  it,  with  those 
described  by  Tomes,  and  lastly,  from  the  circumstance  that  bone  treated 
with  hydrochloric  acid,  as  well  as  when  calcined,  both  present  a  perfectly 
homogeneous  substance  without  vacuities,  it  may  be  assumed  that  the 
osseous  tissue  consists  of  an  intimate  mixture  of  inorganic  and  organic 
compounds,  in  the  form  of  closely  connected  minute  granules. 

§  91.  Bone  Cavities  or  Cells,  and  Canaliculi  (lacunce  et  canaliculi 
ossium).  —  In  dried  sections  of  bone,  there  are  visible,  scattered  through- 
out the  entire  osseous  substance,  in  all  the  lamellae,  microscopic  melon- 
seed-shaped  corpuscles,  with  numerous,  fine,  ramified,  and  partially 
anastomosing  rays,  whose  opaque  and  white  color  (as  viewed  by  direct 
light)  is  due,  not  to  the  deposition  of  calcareous  salts,  as  was  formerly 
supposed,  and  on  which  account  they  were  termed  "  bone,"  or  "  calca- 
reous corpuscles,"  but  simply  to  their  being  filled  with  air.  In  fresh 
bone,  not  yet  deprived  of  its  watery  constituents,  nothing  can  be  seen 
in  these  bone-cells  or  lacunae  but  clear  contents  with  a  nucleus,  which 
may  best  be  described  as  the  nutritive  fluid  of  the  bone,  and  conse- 
quently the  designation  above  given  to  these  cavities  is  the  most  suitable. 

The  lacunce  are  elliptical,  flattened  cavities,  having  an  average  length 
of  0-01  of  a  line,  0-004  of  a  line  wide,  and  0-003  of  a  line  thick,  which 
give  off  both  from  the  borders,  and  particularly  from  the  surfaces,  a 
great  number  of  very  fine  canals,  measuring  0-0005-0-0008  of  a  line  in 
diameter  —  the  bone  canaliculi  above-mentioned  (Figs.  115,  116,  and  117) 
The  lacunae  are  equally  numerous  in  both  of  the  lamellar  systems  before. 

tebrata,  we  have  bone  tissue  without  obvious  granularity,  and  without  obvious  structure  ; 
and  although  it  forms  but  a  small  part  of  the  general  mass,  yet  from  its  constant  presence 
at  all  ages  and  in  all  subjects,  it  must  be  regarded  as  an  integral  and  normal  part  of  mam- 
marial  bone.  The  granular  condition  of  bone  tissue  is  tolerably  obvious  in  all  preparations, 
though  it  is  much  more  marked  in  some  specimens  than  in  others.  The  amount  of  the 
component  granules  varies  in  different  parts  of  the  same  specimen,  and  in  specimens  taken 
from  different  parts  of  the  skeleton.  Thus,  in  one  situation,  we  may  see  laminae  with  a 
highly  transparent  part  gradually  merging  into  a  transparent  tissue,  while  in  another  the 
lamince  may  be  granular  throughout.  Again,  in  young  bone  developed  in  cartilage,  the  part 
between  the  cells  becomes  highly  granular,  fragments  of  which  may  be  found  in  certain 
adult  bones,  as  in  the  petrous  portion  of  the  temporal  bone.  Bone  near  the  articular  surface 
frequently  presents  a  well-marked  granularity." 

We  may  remark,  in  addition  to  this  very  just  account  of  the  minute  structure  of  bone,  that 
of  the  lower  vertebrata  above  referred  to,  the  Skate  offers  one  of  the  best  examples  of 
structureless  bone,  in  those  polygonal  plates  which  are  developed  (not  on  the  surface,  as  is 
commonly  said,  but)  in  the  interior  of  the  cartilaginous  skeleton.  —  TRS.] 


276 


SPECIAL    HISTOLOGY. 


described,  and  are  placed  so  close  together,  that,  according  to  Harting 
(1.  c.,  p.  78),  from  709  to  1120,  or,  on  the  average,  910  of  them 
occur  within  the  space  of  a  square  millimeter.  They  lie  for  the 
most  part  within  the  lamellae,  but  also  between  them,  and  are  in- 
variably placed  with  their  broad  sides  parallel  with  the  surfaces  of 
the  lamellae.  The  canaliculi  proceeding  from  them  are  much  branched, 
and  penetrate  the  osseous  substance  in  all  directions,  their  course 
being  irregular,  and  often  actually  curved.  They  proceed  prin- 
cipally, however,  in  the  first  place,  from  both  surfaces  of  the  lacunae 
straight  through  the  lamellae ;  and  secondly,  parallel  with  the  Ha- 
versian  canals,  from  the  two  poles  of  the  lacunae.  It  is  only  in 
certain  limited  spots  that  these  canaliculi  present  ccecal  termina- 


Fig.  115. 

ym?**- 


Fig.  116. 


tions ;  everywhere   else  some  of  them  anastomose  in  the  most  various 
ways   with    the  canaliculi  of   the   neighboring   lacunae,    whilst  others 

FIG.  115. — From  a  transverse  section  of  the  shaft  of  the  humerus;  magnified  300  diam.: 
a,  Haversian  canals;  6,  lacunae  with  their  canals,  in  the  Haversian  lamellae;  c,  lacunae  of 
the  interstitial  lamellae ;  d,  lacunae  with  unilateral  canaliculi  proceeding  to  the  surface  of 
the  Haversian  system. 

FIG.  116. — Section  parallel  with  the  surface  from  the  shaft  of  a  human  femur  •  magnified 
100  diam. :  a,  vascular  canals:  6,  lacunae  seen  from  the  side,  belonging  to  the  lamellae  of 
these  canals  ;  c,  lacunae  viewed  on  the  flat  side,  in  lamellae  which  are  cut  horizontally. 


THE     OSSEOUS    SYSTEM. 


277 


communicate  with  the  vascular  canals,  the  medullary  cavities,  and  the 
medullary  spaces  or  cancelli  of  the  spongy  substance,  or  open  on  the 
surface  of  the  bone.  The  entire  osseous  substance,  therefore,  is  pene- 
trated ly  a  connected  system  of  cavities  and  canaliculi,  by  means  of 
•which  the  nutritive  juice  secreted  by  the  vessels  is  conveyed  into  its 
densest  tissue. 

The  lacunae  and  canaliculi  do  not  exhibit  precisely  the  same  condi- 
tions in  every  part  of  the  bones.  In  the  lamellar  systems  of  the  Ha- 
versian  canals,  as  seen  in  a  transverse  section,  the  elongated  lacunae, 
by  reason  of  their  curvature,  lie  as  it  were  concentric  to  the  canal,  and 
their  excessively  numerous  pores  or  canaliculi  necessarily  produce  a 
very  close  striation  radiating  from  the  vascular  canal  (Fig.  115). 
The  lacunae  are  sometimes  extremely  numerous,  sometimes  more 
scanty;  in  the  former  case  they  are,  for  the  most  part,  arranged 
in  tolerably  regular  alternation,  or  one  behind  the  other  in  the 
direction  of  the  radius  of  the  lamellar  system ;  but  they  are  also 
frequently  disposed  very  irregularly,  either  crowded  together  (vide 
the  lower  part  of  Fig.  115),  or  separated  by  wider  interspaces.  In 
horizontal  and  longitudinal  sections  of  Haversian  canals  (Fig.  116), 
when  the  section  has  passed  through  the  middle  of  a  canal,  the 
lacunae  appear  narrow  and  elongated,  and  disposed  in  rows  one  be- 
hind the  other,  and  in  numerous  layers  parallel  with  the  canal ;  and 
also  furnished  with  numerous  canaliculi,  which  proceed  for  the  most  part 

Fig.  117. 


directly  inwards  and  outwards  (consequently  transversely  through  the 
lamellae),  but  partly  in  a  direction  parallel   with  the  long   axis  of  the 

FIG.  117. — Lacunae  viewed  on  the  flat  side,  with  the  canaliculi,  from  the  parietal  bone; 
magnified  450  diam.:  the  spots  on  the  lacuna?  or  between  them  belong  to  canaliculi,  which 
are  cut  across,  or  are  the  openings  of  canaliculi  into  the  lacunae  ;  a  a  a,  groups  of  transverse 
sections  of  canaliculi,  each  group  belonging  to  a  lacuna  which  has  been  destroyed  in  the 
making  of  the  section. 


278  SPECIAL    HISTOLOGY. 

canal.  If  the  section  strike  the  surface  of  a  system,  the  superficial 
lacunas  come  into  view,  presenting  very  elegant  forms,  rounded  or  oval 
(Figs.  115  d,  and  117),  surrounded  in  an  irregular  manner  by  a  complete 
tuft  of  canaliculi,  which  look  directly  towards  the  observer,  and  con- 
sequently appear  more  or  less  shortened,  and  by  a  smaller  number  of 
other  canaliculi  distributed  on  the  surface  of  the  lamellae.  Occasion- 
ally, even  in  the  thinnest  parts  of  a  section,  there  occurs  a  tuft  of  canali- 
culi, cut  across  transversely,  and  without  the  lacuna  to  which  they 
belong,  whence  these  portions  of  bone  exhibit  a  sievelike  aspect.  All 
the  canaliculi  arising  from  the  inner  aspect  of  the  innermost  lacunae  of 
an  Haversian  system,  proceed  towards  the  canal,  with  which  they,  by 
this  means,  communicate,  as  may  be  clearly  seen  in  thin,  perpendicular, 
and  transverse  sections  of  bones  filled  with  air,  and  in  the  walls  of 
medullary  canals  laid  open  longitudinally.  From  the  borders  and  ex- 
ternal aspect  of  the  same  lacunae  other  canaliculi  are  given  off,  which  per- 
haps occasionally  terminate  in  blind  extremities,  but  for  the  most  part 
communicate  with  those  of  the  neighboring,  and  particularly  of  the  outer 
lacunae.  The  succeeding  rows  of  lacunae  are  all  mutually  connected  in  a 
similar  way,  and  thus  the  network  of  canaliculi  and  lacunae  extends  to  the 
outermost  lamellae  of  the  system,  where  the  lacunae  either  commuincate 
with  those  of  the  contiguous  systems  or  of  the  interstitial  lamellae,  or 
terminate  independently,  in  which  latter  case  (Fig.  115  d)  all  the  ca- 
naliculi, or  at  least  most,  and  the  longest  of  them,  proceed  inwards,  that 
is  to  say,  towards  the  vascular  canal,  from  which  they  derive  their 
nutritive  fluid. 

In  the  interstitial  osseous  substance  between  the  Haversian  systems, 
•when  it  exists  in  small  quantity,  the  few  lacunae,  frequently  not  more 
than  from  1  to  3  in  number,  are  disposed  more  irregularly,  and  also 
present  a  rounded  form  (Fig.  115  e);  when  the  interstitial  substance  is 
more  abundant,  and  distinctly  lamellar,  the  lacunae  are  also  disposed 
more  regularly,  with  their  sides  parallel  to  those  of  the  lamellae.  The 
canaliculi  of  these  lacunae,  in  like  manner,  communicate  with  each 
other,  and  with  those  of  the  neighboring  systems.  In  the  outer  and 
inner  fundamental  lamellae,  lastly,  the  lacunae  are  all  placed  with  their 
surfaces  parallel  with  those  of  the  lamellae,  and  consequently  looking, 
for  the  most  part,  inwards  and  outwards,  or  towards  the  centre  and 
periphery  of  the  bone.  In  transverse  sections  they  precisely  resemble 
those  of  the  Haversian  systems,  only  that  they  are  but  little  or  not  at 
all  curved,  except  in  the  smallest  cylindrical  bones.  In  longitudinal 
sections,  whether  perpendicular  or  parallel  to  the  surface,  they  present 
the  conditions  above  described,  with  this  limitation,  however,  that  a 
larger  number  of  lacunae,  of  course,  are  seen  in  the  same  space  in  the 
latter  case  than  in  the  former,  and  also  that  the  sievelike  aspect  described 
above  is  more  frequently  observed,  giving  the  bone  considerable  resem- 


THE    OSSEOUS    SYSTEM.  279 

blance  to  certain  sections  of  teeth  (Fig.  117).     The  canaliculi  of  these 
lamellae  communicate,  in  part  as  usual  with  each  other,  in  part  open  on 
the  external  and  internal  surfaces  of  the  bone  (Fig.  118).     At  the  points 
of  insertion  of  tendons  and  ligaments 
into   the  bones,   the   canaliculi  of  the 
outermost   lacunae   probably  terminate 
in  blind  extremities  ;  a  condition  which 
obtains  in  every   case,  in   those  parts 
of  bones  which   are  covered  with  car- 
tilage   (articular  ends,  ribs,  surfaces  of 
the   bodies  of  the  vertebrae,    &c.)     In  I 
the   rods,    fibres,    and    plates    of    the  1 
spongy  substance,   the  lacunae  are  dis-  fe 

posed  in  every  possible  direction,  but  for  the'  most  part,  with  their  long 
axis  parallel  to  that  of  the  fibres,  bars,  &c.,  and  with  their  flat  surfaces 
directed  towards  the  cancelli.  They  anastomose  also,  in  these  situa- 
tions, by  means  of  their  canaliculi ;  and  the  most  superficial  lacunae 
open  freely  into  the  cancelli. 

The  size  and  shape  of  the  lacunae,  in  man,  upon  the  whole,  vary  but 
little.  By  far  the  greater  number  are  melon-seed-shaped  or  lenticular, 
some,  more  fusiform  or  spherical.  In  sections  of  bone  well  filled  with 
air,  in  which  alone  I  have  made  my  measurements,  I  find  their  average 
length  to  be  0-01-0-014  of  a  line,  frequently  under  and  above  that  size, 
or  from  0-006  to  0-016,  rarely  0-02  or  even  0-024  of  a  line  (cranial 
bones,  lower  jaw).  The  breadth,  measured  in  horizontal  sections,  is 
0-003-0-006  of  a  line;  in  transverse,  it  is  usually  somewhat  greater,  or 
as  much  as  0*008,  or  even  0*01  of  a  line,  because  the  limits  between  the 
canaliculi  and  lacunae  cannot  always  be  accurately  defined.  Their  thick- 
ness or  depth,  lastly,  in  the  smallest  lacunae,  is  0-003-0-004,  and  in  the 
larger  0-002-0-004  of  a  line.  The  diameter  of  the  spherical  lacunae  is 
0-006-0-008  of  a  line.  The  canaliculi  are,  on  the  average,  0-008-0-016 
of  a  line  long,  seldom  less  or  more,  up  to  0-02  and  0-024  of  a  line;  in 
diameter  they  measure  0-0004  of  a  line ;  at  the  finest  extremities,  0-0005- 
0-0008,  on  the  average;  0-0008-0-001  of  a  line,  at  their  origin  from  the 
lacunae.  Their  true  distance  apart,  in  horizontal  sections,  in  which  they 
appear  as  holes,  is  0*0008-0-002  of  a  line;  in  transverse  sections,  in 
which  they  produce  the  radiating  striae,  in  consequence  of  their  being 
viewed  in  several  planes,  they  appear  to  be  somewhat  closer  together,  or 
at  distances  varying  from  0-0008-0-0012  of  a  line.  The  circumference 

FIG.  118. — Portion  of  the  surface  of  the  tibia  of  the  calf,  viewed  on  the  external  aspect,    , 
magnified   350  diam. :  the  numerous  points  are  the  openings  of  the  canaliculi ;  the  dark, 
larger,  indistinct  spots  indicate  the  lacunae  to  which  these  canaliculi  belong,  appearing  from 
a  greater  depth. 


280  SPECIAL    HISTOLOGY. 

of  a  lacunas,  together  with  the  radiating  canaliculi  belonging  to  it,  forms 
an  imperfect  sphere,  having  a  diameter  of  from  0-02  to  0-034  of  a  line; 
with  reference  to  which,  however,  it  must  not  be  forgotten,  that  individual 
canaliculi  transgress  the  usual  length  of  the  others,  as  I  have,  in  fact, 
measured  anastomoses  between  two  lacunas  of  the  length  of  0*04-0*045 
of  a  line. 

The  contents  of  the  lacunce^  according  to  the  later  investigations  of 
Bonders,  Virchow,  and  myself,  appear  very  closely  to  resemble  those  of 
the  cells  of  cartilage  during  life  ;  that  is  to  say,  they  are  clear,  probably 
viscid  fluid,  with  a  nucleus.  If  bone-cartilage  be  boiled  in  water  or 
caustic  soda  for  1  or  2  minutes,  these  nuclei  often  show  themselves  very 
distinctly ;  or  opaque  corpuscles  make  their  appearance,  which  must  be 
regarded  as  the  contracted  cell-contents  including  the  nucleus,  and  analo- 
gous to  the  corpuscles  in  cartilage.  A  peculiar  phenomenon  is  seen  to 
occur,  when  bone  is  macerated  in  hydrochloric  acid,  which  was  first 
noticed  by  Virchow  in  a  diseased,  and  afterwards  in  healthy  bone,  and 

by  myself  in  the  cementum  of  the  horse's  tooth, 
— the  lacunae  become  isolated,  having  longer  or 
shorter  processes,  and  appear  like  independent 
structures,  or  a  sort  of  stellate  cells.  This 
phenomenon  seems  to  depend  simply  upon  the 
circumstance,  that  the  tissue  immediately  sur- 
rounding the  lacunae  offers  more  resistance  to 
the  action  of  the  acid  than  it  does  elsewhere. 
In  the  cementum  of  the  horse's  tooth,  cells  also 
enclosing  the  lacunae,  and  even  Haversian  ca- 
nals, may  be  isolated, — the  best  proof,  that  everything  which  thus  pre- 
sents itself  in  an  isolated  form,  is  not  necessarily  a  morphological  unity.* 

FIG.  119. — A  bone  spicule  from  an  apophysis,  with  distinct  lacunae  and  nuclei.  Boiled  in 
water,  and  magnified  350  diameters. 

*  [It  is  of  very  great  importance  in  histology  to  keep  in  mind  the  caution  expressed  in 
the  last  paragraph  of  the  text  (see  below,  note  §  101),  which  applies  as  well  to  optical  as  to 
chemical  distinctness. 

Tomes  and  De  Morgan  assert  that  both  the  lacuna  and  canaliculi  have  parietes,  which  are 
manifested  by  appearances  similar  to  those  observed  in  the  dentinal  tubes.  They  some- 
times found  the  lacunce  and  canaliculi  filled  up  to  a  great  extent  with  solid  matter,  so  as  to 
leave  only  a  small  space  in  the  centre. 

An  important  modification  of  the  lacunce,  is  described  and  figured  by  these  authors  (1.  c.,  p. 
8)  in  the  circumferential  laminae.  Elongated  tubes  pass,  in  bundles  or  singly,  more  or  less 
obliquely  from  the  surface  towards  the  interior  of  the  bone.  When  long,  they  are  sometimes 
bent  once  or  twice  at  a  sharp  angle.  They  have  parietes,  and  are  connected  laterally  with 
the  canaliculi.  They  occur  irregularly  in  the  circumferential  lamina?,  and  in  these  only. 
[Similar  tubes  exist  in  the  cementum  of  the  Teeth.] 

We  can  confirm  Messrs.  Tomes  and  De  Morgan's  statement  that  the  nuclei  may  be  found 
without  difficulty  in  recentjjone,  and  they  may  always  be  brought  out  with  great  distinctness 
by  the  action  of  dilute  hydrochloric  or  strong  acetic  acid.  This  is  especially  the  case  in 


THE     OSSEOUS    SYSTEM.  281 

§  92.  The  Periosteum. — Among  the  soft  tissues  appertaining  to 
bone,  the  periosteum  is  one  of  the  most  important.  It  is  a  more  or  less 
transparent,  slightly  glistening  or  whitish  yellow,  vascular,  extensible 
membrane,  investing  a  great  part  of  the  surface  of  bones,  and  contribut- 
ing most  importantly  to  their  nutrition,  by  the  numerous  vessels  which 
it  sends  into  their  substance. 

The  periosteum  is  not,  everywhere,  constituted  alike.  Opaque,  thick, 
and  for  the  most  part  with  the  glistening  aspect  of  tendinous  structures 
where  it  is  covered  only  by  the  skin,  or  is  connected  -with  fibrous  parts, 
such  as  ligaments,  tendons,  fascice,  and  the  dura  mater  cerebri,  it  is,  on 
the  other  hand,  thin  and  transparent  in  situations  where  muscular  fibres 
arise  directly  from  it  without  the  intervention  of  tendon,  and  also  on  the 
diaphyses,  where  the  muscles  nearly  rest  upon  the  bone,  as  on  the  ex- 
ternal surface  of  the  cranium  (pericranium),  in  the  vertebral  canal,  and 
in  the  orbit  (periorbita).  Where  mucous  membrane  rests  upon  bone, 
the  periosteum  is,  in  most  cases,  very  intimately  united  to  it  by  the  sub- 
mucous  connective  tissue,  so  that  the  two  cannot  be  separated,  and  con- 
stitute a  single  membrane,  which,  as  in  the  palate,  alveolar  processes, 
nares,  &c.,  is  of  greater,  or,  as  in  the  maxillary  sinus,  tympanum,  ethmoid 
cells,  &c.,  of  less  thickness. 

The  connection  of  the  periosteum  with  the  bone  itself  is  either  more 
lax,  consisting  in  simple  apposition,  and  by  more  delicate  vessels  which 
penetrate  the  bone,  or  more  intimate,  taking  place  by  means  of  larger 
vessels  and  nerves,  and  by  numerous  tendinous  filaments.  The  former 
mode  of  connection  is  found  especially  where  the  periosteum  is  thin,  and 
the  osseous  substance  more  compact,  as  in  the  diapJiyses,  on  the  inner 
and  outer  surfaces,  and  in  the  sinuses  of  the  cranium  ;  the  latter,  where 
the  periosteum  is  thicker,  and  the  compact  substance  thinner,  as,  for 
instance,  in  the  apophyses,  in  the  short  bones,  palate,  and  at  the  basis 
of  the  cranium. 

With  respect  to  the  intimate  structure  of  the  periosteum,  it  will  be 

young  bone.  In  old  bone  we  have  frequently  been  unable  to  discover  them.  Tomes  and 
De  Morgan,  however,  state  that  the  nuclei  are  visible  in  sections  of  a  fossil  bone  (supposed 
of  a  Pterodactyle)  in  their  possession. 

Another  peculiar  condition  of  the  "  lacunal  cells,"  described  by  these  authors,  is  their  ossi- 
fication. They  found  the  light  and  spongy  bones  of  old  people  to  yield,  if  broken,  a  white 
powder,  which  was  composed  of  large  cells  detached  or  united  into  masses.  They  are 
spherical,  and  contain  a  dark  granular  nucleus,  which  is  surrounded  by  a  thick  transparent 
wall.  Similar  cells  may  be  found  adherent  to  the  walls  of  the  Haversian  canals  and  can- 
celli;  and  in  this  case  their  nuclei  have  assumed  the  form  of  lacuna,  and  the  canaliculi  of 
adjacent  lacuna  advance  into  them.  Similar  cells  may  be  found  in  most  preparations  of 
adult  bone  (1.  c.,  p.  12). 

We  must  confess  that  we  doubt  the  assumption  of  a  lacunal  form  by  the  "nucleus"  in 
these  cases.  We  have  repeatedly  examined  these  bodies,  but  if  the  nucleus  was  visible  at 
all,  we  found  it  unchanged,  and  often  adhering  to  one  side  of  the  lacimce.  Again,  it  is  ques- 
tionable whether  they  may  not  rather  be  compared  to  the  globules  of  dentine  than  to  cells. 
— TRS.] 


282  SPECIAL    HISTOLOGY. 

found  to  present,  almost  universally,  excepting  where  muscles  arise 
directly  from  it,  two  layers,  which,  although  closely  connected,  differ, 
more  or  less  distinctly,  in  their  structure.  The  outer  layer  is  composed 
chiefly  of  connective  tissue,  with  occasional  fat-cells,  and  is  the  principal 
seat  of  the  true  periosteal  vessels  and  nerves,  whilst  in  the  inner  layer, 
elastic  fibres,  commonly  of  the  finer  sort,  constitute  continuous,  and  often, 
very  thick  networks — true  elastic  membranes — superimposed  one  upon 
another,  the  connective  tissue  forming  the  less  important  element.  Nerves 
and  vessels  occur  in  this  layer  also,  but  they  do  little  more  than  merely 
pass  through  it,  being  destined  for  the  bone  itself. 

The  parts  of  the  surface  of  bones  unprovided  with  periosteum  are : 
1.  The  articular  extremities  covered  with  cartilage,  and  all  other  places 
where  the  bone  is  covered  with  cartilage  or  fibro-cartilage.  2.  Where 
ligaments  and  tendons  are  attached  to  the  borders  and  surfaces  of  bones 
at  a  certain  angle,  as,  for  instance,  at  the  insertions  of  the  ligamenta 
flava,  intervertebralia,  iliosacra,  interossea,  teres  ossis  femoris,  patellse, 
&c.,  of  the  tendons  of  the  deltoid,  coracobrachialis,  popliteus,  iliopsoas, 
triceps,  sura?,  quadriceps  femoris,  glutcei,  &c.  In  all  these  situations, 
the  tendons,  ligaments,  and  cartilages,  are  attached  directly  to  the  bone, 
as  has  been  already  in  part  described,  and  not  a  trace  of  periosteum  can 
be  detected. 

§  93.  Marrow  of  the  Bones. — Almost  all  the  larger  cavities  in  the 
bones  are  occupied  by  a  soft,  trasparent,  yellowish  or  reddish,  highly 
vascular  substance,  the  Marrow  (medulla  ossium).  In  the  cylindrical 
bones,  this  substance  is  found  in  the  medullary  canal,  and  in  the  cancelli 
of  the  apophyses,  whilst  it  is  wanting  in  the  compact  substance,  unless  it 
be  in  the  larger  canals;  the  same  is  the  case  in  the  flat  and  short  bones, 
the  cancelli  of  which  are  filled  with  marrow  ;  but  the  diploe  of  the  flat 
cranial  bones,  besides  the  marrow,  also  contains  large  veins,  of  which 
more  will  be  said  afterwards.  In  accordance  with  what  has  been  re- 
marked, these  venous  spaces,  the  canales  nutritii,  Haversian  canals,  and 
the  above  described  nerve-canals  and  air-cavities  of  the  bones,  contain 
no  marrow. 

The  marrow  appears  in  two  forms,  one  yellow,  the  other  red.  The 
former,  as  a  semifluid  substance,  occurs  principally  in  the  long  bones; 
and  according  to  Berzelius,  consists,  in  the  humerus  of  the  Ox,  of  96*0 
fat,  1-0  connective  tissue  and  vessels,  and  3-0  fluid  with  extractive  matter, 
such  as  is  found  in  muscle ;  whilst  the  latter  occurs  in  the  apophyses, 
flat  and  short  bones,  above  all  in  the  bodies  of  the  vertebra?,  the  basis 
cranii,  the  sternum,  &c.,  and  is  distinguished  not  only  by  its  reddish  or 
red  colour  and  less  consistence,  but  also  by  its  chemical  composition ; 
for,  according  to  Berzelius,  this  substance,  in  the  diploe,  contains  75-0 


THE    OSSEOUS    SYSTEM.  283 

water,  25-0  solid  matters,  such  as  albumen,  fibrin,  extractive  matter, 
and  salts,  similar  to  those  of  muscle,  and  merely  traces  of  fat.  With 
respect  to  its  structure,  it  presents,  besides  vessels  and  nerves,  connective 
tissue,  fat-cells,  free  fat,  a  fluid,  together  with,  lastly,  peculiar  minute 
cells,  marrow-cells.  Connective  tissue  and  fat  are  universally  present, 
though  in  very  various  quantities.  The  former,  on  the  surface  of  the 
larger  medullary  masses  of  the  difapJiyses,  is  of  rather  firmer  consistence, 
but  cannot  properly  be  described  as  a  medullary  membrane  (endosteum, 
periosteum  internum),  because  it  does  not  admit  of  being  separated  as 
a  continuous  structure.  In  the  interior  of  the  marrow  in  the  spongy 
bones,  scarcely  any  connective  tissue  can  be  detected  except  in  the  larger 
masses  of  it,  whilst  in  the  diapJiyses,  this  tissue  can  be  readily  demon- 
strated as  a  very  lax  and  delicate,  areolated  structure,  containing  the  fat 
and  supporting  the  vessels  and  nerves.  Its  elements  correspond  with 
those  of  the  lax  connective  tissue  (vide  §  24) ;  although,  as  far  as  I  have 
seen,  it  does  not  contain  any  elastic  filaments.  Fat-cells  of  0-016-0-032 
of  a  line,  not  unfrequently  with  a  distinct  nucleus,  occur  in  large  quanti- 
ties in  the  yellow,  more  dense  marrow,  quite  as  abundantly  as  in  the 
panniculus  adiposus,  but  for  the  most  part  not  aggregated  into  distinct 
lobules.  In  the  reddish  marrow,  when  expressed,  they  are  more  rare; 
and  in  the  red  pulp  of  the  bodies  of  the  vertebrae  and  of  the  flat  cranial 
bones,  they  occur  only  in  very  minute,  scanty  accumulations,  or  alto- 
gether isolated,  to  which  circumstance,  according  to  Berzelius,  is  owing 
the  small  quantity  of  fat  in  the  diploe.  In  dropsical  marrow  these  cells 
are  frequently  only  half  filled  with  fat,  or  with  but  one  or 
more  globules,  containing,  besides,  a  large  quantity  of 
serum ;  and  in  hypersemia  of  the  bones,  they  appear  occa- 
sionally to  be  diminished  in  size,  and  occasionally  elongated 
and  fusiform.  Free  fat-globules,  and  a  clear  or  yellowish 
fluid,  are  often  met  with  in  the  softer  kinds  of  marrow, 
and  frequently  in  considerable  quantity.  That  the  former 
have  not  been  set  free  from  cells,  in  the  preparation  of  the 
specimen,  may  be  satisfactorily  shown,  but  it  must  remain  uncertain 
whether  or  not  they  are  to  be  referred  to  cells  that  have  ceased  to  exist. 
Lastly,  there  occur,  together  with  some  fluid,  in  all  the  red,  or  even  only 
reddish  marrow  (never  in  the  yellow),  minute  roundish,  nucleated  cells, 
exactly  like  those  of  the  young  medulla  (vid.  infra,  fig.  132).  These  me- 
dulla-cells correspond  in  every  particular  with  those,  which  Hasse  and 
I  ("  Zeitsch.  f.  ration.  Medicin,"  Bd.  V.)  found  in  the  hypersemiated  red 
marrow  of  the  articular  extremities  of  the  cylindrical  bones,  but  never- 
theless normally  exist  in  the  vertelrce,  the  true  cranial  bones,  in  the 
sternum,  and  in  the  ribs,  whilst  they  are  wanting  in  the  long  and  short 

FIG.  120. — Two  fat-cells  from  the  marrow  of  the  human  femur :  a,  nucleus;  6,  cell-mem- 
brane ;  c,  oil ;  magnified  300  diameters. 


284  SPECIAL    HISTOLOGY. 

bones  of  the  extremities,  and  in  the  scapula  and  os  innominatum,  occur- 
ring apparently  in  variable  number  in  the  bones  of  the  face.* 

§  94.  Connections  of  the  Bones. — A.  synarthrosis,  connection  without 
articulation. 

1.  By  suture.    In  this  mode  of  connection,  the  bones  are  united  by 
an  extremely  thin,  membranous,  whitish  streak,  to  which  authors  have 
incorrectly  given  the  name  of  sutural  cartilage.     It  is  composed  merely 
of  connective  tissue,  which,  like  that  of  the  ligaments,  extends,  in  short, 
parallel  fasciculi,  from  the  border  of  one  bone  to  that  of  the  other,  and 
is  characterized  solely  by  the  presence  of  numerous,  short,  unequal-sized, 
usually  elongated  nuclei.     This  sutural  ligament,  as  it  may  be  termed, 
is  very  evident  as  long  as  the  cranial  bones  are  still  growing,  at  the  same 
time,  that  it  is  softer  and  differently  constituted  (vide  infra).     As  the 
growth  of  the  cranium  approaches  its  completion,  this  tissue  gradually 
disappears,  becomes  firmer,  and,  in  old   age,   seems,   in  many  places, 
especially  on  the  inner  part  of  the  sutures,  and  even  before  their  com- 
plete obliteration,  to  be  entirely  removed. 

2.  Connection  by  ligament,  syndesmosis,  is  effected  by  means  of  fibrous 
and  elastic  ligaments.     The  fibrous  ligaments,  constituting  the  majority 
of  the  ligaments,  are  white  and  glistening,  corresponding  in  their  struc- 
ture, partly  with  the  aponeuroses  and  ligaments  of  the  muscles,  and 
partly  with  the  true  tendons. 

Elastic  ligaments  (Fig.  121),  are,  the  ligamenta  flava,  between  the 
arches  of  the  vertebrae,  and  the  ligamentum  nuchse,  which,  however,  is 
not  nearly  so  well  developed  in  man,  as  in  some  others  of  the  Mammalia. 
The  ligamenta  flava  are  yellowish,  highly  elastic,  strong  ligaments,  the 
elastic  elements  of  which,  in  the  form  of  roundish  polygonal  fibres,  0-0015 
-0-004  of  a  line  thick,  united  into  a  dense  network,  run  parallel  with  the 
long  axis  of  the  vertebral  column,  and  give  the  longitudinal,  fibrillar 
aspect  to  the  ligaments.  Between  these  fibres,  which  are  not  collected 
either  into  fasciculi  or  lamellce,  but  are  continuously  connected  through- 
out the  entire  thickness  of  each  yellow  ligament,  there  is  interposed  some 
connective  tissue,  upon  the  whole  in  small  quantity,  but  demonstrable  in 
every  preparation,  and  occurring  in  the  form  of  lax  undulating  fasciculi, 

*  [These  nucleated  medulla-cells  exist  in  great  number  in  the  superior  maxillary  bone  of 
Man  and  of  many  of  the  Vertebrata.  Several  of  them  are  sometimes  enclosed  in  a  common 
cell-wall,  forming  a  variety  of  cell,  frequently  seen  in  pathological  formations,  viz.  the 
parent-cell  of  the  German  authors,  the  plaque  a  noyaux  multiples  of  Robin. 

The  occurrence  of  nucleated  cells  in  the  normal  medulla  of  the  bones  of  the  face  has  been 
mostly  overlooked,  and  has  hence  given  rise  to  many  errors  on  the  part  of  pathologists.  In 
the  description  of  morbid  changes  of  the  bones  of  the  face,  especially  in  those  of  the  superior 
maxillary  bone,  representations  are  frequently  given  of  small  cancer-cells  or  nuclei,  taken 
from  the  interior  of  the  bone,  which  are  but  the  normal  nucleated  cells  of  the  medulla. 
Many  tumors  of  the  upper  jaw  have  thus  been  pronounced  cancerous,  which  were  simply 
non-malignant  hypertrophies  of  the  bone. — DaC.] 


THE    OSSEOUS    SYSTEM. 


285 


which  are  arranged  parallel  with  the  principal  direction  of  the  elastic 

fibres.  According  to  Todd  and  Bow-  Fig.  121. 

man  (p.  72),  the  stylo-hyoid,   and 

internal  lateral  ligament  of  the  lower 

jaw,  are,  also,  chiefly  composed  of 

strong  elastic  fibres. 

3.  By  cartilage,  synchondrosis. 
This  mode  of  connection  is  effected 
either  by  cartilage  alone,  or 'asso- 
ciated with  fibro-cartilaginous  and 
fibrous  tissue.  The  former  condition 
is  observed  in  the  adult,  only  between 
the  ribs  and  sternum,  where,  how- 
ever, properly  speaking,  a  true  syn- 
chondrosis exists  only  in  the  case  of 
the  first  rib,  the  rest,  from  the  second 
to  the  seventh,  being  connected  with 
the  sternum  at  the  anterior  extre- 
mity by  articulation ;  whilst  the 
false  ribs  are  either  free  at  the  ex- 
tremity, or  are  incurved  one  beneath 
the  other.  In  the  symphysis  pubis, 
sacro-iliac  synchondrosis,  and  the 
junctions  of  the  bodies  of  the  verte- 
brce,  the  surfaces  of  the  bones  are 
covered  immediately  by  a  layer  of 
true  cartilage,  which,  in  the  two 
former  situations,  is  directly  connected  with  the  opposite  layer,  and  in  the 
latter  by  means  of  a  fibro-cartilaginous  tissue,  and  is  externally  encircled 
by  fibro-cartilaginous,  and  fibrous,  concentric  layers.  In  the  two  former 
of  these  instances,  there  is,  not  unfrequently,  a  cavity  in  the  interior  of 
the  connecting  substance,  so  that  the  sacro-iliac  sychondrosis,  in  particu- 
lar, may  also  be  regarded  as  a  sort  of  articulation  (Zaglas). 

The  intervertebral  ligaments,  or  ligamentous  discs,  of  the  bodies  of 
the  vertebras,  consist,  1,  of  exterior  concentric  layers  of  fibro-cartilage, 
and  whitish  connective  tissue ;  2,  of  a  central,  principally  fibro-cartila- 
ginous substance ;  and  3,  of  two  cartilaginous  layers  applied  immedi- 
ately upon  the  bones. 

The  concentric  lamellae  consist  of  alternate  layers  of  connective  tissue 
and  of  fibro-cartilage,  which  latter,  even  in  fresh  transverse  sections, 

FIG.  121. — A,  a  transverse  section  through  a  portion  of  the  ligamentum  nuchce  of  the  Ox, 
magnified  350  diameters,  and  treated  with  soda :  a,  connective  tissue,  apparently  homoge- 
neous; 6,  transverse  section  of  the  elastic  fibres  (O004-001  of  a  line  in  diameter).  J5,  elastic 
fibres;  a,  from  a  human  lig.  subflavum,  together  with  some  connective  tissue,  6,  between 
them,  magnified  450  diameters. 


286  SPECIAL    HISTOLOGY. 

may  be  recognized  as  dull  yellow  streaks,  which  become  hard  and  trans- 
parent in  water.  The  fibro-cartilage,  on  microscopic  examination,  pre- 
sents minute,  elongated  cartilage  cells,  disposed  serially  in  a  fibrous 
tissue,  differing  from  connective  tissue  in  its  greater  rigidity,  the  absence 
of  distinct  fibrils,  its  great  resistance  to  alkalies  and  acetic  acid,  and  the 
total  absence  of  elastic  fibres. 

The  whitish  layers  of  the  outer  laminae,  although  their  fibrils  are 
rather  more  rigid  than  those  of  the  common  ligaments  and  tendons,  are 
less  easily  separated,  and  present 'but  few  fusiform  cells,  and  frequently 
no  elastic  fibres  whatever  among  them,  must  nevertheless,  at  present,  be 
regarded  as  composed  of  connective  tissue.  These  laminae  are  from  J 
to  j  of  a  line  and  more  in  thickness,  and  form  entire  circles  or  segments 
of  such,  which,  alternating  with  the  somewhat  thinner,  and  also  fre- 
quently incomplete,  rings  of  fibro-cartilage,  with  which  they  are  closely 
connected,  together  with  the  latter  constitute  the  larger  half  of  the  in- 
tervertebral  ligaments.  The  general  direction  of  the  fibres  of  both  sets 
of  laminae  is  from  above  to  below.  They  are,  however,  invariably 
oblique,  so  that  those  of  the  different  layers  cross  each  other.  Besides 
which,  it  must  be  remarked,  that  the  individual  layers  themselves  also 
exhibit  a  more  or  less  distinctly  foliated  structure,  constituted  in  such  a 
manner  that  the  fine  lamellae,  in  the  portions  composed  of  connective 
tissue,  observe  the  same  direction  as  the  layers  themselves,  whilst  in  the 
fibre-cartilaginous  portions  they  are  disposed  more  in  the  direction  of 
the  radius  of  the  ligamentous  disc. 

The  softer  central  substance  of  the  intervertebral  ligaments,  or  the 
gelatinous  nucleus  of  authors,  does  not  differ,  essentially,  from  the  por- 
tions above  described ;  for,  even  in  this  situation,  layers  of  connective 
tissue  occur,  although  they  gradually  diminish  in  proportion  to  the 
fibro-cartilage,  and  are  less  distinctly  defined.  The  nearer  we  approach 
the  centre,  the  less  evident  is  any  trace  of  an  alternation  of  different 
122  layers,  and  of  a  concentric  ar- 

rangement of  them ;  the  whole 
becomes  transparent,  soft,  and, 
finally,  almost  homogeneous.  The 
microscope  shows  the  predomi- 
nance of  fibro-cartilage,  with 
large  cells  (0-012-0-024  of  a 
line),  frequently  one  within  the 
other  (Fig.  122) ;  the  uniformly  thickened  walls  of  which,  composed  of 

FiG.  122. — Cells  from  the  gelatinous  nucleus  of  the  lig.  intervertebralia :  1,  large  parent 
cell,  a,  with  a  septum  derived  from  two  secondary  cells  of  the  first  generation,  and  five 
secondary  cells,  6,  of  the  second  generation ;  with  concentrically  thickened  walls  and 
shrunken  nuclei,  c,  in  the  small  cell  cavities:  2,  parent  cells,  a,  with  two  secondary  cells, 
separated  by  a  delicate  septum,  6,  and  which,  with  uniformly  thickened  walls,  contain  a 
minute  cavity  and  shrunken  nucleus,  c. 


THE     OSSEOUS     SYSTEM.  287 

concentric  layers,  often  enclose  merely  a  minute  cavity,  with  a  shrunken 
nucleus;  and  besides  these,  smaller  cells  frequently  in  process  of  dissolu- 
tion, isolated  or  aggregated  together  ;  and,  lastly,  an  indistinctly  fibrous 
or  granular  matrix,  not  unfrequently  observed  in  a  state  of  disintegra- 
tion, and  a  considerable  quantity  of  fluid  contained  in  larger  or  smaller 
areolar  spaces  in  it.  The  more  central  portions  of  this  fibrous  substance 
gradually  pass  into  a  thin,  hard,  yellowish  lamella  of  true  cartilage,  with 
thickened  cells,  not  unfrequently  beset  with  calcareous  particles,  which 
adheres  to  the  bone  not  unlike  an  articular  cartilage,  though  less  firmly. 
More  externally  we  find  a  cartilaginous  substance,  in  the  form  of  isola- 
ted, minute,  discoid  plates  or  particles,  which  appear  to  be  in  more  im- 
mediate connection  with  the  fibro-cartilaginous  portions,  and  between 
these  a  connective  tissue,  with  scattered  cartilage-cells,  as  in  the  inser- 
tions of  the  tendons  into  the  bones  (vide  §  81).  The  more  exterior  por- 
tions of  the  surfaces  of  the  bodies  of  the  vertebrae,  corresponding  to  these 
parts  of  the  discoid-ligaments,  are,  in  contradistinction  to  the  more  in- 
ternal portions,  as  it  were  porous,  after  the  removal  of  the  ligamentous 
layer ;  the  medullary  cavities  or  cancelli  then  being  exposed.  The 
pores  or  cancelli  are  closed  only  by  the  cartilaginous  substance  of  the 
disc,  whilst  the  fibrous  tissue,  with  its  vertical  fibres,  is  firmly  connected 
with  the  interspaces  between  them. 

Between  the  sacrum  and  coccyx,  and  the  individual  coccygeal  verte- 
brae, are  interposed  the  so-called  false  intervertebral  ligaments,  consist- 
ing of  a  more  uniform  fibrous  substance,  without  any  gelatinous  nucleus. 
The  separate  bones  of  the  sacrum,  at  an  early  period,  have  true  inter- 
vertebral  ligaments  between  them,  which  afterwards  become  ossified 
from  without  to  within,  but  in  such  a  way,  nevertheless,  that  even  in  the 
adult,  traces  of  the  ligament  may  still  be  perceived  in  the  centre.  With 
respect  to  the  nature  of  the  fibres  of  the  intervertebral  ligaments,  Don- 
ders  is  inclined,  especially  from  the  consideration  of  their  chemical  re- 
lations, to  regard  almost  all  of  them,  not  as  connective  tissue,  but  as 
analogous  to  the  matrix  of  true  cartilage,  as  is  also  H.  Meyer  (p.  300, 
et  seq.,  and  p.  310).  This  opinion  may  be  correct,  as  regards  the  cen- 
tral, nuclear  portion,  and  the  fibro-cartilaginous  laminae  of  the  outer 
portions,  but  hardly  so  with  respect  to  the  purely  fibrous  parts  of  the 
latter.  I  believe,  moreover,  that  it  is  not  by  chemistry,  but  by  the 
study  of  the  development  of  these  tissues,  that  the  question  will  be 
solved,  because,  although  manifest,  visible  distinctions  exist  between  the 
fibrils  of  connective  tissue  developed  from  cells,  and  the  fibrous  inter- 
cellular substance,  viewed  from  a  genetic  point  of  view,  chemistry  pro- 
bably is  not  in  a  condition  to  distinguish  one  from  the  other.*  The  in- 

*  [In  our  note  on  the  connective  tissue,  we  have  already  expressed  the  views  we  enter- 
tain of  the  homologies  of  the  elements  of  cartilage  and  connective  tissue  ;  and  we  need 
merely  add  that  we  know  of  no  locality  in  which  the  transition  of  the  matrix  of  cartilage 


288  SPECIAL    HISTOLOGY. 

tervertebral  ligaments  are  liable  to  various  forms  of  degeneration  ;  they 
may  become  ossified,  from  their  cartilaginous  lamellae  outwards,  the 
true  fibrous  substance  probably  at  the  same  time  disappearing ;  and  in 
this  way  anchylosis  of  two  vertebrae  frequently  takes  place.  They  may 
become  atrophied,  easily  broken  down,  arid  disintegrated,  either  in  the 
nuclear  portion,  or  elsewhere  in  circumscribed  spots,  into  a  dirty  gru- 
mous  matter.  And  lastly,  it  would  appear  that  although  in  the  normal 
state,  they  contain  no  vessels,  vessels  may,  under  certain  morbid  condi- 
tions, be  developed  in  them  ;  at  all  events,  extravasations  of  blood  are 
not  unfrequently  met  with,  most  generally  close  to  the  bones  or  in  con- 
nection with  them. 

In  the  sympJiysis  pubis,  the  cartilaginous  layer,  which  is  thickest  in 
the  centre  and  anteriorly,  and  connected  with  the  bones  by  a  very  un- 
even surface,  consists,  at  the  sides,  where  it  is  from  J  to  1  line  thick, 
of  true  cartilage,  with  a  homogeneous,  finely  granular  matrix  and  sim- 
ple cells,  measuring  0-01-0-024  of  a  line.  In  the  centre,  the  matrix  is 
softer  and  fibrous,  and  in  this  situation  (more  particularly,  it  would 
appear,  in  the  female  sex),  there  occasionally  exists  an  irregular  narrow 
cavity,  with  uneven  walls,  and  containing  a  somewhat  slimy  fluid,  origi- 
nating evidently  in  a  solution  of  the  innermost  cartilaginous  layers,  and 
of  which  manifest  traces  may  be  perceived  in  the  cartilaginous  substance 
immediately  enclosing  it.  The  outer  layers  of  the  symphysis,  which,  as 
is  well  known,  are  most  developed  anteriorly  and  superiorly,  do  not 
arise,  with  the  exception  of  the  outermost  lamellae  composed  of  pure 
connective  tissue,  directly  from  the  bones,  but,  properly  speaking,  unite 
only  the  outer  portions  of  the  above-described  cartilaginous  layers,  and 
consist  principally  of  a  fibrous  substance,  to  all  appearance  identical 
with  connective  tissue,  and  occasionally  containing  cartilage  cells. 

The  formation  of  the  bone-corpuscles,  as  they  are  termed,  may  be 
traced  perhaps  more  clearly  in  the  symphysis  than  anywhere  else,  except 
in  rachitic  bone  (Fig.  124).  For  at  its  osseous  borders  there  are  always 
to  be  found,  either  half  projecting  from,  or  entirely  lodged  in,  the  carti- 
lage, isolated,  nucleated  bone-corpuscles  or  cells,  with  homogeneous,  and 
(from  calcareous  salts)  granular  walls,  measuring  0-012-0-016  of  a  line 
with  respect  to  which,  from  their  development  and  from  the  considera- 
tion of  the  contiguous  cartilage-cells,  all  of  which  present  more  or  less 
thickened  walls  and  rudiments  of  calcareous  deposits,  not  the  smallest 
doubt  can  be  entertained.  Well-characterized,  half  and  wholly  ossified 
parent  cells  of  the  same  kind,  with  two  secondary  cells,  and  measuring 
0*015-0-03  of  a  line,  up  to  some  including  ten  or  twenty  secondary  cells 

into  the  pseudo-fibrillated  collagenous  portion  of  connective  tissue  is  more  unmistakably 
exhibited,  than  in  the  intervertebral  cartilages  of  a  young  animal,  e.g.,  a  kitten.  We  have, 
in  that  note,  endeavored  to  show  that  the  notion  of  the  existence  of  any  real  difference  in 
the  development  of  the  fibrillated  element  in  the  different  forms  of  connective  tissue  is  un- 
founded.— TRS.] 


THE    OSSEOUS    SYSTEM.  289 

and  having  a  length  of  0'05  of  a  line,  may  be  distinctly  noticed  in  almost 
every  preparation. 

Fig.  123. 


The  sacro-iliac  synchondrosis  is  effected  by  means  of  a  flattened  layer 
of  cartilage,  f-1  J-  of  a  line  in  thickness,  which  is  closely  attached  to  the 
articular  surfaces  of  the  corresponding  bones,  between  which  it  is  inter- 
posed. The  cartilage-cells  close  to  the  bone  are  flattened,  with  their 
surfaces  directed  towards  it,  and  present  beautiful  transitionary  forms 
into  half  and  wholly  isolated  bone-cells,  which  exist  on  the  border  of  the 
bone.  In  the  interior  of  this  cartilaginous  layer,  according  to  Zaglas, 
there  is  always  a  narrow  cavity,  which  separates  the  cartilaginous  layers 
of  the  two  bones  completely,  or  almost  completely,  from  each  other.  It 
contains  a  synovia-like  fluid,  and  is  bounded  by  smooth  and  even  walls, 
which  differ  from  the  rest  of  the  cartilaginous  substance  in  their  greater 
hardness,  as  well  as  in  their  structure.  The  matrix  of  these  cartila- 
ginous layers,  in  the  direction  of  the  surface,  is  finely  fibrous;  the  cells 
are  all  of  large  size  (as  much  as  0'035  of  a  line),  with  numerous  secondary 
cells  and  uncommonly  thick  walls,  so  that  the  cavities,  even  of  the  se- 
condary cells,  often  appear  extremely  contracted  ;  but  they  do  not  exhi- 
bit any  distinct  indication  of  pore-canals  or  calcareous  deposit. 

The  costal  cartilages  are  invested  by  a  strong  perichondrium,  composed 
of  connective  tissue  and  numerous  elastic  elements,  which  commences  at 
the  sternal  end  in  connection  with  the  synovial  membrane  there  existing, 
and  at  the  other  is  continuous  with  the  periosteum  of  the  ribs.  The 
cartilage,  which  is  in  connection  with  this  membrane  by  a  roughened 
surface,  is  of  considerable  firmness  although  elastic,  pale,  yellow,  or  in 
thin  sections,  exhibiting  a  transparent  blue  tint,  internally  almost  always, 

FIG.  123. — Cartilaginous  border,  towards  the  cartilage  of  the  symphysis  in  Man;  a,  carti- 
lage cells  with  thickened  walls;  6,  the  same  undergoing  ossification;  c,  cells  nearly  ossified, 
with  homogeneous  walls  free  in  the  matrix  of  the  cartilage ;  d,  similar  cells  with  calcareous 
granules:  e,  ossified  cells  at  the  border  of  the  matrix  of  the  bone  containing  calcareous  gra- 
nules, and  half  projecting  from  it. — Magnified  350  diameters. 

19 


290 


SPECIAL    HISTOLOGY. 


Fig.  124. 


in  certain  spots,  of  a  yellowish-white  color,  with  a  silky  lustre.  Its 
matrix  in  the  latter  situations  presents  a  fibrous  structure,  and  elsewhere 
a  finely  granulated  aspect.  The  outermost  cells,  to  the  depth  of  0-06— 
0-1  of  a  line,  are  elongated,  flattened,  parallel  to  the  surface,  most 
usually  small  (sometimes  not  more  than  0-006  of  a  line),  but  sometimes 
larger,  and  filled  with  one  or  even  many  secondary  cells,  one  placed  be- 
hind the  other ;  more  internally,  without  entirely  losing  their  flattened 
figure,  they  are  larger  (most  of  them  0-03-0-05  of  a  line),  oval,  and 
round,  and  lie  with  their  surfaces  towards  the  ends  of  the  cartilage,  and 
with  their  long  axis  for  the  most  part  in  the  direction  of  the  radius  of 
the  transverse  section  of  the  rib ;  in  many  cases,  however,  they  are  dis- 
posed more  irregularly.  The  largest  of  these  cells  (measuring  as  much 
as  0-08  or,  even  0-1  of  a  line),  are  found  in  the  fibrous  spots,  and  they,  in 
common  with  all  the  interior  cells,  contain  secondary  cells,  in  varying, 
frequently  in  very  considerable  number  (as  many  as  60  according  to 
Ponders).  The  most  remarkable  characteristic  of  the  elementary  tissue 

of  the  costal  cartilage  is  the 
large  quantity  of  fat  con- 
tained in  it.  In  the  adult, 
every  cell,  excepting  the 
most  superficial,  contains, 
larger  or  smaller  (from 
0-0016-0-008  of  a  line), 
sometimes  spherical,  some- 
times more  irregular  fat- 
drops,  which  frequently  so 
surround  the  nucleus  as  en- 
tirely to  conceal  it  from 
view  (Fig.  124  a,  5),  whence 
it  has  been  assumed,  though 
not  quite  correctly,  that  the 

fat  is  seated  in  the  latter.  The  cartilage  on  the  greater  cornu  of  the 
os  hyoides,  and  between  the  body  and  the  greater  cornu,  and  the  incon- 
stant cartilaginous  appendage  to  the  styloid  process,  differ  in  no  respect 
from  costal  cartilage,  only  that  the  cartilage  cells  in  those  instances  do 
not  always  contain  large  fat-globules. 

The  costal  cartilages  frequently  become  ossified  in  old  age ;  but  this 
ossification,  as  well  as  the  fibrillation  of  the  matrix,  must  not  be  re- 
garded as  a  normal  process,  nor  be  placed  in  the  same  category  with  the 
usual  kind  of  ossification.  The  ossification  is  sometimes  more  limited, 

FiG.  124. — Cartilage  cells  of  Man,  magnified  350  diameters:  a,  parent  cell  with  three  se- 
condary cells  containing  oil,  from  a  costal  cartilage;  6,  two  cells  from  the  same  situation  in 
which  the  globule  of  oil  is  surrounded  by  a  pale  border;  c,  two  cells  with  thickened  walls 
from  the  cartilage  of  the  greater  cornu  of  the  os  hyoides,  which  together  with  the  globule  of 
oil  also  contain  a  distinct  nucleus. 


THE    OSSEOUS    SYSTEM.  291 

sometimes  more  extensive.  In  the  former  case,  it  does  not  proceed 
further  than  to  the  incrustation  of  the  cartilage-cells,  and  of  the  matrix 
in  which  they  are  lodged,  which  has  become  fibrous  ;  in  the  latter,  and 
frequently,  also,  in  the  former,  the  ossification  is  preceded  by  the  forma- 
tion of  hollow  spaces  in  the  cartilage,  in  which  is  deposited  a  cartilage- 
marrow,  containing  vessels,  which  are  connected,  in  part  with  those  of 
the  perichondriwn,  in  part  with  those  of  the  ribs ;  and  the  osseous  sub- 
stance is  more  that  of  normal  bone,  though  almost  always  more  opaque, 
less  homogeneous,  and  with  imperfectly  formed  lacunae,  which  frequently 
contain  a  calcareous  deposit.  Under  the  name  of  cartilage-marrow,  are 
understood  the  medulla-cells,  fat-cells,  bundles  of  connective  tissue  and 
vessels  which  are  presented  instead  of  the  detritus,  afforded  by  the  dis- 
integration of  cartilage,  and  which  may  be  said  to  correspond  in  all  re- 
spects with  those  of  developing  foetal  bone,  and  may  be  readily  observed 
in  ossifying  costal  and  laryngeal  cartilages. 

§  95.  B.  Movable  Articulation  (Diarthrosis). — The  articular  extremi- 
ties of  the  bones,  or  any  other  surfaces  entering  into  the  formation  of  a 
joint,  are  invariably  invested  with  a  thin  layer  of  cartilage,  which  in  the 
middle  of  the  surfaces  covered  by  it,  is  of  tolerably  uniform  thickness, 
gradually  thinning  as  it  extends  outwardly,  and  finally  terminating  with 
a  very  abrupt  edge.  This  articular  cartilage  is  closely  applied  to  the 
bone  with  a  rough,  hollowed  or  raised  surface,  but  is  not  united  to  it  by 
any  interposed  substance  ;  and,  on  the  opposite  surface,  it  is  in  most  joints 
usually  quite  bare,  and  directed  towards  the  cavity  of  the  articulation. 
Sometimes,  however,  it  is  invested  with  a  special  fibrous  membrane,  a 
perichondrium,  which  is  an  immediate  prolongation  of  the  periosteum, 
and  extends  most  generally  only  over  a  small  portion  of  the  cartilage, 
gradually  ceasing  without  any  defined  margin.*  In  some  joints  (shoulder, 
hip)  the  more  secure  lodgment  of  the  articular  head  of  the  bone  is  in- 
sured by  special  cartilaginous  lips.  These  are  firm,  yellowish-white, 
fibrous  rings,  attached,  at  the  border  of  the  articular  cartilage,  by  a 
wider  basis,  immediately  to  the  bone  or  partly  to  the  cartilage.  They 
thin  off  to  an  acute  edge,  and  for  the  most  part  free  and  uncovered  by 
the  synovial  membrane,  or  any  epithelium,  project  into  the  articulation, 
being  exteriorly  in  relation  with  the  periosteum  and  synovial  capsule. 

*  [Reichert,  who  has  paid  particular  attention  to  the  question  of  the  existence  of  an  epi- 
thelium upon  the  articular  cartilages,  says,  that  in  the  foetal  condition  of  Man  and  the  domes- 
tic Mammalia,  an  epithelium  exists  over  the  whole  surface  of  the  synovial  capsules,  and,  on 
the  articular  cartilage,  lies  in  immediate  contact  with  its  substance.  It  resembles  the  epi- 
thelium of  the  vessels.  In  adults,  on  the  other  hand,  he  could  discover  an  epithelium  only 
on  those  parts  of  the  articular  capsules  which  are  not  subject  to  friction  ;  and  here  it  had  the 
same  appearance  as  in  the  foetal  condition.  It  was  wanting  upon  the  articular  cartilages  and 
their  immediate  neighborhood;  but  it  was  not  uncommon  to  meet  with  fine  desquamated 
flakes  of  cartilage  in  the  synovia,  which  fell  readily  into  folds,  and  thus  resembled  a  fibro- 
cartilaginous  tissue  (Bericht,  Mailer's  "  Archiv.,"  1849,  p.  16.) — TRS.] 


292 


SPECIAL    HISTOLOGY. 


Fig.  125. 


As  regards  the  intimate  structure  of  the  parts  just  described,  the 
articular  cartilage,  on  completely  formed  bones  (Fig.  125),  and  under 

normal  conditions,  presents  throughout,  a 
finely  granular,  in  part  almost  homogeneous 
matrix,  in  which  are  lodged  delicate  cartilage- 
cells,  which  towards  the  surface  of  the  carti- 
lage are  numerous  and  flattened,  and  lie 
parallel  to  it;  more  deeply  they  are  oval  or 
rounded,  more  rare,  and  disposed  in  various 
directions;  and  lastly,  close  to  the  bone 
they  are  elongated,  and  placed  vertically 
with  respect  to  the  surface  of  the  bone. 
These  cells  all  have  distinct  walls,  easily  dis- 
tinguished from  the  matrix  by  the  use  of 
acetic  acid,  clear,  frequently  granular  con- 
tents, containing,  however,  but  little  fat,  and 
a  vesicular  nucleus.  They  occur  either 
isolated  or  in  groups,  and  present  very  fre- 
quently two,  four  or  even  more  secondary 
cells,  which  in  the  flat  cells  are  placed  close 
together,  and  in  the  elongated  are  disposed 
in  rows.  On  the  condyle  of  the  lower  jaw, 
as  on  the  corresponding  surface  of  the  tem- 
poral bone,  until  the  bone  is  completely 
formed,  there  is  a  thick  layer  of  very  dis- 
tinctly marked  cartilage-cells,  covered,  to- 
wards the  cavity  of  the  articulation,  by  a 
layer  of  connective  tissue.  This  cartilaginous  layer  disappears  by  de- 
grees, as  the  bone  approaches  its  completion,  and  at  last  there  remains 
beneath  the  layer  of  connective  tissue,  now  become  both  relatively  and 
absolutely  thicker,  merely  an  excessively  thin  and  transparent  lamina, 
the  elements  of  which,  although  morphologically  not  true  bone-cells,  nor 
as  yet  ossified,  still  seem  to  resemble  the  latter  more  closely  than  cartilage- 
cells.  % 

The  cartilaginous  lips  of  the  joints  consist  principally  of  connective 
tissue,  always  containing,  however,  isolated  cartilage-cells  of  a  roundish 
or  elongated  form,  with  a  moderately  thick  membrane,  distinct  nucleus, 
and  occasionally  fat-granules.  I  have  not  as  yet  noticed  parent  cells  in 

FiG.  125. — Articular  cartilage  of  a  human  metacarpal  bone,  cut  perpendicularly:  a,  most 
superficial,  flattened  cartilage  cells;  6,  middle  round  cells;  c,  innermost  cells,  disposed  per- 
pendicularly in  small  rows;  rf,  outermost  layer  of  the  bone  with  ossified  fibrous  matrix  and 
thick- walled  cartilage  cells,  in  this  instance  appearing  dark  from  their  containing  air;  e,  true 
bone-substance;  /,  ends  of  the  cancelli  of  the  apophyses;  g,  one  of  the  cancelli. — Magnified 
90  diameters. 


THE  OSSEOUS  SYSTEM.  293 

this  situation,  whilst  cells  of  the  kind  already  described  in  the  muscular 
system  (§  82),  arranged  in  series,  are  not  unfrequently  met  with,  and 
might  perhaps  be  regarded  as  cartilage-cells,  although  their  nuclei  exhibit 
the  most  evident  indications  of  a  transition  into  nuclear  fibres.  The 
articular  cartilages,  moreover,  during  their  development,  which  will  be 
entered  into  more  particularly  afterwards,  have  no  nerves  or  vessels,  as 
is  the  case  also  with  the  cartilaginous  lips.* 

The  condition  of  the  bone  beneath  the  articular  cartilages,  requires 
special  notice.  It  consists,  in  almost  all  joints,  in  immediate  contiguity 
with  the  cartilage,  oft  a  layer  of  incompletely  formed  bone-substance, 
and,  more  internally,  of  that  tissue  in  its  usual  form  (Fig.  125).  The 
layer  in  question,  which  is  0*04— 0*16,  or  on  the  average  0*12  of  a  line 
thick,  is  composed  of  a  yellowish,  mostly  fibrous,  hard,  and  truly  ossified 
matrix,  containing,  however,  not  a  trace  of  Haversian  canals  or  medul- 
lary cavities,  nor  of  any  perfectly  formed  lacunae ;  instead  of  which  it 
presents  roundish  or  elongated  corpuscles,  aggregated  into  little  masses 
or  rows,  the  larger  of  which  are  0*016— 0-024  of  a  line  in  length,  and 
0-006-0-008  of  a  line  in  breadth,  and  the  smaller  0-006-0-008  of  a  line 
in  length,  and  0-004-0-005  of  a  line  in  breadth,  which  give  thin  sections 
of  the  bone  a  perfectly  opaque  aspect,  and  consequently  might  be 
regarded  as  bone-corpuscles  (lacunae)  filled  with  calcareous  particles,  as 
which  they  have  lately  been  considered  by  H.  Meyer  (1.  c.,  p.  325,  326). 
By  the  addition  of  spirit  of  turpentine,  which,  however,  penetrates  with 
difficulty,  this  error  is  dissipated,  and  it  is  found,  that  as  in  the  case  of 
the  lacunae  of  dried  bone,  the  opaque  aspect  is  due  only  to  the  air  con- 
tained in  them,  and  that  the  bodies  in  question  are  nothing  more  than 
thick-walled  cartilage-cells,  retaining  their  contents  (fat,  nuclei),  present- 
ing occasionally  indications  of  canaliculi,  and  perhaps  also  partly  calci- 
fied ;  in  other  words,  that  they  are  undeveloped  lacunae.  The  layer  in 
which  these  cells  are  lodged,  and  which,  towards  the  cartilage,  is  bounded 
by  a  straight  line,  occasionally  dark  from  calcareous  particles,  and 

*  [Besides  the  elements  above  mentioned,  we  find  according  to  Dr.  Leidy  (see  Am.  Jour,  of 
Med.  Sc.,  April,  1849),  numerous  minute  lacunoe,  as  an  occasional  peculiarity  in  the  structure 
of  articular  cartilage.  These  lacunae  are  described  by  Dr.  Leidy  as  existing  in  greatest  abun- 
dance in  the  deeper  part  of  the  cartilage;  but  decreasing  in  number,  as  its  free  surface  is  ap- 
proached. They  are  lenticular  in  outline,  and  measure  from  l-1200th-l-3 120th  of  an  inch; 
when  well  defined,  they  appear  beneath  the  microscope  more  translucent  than  the  cartilaginous 
matrix  in  which  they  are  situated.  When  viewed  a  little  within  the  focus  of  the  instrument, 
they  are  of  a  deep  black  color,  and  oppose  the  transmission  of  all  light.  Another  peculiarity  de- 
scribed by  Dr.  Leidy  is  the  penetrature  of  the  structure  of  the  cartilage  by  fibres  or  columns 
of  bone.  These  fibres  are  quite  uniform  in  shape  and  structure,  being  compressed  and 
cylindrical ;  in  transverse  sections  they  present  an  elliptical  figure.  They  are  not  numerous, 
and  vary  from  a  size  not  exceeding  a  cell-group  of  5  cells  to  the  size  of  four  or  five  such 
groups.  They  are  concentrically  laminated,  and  also  present  a  radiated  conformation,  resem- 
bling somewhat  the  structure  of  an  Haversian  canal,  but  neither  the  canal  nor  the  Purkin- 
jean  corpuscles  are  discernible  in  them. — DaC.] 


294  SPECIAL     HISTOLOGY. 

towards  the  true  bone  by  a  sinuous  contour,  in  which  the  limits,  as  it 
were,  of  the  individual  lacunse  are  distinguishable,  is  not  found  either 
exclusively  in  bones  not  yet  fully  formed,  as  Gerlach  believes,  nor  only 
at  a  more  advanced  age  (from  30  upwards,  and  particularly  in  old  men), 
as  H.  Meyer  states,  but,  at  all  events  as  far  as  my  observation  extends, 
at  all  ages,  from  the  complete  development  of  the  bone  upwards,  inva- 
riably in  every  articulation,  except  that  of  the  lower  jaw  and  those  on 
the  os  hyoides.* 

The  articular  cartilage  on  the  head  of  the  femur,  in  a  man  25  years 
old,  measured  1— 1J  of  a  line  in  thickness  ;  on  the  condyles  in  the  middle 
1J-,  on  the  margin,  j-1  line  ;  in  ihefovea patellce,  IJ-lf  of  a  line  ;  in  the 
middle  of  the  condyles  of  the  tibia,  1 J  of  a  line  ;  at  the  borders,  J-f  ths 
of  a  line;  in  the  middle  of  the  patella,  1J— If  ths  of  a  line  ;  in  the  glenoid 
cavity  of  the  tibia,  J— Jths  of  a  line,  on  the  body  of  the  astragalus,  on 
the  upper  side,  f  ths,  on  the  under,  J,  on  its  head,  f  ths  of  a  line ;  at  the 
base  of  the  first  metatarsal  bone,  ^— J,  on  its  head  Jd  of  a  line,  on 
the  inner  cuneiform  bone,  in  front,  J-J,  behind,  J-f  ths  of  a  line.  In 
the  foetus,  about  the  middle  period  of  uterine  life,  the  vessels  of  the 
synovia!  membrane,  according  to  Toynbee  ("Phil.  Transact.,"  1841), 
extend  much  further  upon  the  articular  cartilage ;  of  which  fact,  how- 
ever, I  have  been  unable  to  satisfy  myself  in  the  humerus  of  a  five  or 
six  month  foetus,  or  in  new-born  infants.  In  pathological  states  endo- 
genous cell-formation  is  met  with  in  an  unusual  degree  of  perfection,  and 
more  especially  in  all  kinds  of  articular  cartilages ;  in  which  the  parent 
cells,  frequently  of  very  considerable  size,  with  one  or  two  generations 
of  secondary  cells,  and  also  containing  fat,  lie  tolerably  free  in  the  fibrous 
matrix,  and  admit  of  being  readily  isolated  (vide  also  Ecker  in  Rosera 
and  Wunderlich's  "Archiv,"  vol.  II.,  1843,  p.  345).  In  the  adult,  the 
articular  cartilages  are  non-vascular,  although  the  vessels  of  the  syno- 
vial  membrane,  at  their  border,  often  advance  to  some  distance  over  them. 
What  Liston  ("Med.  Chir.  Transact.,"  1840,  pp.  93-4)  describes  as 
"  vessels  in  the  articular  cartilage  of  several  diseased  joints,  and  as  run- 
ning straight  in  parallel  lines  from  the  injected  membrane  of  the  bone 
into  the  cartilage,  and  as  joining  at  their  further  extremities  in  that 
tissue,  thus  forming  long  loops,"  were  certainly  nothing  more  than  the 
normal  vessels  of  cartilage,  which  (vide  infra)  may  be  very  beautifully 
displayed  even  in  individuals  18  years  old.  There  cannot,  therefore,  be 
any  question  of  inflammation  of  the  cartilages  in  the  adult,  though  they 
doubtless  suffer  in  morbid  conditions  of  the  bones  upon  which  they  rest, 
or  in  inflammation  of  the  synovial  membrane.  They  frequently  assume 
a  fibrous  structure,  a  change  which  is  often  attended  with  a  simultaneous 

*  [This  peculiarity  of  the  bone  beneath  the  articular  cartilages  was  first  pointed  out  by 
Dr.  Sharpey  (Quain  and  Sharpey,  5th  ed.,  p.  clviii.),  and  is  particularly  described  by  Tomes 
and  De  Morgan,  1.  c.,  pp.  10,  11.— TRS] 


THE    OSSEOUS     SYSTEM.  295 

increase  in  thickness,  Cruveilhier  ("Diet,  de  He'd,  et  Cbir.  prat."  III., 
514)  having  noticed  fibres  of  this  kind  as  much  as  6  lines  in  length,  thus 
far  exceeding  the  normal  thickness  of  articular  cartilage.  They  some- 
times wear  away  rapidly,  or  even  disappear  altogether  (in  suppuration 
in  the  bone  or  in  the  articulation),  so  that  the  surface  of  the  bone  is  left 
exposed;  they  also  undergo  partial  loses  of  substance;  when  they 
exhibit  ulcerous  excavations,  which  may  penetrate  to  the  bone,  or  com- 
mence on  the  osteal  surface  of  the  cartilage. 

§  96.  The  articular  capsules  (capsulce  s.  membranes  synoviales]  are 
not  closed  capsules,  but  short,  wide  tubular  sacs,  which  are  attached  by 
two  open  ends  to  the  borders  of  the  articular  surfaces  of  the  bones,  and 
thus  connect  them  together.  They  are  essentially  more  or  less  delicate, 
transparent  membranes,  but  are  in  many  situations  so  closely  and  com- 
pletely invested  externally  by  fibrous  layers — the  fibrous  capsules  as  they 
are  termed, — as  on  cursory  inspection  to  present  the  aspect  of  tolerably 
tough  capsules.  These  fibrous  coats  are  met  with  especially  in  situations 
where  the  articulation  is  either  wholly  unprotected,  or  but  thinly  covered 
by  soft  parts,  or  where  a  very  firm  connection  is  required  (as  in  the  hip- 
joint);  they  are  absent  for  the  most  part,  or  are  undeveloped,  where 
muscles,  tendons,  and  ligaments  rest  upon  the  articulation,  or  where,  for 
special  purposes,  the  synovial  membrane  is  exposed  to  more  considerable 
movements  (as  in  the  knee  and  elbow). 

The  relation  of  the  articular  capsules  to  the  bones  and  articular  car- 
tilages, more  precisely  described,  is  as  follows  (Fig.  126) : — The  articular 
capsule  is  attached,  either  simply  to  the  border  of  Fio.  126. 

the  cartilaginous  surface,  extending  thence  directly 
to  the  other  bone  (patella,  amphiarthroses) ;  or  it 
may,  in  the  first  place,  besides  the  border  of  the 
cartilage,  also  invest  a  larger  or  smaller  extent  of 
surface  of  the  bone  itself,  and  then  pass  to  the 
second  bone,  with  which  it  is  connected  in  the  one 
way  or  the  other.  In  either  of  these  cases  the 
synovial  membrane  does  not  adhere  immediately  to 
the  hard  tissues  subjacent  to  it,  but  is  more  or  less 
closely  connected  with  the  periosteum  and  peri- 
chondrium, ultimately  ceasing  without  any  distinct 
margin,  not  far  from  the  border  of  the  articular  cartilage,  with  the 
perichondrium  of  which  it  is  inseparably  united. 

With  respect  to  the  intimate  structure  of  these  tissues,  the  synovial 

FIG.  12G. — Diagram  of  a  transverse  section  of  a  phalangeal  articulation,  partly  after 
Arnold :  a,  bones ;  6,  articular  cartilage ;  c,  periosteum  continuous  with  the  perichondrium  of 
the  articular  cartilage;  d,  synovial  membrane  at  the  edge  of  the  cartilage,  connected  at  first 
with  the  perichondrium ;  e,  its  epithelium. 


296  SPECIAL    HISTOLOGY. 

membranes,  distinct  from  the  fibrous  capsules,  as  they  are  termed, 
which  possess  in  all  respects  the  structure  of  fibrous  ligaments,  consist : 
— 1,  of  a  layer  of  connective  tissue,  with  not  very  numerous  vessels  and 
nerves ;  and,  2,  of  an  epithelium.  The  latter  is  composed  of  from  one 
to  four  layers  of  large  tessellated  cells,  measuring  0-005— 0*008  of  a 
line,  with  roundish  nuclei  of  0-002-0-003  of  a  line.  The  former,  in  its 
innermost  part,  is  constituted  of  a  layer  of  parallel  fasciculi,  with  indis- 
tinct fibrils  and  elongated  nuclei  or  fine  elastic  filaments  ;  more  exter- 
nally of  decussating  bundles,  with  a  fine  elastic  network,  occasionally 
also  of  a  network  of  bundles  of  connective  tissue  of  very  various  thick- 
ness, with  winding  elastic  fibres,  exactly  as  in  the  arachnoid.  Not 
unfrequently,  common  fat-cells  occur,  dispersed  here  and  there  in  the 
meshes  of  the  connective  tissue,  although  upon  the  whole  very  rarely ; 
and  also  a  few  scattered  cartilage-cells,  with  tolerably  thick,  opaque 
walls,  and  a  distinct  nucleus.  The  synovia!  membranes  possess  neither 
glands  nor  papillge,  whilst  they  present  large  adipose  masses  (plicce  adi- 
posce)  and  vascular  pirocesses  (plicce  vasculosce,  plicce  synoviales,  liga- 
menta  mucosa,  of  authors).  The  former,  at  one  time  erroneously  termed 
"  Haversian  glands,"  are  found  principally  in  the  hip-  and  knee-joints, 
in  the  form  of  yellow  or  yellowish-red  soft  processes  or  folds,  and  con- 
sist simply  of  large  collections  of  fat-cells  in  vascular  portions  of  the 
synovial  membrane.  The  latter  are  met  with  in  almost  every  joint, 
constituting,  provided  that  the  blood-vessels  are  filled,  red,  flattened 
projections  of  the  synovial  membrane,  with  an  indented  and  plicated 
margin,  and  furnished  with  minute  processes.  These  folds  are  usually 
placed  close  to  the  junction  of  the  synovial  membrane  with  the  carti- 
lage, upon  which  they  lie  flat,  thus  forming,  in  many  cases,  a  sort  of 
coronal  around  it ;  in  others  they  are  more  isolated,  and  placed  in  other 
parts  of  the  articulation.  In  their  structure,  they  differ  from  the  rest 
of  the  synovial  membrane  principally  in  their  great  vascularity,  con- 
sisting as  they  do  of  little  else  than  minute  arteries  and  veins,  and 
delicate  capillaries  forming  wavy  loops  at  the  edge  of  the  processes,  and 
consequently  they  are  very  similar  to  the  choroid  plexuses  in  the  ven- 
tricles of  the  brain.  Besides  the  vessels,  they  present  a  matrix  of, 
frequently,  distinctly  fibrous,  connective  tissue,  the  usual  epithelium  of 
the  synovial  membrane,  occasionally  solitary  or  numerous  fat-cells,  and, 
more  rarely,  isolated  cartilage-cells.  At  the  edge,  they  are  almost 
invariably  furnished  with  minute,  foliated,  conical,  membranous  pro- 
cesses of  the  most  extraordinary  forms  (often  resembling  the  stems  of  a 
cactus\  which  also  frequently  contain  vessels,  but  are  for  the  most  part 
constituted  merely  of  an  axis  of  indistinctly  fibrous  connective  tissue, 
with  occasional  cartilage-cells,  and  an  epithelium,  very  thick  in  places. 
The  smaller  ones  frequently  consist  even  of  nothing  but  epithelium, 
or  of  little  else  than  connective  tissue. 


THE    OSSEOUS    SYSTEM. 


297 


In  many  joints  there  are  firm,  whitish-yellow,  fibrous  plates,  the 
so-termed  interarticular  carti- 
lages or  ligaments,  which,  either  Fig.  127. 
projecting  in  pairs  from  the  syno- 
vial  capsule,  are  interposed  be- 
tween the  bones  constituting  the 
articulation  (knee),  or  form  a 
single  diaphragm  transversely 
across  the  joint  (articulations  of 
the  jaw,  clavicle,  sternum,  and 
wrist).  These  processes  consist 
of  a  firm,  fibrous  tissue,  the  fibres 
of  which  usually  cross  each  other 
in  various  directions,  and  are  in 
all  respects  closely  allied  to  con- 
nective tissue,  but  presenting  less 
distinct  fibrils  ;  and,  besides  this, 
of  cartilage-cells  and  fine  elastic 
fibres.*  The  cartilage-cells,  in  the 
most  superficial  layers,  are  more 
solitary,  in  the  deeper,  disposed 
more  in  rows  and  smaller,  ultimately  being  replaced  by  fine  elastic  fibres, 
a  certain  number  of  which,  at  all  events,  appear  to  originate  from  cells 
resembling  the  cartilage-cells.  The  interarticular  ligaments,  which, 
from  what  has  been  said  respecting  them,  must  be  enumerated  among 
the  fibro-cartilages,  are  not  covered  by  synovial  membrane,  though  they 
probably  have  an  epithelial  investment  at  the  attached  border,  but  only 
for  a  small  extent, — never  over  the  entire  surface.  The  articular  liga- 
ments, with  the  exception  of  the  softer  ligamentum  teres,  are  composed 
of  the  same  firm  connective  tissue  (in  the  costal  ligaments  containing 
cartilage-cells),  as  that  of  which  the  tendons  and  the  fibrous  ligaments, 
elsewhere,  are  constituted.  The  internal  ligaments  (lig.  cruciatce),  how- 
ever, present  softer  connective  tissue,  containing  vessels,  and  covered 
with  epithelium. 

FIG.  127. — From  the  synovial  membrane  of  a  phalangeal  articulation  :  ^f,  two  non- vascular 
appendages  of  the  synovial  processes,  magnified  250  diameters :  a,  connective  tissue  in  its 
axis ;  6,  epithelium  (in  the  peduncle  of  the  larger  process  not  distinctly  cellular)  continuous 
with  that  on  the  free  borders  of  the  process ;  c,  d,  cartilage-cells ;  7?,  four  cells  from  the 
epithelium  of  the  synovial  membrane  of  the  knee,  one  with  two  nuclei;  magnified  350  dia- 
meters. 

*  [These  interarticular  fibro-cartilages  lose  in  old  persons  their  distinct  fibrous  structure, 
and  assume  a  yellow  or  brownish  color.  Yet  they  never,  according  to  Virchow  (Archiv.  f. 
Path.  Anat.),  become  entirely  homogeneous,  since  a  careful  examination  will  always  permit 
two  directions  of  their  fibres  to  be  recognized,  viz. :  one  parallel  to  the  free  edge,  and  the 
other  running  vertically  towards  it. — DaC.] 


298 


SPECIAL    HISTOLOGY. 


Fig.  128. 


Within  the  synovial  capsules  is  contained,  in  small  quantity,  a  clear 
yellowish  fluid,  which  may  be  drawn  out  into  threads, — the  synovia, 

— and  which,  in  its  chemical  composition,  ap- 
pears very  closely  to  resemble  mucus,  and 
particularly  in  its  containing  mucin  in  solu- 
tion. Examined  under  the  microscope,  in  its 
normal  condition,  this  secretion  exhibits  no- 
thing worthy  of  much  remark,  consisting  simply 
of  fluid  which  is  rendered  turbid  by  acetic 
acid,  and  very  frequently  contains  epithelial 
cells,  which  have  often  undergone  a  fatty  meta- 
morphosis, nuclei  of  such  cells,  and  fat  globules  ; 
under  conditions  not  quite  normal,  it  may  also 
contain  blood-  and  lymph-corpuscles,  detached 
portions  of  the  synovial  processes  of  the  arti- 
cular cartilage,  and  a  structureless  gelatinous 
substance. 

The  normal,  healthy  synovia,  which  in  the  Ox,  according  to  Frerichs 
(Wagn.  "  Handb."  III.  1),  contains  91-8  water,  0*5  mucus  and  epithe- 
lium, O07  fat,  3-5  albumen  and  extractive  matter,  and  0'9  salts,  is  a 
secretion,  not  having  essentially  any  formed  elements  in  it,  which 
simply  exudes  from  the  vessels  of  the  synovial  membrane  with  the  inter- 
mediation of  the  epithelium  ;  and,  in  fact,  from  all  its  vascular  processes, 
which  are  destined  as  it  were  for  this  special  function,  and  always  exist 
at  the  border  of  a  cartilage  requiring  a  lubricating  covering.  The  non- 
vascular  appendages  of  these  processes  give  origin  to  the  "  loose  carti- 
lages," as  they  are  termed ;  they  do  this  by  their  increasing  in  size  and 
solidity,  and  becoming  detached  from  the  vascular  folds.  These  bodies 
are  also  met  with  in  mucous  bursae  and  the  sheaths  of  tendons,  which 
are  also  furnished  with  vascular  folds  (vid.  sup.  §  82) ;  they  consist  of 
connective  tissue  with  elongated  nuclei,  coated  with  epithelium,  and, 
though  not  always,  contain  a  variable  number  of  scattered  fat-  and  true 
cartilage-cells ;  and  they  are  not  developed  externally  to  the  synovial 
membrane,  but  from  an  outgrowth  of  that  membrane  itself.  Similar 
solid  bodies,  moreover,  may  probably  be  produced  in  other  ways ; 
Bidder  ("Zeitsch.  f.  rat.  Medicin,"  vol.  Hi.,  p.  99,  et  seq.),  at  all  events, 
and  Virchow  ("  Med.  Zeitung,"  1846,  Nos.  2  and  3)  have  observed 
similar  bodies  presenting  no  trace  of  organization.  I  am  inclined,  with 
Virchow,  who  has  actually  demonstrated  the  presence  of  fibrin  in  them, 
to  regard  them,  in  many  cases,  as  fibrinous  exudations,  and  in  others  as 

FIG.  128. — From  the  falciform  ligament  of  the  knee:  a,  a  filament  of  connective  tissue 
with  oval  cells  disposed  in  a  series,  and  resembling  cartilage-cells ;  b,  a  similar  filament 
with  more  elongated  cells  and  nuclei. 


THE     OSSEOUS    SYSTEM.  299 

solidified  deposits  from  the  synovia,  which  latter  supposition  is  supported 
by  the  frequent  occurrence  of  curdy,  more  or  less  consistent,  structure- 
less masses,  evidently  inspissated  synovia,  in  the  tendinous  sheaths  of 
the  hand.  Portions  of  bone,  also,  detached  from  outgrowths  at  the  cir- 
cumference of  the  articular  ends  of  the  bones,  may  find  their  way  into 
the  interior  of  the  articulation.  The  plicce  adiposce  have  perhaps  less 
to  do  with  the  formation  of  the  synovia  than  with  the  mechanism  of  the 
joint,  serving  the  purpose  of  filling  up  hollows. 

§  97.  Physical  and  chemical  properties  of  the  Bones,  and  their  acces- 
sory Organs. — The  bones  are  composed,  besides  a  small  quantity  of 
water  (3-78,  according  to  Stark  in  the  compact  substance),  and  fat  (2-3g 
Bibra),  principally  of  a  substance  affording  gelatine,  and  of  inorganic 
elements.  The  latter,  in  the  adult,  constitute  two-thirds  (68-82  Bibra) 
of  dry  bone,  and  are  nearly  all  left  when  the  bone  is  calcined  ;  in  which 
case,  if  due  care  be  taken,  the  bone  completely  retains  its  external 
aspect,  although  it  may  be  readily  reduced  to  a  white,  opaque,  friable, 
heavy  powder,  the  so-termed  ubone  earth."  This  consists  chiefly  of 
57-59J  basic  phosphate  of  lime  (according  to  Heintz,  3  atoms  base,  1 
atom  acid),  of  carbonate  of  lime  (7-8 g)  and  traces  of  fluate  of  lime, 
phosphate  of  magnesia,  silex  (traces),  arid  alkaline  salts.  A  small  part 
of  the  salts  of  bone  is  also  contained  in  the  walls  of  the  vessels  and  in 
the  lacunae,  and  this  part  is  dissolved  in  water.  The  collagenous  sub- 
stance is  the  so-termed  bone,  formative,  or  ossifying  cartilage.  It  is 
obtained  when  bone  is  treated  at  a  low  temperature  with  dilute  hydro- 
chloric, or  nitric  acid,  in  the  form  of  a  soft,  flexible,  elastic,  light-yel- 
lowish, cartilaginous,  transparent  substance,  retaining  accurately  the 
shape  of  the  bone.  This  bone-cartilage  constitutes  about  J  of  the  dry 
bone,  putrefies  when  moist,  and  when  dried,  may  be  burnt  away,  leaving 
a  small  quantity  of  ash.  It  is  dissolved  by  boiling,  and  from  its  com- 
bination with  water  is  produced  the  gelatine,  usually  to  the  amount  of 
3  or  4  times  its  volume,  and  which  may  also  be  obtained  directly  by 
long  boiling  of  the  bone  in  a  Papin's  digester. 

With  regard  to  the  mode  in  which  the  principal  constituent  elements 
of  the  osseous  tissue  are  combined,  it  is  certain  that  the  bone  earth  does 
not  exist  as  a  distinct  deposit  in  any  of  the  constituent  parts  of  healthy, 
fully  formed  bone,  but  rather,  although  in  a  solid  form,  only  in  a  very 
intimate  union  with  the  tissue.  Since  both  the  cartilage  and  the  cal- 
cined bone  retain  the  figure  of  the  bone,  in  all  its  particulars,  indepen- 
dently of  each  other,  there  can  be  no  doubt,  but  that  the  most  intimate 
union  of  the  two  substances  exists  throughout  the  entire  bone,  which, 
however,  cannot  be  regarded  as  a  chemical  combination,  principally  for 
the  reason,  that  the  proportional  relations  between  the  collagenous  sub- 
stance and  the  phosphate  of  lime  are  very  variable  ;  and  that,  by  simple 


300  SPECIAL    HISTOLOGY. 

boiling  under  an  increased  pressure,  the  gelatine  is  separated  from  the 
calcareous  salts. 

The  physical  properties  of  the  bones  correspond  with  their  composi- 
tion. Their  hardness,  density,  and  rigidity  are  due  to  the  earthy, 
whilst  their  elasticity  and  flexibility  depend  upon  the  organic  constitu- 
ents. In  the  normal  bone  of  the  adult,  the  two  principal  constituents 
are  united  in  such  proportions,  that  the  bones,  together  with  consider- 
able hardness  and  rigidity,  have  a  certain  degree  of  elasticity,  though 
slight,  so  that  they  possess  a  considerable  resisting  power,  and  are 
broken,  though  not  very  readily,  by  the  application  of  greater  mechani- 
cal force.  At  an  earlier  age,  when  the  cartilage  is  in  greater  relative 
proportion,  the  hardness  of  the  bones  is  much  less,  their  sustaining 
power  consequently  less  considerable,  and  they  are  more  liable  to  be 
bent ;  whilst  on  the  other  hand,  owing  to  their  greater  elasticity,  they 
are  much  less  liable  to  be  broken.  This  is  the  case  in  a  much  higher 
degree  in  rachitis,  in  which  morbid  condition,  the  organic  constituents 
amount  to  from  70  to  80  per  cent.  A  condition  the  reverse  of  this  is 
observed  in  old  age,  when  the  bones,  though  certainly  harder,  are  more 
brittle,  and  therefore  more  readily  fractured,  to  which  liability,  however, 
the  rarefaction  of  the  tissue  which  takes  place  in  consequence  of  age, 
partly  contributes.  The  inflammability  of  bone  depends  upon  its 
organic  basis,  and  its  capability  of  resisting  putrefaction  to  the  inor- 
ganic constituents.  The  latter  being  so  intimately  combined  with  the 
animal  tissues,  serve  as  a  protection  to  them,  so  that  bones  from  ancient 
burial-places,  and  those  of  fossil  animals  still  retain  the  full  proportion 
of  cartilage. 

The  true  cartilages,  even  in  the  foetus,  contain,  in  their  organic  basis, 
from  50  to  75  per  cent,  of  water,  3  to  4  per  cent,  of  salts  (chiefly  of 
soda  and  carbonate  of  lime,  and  also  some  phosphate  of  lime  and  mag- 
nesia). The  organic  basis  has  been  hitherto  supposed  to  consist  entirely 
of  cJwndrin,  a  substance  allied  to  gelatin,  soluble  in  boiling  water  and 
gelatinising  as  it  cools;  but  it  was  noticed  by  Bruns  (p.  216),  that  the 
matrix  and  the  cells  of  cartilage  were  not  equally  soluble  in  water,  and 
Mulder  and  Donders  have  rendered  it  probable  that  the  cliondrin,  which 
had  hitherto  been  investigated,  is  not  a  simple  substance,  and  that  the 
cartilages  consist  of  several  bodies  of  different  natures,  the  matrix,  and 
the  membranes  of  the  parent  cells,  their  contents,  and  the  secondary 
cells,  of  which  the  first  is  more  soluble  in  water,  potass,  and  sulphuric 
acid,  than  the  others. 

The  fibro-cartilages  (cartilages  containing  connective  tissue)  have 
been,  as  yet,  but  little  investigated.  J.  Muller,  in  the  interarticular 
cartilages  of  the  knee  of  the  Sheep,  found  no  chondrin  ;  whilst  Donders, 
on  the  other  hand,  met  with  it  in  the  intervertebral  ligaments  ("  Holl. 
Beitr.,"  p.  264);  he  did  not  determine  whether  they  also  contained 
gelatin.  According  to  Virchow,  the  gelatinous,  nuclear  portion  of  these 


THE    OSSEOUS    SYSTEM.  301 

ligaments,  in  the  new-born  child,  consists  of  a  substance  very  nearly 
allied  to  that  of  "colloid"  (Wurzb.  "  Verhandl.,"  II.  283).  The  liga- 
ments have  the  same  chemical  composition  as  the  tendons. 

§  98.  Vessels  of  the  Bones  and  their  accessory  Organs. — A.  Blood- 
vessels. The  periosteum,  besides  the  numerous  vessels  passing  to  the 
bone  by  which  it  is  traversed,  presents  in  its  outer  layer,  composed  of 
connective  tissue,  a  tolerably  close  network  of  minute  capillaries  (0-005 
of  a  line).  The  blood-vessels  of  the  bone  itself  are  very  numerous,  as 
may  be  seen  in  injected  specimens,  and  also  in  recent  bone  full  of  blood. 
In  the  long  bones,  the  marrow  and  the  spongy  substance  of  the  articular 
ends  are  supplied  by  particular  vessels,  as  is  also  the  compact  substance 
of  the  shaft.  The  former,  or  vasa  nutritia,  enter  the  bone  through  large 
special  canals,  one  or  two  of  which  are  found  in  the  diaphyses,  and 
many  in  the  apophyses.  These  vessels,  with  the  exception  of  a  few 
twigs  given  off  to  the  innermost  Haversian  canals  of  the  compact  sub- 
stance, and  which  possess  all  the  tunics  proper  to  the  vessels  elsewhere 
(even  to  the  muscular),  ramify  in  the  marrow,  where  they  form  a  true 
capillary  plexus — the  vessels  in  which  vary  in  size  from  0-004  to  0-0052 
of  a  line.  The  vessels  of  the  compact  substance  arise,  in  great  part, 
from  those  of  the  periosteum,  very  soon  lose  the  muscular  coat,  and 
form,  in  the  Haversian  canals,  which  they  either  occupy  by  themselves, 
or  together  with  some  medullary  substance,  a  network  of  wide  canals, 
which  from  their  structure,  can  only  in  the  most  trifling  extent  be  re- 
ferred to  the  capillary  system,  most  of  them  possessing  a  layer  of  con- 
nective tissue  and  an  epithelium,  and  as  it  is  only  in  the  larger  canals 
that  fine  capillaries  co-exist  with  the  main  vessel.  The  venous  blood  is 
returned  from  all  the  long  bones,  in  three  ways : — 1,  by  a  large  vein 
accompanying  the  nutritious  artery,  the  ramifications  of  which  it  fol- 
lows ;  2,  by  numerous  large  and  small  veins  at  the  articular  extremities  ; 
and,  3,  lastly,  by  many  small  veins,  which  arise  independently  of  each 
other  from  the  compact  substance  of  the  diaphyses,  in  which  their  roots, 
as  is  correctly  stated  by  Todd  and  Bowman,  occupy  the  wider  spaces 
and  sinuses,  or  pouch-like  excavations,  which  are  very  evident  even  in 
sections  of  bone. 

All  the  vessels  of  bone, — the  medullary  vessels  of  the  apophyses  and 
of  the  diaphyses,  as  well  as  the  vessels  of  the  compact  substance, — 
communicate  in  a  multiplicity  of  ways,  so  that  the  vascular  system 
throughout  the  entire  bone  constitutes  a  continuous  whole,  in  which  it 
is  possible  for  the  blood  from  any  one  part  to  reach  every  other  part ; 
for  it  was  observed  by  Bichat  ("  Anat.  Ge'ne'ral.,"  1812,  III.  p.  37),  in 
an  injected  tibia,  the  nutritious  artery  of  which  was  obliterated,  that 
the  bifurcation  of  the  vessel  in  the  medullary  canal  was  well  injected, 
and  that  the  nutrition  of  the  marrow  was  evidently  unaffected. 


302  SPECIAL    HISTOLOGY. 

In  the  short  bones,  the  bloodvessels  present  pretty  nearly  the  same 
conditions  as  they  do  in  the  apopliyses  of  the  long  bones  ;  the  arteries 
and  veins  of  larger  and  smaller  size  entering  and  quitting  the  bone  at 
numerous  points  on  the  surface,  and  sometimes,  as  in  the  posterior 
aspect  of  the  bodies  of  the  vertebra?,  in  very  large  trunks, — the  vence 
basi-vertebrales  of  Breschet,  furnishing  a  capillary  plexus  to  the 
medulla,  and  also  penetrating  into  the  few  Haversian  canals  of  these 
bones. 

In  the  jto  bones,  such  as  the  scapula  and  os  innominatum,  there  are 
distinct  nutritious  foramina  for  the  larger  arteries  and  veins  ;  the  com- 
pact substance  receiving  finer  vessels  from  the  periosteum,  and  the 
spongy  substance  being  supplied  by  numerous  and  even  large  vessels, 
as  in  the  neighborhood  of  the  articular  cavities.  In  the  flat  cranial 
bones,  the  arteries,  for  the  most  part,  enter  both  the  cortical  and  spongy 
substance  from  without,  on  both  surfaces,  presenting  the  usual  conditions, 
whilst  the  vence  diploeticce,  as  they  are  termed,  have  only  their  extremi- 
ties free  in  the  medulla,  as  in  other  bones,  their  trunks,  and  larger  and 
smaller  branches  running  independently  and  generally  unassociated 
with  medullary  substance  in  large,  arborescent,  special  channels,  the  so- 
termed  "canals  of  Breschet,"  which  open  at  determinate  points  with 
large  apertures  (emissaria  Santorini),  and  communicate  freely  with  the 
veins  of  the  dura  mater,  with  respect  to  which  relations,  however,  works 
on  special  anatomy  must  be  consulted.  The  size  and  number  of  the 
veins  in  the  cranial  bones,  is,  moreover,  extremely  variable,  and  they 
are  constantly  becoming  obliterated,  particularly  in  old  age,  concomi- 
tantly  with  the  frequent  diminution  of  the  diploe,  on  which  account  also 
the  venous  canals  and  their  openings  (emissaria)  are  of  such  variable 
dimensions. 

The  articular  and  other  cartilages  of  the  osseous  system,  even  the 
fibro-cartilages,  in  the  adult,  normally  contain  no  vessels  at  all,  except 
those  of  the  perichondrium,  which  however  in  this  respect  is  far  inferior 
to  the  periosteum.  But  it  may  happen,  that  as  in  the  costal  cartilages 
in  the  middle  period  of  life  and  afterwards,  vessels  make  their  appear- 
ance, in  which  case  partial  ossification  frequently  either  precedes  or 
follows.  The  fibrous  ligaments  are  poorly  supplied  with  vessels,  and  par- 
ticularly the  elastic  ligaments,  and  in  this  respect  may  be  arranged  with 
the  tendons,  whilst  the  synovial  membranes  are  characterized  by  the 
considerable  number  of  their  bloodvessels.  The  above  described  synovial 
folds  are  especially  rich  in  this  respect,  as  is  also  the  synovial  membrane 
itself,  which,  everywhere  beneath  the  epithelium,  contains  a  pretty  close 
plexus  of  canals,  from  0-004-0-01  of  a  line  in  diameter. 

B.  Lymphatics  in  bone,  have  been  described  by  some  older  and  more 
recent  authors  (vid.  Mikrosk.  "  Anat.,"  II.  1,  336),  but  their  existence 
is  still  not  the  less  doubtful,  and  I  have  in  vain  endeavored  to  find  such 


THE     OSSEOUS     SYSTEM.  303 

vessels.  With  respect  to  the  other  parts  of  the  osseous  system,  the  only 
question  can  be,  as  to  whether  the  periosteum  and  articular  capsules 
possess  lymphatics.  In  the  former,  they  have  not  yet  been  observed, 
whilst  in  the  latter  their  existence  has  been  asserted  by  several  authors, 
Cruveilhier,  for  example.  It  must  be  confessed,  however,  that  it  has 
not  been  by  any  means  proved  that  they  arise  in  these  structures,  at  all 
events  it  appears  to  me  to  be  very  doubtful,  whether  the  synovial  mem- 
branes themselves  contain  vessels  of  this  kind,  whilst  it  is  perhaps  certain 
that  lymphatics  do  exist  in  the  loose  connective  tissue  surrounding  the 
articular  capsules,  and  between  them  and  the  periosteum  of  the  apophy- 
ses,  particularly  at  the  knee. 

§  99.  Nerves  of  the  Osseous  System. — The  periosteum  is  abundantly 
supplied  with  nerves,  the  majority  of  which,  however,  do  not  belong 
properly  to  it,  but  to  the  bone  (vid.  infra).  With  respect  to  the  proper 
periosteal  nerves,  it  appears  that  their  number,  on  the  whole,  is  not 
considerable,  so  that  even  in  some  places  they  may  be  entirely  absent, 
as  in  the  neck  of  the  femur,  and  beneath  certain  muscles  (glutceus 
minimus,  peroncei,  &c.) ;  but  there  are  perhaps  but  few  bones  in  which 
they  do  not  exist  in  one  part  or  another.  These  nerves  lie  in  the  same 
layer  as  the  vessels,  sometimes  along  the  larger  branches,  sometimes  by 
themselves,  arising,  at  all  events  in  part,  from  the  larger  nerves  of  the 
bone  itself,  and  are  manifestly  distributed  over  considerable  spaces, 
although  their  ramifications  and  anastomoses  are  scanty.  In  the  larger 
trunks  of  these  nerves  the  primitive  fibres  measure,  most  generally  0-002 
-0-004  of  a  line,  though  their  size  gradually  lessens,  partly  owing  to 
actual  divisions,  which  I  have  seen  with  the  utmost  distinctness  in  the 
periosteum  of  the  fossce  infra-spinata,  and  iliaca  in  man,  and  J.  N. 
Czermak  in  that  of  the  frontal  bone  in  the  Dog ;  and  in  part  by  a 
gradual  attenuation,  to  a  diameter  of  0-0012-0-0016  of  a  line,  many, 
and  perhaps  all,  terminating  with  free  extremities.  On  the  articular 
ends  of  many  bones,  such  as  those  of  the  elbow,  knee,  and  knuckle-joints, 
I  have  noticed  the  nerves  to  be  more  abundant  than  elsewhere,  ramify- 
ing and  anastomosing  in  the  vascular  connective  tissue  covering  the 
periosteum,  and  following  principally  the  course  of  the  blood-vessels  5 
but  in  these  situations,  divisions  and  terminations  of  the  primitive  fibres 
did  not  come  under  my  observation. 

The  nerves  of  the  bone  itself,  which,  with  the  exception  perhaps  of 
the  ossicula  auditus  and  sesamoid  bones,  are  universally  present,  do  not 
exhibit  exactly  the  same  conditions  in  all  bones.  In  the  larger  cylin- 
drical bones,  they  penetrate,  in  company  with  the  nutrient  vessels,  in 
the  form  of  one,  or  where  two  nutrient  foramina  exist,  of  two,  pretty 
considerable  trunks  (measuring  as  much  as  0*16  of  a  line),  visible  to  the 
naked  eye,  directly  into  the  medullary  cavity,  and  are  there  distributed 


304  SPECIAL    HISTOLOGY. 

into  the  medulla,  following  the  course  of  the  vessels,  though  not  always 
in  apposition  with  them,  towards  the  apophyses,  and  forming  multifarious 
ramifications,  but,  at  least  as  far  as  I  have  seen,  only  few  anastomoses. 
In  the  second  place,  all  these  bones  also  present,  in  the  apophyses,  nu- 
merous finer  nerves,  accompanying  the  equally  numerous  blood-vessels 
directly  into  the  spongy  substance,  and  ramifying  in  the  medulla ;  and 
thirdly,  extremely  delicate  filaments  are  sent  even  into  the  compact  sub- 
stance of  the  diaphyses,  in  company  with  the  minute  arteries  by  which 
it  is  penetrated.  There  can  be  no  doubt  that  these  filaments  are  dis- 
tributed in  the  compact  substance,  although  I  have  never  succeeded  in 
finding  them  within  it.  The  smaller  cylindrical  bones  of  the  hand  and 
foot  present  the  same  conditions  with  respect  to  their  nerves  as  the 
larger  ones,  except  that  in  them,  on  account  of  the  undeveloped  con- 
dition of  the  medullary  cavities,  the  numerous  nerves  are  not  so  regu- 
larly divided  into  apophysal  and  diaphysal. 

Of  the  short  bones,  I  have  found  the  vertebra?  to  be  the  most  abun- 
dantly supplied  with  nerves,  and  especially  their  bodies.  The  nerves 
enter  posteriorly  in  company  with  the  arteries  and  veins  (vence  basi-ver- 
tebrales),  as  well  as  anteriorly  and  on  the  sides,  together  with  the  vessels, 
arid  are  distributed  in  the  marrow  of  the  spongy  substance.  In  the 
astragalus  also,  calcaneum,  os  naviculare,  cuboideum,  and  Cuneiforms 
internum,  I  have  noticed,  in  the  larger,  several,  and  in  the  smaller,  at 
least  one  nervous  filament. 

In  the  scapula  and  os  innominatum,  the  nerves  are  very  numerous, 
entering  these  bones  chiefly  at  the  points  before  indicated,  with  the 
larger  vessels,  sometimes  on  the  expanded  portion,  sometimes  in  the 
neighborhood  of  the  articular  cavities.  In  the  sternum  also,  and  in 
the  flat  cranial  bones,  the  existence  of  nerves  is  demonstrated  without 
difficulty.  In  the  latter,  I  have  observed,  even  in  the  new-born  infant, 
in  the  occipital  and  parietal  bones,  nerves  entering  through  the  fora- 
mina emissaria,  which  at  this  period  also  contain  an  artery  ;  and  in  the 
adult,  there  are  found  in  the  parietal,  frontal,  and  occipital  bones, 
although  rarely,  yet  occasionally,  microscopic  filaments  on  the  smaller 
arteries,  which  enter  the  compact  substance  from  without,  and  probably 
penetrate  as  far  as  the  diploe. 

From  these  observations,  together  with  those  of  Kobelt,  Beck,  Engel, 
Luschka,  &c.,  there  can  be  no  doubt  that  the  bones  are  richly  supplied 
with  nerves.  With  respect  to  the  origin  of  these  nerves,  they  have 
already  been  traced  by  previous  observers  to  the  cerebral  and  spinal 
nerves,  as  for  instance  the  nerves  of  the  diaphyses  of  the  femur,  tibia 
and  humerus,  to  the  nn.  cruralis,  tibialis,  ischiaticus,  and  perforans 
Casseri,  as  well  as  a  nerve  of  the  frontal  bone  to  the  n.  supraorbitalis, 
which  observations,  as  far  as  they  relate  to  the  tibial  nerve,  have  been 
confirmed  by  my  own,  and  by  those  of  Luschka  in  the  case  of  certain 


THE    OSSEOUS     SYSTEM.  305 

of  the  cranial  bones,  and  of  the  vertebrae.  Nevertheless,  the  sympa- 
thetic participates  in  their  formation,  as  Luschka,  and  before  him, 
Kobelt  have  observed  with  respect  to  the  vertebral  nerves.  Microsco- 
pical examination  confirms  this,  inasmuch  as  the  nerves  of  bone,  in  their 
trunks  and  terminations,  resemble  in  every  respect  the  sensitive  branches 
of  the  spinal  nerves,  and  contain,  in  the  trunks,  one-third  of  fibres, 
measuring  0-005-0-006  of  a  line;  two-thirds  measuring  0-002-0-004 
of  a  line ;  in  the  larger  branches  the  majority  of  the  fibres  measure 
0-002-0*003,  but  some  as  much  as  0*006  of  a  line;  and  lastly,  in  the 
finest  ramifications,  fibres  of  not  more  than  0*0012—0-0016  of  a  line. 
The  periosteal  nerves,  also,  which  may  frequently  be  seen  to  be  con- 
nected with  the  nerves  of  the  bone,  and  may  be  traced  to  the  nerves  of 
the  extremity,  are  derived,  probably  in  the  greater  proportion,  from  the 
spinal  nerves,  although  even  in  their  case,  perhaps,  some  participation 
of  the  sympathetic  cannot  be  denied. 

How  the  nerves  of  bone  terminate,  I  have  not  observed,  and  can  only 
remark,  that  from  the  nerves  in  the  marrow,  extremely  delicate  branches, 
composed  of  neurilemrna  and  one  or  two  fibrils,  are  ultimately  developed; 
but  as  to  what  becomes  of  these  I  am  ignorant.  It  is  also,  perhaps, 
worthy  of  notice,  that  in  two  situations,  before  their  entrance  into  the 
bone,  I  have  observed  Pacinian  bodies  on  the  nerves ;  viz.  on  the  dia- 
physal  nerve  of  the  tibia,  two  lines  before  its  entrance  into  the  foramen, 
I  noticed  a  single  body,  and  two  others  on  the  largest  nerve  of  the  me- 
tatarsal  bone  of  the  great  toe,  also  just  before  it  entered  the  bone. 

I  have  never  yet  detected  nerves  in  the  ligaments,  in  Man  (the  liga- 
mentum  nuchce  of  the  Ox  contains  some  fine  nervous  twigs,  accompany- 
ing minute  arteries ;  the  twigs  measuring  0*004  of  a  line,  with  fine  fibres 
of  0-012-0*0015  of  a  line),  but  have  no  doubt  that  they,  like  the  tendons, 
inasmuch  as  that  they  contain  vessels,  are  also  furnished  with  a  few 
scattered  nerves.  On  the  other  hand,  the  interosseous  membrane  of  the 
leg  contains  filaments  derived  from  the  interosseal  nerve,  which,  formed 
of  from  one  to  three  fibrils,  measuring  0*003-0*004  of  a  line,  present 
distinct  ramifications  and  free  terminations  of  the  primitive  fibrils.  A 
nerve  of  0-03  of  a  line,  which  together  with  an  artery  entered  the  fibrous 
external  part  of  the  symphysis  pubis,  may  here  be  mentioned.  With 
regard  to  the  cartilages,  I  have  as  yet  noticed  only  in  the  cartilage- 
canals  in  the  septum  narium  of  the  Calf,  together  with  vessels  (arteries), 
very  distinct,  fine  nervous  twigs,  measuring  0*006—0*01  of  a  line,  with 
fibres  of  0-0012-0-0016  of  a  line  thick.  In  the  articular  capsules  nume- 
rous nerves  exist,  although  they  belong  principally  to  the  so-called  fibrous 
capsules,  and  to  the  loose  connective  tissue  external  to  the  synovial 
membrane.  In  the  knee  I  have  seen  nerves,  even  in  the  true  synovial 
membrane,  although  in  general  they  are  rare,  and  are  most  distinct  in 
the  large  vascular  processes,  which  besides  arteries,  contain  nerves  of 

20 


306  SPECIAL    HISTOLOGY. 

0-007-0-008  of  a  line,  with  fine,  also  dividing  filaments  of  0-0008-0-002 
of  a  line.  I  have  also  seen  in  the  synovial  membrane  itself,  close  to  the 
condyles  of  the  femur,  tolerably  numerous  nerves  composed  of  delicate 
fibres. 

§  100.  Development  of  the  Bones. — In  respect  of  their  development, 
the  bones  fall  into  two  groups,  viz.,  into  those  which  are  preformed  in  a 
cartilaginous  state  (primary  bones),  and  into  those  which  from  a  small 
beginning  are  developed  in  a  soft  blastema  (secondary  bones).  The  former, 
while  yet  in  the  cartilaginous  condition,  present  all  their  essential  parts 
(diaphyses  and  apophyses,  body,  arches,  and  processes,  &c.),  and  as  far 
as  their  cartilaginous  basis  is  concerned,  originate  like  other  cartilages, 
and  continue  to  grow  more  or  less  in  the  same  manner.  They  afterwards 
become  ossified  (in  man,  all  of  them)  from  within  to  without,  transform- 
ing a  portion  of  the  cartilage  completely  into  bone,  so  that  what  was  the 
perichondrium  becomes  the  periosteum,  and  afterwards  attaining  their 
ultimate  figure,  partly  by  means  of  the  remaining  cartilage,  which  con- 
tinuing to  grow  with  them  is  successively  ossified,  and  partly  by  means 
of  a  soft,  ossifying  blastema,  which  is  deposited  layer  upon  layer  on  the 
inner  surface  of  the  periosteum.  In  the  second  group,  the  bone  is  formed 
from  a  very  limited,  soft,  non-cartilaginous  basis,  and  continues  to  grow 
at  the  expense  of  that  substance,  which  is  continually  developed  anew, 
first  at  the  margins  only,  but  afterwards  also  on  the  surfaces.  When 
these  bones  have  attained  a  certain  size,  the  blastema  out  of  which  they 
have  hitherto  been  developed  may  become,  partially,  cartilaginous,  in 
which  case  the  cartilage  stands  in  the  same  relation  to  the  bone  as  it 
does  in  the  former  instance.  The  greatest  part  of  their  formative  sub- 
stance, however,  always  remains  in  a  soft  condition,  and  from  it,  without 
its  ever  becoming  cartilaginous,  the  principal  bulk  of  the  bone  is  produced. 

Frequently  as  the  development  of  the  osseous  tissue  has  already  been 
discussed,  still,  in  a  general  point  of  view,  the  mode  in  which  the  bones, 
as  organs,  originate  has  hitherto  been  little  considered,  and  I  believe 
that  I  was  the  first,  in  my  "Zootomical  Report,"  Leipzig,  1849,  to  es- 
tablish the  principal  features  of  the  process,  and  in  my  "  Microscopical 
Anatomy,"  II.  1,  p.  344,  et  seq.,  to  trace  it  in  its  more  particular  details. 
H.  Meyer  (1.  c.)  agrees  with  me  in  most  of  the  essential  points,  whilst 
Robin  advances  many  different  views,  with  which  I  do  not  accord,  and 
has  to  some  extent  entirely  misunderstood  my  statements. 

§  101.  The  primary  cartilaginous  Skeleton  of  the  human  body,  al- 
though less  complete  than  the  subsequent  osseous  framework,  is  still 
sufficiently  extensive.  We  find  as  portions  of  it :  1.  A  complete  verte- 
bral column,  with  as  many  cartilaginous,  as  there  are  afterwards  osseous 


THE     OSSEOUS    SYSTEM.  307 

vertebra,  with  cartilaginous  processes,  and  with  intervertebral  ligaments. 
2.  Cartilaginous  ribs,  and  a  cartilaginous,  entire  sternum.  3.  Wholly 
cartilaginous  extremities,  with  as  many  and  similarly  formed  pieces  as 
there  are  afterwards  bones,  with  the  sole  exception  of  the  pelvic  carti- 
lages, which  constitute  a  single  mass.  4.  And  lastly,  an  incomplete 
cartilaginous  cranium.  This  primordial  cranium,  as  it  is  termed 
("Mikrosk.  Anat.,"  tab.  iii.  figs.  1-3),  forms  originally  a  continuous 
cartilaginous  substance,  which  corresponds,  for  the  greater  part,  with 
the  occipital  bone  (except  the  upper  half  of  the  expanded  portion),  the 
sphenoid  (except  the  lamina  externa  of  the  pterygoid  process),  the  mas- 
toid  and  petrous  portions  of  the  temporal  bone,  the  ethmoid,  the  inferior 
turbinated  bones,  the  ossicula  auditus  and  the  hyoid  bone ;  but  it 
also  presents  some  cartilaginous  portions,  which  never  become  ossified, 
either  remaining  in  the  cartilaginous  conditions  during  life,  or  afterwards 
disappearing;  as  for  instance,  Meckel's  process,  two  cartilaginous  la- 
mellae below  the  nasal  bones,  a  narrow  cartilaginous  band  connecting  the 
styloid  process  with  the  os  hyoides,  and  two  others,  one  of  which  extends 
from  the  outer  part  of  the  ala  parva  laterally  to  the  lamina  cribrosa, 
whilst  the  other  stretches  upwards  and  forwards  from  the  cartilaginous, 
mastoid,  and  petrous  portions  of  the  temporal  bone.  Consequently,  in 
the  cartilaginous  cranium  of  man,  the  vault  of  the  skull  is  totally  want- 
ing, and  almost  all  the  lateral  portions,  as  wrell  as  nearly  all  of  what 
afterwards  becomes  the  facial  bones ;  nevertheless,  at  all  events  in  the 
true  cranium,  the  parts  not  formed  of  cartilage  are  closed  by  a  fibrous 
membrane,  representing  in  fact  the  further  development  of  the  soft,  pri- 
mordial, cranial  capsule,  so  that  the  cranium  at  this  time,  though  only  in 
part  cartilaginous,  is  yet  fully  as  complete!,  as  at  an  earlier  period,  and 
always  corresponds  to  its  original  soft  rudimental  form.  In  other  Mam- 
malia, as  for  instance,  in  the  Pig,  the  cranium  is  much  more  completely 
cartilaginous  ("Microskop.  Anatomy,"  tab.  iii.  figs.  4,  5). 

The  complete  development  of  the  primordial  cartilage,  considered 
liistologiealty,  has  not  yet  been  accurately  traced  in  all  its  stages,  either  in 
man  or  in  mammalia.  If  we  wish,  therefore,  to  obtain  anything  like  a 
sufficient  idea  of  it,  we  must  at  present  have  recourse  in  a  great  measure 
to  the  lower  Vertebrata.  If  the  cartilage  of  the  spinal  column  and  of 
the  head  be  examined  in  the  latrachian  larva,  it  is  readily  seen,  that 
they  are  invariably  constituted,  while  still  in  the  soft  state,  of  the  same 
formative  cells  with  vitelline  corpuscles,  as  all  the  other  organs.  Before 
the  development  of  the  external  branchiae,  these  cartilage-cells  present 
the  form  of  closely  approximated  spherical  cells,  0-007  to  0-009  of  a  line 
in  size,  with  nuclei  measuring  0-0045-0-006  of  a  line,  and  filled  with  the 
well-known  vitelline  corpuscles;  afterwards,  when  the  branchiae  have 
made  their  appearance,  the  granular  contents  of  the  cells  begin  to  dis- 
appear, from  within  to  without,  whilst  the  nuclei  become  more  distinct, 


308  SPECIAL    HISTOLOGY. 

lying  in  a  clear  fluid  within  them,  and  at  the  same  time  the  cells  slowly 
increase  in  size.  When  the  branchise  have  disappeared,  all  the  cartilage- 
cells  are  already  quite  transparent,  with  distinct  nuclei  and  walls,  and 
they  now  gradually  increase  to  the  size  of  0-018-0-024  of  a  line,  and 
the  nuclei  to  that  of  0-005  and  0-007  of  a  line ;  the  cells,  from  their 
mutual  pressure,  become  polygonal,  and  constitute  one  of  the  most 
delicate  cellular  tissues  possible.  They  now  also  begin  to  multiply  by 
endogenous  cell-formation  around  portions  of  the  contents  (Nageli),  so 
that  in  each  cell  two  secondary  cells  are  formed  around  the  two  nuclei 
produced  from  the  original  nucleus,  and  entirely  fill  it;  at  the  same  time 
they  again  increase,  though  very  slowly,  particularly  in  certain  carti- 
lages of  the  head,  until  they  attain  a  size  of  0-013-0-018  of  a  line,  and 
in  some  places  of  not  more  than  0-006—0-013  of  a  line;  whilst  between 
them,  a  thick  interstitial  substance  is  formed  out  of  the  coalesced  walls 
of  the  different  generations  of  cells.  With  respect  to  man  and  the 
mammalia,  it  can  only  be  stated  as  a  supposition,  that  the  cartilage-cells 
originate  in  a  modification  of  the  primordial  formative  cells.  This  sup- 
position is  favored  by  the  circumstance,  that  in  a  human  embryo  of 
eight  or  nine  weeks,  the  outer  extremities  of  which  were  just  developed, 
they  presented  scarcely  a  trace  of  formed  cartilage,  the  innermost  cells 
of  the  rudimentary  extremities  being  hardly  distinguishable  from  the 
outer.  They  were  0-004-0-006  of  a  line,  in  size,  spherical,  with  grayish 
granular  contents,  and  indistinct  nuclei  of  0-003  of  a  line,  and  formed  a 

tissue  of  some  consistence,  without  any  appre- 
,0  ciable  interstitial  substance.  The  correspond- 
ing cells  in  the  embryo  of  a  sheep  6-7  lines 
in  length  were  somewhat  larger,  although  the 
embryo  was  smaller  than  the  human  foetus 
above  noticed.  In  this  case  (Fig.  129)  they 
measured  for  the  most  part,  0-006-0-01  of  a 
line,  had  distinct  walls,  nuclei,  and  clear, 
aqueous,  only  slightly  granular  contents,  and 

were  lodged  in  a  scanty  homogeneous  interstitial  substance,  so  that  they 
were  only  partially  or  not  at  all  in  contact  with  each  other.  The  contents 
of  only  a  very  few  cells  were  still  in  the  opaque  condition,  and  these 
were  without  any  visible  nucleus,  others  exhibited  the  commencement  of 
transparency  from  the  metamorphosis  of  their  contents.  The  further 
development  of  the  cartilage  up  to  the  end  of  foetal  life,  except  in  its 
ossification,  presents  these  characteristics,  viz.:  (1.)  That  the  cells  pre- 
cisely like  those  in  the  batrachian  larva,  continually  increase  by  endo- 
genous cell-formation,  whilst  precisely  as  in  the  same  instance,  there  is  no 

FiG.  129. — Cartilage-cells  from  the  humerus  of  an  embryo  of  the  Sheep,  6  lines  long: 
a,  cells  with  nucleus  and  clear  contents  (two  cells  retain  remains  of  the  earlier  thick  con- 
tents) ;  6,  cells  with  consistent  contents,  without  visible  nucleus;  c,  intercellular  substance. 


THE    OSSEOUS     SYSTEM.  309 

indication  whatever  afforded,  of  the  production  of  cells  independently  of 
those  already  in  existence;  and  (2.)  That  the  interstitial  substance, 
which  in  this  case  is  manifestly  formed,  for  the  greater  part,  indepen- 
dently of  the  cell  membranes,  is  always  increasing.  With  respect  to 
the  cells,  they  are  in  the  second  costal  cartilage  of  a  four-month  foetus, 
according  to  Harting,  0*0036  of  a  line  long,  0-0023  of  a  line  wide,  and 
consequently  their  aggregate  bulk  pretty  nearly  corresponds  with  that 
of  the  interstitial  substance.  In  the  embryo  of  the  Pig,  3*5  lines  long, 
the  space  occupied  by  the  nucleated,  clear,  thin-walled  cells,  is,  accord- 
ing to  Schwann,  thrice  as  great  as  that  taken  up  by  the  interstitial  sub- 
stance. In  a  five-months'  human  embryo,  I  have  myself  noticed  the 
cartilage-cells,  0-003-0-008  of  a  line  in  diameter,  with  and  without 
secondary  cells,  some  with,  and  some  without  distinct  walls,  and  sepa- 
rated from  each  other  by  a  perfectly  homogeneous  substance,  0*002- 
0*005  of  a  line  thick.  In  the  new-born  child  they  measure,  according 
to  Harting,  0-032-0028mm  in  length,  and  0-0072mm  in  breadth,  and  are 
three  or  four  times  as  numerous  as  in  the  foetus  at  four  months ;  but  on 
the  other  hand,  they  occupy  considerably  less  space,  proportionally, 
than  the  interstitial  substance,  the  bulk  constituted  by  which  is  more 
than  double  that  of  the  cells.  After  birth,  in  the  non-ossifying  carti- 
lages, the  interstitial  substance  and  the  cells  increase  in  pretty  nearly 
an  equal  ratio,  so  that  their  relative  proportions  in  the  adult  are  about 
the  same  as  in  the  infant  at  birth.  In  the  adult  the  cells  are  from  8  to 
12  times  larger  than  in  the  new-born  child  (Harting),  but,  according  to 
him,  their  number  is  diminished,  so  that  they  amount  to  not  more  than 
half  of  what  existed  in  the  child,  which  is  explained  upon  the  supposition 
of  a  coalescence  of  the  cells.  The  numbers  given  by  Harting  do  not 
appear  to  rne  to  afford  sufficient  ground  for  the  establishment  of  his  posi- 
tion; and  even  should  it  be  established,  I  cannot  agree  in  the  explana- 
tion offered,  not  being  a-ware  of  a  single  fact  in  favor  of  the  notion  of  a 
coalescence  of  cartilage  cells.* 

*  [We  have  deferred  to  this  place  the  remarks  we  have  to  make  with  regard  to  the  struc- 
ture of  the  cartilage,  and  its  mode  of  growth;  as  a  just  conception  upon  this  subject  appears 
to  us  to  be  essentially  necessary  to  a  comprehension  of  the  mode  of  development  of  Bone, — 
in  fact,  we  might  say,  to  clear  notions  upon  the  structure  of  the  tissue's  generally ;  for  as  we 
shall  show  more  at  length  below,  it  was  upon  the  structure  of  cartilage,  and  what  he 
supposed  to  be  its  similarity  to  that  of  vegetable  tissue,  that  Schwann  based  the  whole 
nomenclature  of  his  cell  theory. 

Now  we  may  so  far  anticipate  what  we  shall  have  to  show  hereafter,  as  to  premise  that 
Schwann  was  misled  upon  two  essential  points, — the  first  being  the  supposition  that  the 
histological  elements  of  plants  and  animals  are  primarily  independent  cells ;  the  second,  the 
notion  that  the  "  nucleus"  of  the  animal,  is  homologous  with  the  nucleus  of  the  vegetable 
tissue.  It  is,  we  believe,  from  the  inextricable  confusion  produced  by  these  fundamental 
mistakes,  which  have  been  adopted  by  almost  all  Schwann's  successors,  that  one-half  of  the 
controversies  with  respect  to  the  structure  of  cartilage  and  the  process  of  ossification  have 
arisen.  And  yet  to  one  who  is  free  from  them,  nothing  can  be  simpler. 

We  have  already  (note  p.  56)  referred  to  the  structure  of  foetal  cartilage,  but  it  may  here 


310  SPECIAL     HISTOLOGY. 

§  102.  Metamorphoses  of  the  primordial  cartilaginous  Skeleton. — Of 
the  primordial  cartilages,  one  portion  undergoes  further  development 
with  the  rest  of  the  skeleton,  constituting  the  permanent  cartilages  of 

be  described  more  at  length.  We  found  the  cartilage  of  the  septum  nasi  of  a  four-months' 
human  foetus  to  be  composed  of  a  homogeneous,  soft  matrix,  without  structure  of  any  kind, 
in  which  lay  imbedded,  rounded  or  irregular  vesicular  bodies,  varying  in  diameter  from 
S0W~WWth  of  an  inch;  tne  commonest  size,  however,  being  ^i^-^-^th.  These 
"  corpuscles"  frequently  contained  one  or  more  granules,  sometimes  very  small,  sometimes 
larger,  and  of  a  distinctly  fatty  nature;  such  fatty  granules,  also,  were  sometimes  to  be  found 
in  the  matrix  around  the  corpuscles. 

The  cavities  in  which  they  lay,  were,  for  the  most  part,  just  large  enough  to  contain  them, 
and  presented  no  walls  or  sharp  lines  of  demarcation  of  any  kind  from  the  surrounding 
substance. 

When  the  corpuscles  were  as  large  as  j^^th  of  an  inch,  they  occasionally  contained  a 
round  body  of  rather  less  than  ^^g^th,  as  a  "  nucleus." 

The  matrix  was  in  some  parts  pale  and  indifferent ;  but  where  the  tissue  had  taken  on 
its  definitely  cartilaginous  nature,  the  chondrinous  substance  into  which  it  was  converted  re- 
fracted the  light  much  more  strongly.  In  this  part  also,  the  cavities  in  which  the  corpuscles 
lay,  were  often  of  considerably  larger  dimensions  than  the  latter,  and  their  walls  exhibited  a 
sharp,  dark  line  of  definition  from  the  surrounding  substance,  which  was  often  brought  out 
much  more  strongly  by  the  action  of  acetic  acid.  It  appeared,  in  fact,  that  the  conversion 
into  chondrin  had  not  quite  reached  the  inner  surface  of  the  cavities,  and  hence  they  were 
chemically  and  optically  distinguished  from  the  surrounding  substance. 

Now,  of  course,  it  matters  very  little  what  names  are  given  to  these  parts,  so  long  as  they 
are  used  only  in  one  sense.  Schwann  considered  the  corpuscles  to  represent  the  "  nuclei"  of 
plants,  and  therefore  gave  them  that  name.  Henle,  Reichert,  Kolliker,  and  nearly  all  their 
compatriots,  Todd  and  Bowman,  Leidy  and  Sharpey — follow  him.  As  a  consequence,  they 
consider  the  wall  of  the  cavities  to  represent  the  cellulose  "cell-wall''  in  plants;  and  there 
has  been  much  controversy  as  to  how  much  of  the  matrix  of  the  cartilage  results  from  the 
union  of  these  "  cell-walls,"  how  much  from  the  development  of  an  intercellular  substance ; 
a  controversy  which  has  extended  itself  to  the  determination  of  the  homolcgies  of  the  ele- 
ments of  every  tissue.  We  must  confess,  it  seems  to  us  that  the  disputants  have  been 
fighting  for  a  shadow. 

If,  in  fact,  the  youngest  cartilage  be  composed  of  cells  with  distinct  walls  enclosing  the  cor- 
puscles, of  course  these  cells  may  be  united  by  an  intermediate,  "  intercellular"  substance ; 
and  it  will  be  an  important  question  to  determine  in  the  further  course  of  development 
what  arises  from  the  walls  and  what  from  the  substance  which  unites  them.  But  if,  on  the 
other  hand,  all  this  be  pure  hypothesis;  if  young  cartilage  be,  as  we  have  said,  composed  of 
nothing  but  a  continuous,  homogeneous  matrix,  in  which  the  corpuscles  are  imbedded,  but 
in  which  no  other  structure  exists,  what  becomes  of  the  controversy  ? 

We  believe  that  not  merely  will  the  account  we  have  given,  be  found  to  be  correct,  by 
any  one  who  will  without  prejudice  examine  into  the  subject,  but  it  seems  to  result  from  the 
observations,  even  of  those  who  have  interpreted  the  facts  otherwise. 

Schwann  ("  Mikros.  Unters.,"  pp.  112,  113)  describing  the  development  of  the  cartilage  of 

Pelobates,  says :  "  The  new  cells  arise  in  the  cytoblastema  (matrix  nobis) We  see 

at  first  mere  cell-nuclei  (corpuscles  nobis),  which  are  somewhat  smaller  than  the  nuclei  of 
the  full-grown  cells,  a,  6;  partly  nuclei,  which  are  closely  surrounded  by  a  cell,  c,  c;  in 
short,  all  transitional  forms,  from  mere  cell-nuclei  and  nuclei  surrounded  by  small  «ells,  to 
fully  formed  cells ;  so  that  here,  development  takes  place  as  in  small  cells,  and  the  nucleus 

is  their  actual  cytoblast The  cell-membrane  becomes  distinct  only  in  the  full-grown 

state." 

In  the  next  page,  Schwann  speaks  of  the  free-swimming  nucleated  corpuscles  which  he 
obtained  from  the  ossifying  cartilage  of  a  fcetal  pig,  and  which  he  considers  to  be  identical 
with  the  bodies  already  described  in  Pelobates.  In  reality,  however,  these  bodies  are  not 


THE    OSSEOUS    SYSTEM.  311 

the  nose,  joints,  symphyses,  and  synchondroses ;  a  second  disappears 
altogether  in  the  course  of  development  (certain  cranial  cartilages,  vide 

cells  in  the  same  sense,  being  merely  the  nuclei  of  Schwann  and  the  nucleated  form  of  the 
corpuscles  to  which  we  have  referred  above. 

Whatever  Schwann's  words  may  indicate,  then,  his  observations  tend  to  precisely  the 
same  conclusion  as  our  own. 

Henle  ("  Allg.  Anat,"  pp.  803-808)  follows  Schwann,  and  equally  fails  to  discriminate  the 
cells  in  Pelobaies  from  the  "  cells"  in  the  fostal  pig. 

Reichert  (in  his  admirable  work,  "  Ueber  das  Bindegewebe,"  1845)  recognizes  the  fact  that 
the  cartilage-corpuscles  are  "  nuclei"  in  Schwann's  sense,  and  refers  the  appearance  of  a 
distinct  wall  in  the  cavities,  to  an  optical  delusion.  He  asserts  that  young  cartilage  is  com- 
posed of  distinct  cells  closely  united  together,  without  any  measurable  intercellular  sub- 
stance ;  as  the  cartilage  grows,  the  latter  increases,  and  eventually  the  cell-walls  disappear. 
The  only  evidence  of  the  existence  of  these  cells  and  intercellular  substance  offered  by 
Reichert,  however,  is  the  mode  in  which  the  tissue  may  be  broken  up  ;  a  kind  of  evidence 
whose  value  the  purport  of  the  rest  of  his  book  is  to  reduce  (and  most  successfully)  to 
nothing. 

In  effect,  therefore,  Reichert's  observations  come  to  the  result  already  stated,  that  the 
festal  cartilage  is  composed  of  a  homogeneous  matrix,  in  which  the  corpuscles  are  dis- 
persed. 

Robin  ("  Observations  sur  1'Osteogenie")  takes  nearly  the  same  view  of  the  structure  of 
cartilage  as  that  we  have  indicated.  "  Cartilage  is  composed,"  he  says,  "  of  a  homogeneous, 
amorphous,  dense,  elastic,  hyaline  basis  (substance  fondamentale],  in  which  cavities  are  hollowed 
out, — cartilage-cavities.  In  each  of  these  cavities  we  find  one  or  many  (sometimes  20  to  30) 
cells, — cartilage-cells^  whose  parietes  cannot  be  demonstrated  to  be  distinct  from  their  cavity. 

These  cells  are  more  or  less  granular,  and  have  a  nucleolated  nucleus In  the  foetus, 

up  to  the  age  of  four  or  five  months,  more  or  less,  the  cartilage  cavities  do  not  enclose  one  or 
more  cells,  but  one  or  many  masses  of  yellowish  granulations,  all  of  nearly  the  same  size. 
These  masses  are  more  or  less  distinctly  defined  at  their  edges,  in  general  indistinctly,  and 
nearly  reproduce  the  form  of  the  cavity  without  ever  filling  it.  They  may  be  called  carti- 
lage-corpuscles. Authors  have  not  generally  remarked  this  fact.  By  degrees  the  cells  which 
replace  these  corpuscles  are  developed.  These  cells  are  formed  all  at  once  ;  but  the  grades 
of  the  process  as  regards  the  commencing  cell  or  the  pre-existing  granulations  are  as  yet  but 

little  known Some  authors  wrongly  call  the  cavities  excavated  in  the  fundamental 

substance,  cartilage-cells  ;  and  to  the  true  cartilage-cells  and  masses  of  yellowish  granulations 
or  corpuscles,  referred  to  above  as  existing  in  the  fostal  state  alone,  they  give  the  name  of 
contents.'''1 

Remak  (:{  Ueber  die  Entstehung  des  Bindegewebes  und  des  Knorpels,"  Muller's  "  Archiv," 
1851-2)  appears  to  have  been  the  first,  definitely  to  recognize  the  cartilage-corpuscles,  as  the 
homologues  of  the  primordial  utricles  of  plants, — a  great  step,  and  one  which  appears  to  us 
to  lead  to  most  important  consequences.  Like  Schwann,  however,  led  away  by  the  gene- 
rally assumed  anatomical  independence  of  the  vegetable  cells,  Remak  interprets  the  struc- 
ture of  cartilage  in  the  same  manner,  and  speaks  of  the  secretion  of  the  chondrinous  wall 
by  the  primordial  utricles,  as  "  parietal-substance"  within  the  primary  cell-membranes. 
He  adduces  no  evidence,  however,  that  the  facts  are  other  than  as  we  have  stated  them 
to  be. 

Virchow  ("  Die  Identitat  von  Knochen-,  Knorpel-,  und  Bindegewebe-ktfrperchen  so  wie 
uber  Schleirngewebe,"  "  Verhandlung  d.  Phys.  Med.  Gesellschaft,"  1852)  is  an  important  wit- 
ness in  this  matter.  He  says,  "  I  have  anew  convinced  myself  that  the  so-called  cartilage- 
corpuscles  are  actual  cells  which  lie  in  a  cavity  of  the  basis  (Grundsubstanz},  or  in  a  cell- 
cavity  presenting  a  double  contour,  and  possess  a  membrane,  granular  contents,  and  a  fre- 
quently nucleolated  nucleus.  In  the  neighborhood  of  the  line  of  ossification,  in  growing 
cartilages,  as  well  as  in  the  young  callus-cartilage  of  fractures,  these  cells  are  of  very  large 
size,  clear,  and  round ;  in  the  neighborhood  of  the  articular  extremities,  excessively  small, 


312  SPECIAL    HISTOLOGY. 

§  101) ;  the  third  and  greatest  part,  ultimately  becomes  ossified,  and 
constitutes  all  the  bones  of  the  trunk  and  extremities,  and  a  great  part 
of  those  of  the  cranium.  All  these  bones  are  ossified,  essentially  in  the 

compressed,  and  dark.  Under  favorable  circumstances,  the  cells,  in  simple  cartilage,  may 
be  isolated,  and  their  peculiar  relations  with  regard  to  acetic  acid,  which  generally  renders 
them  darker  and  collapsed,  may  be  exhibited.  Water  also  causes  them  to  collapse,  and 
they  thus  occasionally  form  peculiar,  jagged  corpuscles,  which  one  might  be  readily  tempted 
to  confound  with  branched  cells.  The  larger  the  original  cell  was,  so  much  the  more 
branched  does  its  collapsed  mass  appear." (p.  152.)  "It  might  have  been  ex- 
pected that  in  the  course  of  ossification  of  the  cartilage,  these  cells  would  be  seen  to  pass 

into  the  irregular,  anastomosing  bone-corpuscles ;  but  nothing  of  the  kind  is  visible 

A  point  of  difficult  determination  is,  in  general,  the  existence  of  actual  cells  in  the  small  flat 
cavities  of  cartilage,  e.  g.  towards  the  surface.  Very  frequently  it  would  here  seem  as  if  the 
membrane  of  the  cell  had  coalesced  with  the  intercellular  substance,  and  only  the  contents 
with  the  nucleus  had  remained  behind.  But  on  careful  investigation  especially  under  the 
prolonged  operation  of  acetic  acid,  frequently  after  maceration  in  hydrochloric  acid,  we 
clearly  see  a  complete  cell  with  a  nucleus  and  contents  in  the  cavity"  (p.  153). 

Virchow  gives  no  figures,  but  the  above  passages  furnish  so  accurate  an  account  of  what 
we  have  ourselves  seen  in  young  and  in  fully-formed  cartilage,  that  we  have  thought  we 
could  not  do  better  than  cite  them.  The  jagged  appearance  of  the  corpuscles  to  which  he 
refers,  is  very  common,  and  we  have  been  led  to  suspect  that  it  may  arise  from  the  same 
cause  as  the  very  similar  appearance  often  exhibited  by  the  colorless  corpuscles  of  the  blood, 
viz.,  a  protean  throwing  out  of  processes. 

When  Virchow,  however,  describes  the  passage  of  these  "  cells"  into  the  branched  or 
stellate  corpuscles  of  fibro-cartilage,  and  considers  the  latter  to  be  metamorphosed  cartilage- 
corpuscles,  he  confounds  together  things  which  are  essentially  different.  Careful  examina- 
tion of  foetal  fibro-cartilage,  e.  g.  the  intervertebral  fibro-cartilage  of  the  Kitten,  shows  that 
the  stellate  body  is  the  wall  of  the  cartilage  cavity,  with  processes  which  run  out  from  it,  the 
original  corpuscle  remaining  in  the  interior  of  the  cavity,  either  unchanged  or  becoming 
gradually  lost,  or  fused  into  one  mass  with  its  walls. 

The  account  of  the  structure  of  cartilage  given  by  Tomes  and  De  Morgan  (1.  c.,  pp.  15, 
16)  in  all  essential  points  agrees  with  that  of  Virchow.  They  call  the  corpuscles,  granular 
cartilage  cells. 

To  recapitulate  : — the  facts  contained  in  other  observations,  as  apart  from  the  interpretation, 
appear  to  agree  perfectly  with  our  own ;  the  result  of  which  is,  that  in  the  fcetal  state,  car- 
tilage is  composed  of  a  homogeneous  matrix,  in  which  lie  the  corpuscles,  in  cavities  which 
they  just  fill ;  that  their  relation  to  the  matrix  is  exactly  that  of  the  primordial  utricles  to 
the  cellulose  wall  in  plants,  and  that  like  this  they  may  or  may  not  develop  a  nucleus ;  that 
with  age  they  enlarge,  but  not  so  fast  as  the  cavities,  the  walls  of  which  become  chemi- 
cally altered  into  chondrin,  a  change  which  often  takes  place  in  such  a  manner  as  to  give 
rise  to  a  lamination  or  to  a  difference  in  composition  of  the  inner  and  outer  portions.  If  the 
cartilage  be  converted  into  fibro-cartilage,  the  outer  part  becomes  changed  into  collagen, 
while  an  alteration  into  a  substance  resembling  elastic  fibre,  is  effected  in  the  inner  portion, 
and  in  the  direction  of  certain  lines  radiating  from  it,  just  as  we  have  seen  the  elastic  ele- 
ment to  be  developed  in  connective  tissue  (see  §  on  Connective  Tissue). 

So  much  for  the  structure  of  cartilage:  with  regard  to  its  development  and  multiplication 
we  must  equally  demur  to  the  statements  in  the  text.  It  is,  indeed,  very  true,  that  no  new 
cartilage-cells  arise  independently  of  those  which  pre-exist:  but  in  opposition  to  Professor 
Kolliker  we  must  agree  with  Leydig,  Robin,  Remak,  and  Tomes  and  De  Morgan,  that  the 
multiplication  of  the  cartilage-cells  invariably  takes  place  by  a  process  of  division  exactly 
analogous  to  that  which  occurs  in  plants.  So  far  as  we  have  seen  (and  in  ossifying  carti- 
lages, and  in  that  of  the  Skate,  it  is  easy  to  trace  the  process),  the  corpuscles  first  become  con- 
stricted, being  found  occasionally  of  an  hour-glass  shape;  and  eventually  divide.  The 
matrix  then  grows  in,  so  as  to  separate  the  two,  and  the  process  of  fission  is  complete. — TRS.] 


THE     OSSEOUS     SYSTEM.  313 

same  way.  At  one  or  more  points  (puncta  ossificationis),  in  their  inte- 
rior, a  deposition  of  calcareous  matter  commences,  simultaneously  with 
a  change  in  the  cartilaginous  elements ;  which  transformation  proceeds 
on  some  or  on  all  sides,  continually  converting  additional  portions  of  the 
cartilage  into  bone.  Whilst  this  is  going  on,  the  cartilage,  in  most  cases, 
ceases  to  grow  in  one  direction,  and,  consequently,  is  there  soon  entirely 
converted  into  bone,  whilst  in  others  its  growth  continues,  so  that  a  new 
cartilaginous,  plastic  material  is  furnished  for  the  progressive  increase 
of  the  bone,  which  material,  as  in  the  epiphyses  of  the  cylindrical  bones, 
is  sometimes  developed  into  distinct  ossific  centres  or  nuclei.  When  the 
whole  of  the  cartilage  has  been  converted,  and  its  perichondrium  become 
periosteum,  the  bone  does  not  cease  to  enlarge,  but  a  new  and  peculiar 
mode  of  formation  is  now  set  up,  in  all  these  places,  until  its  growth  is 
completed.  This  consists  in  the  ossification,  from  that  surface  which  is 
in  contact  with  the  bone,  of  an  organized,  soft,  plastic  material,  which 
is  deposited  on  the  inner  surface  of  the  highly  vascular  periosteum,  and 
in  proportion  as  this  conversion  into  bone  takes  place  on  the  one  side, 
fresh,  fluid  materials  for  it  are  afforded  by  the  periosteum  on  the 
other. 

§  103.  Changes  in  the  ossifying  Cartilage. — The  active  vegetative 
process  in  the  cartilage-cells  when  ossification  is  going  on,  depends  upon 
this, — that  the  cells  which  were  hitherto  of  small  size,  and  contained  but 
few  secondary  cells,  begin  to  grow,  and  successive  generations  of  cells 
to  be  produced  in  them,  as  may,  also,  be  seen  at  the  ossifying  margins 
of  bones  already  existing,  in  which  situation  larger  cells  may  be  noticed 
close  to  the  bone,  and  others,  which  are  smaller  in  proportion  to  their 
distance  from  it.  All  the  cells  which  are  engaged  in  the  incipient  for- 
mation of  the  bone,  present  clearer  and,  less  frequently,  granular  con- 
tents, a  distinct,  vesicular,  round  nucleus,  with  nucleolus  and  readily 
distinguishable  walls ;  they  are  very  quickly  altered,  however,  on  the 
addition  of  water,  acetic  acid,  alcohol,  and  by  drying,  &c.,  so  that  the 
contents  contract  around  the  nucleus,  and  form  a  roundish,  elongated, 
irregular,  even  stellate,  granular,  opaque  body  (cartilage-corpuscle  of 
authors).  Their  size  and  mode  of  grouping  vary,  not  inconsiderably, 
according  to  age  and  situation.  With  respect  to  the  former,  they  exhibit 
during  embryonic  life  a  constant  increase,  whilst  after  birth  they  appear 
to  retain  a  uniform  size ;  and,  as  regards  the  latter,  it  may  be  stated  as 
a  law,  that  where  the  ossification  of  the  cartilage  proceeds  in  one  direc- 
tion only,  the  cells,  at  the  osseous  border,  are  disposed  in  rows.  This  is 
most  distinctly  seen,  as  has  been  long  well  known,  in  the  extremities  of 
the  diaphyses  of  the  larger  cylindrical  bones,  where  the  rows  of  cells  are 
very  prettily  arranged  in  parallel  lines  close  together,  and  are  of  con- 
siderable length ;  it  is  also  evident  in  the  other  long  bones,  as  well  as  in 


314 


SPECIAL    HISTOLOGY. 


many  others  where  the  cartilage  ossifies  only  on  one  side,  as  in  the  con- 
necting surfaces  of  the  vertebrce.  Where,  however,  the  ossific  nuclei  in 
the  centre  of  a  cartilage  enlarge  on  all  sides,  the  cartilage-cells  are  con- 
fusedly grouped  in  roundish,  or  oval,  irregular  little  masses,  as  in  the 
short  bones  at  their  first  formation,  and  in  the  epiphyses.  An  accurate 
comparison  of  the  cells  which  are  closer  to  the  ossifying  margin,  with 
those  more  remote  from  it,  and  of  the  groups  formed  by  them,  at  once 


I  Sg 


shows  that  their  particular  disposition  is  directly  related  to  their  mode 
of  increase.     Each  individual  group  (or  even  two  of  them)  corresponds, 

FIG.  130. — Perpendicular  section  from  the  ossifying  border  of  the  shaft  of  the  femur  of  a 
child  a  fortnight  old :  a,  cartilage,  in  which  the  cells  the  nearer  they  are  to  the  ossifying 
border  are  placed  together  in  more  extended  longitudinal  rows;  6,  ossifying  border,  the  dark 
streaks  indicate  the  progressive  ossification  in  the  intercellular  substance,  the  clearer  lines 
the  cartilage-cells  which  ossify  subsequently;  c,  compact  layer  of  bone  near  the  ossifying 
border ;  rf,  the  substantia  spongiosa  formed  in  the  osseous  substance  by  resorption,  with  can- 
celli,  the  contents  of  which  are  not  shown. — Magnified  20  diameters. 

FIG.  131. — Femur  of  a  child  a  fortnight  old,  natural  size:  a,  substantia  compacta  of  the 
shaft;  6,  medullary  cavity;  c,  substantia  spongiosa  of  the  shaft;  d,  cartilaginous  epiphysis  with 
vascular  canals;  e,  osseous  nucleus  in  the  inferior  epiphysis. 


THE     OSSEOUS     SYSTEM.  315 

in  a  certain  measure,  with  a  single  primordial  cell,  and  represents  all  the 
descendants  which  in  course  of  development  have  proceeded  from  it.  In 
the  one  case,  all  these  newly-formed  cells  are  disposed,  one  behind  the 
other,  in  a  single  or  double  linear  series ;  and  in  this  way  are  produced, 
by  their  further  increase,  the  rows  of  cells  above  described,  whilst  in  the 
other  they  constitute  a  more  globular  mass.  The  primordial  cells  (first 
parent-cells)  during  this  procedure,  sometimes  disappear  as  distinct  or- 
ganisms, owing  to  the  coalescence  or  fusion  of  their  walls  with  the  inter- 
stitial substance,  sometimes  not ;  and  the  same  holds  good  with  those  of 
the  subsequent  generations.  The  latter  is  usually  the  case  in  the  rounded 
masses  of  cells,  owing  to  their  smaller  size,  and  around  them  a  contour 
line  may  for  the  most  part  be  recognized,  which  is  nothing  more  than 
the  distended  wall  of  the  first  cell ;  whilst  in  the  rows  of  cells,  the  walls 
of  the  original  cells  are  not,  usually,  so  merged  in  the  intercellular  sub- 
stance as  to  escape  recognition.  The  entire  matrix,  in  which  the  just- 
described,  enlarged,  and  actively  multiplying  cells  are  enclosed,  varies 
very  considerably  in  thickness  in  the  different  cartilages  ;  scanty  around 
the  osseous  nuclei  in  the  epiphyses  and  short  bones,  it  is  J  to  J  a  line 
thick  in  the  diapliyses.  It  is  universally  characterized  by  its  yellowish, 
transparent  color,  and  its  streaky,  apparently  fibrous  fundamental 
structure,  from  the  other  cartilaginous  parts,  which  are,  as  usual,  bluish- 
white,  with  a  homogeneous  or  granular  interstitial  substance. 

The  vessels  met  with  in  the  ossifying  cartilages  constitute  a  phenome- 
non well  worth  attention ;  from  the  middle  of  foetal  life  onwards,  they 
occur  in  many  situations,  preceding  by  a  shorter  or  longer  time  the 
appearance  of  the  osseous  nuclei,  and  accompanying  their  increase.  I 
have  observed  them  in  the  articular  cartilage  of  the  epiphyses  of  the 
long  bones  even  in  a  person  18  years  old.  They  entered  the  cartilage 
in  great  number,  perpendicularly  from  the  bone,  ramifying  and  terminat- 
ing a  little  below  its  free  surface.  The  cartilage-vessels  invariably  lie 
in  wide  canals  (measuring,  even  in  a  five  months'  foetus,  0'02— 0*04  of 
a  line),  excavated  in  the  cartilage,  and  bounded  by  narrow,  elongated 
cartilage-cells, — the  vascular  canals  of  cartilage,  or  cartilage  canals, — 
which  enter  the  cartilage  from  the  perichondrium,  and,  when  a  vascular 
ossific  nucleus  exists  (diaphysis),  also  from  the  border  of  the  ossifying 
portion  itself  (though  in  less  number,  at  all  events  at  an  earlier  period), 
penetrate  it  in  straight  lines,  in  various  directions,  giving  off  a  few 
branches,  and,  to  all  appearance  without  any  anastomoses,  or  other  kind 
of  interconnection,  end,  for  the  most  part,  in  blind,  club-shaped  dilata- 
tions. These  canals  are  produced  by  a  resolution  of  the  elements  of  the 
cartilage,  in  the  same  way  as  the  medullary  cavities  of  the  bone  itself, 
originally  contain  a  plastic  material  composed  of  minute  rounded  cells 
(cartilage-marrow),  corresponding  to  the  foetal  cartilage- marrow,  and 
develop  in  a  short  time  out  of  this  material,  true  sanguiferous  vessels, 


316  SPECIAL    HISTOLOGY. 

and  a  wall  composed  of  more  or  less  developed  connective  tissue,  and 
subsequently  also  of  elastic  fibrils.  As  concerns  the  vessels  themselves, 
I  have  sometimes  found,  in  a  canal,  only  one  large  vessel  (frequently 
very  distinctly  arterial,  with  muscular  walls),  sometimes  two  such,  some- 
times capillaries  in  various  numbers,  but  I  am  unable  to  explain  how  the 
circulation  is  carried  on  in  these  vessels.  There  must  either  be  anasto- 
moses between  the  vessels  of  different  canals,  or  if  the  latter  be  really 
closed,  arteries  and  veins  both  probably  exist  in  one  and  the  same  canal. 
The  object  of  these  vessels  of  cartilage  appears  to  be  one  of  a  double  cha- 
racter; in  the  first  place,  to  convey  the  materials  requisite  for  its  growth 
and  further  development ;  and  secondly,  to  promote  the  ossification. 
The  former  of  these  functions  is  very  manifestly  carried  out  in  the  thick 
epiphysal  cartilages,  which  grow  to  such  a  length  before  they  become 
ossified,  and  even  afterwards  continue  to  enlarge ;  and  the  latter  is  pro- 
bably effected  principally  in  the  short  bones,  which  do  not  contain  vessels 
until  just  before  the  commencement  of  ossification.  Notwithstanding 
this,  however,  it  is  not  intended  to  imply,  that  a  cartilage  cannot  grow, 
nor  become  ossified  without  vessels ;  but  although  the  latter  condition 
does  in  fact  obtain  in  animals,  and  probably  also  in  man,  normally  in 
certain  situations  (on  the  appearance  of  the  first  points  of  ossification  of 
the  embryo,  those  of  the  ossicula  auditus,  &c.),  still,  this  does  not  prove 
that  the  vessels  when  existing  have  no  concern  in  the  processes  adverted 
to ;  and  consequently  it  cannot  be  admitted,  as  lately  supposed  by-  H. 
Meyer,  that  they  are  to  be  regarded  in  the  light  of  accidental  produc- 
tions, and  as  standing  in  no  necessary  relation  with  the  development  of 
the  bone. 

§  104. —  Ossification  of  the  Cartilage. — The  ossification  of  the  matrix 
generally  precedes  in  some  degree  that  of  the  cartilage-cells ;  and, 
under  normal  conditions,  is  primarily  effected  by  a  granular  deposition 
of  calcareous  salts  (calcareous  granules  as  they  are  termed).  Where 
the  cells  are  disposed  in  rows,  at  the  ossifying  border,  this  deposition 
of  earthy  matter  always  proceeds  in  the  fibrous  substance  between  the 
rows  of  cells,  forming  processes,  which,  in  a  longitudinal  section,  assume 
the  appearance  of  pointed  teeth,  and  surround  the  lowest  portions  of 
the  rows  of  cells  like  short  tubes.  The  same  disposition,  essentially,  is 
also  manifested  in  other  situations,  where  the  cartilage  cells  constitute 
more  rounded  groups,  only,  that  in  this  case  the  ossifying  matrix  sur- 
rounds them  more  in  a  reticular  manner.  The  calcareous  granules  or 
particles,  the  first  visible  deposit  of  the  earthy  salts  of  bones,  are  of 
a  rounded  angular  figure,  white  by  reflected,  opaque  by  transmitted 
light,  easily  dissolved  with  effervescence  in  acids,  and  differing  in  size 
in  different  bones,  from  immeasurable  minuteness  up  to  O'OOl,  or  even 
1-002  of  a  line;  their  size,  however,  does  not  appear  to  be  regulated 


THE    OSSEOUS    SYSTEM. 


317 


Fig.  132. 


by  period  or  situation,  although  there  is  no  doubt  that  they  are  fre- 
quently, in  one  place,  of  uniform  minuteness,  and  in  others  uniformly 
of  coarser  character,  but  rather  by  some  change  occurring  in  the  supply 
of  plastic  material  to  the  ossifying  border.  If  this  earthy  deposit  be 
traced  in  microscopical  sections,  from  the  margin  of  the  ossification  into 
the  interior  of  the  young  bone,  it  will  be  apparent,  that  it  is  to  it,  for 
a  certain  distance,  although  with  diminishing  distinctness,  that  the 
granular  and  opaque  aspect  of  the  margin  itself  is  due ;  the  substance 
gradually  becomes  more  homogeneous,  clearer,  and  more  transparent, 
ultimately  acquiring  the  aspect  of  perfect  bone.  According  to  all 
appearance,  the  primordial  earthy  granules  or  particles  become  gradu- 
ally fused  together,  and  thus  impregnate  the  whole  tissue  of  the  matrix 
of  the  cartilage,  instead  of,  as 
before,  separate  portions,  and 
thenceforth  disappear  as  iso- 
lated, distinguishable  parti- 
cles. 

With  respect  to  the  forma- 
tion of  the  bone-cells,  I  believe, 
that  owing  to  the  discovery 
of  an  excellent  subject  for 
their  observation,  viz.,  rachitic 
bone,  I  have  put  the  matter, 
as  regards  the  most  essential 
particulars,  in  a  clear  point 
of  view.  The  bone-cells  are 
formed, — as  Schwann  thought 
possible,  and  Henle  supposed, 
from  analogy  with  the  ligni- 
fied  vegetable  cell  with  pores 
or  dotted  canals, — from  the 
cartilage-cells,  by  the  thick- 
ening of  their  wall,  with  the 
simultaneous  formation  of 
canalicular  vacuities  in  it, 
and  its  ossification.  In  the 
ossifying  shaft  of  a  rickety 
bone  (Fig.  132)  the  morpho- 
logy of  this  process  may  be  most  beautifully  observed.  If  the  rows  of 

FIG.  132.— From  the  ossifying  border  of  the  condyle  of  the  femur  of  a  rachitic  child, 
two  years  old,  a,  cartilage  cells,  simple  and  parent  cells  in  series ;  6,  more  homogeneous  j 
c,  striated  matrix  between  them;  d,  cartilage-cell.s  at  the  commencement  of  their  trans- 
formation into  bone-cells  ;  e,  the  same  further  advanced,  with  very  much  thickened  walls, 
indication  of  canaliculi,  commencing  deposition  of  calcareous  matter  in  the  walls,  whence 
their  darker  color,  though  still  with  distinct  nuclei ;  /,  bone-cells  still  more  developed  and 
more  ossified,  in  an  equally  ossified,  matrix. — Magnified  300  diameters. 


818  SPECIAL    HISTOLOGY. 

cartilage-cells  of  the  ossifying  border,  which  in  this  case  are  of  larger 
size,  be  traced  from  without  to  within,  it  will  soon  be  found,  that  at 
the  point  where  the  deposition  of  calcareous  salts  (which  takes  place 
for  the  most  part  without  the  formation  of  the  calcareous  granules) 
commences,  they  exhibit,  instead  of  a  membrane  indicated  by  a  single, 
tolerably  strong  line,  a  thicker  coat,  which  on  the  inner  side  presents 
delicate  indentations.  Even  when  the  thickness  of  this  membrane 
does  not  exceed  0*001  of  a  line  (Fig.  132,  d),  it  is  obvious  that  the  car- 
tilage-cells are  about  to  be  transformed  into  bone-cells ;  and  this  be- 
comes still  more  evident,  when,  further  on  in  the  bone,  the  thickness 
of  the  membranes  in  question,  together  with  the  simultaneous  diminu- 
tion of  the  cavity  of  the  cell,  is  seen  to  be  constantly  increasing,  the 
indentations  of  the  interior  contour  line  to  become  more  and  more 
marked,  and,  accompanying  the  progress  of  these  changes,  the  walls  to 
become  more  and  more  dark  from  the  addition  of  calcareous  matter 
(Fig.  132,  e).  The  slow  ossification  of  the  matrix  between  the  cells  is 
very  favorable  to  the  observation  of  these  changes,  allowing  not  only  of 
the  accurate  investigation  of  the  first  alterations  in  the  cartilage-cells, 
but  also  of  their  subsequent  conditions,  at  a  time  when  they  must  be 
termed  bone-cells  and  lacunce,  being  traced  step  by  step.  To  this  cir- 
cumstance alone  is  also  due  the  establishment  of  the  interesting  fact, 
that  cartilage-cells,  enclosing  secondary  cells  within  them,  are  converted, 
as  a  whole,  into  a  single,  compound  bone-cell.  Cells  of  this  kind -are 
very  frequently  met  with,  having  two  cavities,  which  cells,  according  to 
their  degree  of  development,  are  sometimes  wide  and  furnished  with 
short  prolongations,  and  sometimes  from  their  contracted  cavity  and 
long  canaliculi,  resemble  in  all  respects  perfect  bone-lacunae.  Com- 
pound cells,  with  3,  4,  and  5  cavities,  each  with  the  remains  of  the 
original  contents  and  nucleus,  occur  more  rarely,  though  even  such  are 
occasionally  to  be  found  in  almost  every  preparation.  The  cartilage- 
cells  lying  free,  and  inclose  apposition,  though  in  a  non-ossified  matrix, 
having  thus  evidently  become  transformed  into  bone-cells  with  nuclei 
and  other  contents,  the  ultimate  changes  now  take  place  from  which  the 
rickety  bone-substance  acquires  pretty  nearly  the  nature  of  the  sound 
tissue.  These  changes,  in  as  far  as  they  effect  the  bone-cells,  chiefly 
depend,  in  the  first  place,  upon  the  commencement  of  ossification  in 
the  matrix,  but  without  any  primary  formation  of  calcareous  particles ; 
and  secondly,  upon  the  continually  increasing  deposition  of  earthy  mat- 
ter in  it,  and  in  the  thickened  cell-walls,  owing  to  which,  the  new  bone- 
substance,  to  the  naked  eye,  becomes  more  and  more  white,  and  under 
the  microscope  appears  more  and  more  dark  and  transparent ;  it  now, 
also,  becomes  more  homogeneous,  and  the  abrupt  limits  of  the  bone-cells 
gradually  less  and  less  defined,  till  at  last  they  appear,  not  as  cellular 
organisms  lodged  in  the  matrix,  but  to  be  confused  with  it,  being  recog- 


THE     OSSEOUS    SYSTEM.  319 

nizable  only  from  their  peculiar  stellate  cavities, — the  so-terined  bone- 
corpuscles,  or  lacuna?  and  canaliculi. 

With  the  knowledge  thus  obtained  of  the  formation  of  the  lacunae  in 
rachitic  bone,  the  endeavor  to  arrive  at  an  insight  into  the  same  process 
in  normal  bone,  is  no  longer  attended  with  as  much  difficulty  as  before, 
when  the  inquirer  was  involved  in  a  maze  of  hypotheses  of  the  most 
various  kinds,  and  all  without  any  certain  foundation.  The  investigation 
of  the  conditions  attending  the  development  of  bone,  both  in  man  and 
other  animals,  must  nevertheless  still  be  regarded  as  troublesome,  and 
frequently  little  worth  the  pains  bestowed  upon  it.  It  is,  perhaps,  cer- 
tainly manifest  (vid.  "Mik.  Anat.,"  tab.  iii.  fig.  6),  that  the  bone-cells, 
a  little  beyond  the  limit  of  ossification,  become  thickened,  and,  still 
presenting  the  remains  of  their  cavity  and  the  nucleus,  beset  with  cal- 
careous particles ;  and  although  such  incrusted  cells  may  even  be  isolated, 
yet  the  mode  in  which  the  changes  are  effected  further  on,  is  not,  beyond 
a  short  distance,  I  must  affirm,  to  be  seen  with  anything  like  the  dis- 
tinctness that  it  is  in  rachitic  bone,  because,  more  internally,  the  newly- 
formed  medulla  with  its  vessels,  and  the  calcareous  particles,  render 
almost  everything  indistinct;  and  it  is  not  till  we  get  to  the  homogeneous 
and  more  transparent  osseous  tissue  beyond,  that  distinct,  but  almost 
perfectly-formed  lacunae  come  into  view.  Nevertheless,  from  all  that 
we  see,  there  cannot  be  the  least  doubt,  but  that  the  processes  are 
essentially  the  same  as  in  rachitis,  only,  that  in  the  healthy  bone  the 
ossification  of  the  thickened  walls  of  the  cartilage  cells,  presents  two 
stages,  instead  of  only  one,  as  in  the  former  case,  inasmuch  as  they  first 
appear  granular  from  the  deposition  of  the  calcareous  particles,  and 
afterwards  homogeneous.  Moreover,  even  in  perfectly  normal  bone,  in 
the  adult,  I  have  met  with  places  (some  of  which,  independently  of  me, 
have  also  been  lately  described  by  H.  Meyer  (1.  c.) ),  such  as  the  sym- 
physis  pubis,  the  synchondroses  of  the  vertebral,  and  those  of  the  ilium, 
sacrum,  and  the  points  of  insertion  into  the  bones  of  certain  tendons 
containing  cartilage-cells.  In  all  of  these  situations,  at  the  line  of 
junction  between  the  cartilage  or  tendon  and  the  bone,  cartilage-cells  of 
the  most  characteristic  aspect  may  be  seen,  lying  free  in  the  cartilaginous 
matrix,  and  presenting  the  most  various  degrees  of  transformation  into 
bone-cells ;  some,  in  particular,  having  thickened  walls,  and  a  more  or 
less  copious  deposit  of  calcareous  particles ;  while  others  are  almost 
perfectly-formed  bone-cells,  with  pores  and  a  more  homogeneous  wall 
(Fig.  123) ;  so  that  I  am  able  to  afford  a  certain  support  to  the  state- 
ment given  above  with  respect  to  the  mode  of  origin  of  the  bone-cells, 
by  the  conditions  presented  in  normal  tissues  also.  In  the  last-named 
situations  I  have,  likewise,  very  distinctly  and  very  frequently  noticed, 
half-  or  wholly-ossified  parent-cells,  containing  from  two  to  twelve 
secondary  cells. 


320  SPECIAL    HISTOLOGY. 

There  is  another  point  in  the  development  of  the  bone-cells  still  ob- 
scure, or  at  least  that  has  not  been  directly  observed,  viz.,  how  their 
pores  or  canaliculi  become  branched  cavities,  communicate  with  those  of 
other  cells  and  acquire  open  orifices  in  certain  situations.  All  that  is 
apparent  in  rachitic  bone  and  elsewhere,  is  merely  the  circumstance, 
that  the  thickening  of  the  ossifying  cartilage-cells  does  not  proceed  with 
a  straight  but  with  an  indented  border,  which  is  the  case  in  fact  from 
the  beginning  up  to  their  completion,  and  that  the  bone-cells  have,  at 
first,  more  simple  prolongations  than  afterwards.  Observation  teaches 
nothing  beyond  this.  Now,  as  there  can  be  no  doubt  that  the  canaliculi 
anastomose  very  freely,  and  also,  that  they  frequently  open  on  the  outer 
surface  of  the  bone,  or  into  the  cavities  in  its  interior,  I  do  not  for  a 
moment  hesitate  to  express  the  opinion,  that  the  canaliculi,  arising  as 
simple  branches  from  the  lacunce,  are  continued  or  further  developed  by 
absorption  of  the  already -formed  bone-substance.  How  such  an  absorp- 
tion takes  place,  cannot,  it  must  be  confessed,  be  explained ;  but  that 
affords  no  ground  of  objection  to  the  opinion,  because  we  see  a  similar 
process,  though  on  a  widely-different  scale,  take  place  in  the  formation 
of  the  medullary  cavities  and  cancelli  (vid.  infra).  It  would  appear  to 
me,  that  currents  of  the  nutritive  fluid  in  the  bone  were  chiefly  concerned 
in  this  further  development  of  the  canaliculi;  and  the  more  so,  because 
the  first  rudiments  of  the  canaliculi,  like  the  pore-canals  of  lignifying 
plant-cells,  manifestly  indicate  nothing  more  than  the  points  at  which 
the  ossifying  cartilage-cells  continue  to  admit  and  emit  fluid;  on  which 
account,  also,  their  direction  is  principally  towards  the  internal  and  ex- 
ternal surfaces  of  the  bone,  from  which  the  nutritive  plasma  is  derived. 
It  appears  to  me  highly  probable,  that  after  the  complete  ossification  of 
the  cartilaginous  tissue,  the  nutritive  fluid  derived  from  the  blood-vessels 
of  the  periosteum  and  of  the  medullary  cavities  (1.)  finds  new  ways  for 
itself  towards  the  lacuna?  and  their  prolongations,  which,  as  it  may  be 
said,  alone  are  still  open  to  it,  and  in  this  way  effects  their  opening  on 
the  internal  and  external  surfaces  of  the  bone,  and  (2.)  also  burrows 
passages  from  the  cavities  lying  nearest  to  it,  and  thus  ultimately  pro- 
duces a  ramification  of  them,  and  brings  about  numerous  communications 
between  the  different  cavities.  In  accordance  with  which,  a  secondary 
formation  of  canaliculi  must  take  place,  not  only  in  the  region  of  the 
thickened  walls  of  the  original  cells,  but  also  in  the  osseous  matrix,  and 
this  to  a  considerable  extent,  as  is  at  once  evident,  when  the  distances 
between  the  anastomosing  cavities  are  compared  with  the  diameter  of 
the  original  cartilage-cells. 

The  development  of  the  medullary  spaces  (cancelli)  and  of  the  medulla, 
is  to  a  certain  extent  the  last  act  in  the  transformation  of  cartilage  into 
bone.  The  medullary  spaces  do  not  arise  in  a  coalescence  of  the  cartilage- 
cells,  but  from  a  solution  of  the  more  or  less  perfectly  formed  bone-sub- 


THE  OSSEOUS  SYSTEM.  321 

stance,  exactly  like  the  large  medullary  cavities  of  the  cylindrical  bones. 
This  is  most  distinctly  and  satisfactorily  shown  by  the  examination  of 
the  diaphyses  of  a  sound  or  rachitic  bone,  but  especially  in  the  latter. 
At  the  limit  of  the  ossification  itself,  the  osseous  tissue  for  a  distance  of 
about  I  to  J  of  a  line,  is  quite  compact,  without  a  trace  of  larger  cavi- 
ties, and  is  composed  in  part  of  the  ossified  matrix,  and  in  part  of  car- 
tilage cells,  more  or  less  advanced  in  their  transformation  into  bone- 
cells  ("Mik.  Anat.,"  tab.  iii.) ;  beyond  this  part,  however,  cavities,  at 
first  small,  and  more  internally,  larger,  come  into  view,  the  whole  rela- 
tions of  which  show  most  convincingly  that  they  do  not  originate  in  any 
development  of  the  existing  elements.  They  have  an  extremely  irre- 
gular contour,  are  oval,  or  roundish  and  angular,  and  for  the  most  part 
broader  than  the  cartilage-cells,  appearing  to  be  eaten  out,  as  it  were, 
in  the  substance  of  the  bone,  and  involving  severally  the  compact  tissue, 
matrix,  and  bone-cells.  When  the  borders  and  limitary  surfaces  of  these 
spaces  are  closely  regarded,  it  is,  in  many  instances,  easy  to  notice  bone- 
cells  more  or  less  removed,  half  projecting  from,  or  buried  in  the  wall, 
and  between  them  projections  of  the  ossified  matrix,  so  that  no  doubt 
can  any  longer  be  entertained  with  respect  to  the  origin  of  the  cavities. 
It  must  be  confessed  that  there  is  as  little  to  be  stated,  in  this  case,  as 
in  that  of  the  origin  of  the  analogous  cartilage-canals,  and  the  further 
development  of  the  canaliculi  of  the  bone-cells,  with  respect  to  the 
mode  in  which  this  absorption  takes  place ;  and  the  process  is  even  still 
more  inexplicable,  because,  allowing  that  it  really  does  take  place,  there 
would  then  exist  in  the  ossifying  bone,  at  the  same  time  and  almost  in 
immediate  contiguity,  a  formation  of  bone  and  a  resolution  of  the  tissue, 
but  very  little  less  energetic.  The  above-described  mode  of  formation 
of  the  cancelli)  nevertheless,  is  a  morphological  fact,  and  consequently, 
the  explanation  of  such  a  curious  phenomenon  becomes  a  problem  to  be 
solved  by  chemistry  and  physiology.  As  in  the  diaphyses,  so  in  the 
ossification  of  all  the  other  cartilages,  medullary  spaces  are  formed  by 
the  resorption  of  the  inner  portions  of  that  part  which  is  half  ossified. 
But  it  must  be  stated,  that  these  spaces  do  not  present  the  same  form, 
direction,  and  size  in  every  bone ;  though  with  respect  to  this,  it  is  un- 
necessary to  offer  any  special  remarks,  since  the  relations  of  this 
primitive  spongy  substance  are,  in  the  main,  the  same  as  they  are  after- 
wards. Still,  it  may  be  remarked,  that  in  many  bones,  solitary  spaces 
are  apparently  developed  immediately  from  cartilage-canals,  seeing  that 
some  at  least  of  the  latter,  at  the  limit  of  ossification,  communicate 
directly  with  the  spaces  in  the  bone  ;  and,  moreover,  that  not  unfre- 
quently,  cartilaginous  elements  not  yet  wholly  converted  into  bone-cells, 
are  drawn  into  the  process  of  resolution. 

The  medullary  cavities,  however  they  arise,  are  filled  with  a  soft, 
reddish  substance — foetal  medulla.     This  substance  at  first  consists  of 

21 


322  SPECIAL    HISTOLOGY. 

nothing  but  a  small  quantity  of  fluid  and  many  rounded  cells,  with  one 
or  two  nuclei  and  faintly-granular  contents,  of  which  I  am  unable  to 
say  how  they  originate,  but  only  this  much,  that  they  are  altogether  new 
formations.  In  process  of  time  these  cells,  which  are  in  all  respects 
identical  with  those  which  occur,  in  the  adult,  in  certain  bones  (vid. 
supra),  are  developed  in  the  usual  way  into  connective  tissue,  blood- 
vessels, fat-cells,  and  nerves.  The  formation  of  bloodvessels  proceeds 
with  great  rapidity,  so  that  bones,  very  shortly  after  the  development  of 
the  medullary  spaces,  exhibit  bloodvessels  in  them  ;  that  of  the  fat  and 
nerves  takes  place  more  slowly,  although  the  latter,  at  the  period  of 
birth,  of  course  with  fewer  filaments  than  subsequently,  may  be  very 
readily  perceived  in  the  large  cylindrical  bones,  even  more  readily  than 
in  the  adult,  because  at  this  time  the  medulla  may  be  more  easily  washed 
away  from  them  and  the  great  vessels.  The  fat-cells  at  this  period  are 
but  few  in  number  ;  the  medulla,  in  man  at  least,  being  colored  entirely 
red  by  the  blood  and  the  light  reddish  medulla-cells.  After  birth  they 
gradually  multiply,  till  at  last,  the  marrow,  in  consequence  of  their  great 
increase,  and  the  disappearance  of  the  medulla-cells,  which  are  ulti- 
mately all  transformed  into  the  elementary  tissues  of  the  permanent 
medulla,  acquires  its  subsequent  color  and  consistence. 

In  many  of  the  primarily  cartilaginous  bones  of  Birds  and  Amphibia, 
the  ossification  of  the  cartilage  commences,  according  to  Rathke  and 
Reichert  (1.  c.),  on  the  outer  aspect  of  the  cartilage,  so  that  at  first  a 
cylinder  of  bone  is  formed  with  cartilage  internally  and  at  the  extremi- 
ties. The  remainder  of  the  internal  cartilage  then  affords  space  to  the 
medulla,  whilst  the  epiphyses  are  formed  out  of  that  of  the  extremities. 

If  the  contents  of  the  cartilage-cells,  the  "cartilage-corpuscles"  of 
authors,  be  really  surrounded  by  a  membrane,  as  Yirchow  supposes,  it 
may  be  assumed  that  a  similar  tunic,  analogous  to  the  primordial  utricle 
of  the  plant-cell  (vid.  sup.  §  8),  exists  also  around  the  contents  of  the 
bone-cells,  and  that  it  takes  an  essential  part,  by  its  throwing  out  stel- 
late processes,  in  the  first  formation  of  the  canaliculi,  their  further  elon- 
gation and  ultimate  anastomoses.  In  this  case,  also,  the  stellate  and 
readily  isolated  cartilage-cells  from  an  enchondroma  described  by  Vir- 
chow  (Wurz.  "  Verh.,"  Bd.  1),  around  the  internal  portions  of  which  the 
contours  of  rounded  cells  were  visible,  would  be  intelligible,  and  even  the 
possibility  of  the  isolation  of  stellate  organisms  from  normal  bone  (vid. 
sup.)  be  explicable.  My  exposition  of  the  formation  of  the  lacunae  in 
rachitic  bone,  is  confirmed  by  Rokitansky  and  Virchow  (Wurz.  "  Verh.," 
II.) ;  whilst  Robin  declares  that  it  is  incorrect,  giving  a  description  of 
their  formation  which  is,  to  me,  unintelligible.  I  recommend  to  his 
notice  rachitic  bone,  the  cementum  of  the  horse's  tooth,  and  the  symphy- 
ses  (§  95),  with  which  he  is  manifestly  unacquainted,  and  hope  that  he 


THE     OSSEOUS    SYSTEM.  323 

may  then  be  induced  no  longer  to  regard  Schwann's  and  my  views  as 
antiquated.* 

*  [As  we  have  already  said,  we  must  deny  the  existence  of  endogenous  cell-development 
in  ossifying,  or  any  other  cartilage.  In  fact,  the  process  of  multiplication  of  the  corpuscles 
(nuclei  (?)  of  Kolliker,  granular  cartilage-cells  of  Tomes  and  De  Morgan)  is  so  clear,  that 
we  are  at  a  loss  to  comprehend  how  it  can  be  mistaken.  What  is  meant  in  the  text  by 
"  contents,"  as  distinct  from  the  corpuscles,  we  do  not  know.  Messrs.  Tomes  and  Morgan 
describe  the  real  changes  which  precede  ossification,  very  exactly  in  a  few  words,  thus : 
"  Cartilage  previous  to  its  conversion  into  bone  undergoes  a  rapid  growth,  which  takes  place 
principally  in  the  direction  of  the  long  axis  of  the  future  bone.  Each  granular  cell  becomes 
divided  into  two,  by  segmentation  transverse  to  the  line  of  ossific  advance.  These  are  again 
divided  and  the  process  repeated  from  time  to  time,  until  in  the  place  of  a  single  granular 
cell  we  have  a  long  line  of  cells  extending  from  the  unchanged  cartilage  to  the  point  where 
ossification  has  taken  place"  (1.  c.,  p.  16).  "If  attention  be  directed  to  the  end  of  the  line 
furthest  from  the  bone,  the  cells  will  be  found  small  in  size,  granular,  and  with  a  percepti- 
ble nucleus,  but  without  an  outer  wall,  distinguishable  from  the  hyaline  substance,  which  is 
abundant  between  the  contiguous  lines,  but  small  in  quantity  between  the  cells  composing 
the  lines.  But  if  the  other  end  of  the  line  be  examined,  very  different  conditions  will  be 
observed.  The  granular  cells  will  be  seen  to  have  become  rounded  in  form,  to  have  in- 
creased to  three  times  their  original  bulk,  and  to  possess  well-marked,  circular  nuclei.  ..." 
-p.  17. 

So  far,  our  own  observations  are  in  perfect  accordance  with  those  of  Tomes  and  De  Mor- 
gan. They  go  on,  however,  to  observe,  "  in  addition  to  which,  each  granular  cell  will  have 
acquired  a  thick,  pellucid,  outer  wall ;"  and  with  this  last  statement  we  can  by  no  means 
agree.  Neither  in  Man,  the  Calf,  the  Rabbit,  the  Skate,  nor  in  enchondroma,  have  we  been 
able  to  see  anything  of  the  regular  development  of  such  an  envelop-  in  fact,  in  the  great 
majority  of  instances,  we  have  convinced  ourselves  of  the  absence  of  anything  of  the  kind — 
there  being  nothing  but  a  clear  space  between  the  corpuscle  and  the  ossified  wall  of  the 
cavity  in  which  it  lies.  Bodies  corresponding  with  the  lacunal  cells — cartilage-corpuscles 
that  is,— invested  by  a  thick  coat  of  more  or  less  granular,  calcareous  matter,  may  indeed 
often  be  obtained  free;  but  they  arise,  like  the  corresponding  bodies  in  rickety  bone,  simply 
from  the  deposition  of  calcareous  matter  in  the  cartilage-cavity  before  it  has  taken  place 
in  the  matrix,  or  from  a  want  of  union  between  the  two  deposits ;  and  are  therefore  quite 
accidental. 

The  lacuna,  are  developed,  according  to  these  authors,  by  the  shooting  out  of  the  granular 
cells  into  processes,  and  their  direct  conversion  into  the  lacuna,  the  nucleus  of  the  granule- 
cell  remaining  as  the  nucleus  of  the  lacuna.  On  this  point  also,  we  must  differ  from  them, 
and  agree  with  Virchow  (1.  c.,  note,  §  101)  and  Kolliker  (supra,  §  104),  that  the  development 
of  the  canaliculi  is,  by  a  process  of  resolution,  quite  independent  of  the  corpuscles,  which 
simply  diminish  in  size,  and  either  remain  as  the  so-called  "  nuclei"  of  the  lacunae  or  totally 
disappear.  We  can  especially  recommend  the  Skate  (2)  as  a  subject  in  which  to  trace  the 
process  of  formation  of  lacunae,  as  the  bone  is  homogeneous  and  transparent,  and  in  conse- 
quence of  being  enclosed  in  a  large  mass  of  firm  cartilage,  may  be  cut  with  ease  into  very 
thin  sections.  We  have  observed  it  with  great  clearness  also  in  enchondroma. 

There  is  one  argument  which  seems  to  us  conclusive  on  this  point.  Wherever  the  cana- 
liculi can  be  seen  at  all,  however  young  the  tissue,  they  are  perfectly  clear  and  transparent. 
If.  however,  they  were  formed  by  processes  of  the  granular  cells,  they  ought  to  be  granular, 
and  more  or  less  opaque. 

Taking  the  same  view  of  the  structure  of  cartilage  as  Messrs.  Tomes  and  De  Morgan, 
then,  our  view  of  the  nature  of  the  lacunae,  resulting  from  its  ossification,  agrees  with  that  of 
Professor  Kolliker.  Cartilage  becomes  bone  by  the  deposit  of  calcareous  salts  in  the  matrix 
and  occasionally  in  its  cavities.  The  lacunae  are  spaces  left  round  the  corpuscles,  from 
which,  by  resorption,  processes — the  canaliculi, — are  subsequently  developed.  If  it  be  asked 
how  it  is  that  the  lacunae  may  frequently  be  demonstrated  both  optically  and  chemically  as 


324 


SPECIAL    HISTOLOGY. 


Fig.  133. 


§  105.  Elementary  processes  in  the  Layers  formed  from  the  Perios- 
teum.— The  periosteum  of  the  primarily  cartilaginous  bones,  is  propor- 
tionally very  thick  and  vascular,  consisting,  as  early  as  at  the  fifth 
month,  of  common  connective  tissue  and  fine  elastic  filaments,  the  latter 
of  which  in  process  of  time  become  stronger  and  stronger,  occasionally 
assuming  the  nature  of  elastic  fibres.  On  the  inner  aspect  of  this  fully 
formed  periosteum,  there  is  now  deposited  an  ossijic  blastema  firmly  ad- 
herent to  the  bone  (Fig.  133,  B) ;  so  that  when  the  periosteum  is  re- 
moved, it  generally  remains  upon  it  as  a  moderately  thick,  soft,  whitish 

yellow  lamella,  in  which,  microscopic  ex- 
amination shows  the  existence  of  a  fibrous 
tissue,  with  a  not  particularly  distinct 
fibrillar  formation,  something  like  imma- 
ture connective  tissue,  and  granular,  oval, 
or  round  nucleated  cells,  measuring  0*006 
-0-01  of  a  line.  When  this  lamella  is 
raised  from  the  bone,  it  is  found  to  be 
very  intimately  connected  with  the  most 
superficial  layers,  and  on  its  internal  sur- 
face a  few  little  detached  fragments  of 
bone,  and  scattered  masses  of  reddish,  soft  medulla,  from  the  most  su- 
perficial cancellar  spaces,  wrll  be  observed.  The  bone  thus  laid  bare, 
when  the  removal  of  the  periostea!  layer  has  been  carefully  conducted, 
presents  a  rough,  and  as  it  were  porous  surface,  with  numerous  medul- 
lary spaces,  and  remains,  superficially,  in  spots  of  greater  or  less  extent, 
quite  soft,  pale-yellow,  and  transparent,  whilst  more  internally  it  becomes 
firmer  and  whiter,  ultimately  acquiring  the  usual  appearance  of  perfect 
osseous  tissue.  When  it  is  inquired,  how  the  formation  of  bone,  which 
indubitably  takes  place  in  this  situation,  is  eifected,  we  refer  to  the  blas- 
tema just  described,  the  cells  of  which,  scattered  in  the  fibrillated  con- 
nective tissue,  have  not  the  least  resemblance  to  those  of  cartilage,  but 
appear  exactly  like  the  foetal  medulla-cells,  or  formative  cells  of  the 

FIG.  133. — Transverse  section  from  the  surface  of  the  shaft  of  the  metatarsus  of  the  Calf; 
magnified  45  diam. :  ^?,  periosteum  ;  J3,  ossifying  blastema  ;  C,  young  layer  of  bone,  with 
wide  cavities,  a,  in  which  are  lodged  remains  of  the  ossifying  blastema,  and  reticular  spi- 
culae,  6,  which  towards  the  blastema  present  a  tolerably  abrupt  border;  Z),  more  developed 
layer  of  bone,  with  Haversian  canals,  c,  which  are  surrounded  by  their  lamellae. 


distinct  bodies,  we  must  call  to  mind  the  fact  already  referred  to,  that  in  cartilage,  the  wall 
of  the  cavities  have  frequently  undergone  less  change  than,  or  a  different  change  from,  the 
surrounding  matrix;  and  therefore  appear  both  optically  and  chemically  distinct,  though 
they  are  by  no  means  so,  morphologically :  and,  therefore,  that  there  is  no  difficulty  in  sup- 
posing the  same  thing  to  occur  in  bone.  The  chemical  differentiation  of  the  wall  of  the 
lacuna  is,  in  fact,  exactly  comparable  to  that  of  the  wall  of  the  cavity  which  contains  the 
"  nucleus"  in  connective  tissue,  and  in  fibro-cartilage ;  and  which  gives  rise  to  the  formation 
of  the  elastic  element  in  those  tissues. — TRS.] 


THE     OSSEOUS     SYSTEM.  325 

embryo.  In  fact,  it  is  now,  not  difficult  to  show,  that  the  outermost, 
still  soft  bone-lamellae  pass  into  the  blastema  in  question,  with  their 
separate  spiculae  and  projections,  and  that  (1.)  the  matrix  of  the  bone 
arises  from  its  fibrous  tissue,  by  the  simple  uniform  deposition  of  cal- 
careous salts,  although  usually,  as  it  seems,  without  the  previous  ap- 
pearance of  calcareous  granules  ;  and  (2.)  that  the  bone-cells  are  formed 
out  of  the  formative  cells  of  the  blastema.  With  respect  to  the  latter, 
however,  the  transformation  cannot  be  followed  step  by  step,  as  in 
rachitic  bones.  This  much,  however,  is  always  apparent,  that  the  bone- 
cells  at  first  present  larger  cavities,  less  developed  rays,  and  more  dis- 
tinct nuclei  (the  latter,  as  we  know,  remaining),  and,  as  their  occasion- 
ally visible  outlines  prove,  correspond  entirely  in  size  with  the  cells  just 
mentioned,  so  that  I  do  not  for  a  moment  doubt,  that  they  are  formed 
in  this  situation  exactly  as  they  are  elsewhere.  With  respect  to  the 
development  of  the  ossifying  blastema  itself,  it  is  at  least  clear,  that  it 
is  derived  from  the  numerous  vessels  of  the  foetal  and  young  periosteum  ; 
the  origination  of  its  fibres  from  fusiform  cells,  I  have  very  frequently 
observed  in  man  and  in  animals,  but  with  respect  to  the  cells,  can  only 
state  that  they  occur  of  various  sizes,  and  occasionally  intermixed  with 
free  nuclei. 

The  formation  of  bone  in  this  blastema  occurs  wherever  it  is  in  con- 
nection with  the  bone  ;  it  does  not,  however,  take  place  in  connected  but 
in  interrupted,  reticular  lamellce.  The  roundish  or  elongated  spaces 
(Fig.  133,  a\  which,  from  the  first,  remain  between  the  layers  of  osseous 
tissue,  and  in  the  different  layers  communicate  with  each  other,  are  no- 
thing else  than  the  rudiments  of  the  Haversian  or  vascular  canals  of 
the  compact  substance,  and  contain  a  soft,  reddish  medulla,  which  at 
first  is  obviously  nothing  more  than  the  unossified  portion  of  the  ossific 
blastema,  although  it  sometimes  contains  more  formative  cells  than 
connective  tissue.  The  cells  of  these  spaces  are  very  soon  transformed 
into  the  usual,  light-reddish  medulla-cells,  and  partly  into  vessels  which 
communicate  with  those  of  the  interior  of  the  bone,  and  in  part  also 
with  those  of  the  periosteum,  with  which,  having  once  formed  a  junction, 
they  remain  continuous  during  the  entire  growth  of  the  bone  in  thick- 
ness, so  that  the  formation  of  the  spaces  in  the  bone  is,  at  least  after- 
wards, preindicated  by  those,  which,  in  accordance  with  what  has  been 
said,  proceed  from  the  periosteum  through  the  ossific  blastema  to  the 
bone.  Besides  medulla-cells  and  vessels  as  well  as  some  connective 
tissue,  the  bone-cavities  of  the  periosteal  layers  also  contain  round, 
elongated,  or  dentate,  flattened,  faintly  granular  cellular  corpuscles  of 
Q'01-0'02  of  a  line,  or  more  in  size,  with  from  3  to  12  or  more  vesicu- 
lar nuclei  and  nucleoli,  which  are  probably  referable  to  the  multiplica- 
tion of  the  medulla-cells  (vid.  §  11).  The  periosteal  layers,  which, 
agreeably  to  what  has  been  stated,  are  from  the  first  deposited  in  the 


326  SPECIAL    HISTOLOGY. 

form  of  cribriform  lamellae  around  the  ossific-nuclei  formed  from  carti- 
lage, continue  to  be  produced  so  long  as  the  general  growth  of  the  bone 
goes  on,  essentially  in  the  same  way,  constituting  the  material  by  which 
it  increases  in  thickness  ;  but  at  the  same  time,  more  or  less  important 
changes  are  set  up  in  them ;  the  most  considerable  of  which  take  place 
in  the  large  cylindrical  bones.  In  these,  we  find,  more  distinctly  indeed 
after  birth,  that  a  large  cavity  is  gradually  formed  in  the  interior,  which 
at  first  contains  foetal  medulla-cells,  and  afterwards  perfectly  formed 
medulla.  This  medullary  cavity  is  formed,  in  exact  analogy  with-  the 
medullary  spaces  described  in  the  preceding  paragraphs,  by  the  solution 
of  the  osseous  tissue  of  the  shaft;  at  first,  only  of  that  which  is  formed 
from  the  primitive  cartilaginous  rudiment,  but  soon,  also  of  that  deposi- 
ted from  the  periosteum  upon  the  former,  its  development  proceeding  in 
a  remarkable  manner,  as  long  as  the  general  growth  of  the  bone  con- 
tinues. Whence  it  comes  to  pass,  that,  as  at  the  ends  of  the  diaphyses, 
so  also  on  its  surfaces,  whilst  new  bone  is  continually  deposited  exte- 
riorly, that  which  is  already  formed  is  as  continually  absorbed  in  the 
interior ;  and  in  fact  these  two  processes  are  so  combined,  that  the  bone, 
during  its  development  is,  in  a  certain  measure,  several  times  regenera- 
ted, and,  for  instance  in  the  humerus  of  the  adult,  does  not  contain  an 
atom  of  the  osseous  tissue  which  existed  at  the  time  of  birth,  nor  does 
the  bone  at  that  period  contain  any  of  the  tissue  of  which  it  was  con- 
stituted in  the  embryo  at  three  months.  These  conditions  will  be 
rendered  most  distinctly  intelligible,  and  especially  with  respect  to  the 
periosteal  and  cartilage  layers,  by  means  of  a  diagram  (Fig.  134)  which 
I  have  for  a  long  time  employed  in  my  lectures.  If,  in  this  figure,  we 
compare  the  primordial  bone  E  E  with  the  almost  complete  bone  E4  E4, 
it  is  apparent,  that  in  the  longitudinal  growth  of  the  diaphysis  of  the 
latter  on  both  sides,  at  the  expense  of  the  continually  growing  epiphy- 
sal  cartilage,  an  elongated  cone  of  osseous  substance,  1,  2,  I1  21,  and  3, 
4,  81,  41,  is  produced,  to  which,  ultimately,  the  epiphysal  nuclei  E4  E4, 
also  originating  in  the  cartilage,  are  joined,  whilst,  to  increase  its  thick- 
ness, the  tubular  layer  P,  P1,  P2,  P3,  which  are  constantly  increasing  in 
length  and,  in  the  middle,  in  thickness,  are  applied  to  it.  In  a  cylin- 
drical bone  of  this  kind  consequently,  the  entire  portion  formed  from 
cartilage,  presents  a  figure  of  a  double  cone  with  rounded  bases ;  and 
that  formed  from  the  periosteal  layers,  1,  '2,  3,  4,  P3,  and  I1,  21,  31,  41, 
P3,  the  form  of  an  elongated  tube  thickest  in  the  middle,  and  resem- 
bling an  elongated  vertebra  of  a  Fish,  with  conically  hollowed,  terminal 
surfaces.  The  articular  cartilage  C,  is  the  unossified  portion  of  the 
epiphysal  cartilage,  and  the  medullary  cavity  which  is  not  shown  in  the 
figure  (it  may  be  supposed  to  be  indicated  pretty  nearly  by  the  outlines 
of  the  fourth  bone  E3  E3),  is  formed  by  the  resorption  of  the  entire 


THE    OSSEOUS    SYSTEM. 


327 


osseous  substance  derived  from   the  cartilage   and   periosteum  of  the 
younger  bones ;— in  this  case  the  first  three,  E  E,  E1  E1,  and  E2  E2. 

In  the  cylindrical  bones,  without  a 
medullary  cavity,  and  in  all  other  bones 
containing  nothing  but  spongy  substance 
in  the  interior,  the  absoprtion  does  not 
proceed  to  nearly  the  same  extent  as  it 
does  in  the  above  described  cases,  that  is 
to  say,  only  to  the  production  of  a  looser 
spongy  substance  in  the  interior,  and, 
consequently,  we  find,  for  instance  in  the 
vertebrae,  more  or  less  considerable  re- 
mains even  of  the  earlier  bone-substance. 
In  this  situation  also,  the  absorption  al- 
ways affects  not  merely  the  osseous  nu- 
cleus, formed  from  the  cartilage,  but  like- 
wise the  periosteal  layers,  the  latest  of 
which  only  remain  more  in  their  original 
form,  as  the  substantia  compacta. 

The  Haversian  canals  do  not  originate, 
as  is  sufficiently  apparent  from  what  has 
been  said,  like  the  cancelli  of  the  primary 
bone-substance,  from  a  solution  of  a  pre- 
existing tissue,  but  are  nothing  more  than 
open  cavities,  left  from  the  commence- 
ment, in  the  periosteal  layers.  They  are 
relatively,  of  a  considerable  size  at  an 
early  period  (vid.  also  "Valentin.  Entw." 
p.  262),  measuring  in  the  foetal  humerus 
at  five  months  0-016-0-024  of  a  line  in 
the  femur  at  birth,  according  to  Harting 

(p.  78),  0*10-0-024  of  a  line,  just  as  in  the  most  recently  formed  layers 
also  of  a  later  period.  Their  contents  have  been  already  described.  The 
most  important  circumstance  connected  with  them  remaining  to  be  no- 
ticed, is  the  mode  in  which  their  lamellar  systems  originate.  These 
lamellse  also  are  formed  without  the  intervention  of  cartilage,  and  are 
nothing  more  than  deposits  from  the  contents  of  the  canals,  which  sub- 
Fig.  134.  Diagram  of  the  growth  of  a  cylindrical  bone.  JB,  primary  rudiment,  the  dia- 
physis  ossified  and  the  epiphyses  cartilaginous:  .4,  the  same  bone  in  four  stages  of  further 
advance,  E'PPE1,  E^P'E2,  E3P2P2E3,  E4F3P3E4  ;  P  P'P2P3,  periosteal  layers  of  these  four 
bones;  the  space  contained  within  1,  2,  3,  4,  and  I1,  21,  31,  41,  indicates  the  portion  which 
in  the  largest  bones  is  formed  from  cartilage  ;  E'E',  cartilaginous  epiphyses  of  the  second 
bone;  E2E2,  epiphyses  of  the  third  bone,  in  one  of  which  is  an  osseous  nucleus  ;  E3E3,  E4 
E4,  epiphyses  of  the  fourth  and  fifth  bones,  all  with  larger  epiphysal  nuclei:  G,  articular 
cartilage ;  I,  K,  interstitial  cartilage  between  the  ossified  epiphyses  and  diaphyses. 


328  SPECIAL     HISTOLOGY. 

stance,  as  has  already  been  said,  in  respect  of  its  fibres  and  cells, 
entirely  corresponds  with  the  ossific  blastema  beneath  the  periosteum, 
and,  in  a  certain  degree,  is  merely  an  originally  unossified  remainder  of 
it.  These  conditions  are  easily  observed  in  young  bones,  in  which,  the 
periosteal  layers,  before  they  have  undergone  any  resolution,  are 
rendered  more  and  more  compact  by  these  new,  secondary  lamellae;  but 
even  at  a  later  period  a  more  or  less  ossified  blastema  (always  without 
calcareous  granules)  may  very  frequently  be  perceived  on  the  walls  of 
the  canals  in  question.  Whilst  the  vascular  canals  are  thus,  on  the  one 
side,  undergoing  contraction  by  the  deposition  of  these  secondary  layers, 
which,  just  as  in  the  periosteum  itself,  appear  laminated, — either  be- 
cause the  ossific  blastema  itself  is  so  constructed,  or  because  the  depo- 
sition of  bone  takes  place  with  periodical  pauses, — they  afterwards 
widen,  or  at  least  some  of  them,  by  absorption,  as  for  instance,  the 
canales  nutritii,  the  great  vascular  openings  in  the  apophyses,  &c. ;  and 
the  compact  substance,  as  has  been  already  remarked,  is  also,  in  many 
places  partially,  and  in  some  even  entirely,  absorbed. 

In  what  way  the  bone  increases  in  thickness  in  the  situations  where 
tendons  and  ligaments,  'without  the  intervention  of  periosteum,  are 
directly  implanted  into  it — has  not  yet  been  made  out.  From  the  cir- 
cumstance, that  in  the  adult,  in  many  of  these  situations,  true  cartilage- 
cells  occur  among  the  tendinous  fibres,  and  also,  that  their  passage  into 
bone-cells  may  very  clearly  be  observed,  it  might  perhaps  be  concluded 
that  a  similar  process  may  take  place  at  an  earlier  period  also.  In  fact, 
I  have  seen,  even  in  young  individuals,  at  the  points  of  insertion  of 
many  tendons  and  ligaments  (tendo  Achillis,  lig.  calcaneo-cuboideum, 
aponeurosis  plantaris,  $c.)  into  the  bone,  cartilage-cells,  and  their  meta- 
morphosis into  bone-cells.  Very  frequently,  also,  tendons  and  ligaments 
are  attached  to  portions  of  the  bone  which  remain  long  in  the  cartilagi- 
nous condition,  epiphyses,  tuberositas  calcanei,  £c.,  and  the  growth  of 
these  parts,  of  course,  is  simply  to  be  referred  to  the  cartilage. 

The  formation  of  bone  on  the  inner  aspect  of  the  periosteum  is  a  fact 
long  well  known,  although  it  has,  hitherto,  generally  been  thought,  that 
in  this  situation  also,  it  was  preceded  by  a  thin  cartilaginous  layer,  until 
the  contrary  was  shown  by  Sharpey  and  myself.  Since  the  discovery  by 
Duhamel  ("Me'moires  de  1'Academie  de  Paris,"  1742,  p.  384,  and  1743, 
p.  138),  that  the  bones  of  animals  fed  upon  madder  are  colored  red,  a 
great  number  of  experiments  have  been  made  with  that  substance,  espe- 
cially by  Flourens,  in  growing  animals ;  it  being  at  first  believed,  that 
it  only  colored  those  parts  of  the  bones  which  were  formed  after  its 
administration.  This  method,  however,  has  lost  a  good  deal  of  its  value 
since  it  has  been  shown  by  Rutherford  (in  "  Robert!  Blake,  Hiberni, 
Dissert,  inaugural,  med.  de  dentium  forrnatione  et  structura,  in  homine 


THE     OSSEOUS     SYSTEM.  329 

et  in  variis  aniraalibus,"  Edinb.  1780),  Gibson  ("Memoirs  of  the  Lite- 
rary and  Philosophical  Society  of  Manchester,"  2d  series,  vol.  I.  p.  146), 
Bibra  (1.  c.),  Brulle'  and  Hugueny  (1.  c.),  that  when  animals  were  fed 
upon  madder,  the  whole  of  the  growing  bones,  as  well  as  the  bones  of 
adult  animals,  become  colored,  and  especially  so  wherever  they  are  in 
more  immediate  connection  with  the  bloodvessels;  for  even  the  medulla 
is  colored  (Bibra).  For  which  reason  also,  the  innermost  layers  of  the 
Haversian  canals,  the  periosteal  surfaces,  and  the  vascular,  young  bone- 
substance,  acquire  a  deeper  color.  There  are,  however,  still  some 
points  worth  investigating  in  this  way,  particularly  with  relation  to  the 
more  recent  statements  of  Brulle'  and  HugueVy,  who,  relying  upon  the 
circumstance,  that,  as  they  assert,  the  decoloration  of  growing,  colored 
bones,  is  eifected  merely  by  the  absorption  of  the  colored  portions, 
believe  they  have  found  that  the  cylindrical  bones  also  deposit  osseous 
substance  from  within,  particularly  in  the  apophyses;  whilst  on  the  outer 
surface,  absorption  to  the  same  extent  takes  place  ;  statements  upon 
which  I  will  not,  at  present,  give  any  decided  opinion,  although  at  the 
same  time  I  hold  it  as  quite  certain,  that  in  many  places  an  absorption 
does  take  place,  on  the  exterior  of  the  bone  to  a  greater  or  less  extent.  It 
is  only  by  such  an  absorption  that  the  enlargement  of  the  foramen  mag- 
num from  the  sixth  year  upwards,  at  which  time  the  portions  of  bone 
surrounding  it  are  united,  can  be  explained.  And  the  same  may  be  said 
with  respect  to  the  arches  of  the  vertebrce,  and  numerous  vascular  and 
nerve-openings  (foramen  ovale  and  rotundum  of  the  sphenoid  bone,  fora- 
mina inter  transversaria,  canalis  caroticus,  £c.  $c.\  Consequently,  the 
law  propounded  by  Serres  (Meek.  "  Archiv,"  1822,  p.  455),  that  the 
openings  in  bone  enlarge  by  the  growth  of  the  individual  pieces  by  which 
they  are  bounded,  is  wholly  incorrect,  as  applied  to  the  openings  and 
canals  in  the  middle  of  bones ;  as  had  been  already,  to  some  extent,  de- 
clared by  E.  H.  Weber  and  Henle;  and  even  in  other  cases  it  holds 
good  only  for  the  earliest  periods. 

The  periosteal  layers  present  a  certain  contrast  to  the  osseous  tissue 
developed  from  cartilage.  The  former  constitute  principally  the  firm 
cortex  of  the  primarily  cartilaginous  bone,  and  are  characterized  by  th'e 
occurrence  of  Haversian  canals  and  their  lamellar  systems,  whilst  the 
latter  produces  the  spongy  substance,  and  contains  no  vascular  canals. 
It  must  not,  however,  be  forgotten  that  even  the  periosteal  layers  all 
have,  at  first,  in  a  certain  degree,  a  spongy  structure,  and  in  all  these 
bones,  without  exception,  contribute,  and  frequently  very  essentially,  to 
the  formation  of  the  spongy  substance;  moreover,  that  in  the  cellular 
substance,  which  originates  from  the  cartilage,. in  the  apophyscs  for  in- 
stance, secondary  layers,  similar  to  those  of  the  Haversian  canals,  and 
of  the  spongy  substance  which  is  formed  out  of  the  periosteal  layers, 
only  not  so  much  developed,  appear  to  be  formed.  The  morphological 


330  SPECIAL     HISTOLOGY. 

and  chemical  relations  of  the  matrix  of  these  two  forms  of  osseous 
tissue  have  not  as  yet  been  determined.  On  the  other  hand  the  bone- 
laeunge  of  both  kinds  of  tissue  do  not  present  the  least  difference. 

§  106.  Bones  not  primarily  cartilaginous  occur,  in  Man,  only  in  the 
cranium.  They  originate  outside  the  primordial  cranium,  between  it 
and  the  muscular  system,  and  thus  within  the  structure  constituting  the 
vertebral  system.  They  by  no  means  exist  as  membranous  and  cartila- 
ginous capsules  on  the  first  appearance  of  the  cranium,  their  formation 
not  commencing  till  after  that  of  the  primordial  cranium,  from  a  secon- 
dary blastema,  whence,  in  contradistinction  to  the  other  primary  bones, 
the  formative  material  of  which  exists  prior  to  the  commencement  of 
ossification,  they  are  termed  secondary  bones — or,  also,  because  in  most 
places  they  are  in  contact  with  portions  of  the  primordial  cranium — 
covering  or  overlaying  bones  (belegknochen).  To  this  class  belong,  the 
upper  half  of  the  expanded  portion  of  the  occipital  bone,  the  parietal, 
and  frontal  bones,  the  squamous  portion  and  tympanic  ring  of  the  tem- 
poral bone,  the  nasal,  lachrymal,  malar,  and  palate  bones,  the  upper  and 
lower  jaw,  the  vomer,  and  apparently,  the  internal  lamella  of  the  ptery- 
goid  process  of  the  sphenoid,  and  the  cornua  sphenoidalia.  The  blastema 
of  these  bones,  which  differs  from  that  of  the  primary  bones,  in  its  being 
successively  developed  in  a  membranous  matrix,  simultaneously  with  the 
process  of  ossification,  not  existing  previously  in  any  considerable  quan- 
tity, presents  essentially,  exactly  the  same  conditions  as  that  of  the 
periosteal  layers,  and  is  also  ossified  in  precisely  the  same  way. 

The  notion  that  certain  cranial  bones,  in  man  and  the  Mammalia,  are 
not  developed  from  cartilage,  is  by  no  means  new,  although  the  morpho- 
logy of  the  question  was  first  established  by  Rathke,  Reichert,  Jacobson, 
and  myself;  and  its  histology  by  Sharpey  and  myself.  But  with  respect 
to  the  latter  subject,  a  controversy  still  exists  as  to  the  true  nature  of 
the  ossific  blastema  (as  also,  of  that  of  the  periosteal  layers), — whether 
it  be  a  kind  of  connective  tissue,  as  I  believe,  or  a  sort  of  cartilage,  as 
Reichert  and  A.  Bidder  assert,  with  respect  to  which  more  will  be  found 
in  my  "Mikroskop.  Anat."  pp.  374,  375. 

§  107.  The  secondary  cranial  bones,  all,  in  the  first  instance  com- 
mence in  the  form  of  a  minute,  elongated,  or  rounded,  osseous  nucleus, 
consisting  of  a  portion  of  fundamental  substance  or  matrix,  with  a  few 
lacunae,  and  which  is  surrounded  by  a  small  quantity  of  soft  blastema. 
How  this  nucleus  originates  has  not  yet  been  observed,  although  from 
the  way  in  which  its  growth  proceeds,  it  might  be  assumed  with  certainty, 
that  shortly  previous  to  its  first  appearance,  a  minute  lamella  of  the 
soft  blastema  is  formed  in  the  situation  of  the  future  nucleus,  which 
lamella  spreading  from  a  single  point,  becomes  ossified  by  the  addition 


THE     OSSEOUS     SYSTEM. 


331 


of  earthy  salts  and  the  metamorphosis  of  its  cells.  The  primary  point 
of  ossification  having  thus  appeared,  for  instance  in  the  parietal  bone, 
its  growth  advances  simultaneously  with  the  horizontal  extension  of  the 
membraniform  blastema,  in  such  a  way  that  a  delicate  lamina  composed 
of  reticulated  osseous  spicules  is  shortly  produced,  from  which,  slender 
rays  stretch  out  into  the  still  unossified  blastema  (Fig.  135).  If  this 
formation  be  examined  more  closely,  it  will  be  observed,  that  the  indi- 
vidual bone-spicules  originate  in  the  membranous  blastema,  by  the 
ossification  of  its  elements,  and,  that  to  a  certain  extent,  the  latter  is 
absorbed  in  the  spaces  occupied  by  the  spicules,  remains  of  it  being  left  in 
the  interstices  ;  and  moreover,  that  the  formation  of  the  osseous  elements 
proceeds  exactly  in  the  same  way,  that  it  does  in  the  periosteal  layers ;  the 


Fig.  135. 


Fig.  136. 


A 


..t 


rays  of  bone  as  they  extend  further  into  the  soft  blastema  becoming 
softer  and  paler,  and  containing  less  earthy  matter,  whilst  their  cells 
become  more  and  more  like  the  soft  formative  cells,  till,  at  last,  the  spi- 
cules lose  all  distinct  limitary  outline,  and  are  lost  in  the  blastema.  At 
first,  the  growth  of  these  bones  proceeds  in  a  superficial  plane  only,  the 
rays,  as  they  extend  and  become  connected  by  transverse  branches  con- 
Fig.  135.  Parietal  bone  of  a  fourteen-weeks'  old  foetus;  magnified  18  diameters. 
Fig.  136.  From  the  inner  surface  of  the  parietal  bone  of  a  new-born  child ;  magnified  300 
diameters:  a,  bone  with  lacunae,  still  pale-colored  and  soft;  6,  border  of  the  same;  c,  ossi- 
fying blastema  with  its  fibres  and  cells.  jB,  three  of  these  cells,  magnified  350  diameters. 


332  SPECIAL    HISTOLOGY. 

tinuing  to  add  to  the  size  of  the  original,  reticulated  lamella,  which, 
however,  shortly  begins  to  increase  in  thickness  by  the  deposition  of 
layers  upon  both  sides  of  it ;  the  different  portions,  also,  in  proportion 
to  their  age  becoming  more  and  more  compact.  The  formation  of  the 
thickening  layers  is  to  be  referred  to  the  periosteum,  which  is  found  on 
the  surfaces  of  the  secondary  bones,  very  soon  after  their  formation  has 
begun,  being  developed  either  from  their  original  blastema,  or  from  the 
contiguous  tissues  (perichondrium  of  the  primordial  cranium,  muscular 
and  tendinous  coverings),  and  proceeds  exactly  in  the  same  way  as  in 
the  periosteal  layers  of  the  primary  bones ;  that  is  to  say,  on  the  inner 
side  of  the  periosteum,  a  soft  blastema  is  deposited,  which  gradually 
ossifies,  from  the  bone  outwards,  without  its  ever  being  cartilaginous 
(Fig.  136).  In  this  way  are  now  formed,  chiefly  on  the  outer,  but  also 
on  the  inner  surface  of  the  primary  osseous  lamella,  arid  proceeding 
outwardly  from  it,  successive,  new  laminae,  in  consequence  of  which 
the  rudimentary  bone  continually  increases  in  thickness.  All  these  new 
lamellae,  like  the  primary  one,  are  at  first  perforated  by  reticular  open- 
ings, and  the  various  sized,  roundish  or  elongated  interstices  communi- 
cate with  those  of  the  previously  and  subsequently  formed  layers,  so 
that  the  secondary  osseous  nuclei,  like  the  periosteal  layers,  are  from 
the  first,  penetrated  by  a  network  of  canals,  which,  as  in  those  layers, 
in  part  at  least,  soon  present  the  appearance  of  Haversian  canals.  At 
first,  filled  only  with  a  soft  blastema,  the  remains  of  the  plastic  material 
of  the  various  lamellae,  these  spaces,  in  consequence  of  the  advance  of 
ossification  in  their  interior, — which  sometimes  takes  the  form  of  bridges 
stretching  across  them,  sometimes  of  a  deposit  on  their  walls, — become 
more  and  more  contracted.  Ultimately,  some  are  entirely  closed,  whilst 
others  are  converted  into  true  vascular  canals,  the  vessels  being  de- 
veloped from  their  contents,  which  are  composed  during  the  time  of 
medulla-cells,  and  communicating  with  those  of  the  periosteum.  When 
the  bone  has  arrived  at  this  stage,  its  subsequent  changes  are  readily 
followed.  It  continues  to  increase  in  breadth  and  thickness  by  the  con- 
stant addition  of  new  blastema  on  its  edges  and  surfaces,  until  it  has 
attained  its  typical  form  and  size,  and  at  the  same  time,  by  the  solution 
of  its  compact  substance,  additional  spongy  tissue  (or  even  large  cavities), 
is  formed  in  its  interior,  so  that  eventually,  like  bone  developed  from 
cartilage  and  periosteal  layers,  it  presents,  externally,  compact  sub- 
stance with  Haversian  canals ;  and  internally,  medullary  spaces  (cancelli), 
although  with  distinct  secondary  deposits. 

The  secondary  cranial  bones  ossify,  in  part,  earlier  than  the  primary, 
and  mostly  with  only  a  single  nucleus.  The  soft  blastema  out  of 
which  they  are  formed,  and  which,  so  long  as  the  bones  continue  to 
grow,  is  to  be  found  on  their  surfaces  and  edges,  does  not,  like  carti- 


THE     OSSEOUS     SYSTEM. 

lage,  grow  independently  with  them,  but  is  developed  by  degrees,  from 
a  plasma  successively  secreted  from  the  vessels  of  the  periosteum,  the 
two  lamellae  of  which  are  conjoined  at  the  margin  of  the  ossifying 
plate.  The  cells  of  this  plasma,  the  metamorphosis  of  which,  as  in  the 
periosteal  layers,  cannot  be  followed  in  every  particular,  are  elongated, 
measuring  in  man,  for  the  most  part,  0-006-0-01  of  a  line,  and  pre- 
senting granular  contents  with  oval  nuclei  of  0*0028— 0*00-18  of  a  line. 
Such  of  these  cells  as  are  destined  for  the  growth  of  the  bone  in  thick- 
'ness,  with  the  exception  of  those  of  the  glenoid  cavity  of  the  temporal 
bone,  never  present  the  slightest  resemblance  to  cartilage-cells,  and, 
together  with  their  matrix,  invariably  ossify  without  the  appearance  of 
any  calcareous  particles ;  those  on  the  borders  or  extremities,  on  the 
contrary,  may,  as  it  appears,  subsequently,  take  on  the  nature  of  true 
cartilage.  The  most  striking  example  of  this  kind  occurs  in  the  con- 
dyle  of  the  inferior  maxilla,  where,  even  during  foetal  life,  a  thick  car- 
tilaginous layer  is  deposited,  which  so  long  as  the  growth  of  the  bone 
continues,  precedes  its  longitudinal  growth,  exactly  like  an  epiphysal 
cartilage.  I  have  noticed  the  same  thing  in  the  articular  fossa  of  the 
temporal  bone,  where,  however,  the  cartilage  is  less  developed ;  at  the 
angle  of  the  inferior  maxilla  (in  the  Calf),  and  at  the  anterior  extremi- 
ties of  each  half  of  the  same  bone,  which  are  connected  by  a  semi- 
fibrous,  semi-cartilaginous  substance,  corresponding  very  nearly  with 
the  symphysis.  This  fact  loses  much  of  the  singularity  which  at  first 
sight  attaches  to  it,  when  we  consider  that  all  cartilage  is  at  first  soft, 
and  consists  of  common  formative  cells.  It  is,  consequently,  only  ne- 
cessary that  the  formative  cells  of  the  soft  blastema  of  the  secondary 
bones,  should,  at  a  certain  period,  pass  through  the  same  changes  as 
those  undergone  by  the  formative  cells  of  embryonic  cartilage,  in  order 
to  effect  the  production  of  cartilage  in  the  bones. now  in  question. 
Further  investigation  is  required  to  show,  whether  cartilage  of  this 
kind  also  occurs  as  a  supplementary  addition  to  other  secondary  bones, 
and  to  what  extent,  in  animals.  Still,  it  may  be  noticed,  that  in 
asserting  as  I  have  done,  that  all  ossifications  from  a  soft  blastema 
take  place  without  the  deposition  of  calcareous  granules,  this  statement 
is  only  in  part  correct,  because  it  is  quite  true,  in  many  cases,  that  this 
sort  of  deposition  does  occur  in  them,  though  never  at  an  early  period, 
and,  generally  speaking,  but  rarely.  The  ossifying  margin,  moreover, 
in  these  cases  is  never  abrupt,  as  it  is  in  ossifying  cartilage. 

The  ultimate  changes  of  the  secondary  bones  have  not  yet  been 
closely  investigated.  Their  mode  of  connection  with  each  other,  and 
also  with  primary  bones  by  suture  and  coalescence,  is  tolerably  well 
known.  In  the  vault  of  the  cranium,  for  instance,  as  the  primary 
ossific  points  first  appear  in  the  situation  of  the  tuberosities  of  the 
parietal  and  frontal  bones,  the  bones  are  at  first  placed  widely  asunder, 


334  SPECIAL    HISTOLOGY. 

and  are  connected  merely  by  a  fibrous  membrane,  the  continuation  of 
the  periosteal  lamella  of  each,  and  which  is  united  on  the  internal 
aspect  with  the  remains  of  the  membranous  cranium  of  the  embryo, 
and  with  the  dura  mater.  The  bones  then  continue  to  grow  towards  each 
other,  and  at  last  constantly  advancing  in  the  above-described  continua- 
tion of  the  periosteum,  come  very  nearly  into  contact  at  the  frontal  and 
sagittal  sutures ;  there  remains,  however,  for  a  long  time  one  large  vacuity, 
in  particular,  between  them, — the  anterior  fontanelle, — but  which  closes 
in  the  second  year  after  birth ;  whilst  at  the  same  time,  the  bones, 
which,  up  to  this  period,  adjoined  each  other  with  a  straight  line  of 
juncture,  send  out  interdigitating  tooth-like  processes,  till  ultimately, 
when  their  blastema  is  wholly  consumed,  they  continue  united  only  by 
the  remains  of  the  periosteum  (the  sutural  cartilage,  as  it  is  termed,  or 
better,  the  sutural  ligament),  but  which  also  is  capable  of  becoming 
ossified  sooner  or  later,  and,  indeed,  invariably  first  on  the  inner  aspect 
of  the  suture,  where  the  tooth-like  processes  are  very  little  developed. 
The  changes  of  form  in  the  entire  bones  during  their  development  are 
very  remarkable,  and  have  hardly  been  attended  to.  If  a  parietal 
bone,  for  instance,  of  a  foetus  or  new-born  child,  be  compared  with  that 
of  an  adult,  it  will  be  found  that  the  former  is  much  more  curved,  and 
in  no  way  at  all  represents  a  piece  cut  out  of  the  middle  of  the  latter. 
The  adult  parietal  bone  consequently  must  have  undergone  a  very 
important  alteration  in  the  curvature  of  its  surfaces,  and  this,  as 
mechanical  conditions  are  out  of  the  question,  can  only  have  been 
effected  by  an  unequal  deposition  of  bone  internally  and  externally,  in 
the  middle  and  at  the  borders ;  or  by  deposition  on  the  one  side  and 
absorption  on  the  other.  That  unequal  deposition  does  actually  occur, 
is  seen,  for  example,  in  the  jug  a  cerebralia  and  impressiones  digitatce, 
the  sulci  meningei,  &c. ;  but  it  appears  to  me,  that  the  whole  matter 
cannot  be  understood,  unless  we  assume  that  local  absorptions  also  take 
place  in  certain  situations.  How  otherwise  can  be  explained  the  in- 
crease in  breadth  of  the  superior  orbital  ridge,  the  increase  of  distance 
between  the  frontal  eminences,  even  after  the  ossific  union  of  the  two 
portions  of  the  frontal  bone,  the  change  of  form  of  the  lower  jaw  (the 
greater  distance  between  the  coronoid  processes  and  the  mental  spine,  the 
alteration  in  its  curvature,  the  partial  removal  and  renewal  of  the  alveolce), 
&c.?  We  have  already  seen,  that  in  the  other  bones,  also,  something 
of  the  kind  must  be  presumed  to  take  place,  and,  consequently,  cannot 
hesitate  to  admit  it  in  the  present  case,  although  the  particulars  of  the 
process  be  unknown.  That  this  process  occurs  in  the  interior  of  the 
secondary  bones  has  been  already  mentioned.  The  formation  of  the 
diploe,  which  becomes  more  evident  in  the  tenth  year,  is  to  be  referred 
to  it,  as  is  also  that  of  the  frontal  sinuses,  and  antrum  Highmorianum, 
which  however  does  not  take  place  till  a  later  period. 


THE    OSSEOUS    SYSTEM.  335 

I  would  further  remark,  that  the  secondary  bones,  so  long  as  they  are 
in  a  growing  state,  are  much  more  vascular  than  afterwards,  even  ex- 
ceeding, in  this  respect,  the  periosteal  layers  of  the  other  bones;  on 
which  account  their  medulla,  containing  the  multi-nuclear,  enigmatical 
bodies,  already  referred  to,  is  of  a  redder  color.  The  vessels  enter  these 
bones  at  innumerable  points  on  the  surface,  and,  in  the  different  bones, 
run  in  vertical  or  horizontal  canals.  The  latter  is  the  case  in  the  flatter 
bones,  in  which  the  vascular  channels  run  principally  in  the  longitudinal 
direction  of  the  osseous  rays  proceeding  from  the  primary  point  of  ossi- 
fication; and  the  former,  in  consequence  of  which  the  surface  of  the 
bone  frequently  presents  an  extremely  delicate,  millepore-like  aspect, 
occurs  in  the  thicker  portions.  A  great  many  of  these  canals  after- 
wards become  obliterated,  or,  at  all  events,  very  much  contracted,  whence 
the  surface  of  the  bone  is  rendered  smoother. 

In  conclusion  to  these  remarks  on  the  development  of  the  bones,  I 
will  add  a  few  words  regarding  their  conditions  at  different  periods. 
Valentin  noticed  the  cartilaginous  rudiments  of  the  ribs  in  a  human 
embryo  6  lines  long.  That  of  the  cranium  is  distinctly  recognizable  in 
the  sixth  or  seventh  week,  as  well  as  those  of  the  vertebral  zone  and  that 
of  the  extremities;  those  of  the  extremities  proper  do  not  appear  till  later 
(in  the  eighth  or  ninth  week).  Ossification  commences  as  early  as  the 
second  month,  first  in  the  clavicles  and  lower  jaw  (fifth  to  seventh  week), 
then  in  the  vertebrae,  the  hum er us,  femur,  ribs,  and  the  cartilaginous  por- 
tions of  the  lamina  of  the  occipital  bone.  At  the  end  of  the  second,  and 
beginning  of  the  third  month,  ossification  is  apparent  in  the  frontal  bone, 
scapulce,  bones  of  the  fore-arm  and  leg,  and  upper  jaw ;  in  the  third  month, 
in  the  rest  of  the  cranial  bones,  with  few  exceptions,  the  metacarpal  and 
metatarsal  bones,  and  phalanges ;  in  the  fourth  month,  in  the  ilium  and 
ossicula  auditiis  ;  in  the  fourth  or  fifth  month  in  the  ethmoid,  the  turbi- 
nated  bones,  the  sternum,  pubis,  and  ischium;  in  the  sixth  to  the  seventh 
month,  in  the  os  calcis,  and  astragalus;  in  the  eighth  month,  in  the  os 
hyoides.  At  birth,  the  epipliyses  of  all  the  cylindrical  bones  are  still 
unossified,  with  the  occasional  exception  of  those  at  the  lower  extremity 
of  the  femur  and  upper  end  of  the  tibia  ;  and  besides  these  all  the  carpal 
and  the  five  smaller  tarsal  bones,  the  patella,  sesamoid  bones,  and  the 
last  segment  of  the  coccyx.  After  birth,  up  to  the  fourth  year,  the 
nuclei  of  these  bones  also  make  their  appearance;  but,  in  the  os pisiforme, 
not  till  the  twelfth  year.  The  union  of  most  of  the  epiphyses  and  pro- 
cesses, with  the  diapliyses  takes  place,  in  part  at  the  time  of  puberty,  in 
part  towards  the  end  of  the  period  of  growth.* 

*  [Dr.  Sharpey's  discovery  that  certain  bones  of  the  skull  are  developed  in  the  same  man- 
ner as  those  layers  which  are  formed  under  the  periosteum  in  the  long  bones,  has  been  a 
sort  of  apple  of  discord  among  histologists,  and  has  produced  a  great  variety  of  controversies 
not  only  among  them,  but  among  comparative  anatomists  ;  controversies  whose  heat  has 


336  SPECIAL     HISTOLOGY. 

§  108.  The  vital  phenomena  exhibited  in  the  mature  bones  are  not, 
during  the  vigorous  period  of  life,  accompanied  with  any  notable  or  active 

been  somewhat  increased,  as  we  think,  by  a  want  of  perception  among  the  combatants,  of 
the  fact,  that  several  totally  distinct  questions  are  involved.  These  questions  seem  to  us  to 
be  the  following,  and  we  shall  endeavor  to  consider  them  in  detail. 

1.  Whether  the  tissue  from  which  "secondary"  bone  proceeds  is  cartilage,  or  not? 

2.  Whether  it  is  morphologically  homologous  with  cartilage,  or  not? 

3.  Whether  ossification  takes  place  in  it  in  the  same  manner  as  in  cartilage,  or  not? 
And  as  the  result  of  the  answering  these : — 4.  Whether  the  differences  between  the  two 

tissues  are  sufficient  to  constitute  the  basis  of  a  classification  of  the  bones  or  not? 

1.  To  answer  this  by  saying  with  Meyer  that  every  tissue  which  ossifies  is  cartilage,  is 
simply  to  beg  the  whole  question.     Cartilage  we  hold  to  be  distinguished  from  'indifferent 
tissue,  by  the  fact  of  its  matrix  containing  chondrin.     The  substance  which  in  the  foetus  con- 
tains no  chondrin,  but  will  subsequently  become  a  cartilage — though  in  common  parlance  it 
is  very  convenient  to  call  it  "  foetal  cartilage" — is  no  more  cartilage  than  the  cartilaginous 
basis  of  a  future  bone,  which  might  just  as  properly  be  called  fostal  bone,  is  osseous  tissue. 
There  can  be  no  question  then,  we  think,  that  Ko'lliker  is  in  the  right,  as  against  Reichert, 
Meyer,  and  others,  when  he  says  that  secondary  bone  is  not  developed  from  cartilage,  and 
that,  in  this  respect,  it  may  be  distinguished  from  primary  bone. 

2.  Though  this  matrix  of  secondary  bone,  however,  is  assuredly  not  cartilage,  it  is  another 
matter  whether  it  is,  or  is  not,  morphologically  homologous  with  cartilage.     To  arrive  at  any 
just  conclusion  on  this  head,  it  is  necessary  to  understand  the  precise  structure  of  this  tissue, 
which  Messrs.  Tomes  and  De  Morgan  have  been  the  first  to  point  out :  "  If  attention  be 
directed  to  the  part  furthest  removed  from  the  bone,  it  will  be  seen  that  the  membrane-like 
mass  is  composed  of  oval  cells  with  slight  prolongations  from  the  extremities,  which  are 
frequently  arranged  in  the  form  of  bands  of  fibrous  tissue.     Dr.  Sharpey  has  observed  that 
the  membrane  into  which  the  bone  extends  is  like  fibrous  tissue  in  an  early  stage  of  develop- 
ment; and  this  observation  is  strictly  true  when  confined   to  the  part  indicated,  but  the 
analogy  ceases  [?]as  we  extend  our  examination  towards  the  bone.     Here,  in  the  place 
of  cells  with  elongated  processes,  or  cells  arranged  in  fibre-like  lines,  we  find  cells  aggre- 
gated into  a  mass,  and  so  closely  packed  as  to  leave  little  room  for  intermediate  tissue.    The 
cells  appear  to  have  increased  in  size  at  the  cost  of  the  processes  which  existed  at  an  early 
stage  of  development  and  formed  a  bond  of  union  between  them.  Everywhere  about  growing 
bone,  a  careful  examination  will  reveal  cells  attached  to  its  surface,  while  the  surface  of  the 
bone  itself  will  present  a  series  of  similar  bodies  ossified.     To  those  we  propose  to  give  the 
name  of  osteal  cells,  as  distinguished  from  lacunal  and  other  cells.    In  microscopic  characters, 
the  osteal  cells  closely  resemble  the  granular  cells  of  temporary  cartilage  ;  so  closely,  indeed, 
that  the  latter,  when  detached  from  the  cartilage,  could  not  well  be  distinguished  from  them. 
They  are,  for  the  most  part,  spherical  or  oval  in  form,  and  lie  on  the  surface  of  the  growing 
bone  in  a  crowded  mass,  held  together  by  an  intervening  and  apparently  structureless 
matrix.     Here  and  there  we  find  a  cell  which  has  accumulated  about  itself  an  outer  invest- 
ment of  transparent  tissue,  and  has,  in  fact,  become  developed  into  a  lacunal  cell  destined 
to  become  a  lacuna"  (1.  c.  p.  23). 

The  tissue,  then,  from  which  secondary  bone  immediately  proceeds,  is  composed  of  a 
homogeneous  matrix,  in  which  corpuscles,  identical  with  the  cartilage-corpuscles,  are 
imbedded:  it  is  therefore  identical,  as  Dr.  Sharpey  described  it,  with  young  connective 
tissue;  and  as  we  have  seen  above  (note,  §  101),  and  as  the  authors  state,  with  foetal  carti- 
lage. Though  not  cartilage,  therefore,  it  is  homologous  with  it  (as  is,  indeed,  admitted  by 
Professor  Koiiiker)  ;  a  fact  which  is  still  more  strongly  evidenced  by  the  transition  of  carti- 
lage into  a  similar  tissue,  at  its  edges  (Tomes  andDe  Morgan,  1.  c.  p.  24),  which  may  readily 
enough  be  observed,  and  which  has  been  particularly  shown  by  Reichert  to  occur  between 
the  primary  and  secondary  bones  of  the  skull  ("  Zur  Streitfrage  fiber  die  Gebilde  der  Binde- 
substanz,  ober  die  Spiralfaser  und  iiber  den  Primordial-Schadel,"  Muller's  "  Archiv,"  1S53). 

Now  it  seems  to  us  that  a  tissue  which  is  identical  with  the  embryonic  form  of  cartilage, 


THE  OSSEOUS  SYSTEM.  337 

morphological  changes.  It  is  true  that,  during  this  period,  some  of  the 
processes  above  considered  go  on — such  as  the  enlargement  of  the 
sinuses  in  the  cranial  bones,  of  the  points  of  insertion  of  muscles 

which  passes  into  adult  cartilage,  and  differs  from  cartilage  only  in  the  absence  of  chondrin 
(in/which  respect  ossified  cartilage  agrees  with  it),— is  in  a  morphological  point  of  view 
homologous  with  cartilage. 

3.  With  respect  to  the  third  question, — Sharpey  and  Ko'lliker  are  of  opinion  that  the 
deposit  of  calcareous  matter  and  the  formation  of  lacunas  take  place  in  the  same  manner  as 
in  cartilage,  i.  e.  that  the  calcareous  salts  are  deposited  evenly  through  the  matrix,  leaving 
spaces  round  the  corpuscles  or  "  nuclei,"  from  which  the  canaliculi  are  subsequently  deve- 
loped by  resorption.  Messrs.  Tomes  and  De  Morgan,  on  the  other  hand  (see  passage  cited 
above),  maintain  that  secondary  bone  differs  from  primary,  in  so  far  as  certain  of  the  corpus- 
cles— "osteal  cells/' — "arrange  themselves  side  by  side,  and  together  with  the  transparent 
blastema  in  which  they  lie,  become  impregnated  with  ossific  matter,  and  permanently  fused 
with  the  bone-tissue  with  which  they  lie  in  contact.  By  the  linear  arrangement  of  these 
osteal  cells,  lamination  is  produced.  In  the  case  of  new  laminated  bone,  the  cells  are  simply 
ossified  without  arrangement.  Lying  amongst  the  osteal  cells  will  be  seen  some  which  have 
accumulated  around  them  a  quantity  of  tissue  which  forms  a  thick  investment  to  them  ;  they  then 
become  granular,  and  take  on  in  every  respect  the  characters  of  a  lacunal  cell.  These  are 
found  deposited  at  intervals  along  the  line  of  ossification,  and  becoming  blended  with  the 
general  mass,  the  granular  cell  remaining  as  a  lacuna,  and  sending  out  processes  in  all  direc- 
tions" ("  Abstract  in  Proceedings  of  Royal  Society"). 

We  must  confess  that  all  we  have  seen  leads  us  to  believe  that  the  former  of  these 
accounts  is  correct.  We  have  never  been  able  to  find  evidence  of  any  of  the  corpuscles 
becoming  converted  into  "osteal  cells,"  and  we  believe,  for  the  following  reasons,  that  this 
process  does  not  take  place.  In  examining  the  growing  Haversian  canals  in  Man,  and  par- 
ticularly in  the  Calf,  we  have  very  frequently  found  the  innermost  layer  transparent,  glassy, 
and  structureless — exhibiting  nothing  but  the  corpuscles  (e?)  lying  in  lacuna?  without  canali- 
culi. This  layer  would  be  as  much  as  ^^thof  an  inch  thick;  in  the  layer  (r)  immediately 
external  to  it,  however,  the  "  osteal  cells"  were  exceedingly  well  marked.  The  inner  layer 
looked  like  smooth  ice,  and  the  outer  like  ice  which  had  cracked  into  innumerable  tolerably 
even  portions — but  these  cracks  were  by  no  means  produced  by  the  canaliculi,  which,  as 
yet,  were  hardly  at  all  developed.  Now  it  seems  clear  that  if  the  "  osteal  cells"  were  pro- 
duced by  the  calcification  of  certain  of  the  corpuscles,  they  ought  to  be  more  obvious  in  the 
young,  inner  layer,  than  in  the  outer  ;  whereas  just  the  reverse  occurs.  The  fact  stated  by 
Messrs.  Tomes  and  De  Morgan,  that  lamination  is  less  obvious  in  young  than  in  old  bone, 
tends  to  exactly  the  same  conclusion.  Again,  if  the  granular  substance  between  the  lacunae 
were  composed  of  calcified  corpuscles — "  osteal  cells,"  the  action  of  acids  ought  to  bring  them 
out  as  strongly  as  it  does  those  of  the  lacuna? ;  whereas  neither  in  young  bone  nor  in  old  can 
anything  of  the  kind  be  seen. 

With  respect  to  the  lacunae,  again,  we  have  the  same  remarks  to  make  as  when  speaking 
of  cartilage.  We  have  never  been  able  to  find  any  trace  of  the  development  of  the  corpus- 
cles (granular  cells)  into  lacunae.  As  to  the  tissue  which  accumulates  round  them  and  forms 
an  investment,  we  have  frequently  observed  the  appearance  described  ;  but  this  investment 
was  nothing  but  the  clear,  often  homogeneous,  calcareous  matter,  gradually  encroaching  on 
the  matrix  and  enclosing  the  corpuscles. 

We  consider,  then,  that  the  process  of  ossification  in  primary  and  secondary  bone  is  iden- 
tical; the  deposition  of  the  calcareous  matter  in  granules  or  as  a  homogeneous  infiltration, 
being  of  no  constancy  or  importance.  In  each  case  the  deposit  takes  place  in  the  matrix, 
and  leaves  spaces  (lacunas)  round  the  corpuscles  (nuclei,  granular  cells).  Subsequently,  the 
canaliculi  are  developed  in  the  matrix  by  a  process  of  resorption  ;  while  their  walls  and 
those  of  the  lacuna?  may  or  may  not  become  chemically  differentiated  from  it.  At  the  same 
time,  the  matrix  may  or  may  not  break  up  into  lamina?  and  "  osteal  cells"  or  granules.  Its 

22 


338  SPECIAL     HISTOLOGY. 

and  ligaments,  and  of  the  vascular  channels;  but  a  more  exten- 
sive new  formation  of  bone,  "whether  periosteal  or  in  the  Haversian 
systems,  together  with  a  simultaneous  and  more  considerable  absorption, 
never  occurs  in  them.  It  was  formerly  believed  that  the  coloration  of 
the  bones  of  adult  animals  by  madder,  proved  that  deposition  of 
bone  substance  continued  to  take  place  even  in  them,  it  being  assumed 
that  newly  forming  osseous  tissue  only  became  colored ;  but  since  it 
has  been  shown,  that  bones  already  formed  were  likewise  colored  by 
the  same  agent,  and  that  colored  bones  in  the  adult  did  not  lose  their 
color  (Brulle  and  Hugueny),  this  view  becomes  untenable.  Whether 
in  the  perfect  bone  a  change,  if  not  of  the  elementary  parts,  but  still  of 
the  atoms,  takes  place,  the  same  external  figure  remaining,  is  another 
question,  for  the  solution  of  which  microscopy  affords  no  facts.  This 
much  is  certain,  that  the  organization  of  bone  is  such,  that  notwithstand- 
ing the  rigidity  of  their  structure,  they  are  in  the  most  general  and  most 
intimate  relation  with  the  nutritive  plasma  of  the  blood.  In  every  situ- 
ation where  the  osseous  tissue  is  in  connection  with  vessels,  as  on  the 
external  surface,  in  the  walls  of  the  medullary  cavities  and  cancelli,  and 
those  of  the  Haversian  canals,  millions  of  closely  crowded  minute  open- 
ings exist.  These  convey  the  blood-plasma,  by  means  of  the  canaliculi, 
into  the  lacunae  lying  nearest  to  the  surfaces  mentioned,  from  which  it  is 
then  conducted  by  wider  canaliculi  to  the  more  distant  lacunae,  as  far  as 
the  outermost  layers  of  the  Haversian  lamellae,  and  those  laminae  of  the 
great  lamellar  system  which  are  most  remote  from  the  vessels.  When 
the  enormous  number  of  the  canaliculi  and  their  multifarious  anastomoses 
are  considered,  it  must  be  allowed  that  no  tissue  in  the  human  body  is 
better  provided  for  in  respect  of  the  distribution  of  the  blood-plasma, 
whilst  in  scarcely  any  other  is  the  direct  conveyance  of  the  fluid  to  the 
most  minute  particles  more  immediately  necessary  than  in  it.  There 
can  be  no  doubt  that  the  fluids,  which  this  "  plasmatic  vascular  system" 
(Lessing)  of  the  bones,  obtains  from  the  bloodvessels,  probably  some- 
what modified  by  the  influence  of  the  nucleus  which,  as  I  have  before 
endeavored  to  show,  is  still  retained  in  every  lacunae,  are  most  indis- 
pensably requisite  for  the  maintenance  of  the  bone ;  for  we  see,  that 
when  the  supply  of  blood  to  a  bone  is  impeded  by  the  destruction  of  the 

variability  in  this  respect  is  neither  more  nor  less  remarkable  than  the  greater  or  less  fibril- 
lation of  the  corresponding  element  of  connective  tissue,  or  than  the  inconstancy  of  the  dis- 
position of  the  cleavage  lines  of  the  same  element  in  striped  muscle. 

As  little  is  any  line  of  demarcation  tto  be  drawn  between  primary  and  secondary  bone 
as  regards  the  tissues  from  which  they  proceed.  Indifferent  tissue,  in  which  calcareous 
matter  is  deposited  at  once,  is  the  basis  of  secondary  bone  ;  an  identical  tissue — in  which 
to  serve  a  temporary  purpose  chondrin  is  deposited,  being  subsequently  withdrawn  and 
replaced  by  calcareous  salts — is  the  basis  of  primary  bone.  And  this  paragraph  may 
serve  as  an  answer  to  the  fourth  question.  If  it  be  correct,  we  cannot  imagine  that  any 
distinction  of  the  bones  into  primary  and  secondary,  upon  the  ground  of  their  develop- 
ment or  non-development  from  cartilage,  can  be  other  than  arbitrary. — TRS/] 


THE     OSSEOUS     SYSTEM.  339 

periosteum  or  of  the  medulla,  by  ligature  of  the  vessels  of  the  limb,  or 
by  obliteration  of  the  periosteal  vessels  by  pressure  from  without 
(aneurism,  tumors),  necrosis  of  the  parts  involved  certainly  ensues,  and 
can  scarcely  in  any  case  be  altogether  obviated  by  the  collateral  circula- 
tion which  actually  exists  also  in  the  bones  (vid.  supra].  On  the  other 
hand  we  are  scarcely,  at  present,  in  a  condition  to  say,  how  the  circula- 
tion of  the  plasma  in  the  bones  is  carried  on,  though  its  movement  to  and 
from  vessels  (perhaps  from  the  arterial,  through  several  lamellar  systems 
to  the  venous)  must  probably  be  assumed  ;  or  what  special  changes  in 
the  course  of  the  nutrition  of  bone  take  place  ;  with  the  latter  in  par- 
ticular we  are  unacquainted,  because  the  chemical  investigation  of  these 
changes,  and  especially  of  the  organic  products  of  decomposition,  is  still 
altogether  imperfect. 

That  the  osseous  tissue  is  in  a  state  of  constant,  and  indeed  very 
energetic  molecular  change,  is  evidenced  not  only  in  its  various  morbid 
conditions,  but  also  by  the  alterations  it  undergoes  in  old  age.  These 
alterations  consist  more  especially  in  the  disappearance  of  entire  por- 
tions of  the  bones,  either  externally  or  internally  ;  of  the  former,  an 
instance  is  afforded,  in  the  entire  removal  of  the  alveolar  processes  of 
the  jaws,  and  the  latter  is  seen  in  the  greater  porosity  and  fragility  of 
every  kind  of  bone,  such  as  the  cylindrical  bones  and  those  of  the 
cranium,  in  the  enlargement  of  the  vascular  openings  (vertebrae,  apo- 
pliyses),  and  in  the  greater  roughness  of  the  surfaces  of  the  bones. 
This  senile  atrophy  of  the  bones  may  also  be  attended  consecutively 
with  an  internal  addition  of  bone-substance,  a  sclerosis,  as  it  is  termed, 
as  in  the  flat  bones  of  the  cranium,  in  consequence  of  which,  in  direct 
contrast  to  the  phenomena  elsewhere  presented  by  senile  bone,  the  diploe 
disappears,  its  cancelli  becoming  filled  up  by  new  osseous  tissue,  whilst 
the  venous  spaces  and  foramina  emissaria  are  obliterated  and  the  entire 
bone  rendered  heavier. 

With  this  abundant  vascular  supply,  and  certainly  not  sluggish  mole- 
cular change,  it  cannot  be  surprising  that  the  bones  should  be  so  richly 
furnished  with  nerves,  the  principal  function  of  which  appears  to  me  to 
consist  in  the  regulation  of  the  conditions  of  the  vascular  system,  by 
their  conveying  to  the  central  organ  (spinal  cord)  through  the  sensitive 
fibres  intelligence  of  the  state  of  the  vessels,  of  the  quantity  of  nutri- 
tive fluid  in  the  bone,  and  probably  also  of  the  modus  of  the  molecular 
change  going  on  in  themselves,  and  by  means  of  the  motor  elements 
their  bringing  a  reflex  influence  from  it,  to  the  arteries  and  veins  which 
are  manifestly  furnished  with  contractile  fibres.  These  unconscious  and 
involuntary  alternations  of  influence  of  sensible  and  motor  filaments, 
are,  as  it  appears  to  me,  the  most  important  phenomena  of  the  innerva- 
tion  in  bones,  as  well  as  in  all  other  organs,  the  nerves  of  which  are 
not  constantly  in  relation  with  the  external  world,  and  make  it  intelli- 
gible, why  it  is,  that  no  organ,  containing  nerves  and  vessels  at  all, 


340  SPECIAL    HISTOLOGY. 

possesses  nerves  of  only  one  kind.  It  is  not,  however,  by  this,  intended 
to  imply  that  the  nerves  of  bones  do  not  convey  conscious  perceptions ; 
it  is  possible  that,  through  them,  we  obtain  a  certain  degree  of  know- 
ledge of  the  processes  going  on  in  the  bones,  of  the  degree  of  fulness 
of  the  vascular  system,  the  mechanical  influences  to  which  they  are 
exposed  from  without  in  the  movements  caused  by  the  action  of  the 
muscles,  the  weight  of  the  body,  or  of  external  objects,  in  lifting 
weights,  mastication,  &c. ;  but  in  any  case  this  knowledge  would  be 
very  indeterminate,  and  the  sensation  excited  not  definitely  localized, 
being  confused  in  the  general  feelings  of  fatigue,  effort,  or  relaxation. 
On  the  other  hand,  it  is  quite  certain  that  the  bones,  in  man,  in  many 
diseases,  and  in  consequence  of  mechanical  injury,  afford  pain,  which 
latter  fact  has  also  been  frequently  noticed  in  animals,  at  all  events, 
upon  irritation  of  the  larger  nervous  trunks  of  the  diaphyses.  In  man 
the  apophyseS)  in  particular,  and  the  vertebral  and  cranial  bones,  seem 
readily  to  become  painful,  which  is  explained  by  the  considerable  number 
of  nerves  immediately  in  the  spongy  substance.  The  compact  substance, 
on  the  other  hand,  might  probably  be  regarded  as  scarcely  obnoxious  to 
pain ;  as,  for  instance,  in  resections,  but  not  so  perhaps  the  periosteum, 
which  less  from  its  own  nerves  than  as  the  vehicle  of  those  of  the  bones 
before  they  enter  their  destination,  must  naturally  be  affected  in  the 
same  way  that  they  are.  Whether  the  nerves  of  the  bones  through 
which,  perhaps,  the  conscious  perceptions,  but  in  any  case  the  painful 
impressions  are  conveyed,  be  identical  with  those  through  which  the 
reflex  actions,  above  referred  to,  are  carried  on,  is  not  determined ;  but, 
looking  at  the  origin  of  most  of  the  bone-nerves  from  the  cerebro-spinal 
nerves,  such  an  opinion  might  perhaps  be  maintained,  it  being  premised 
that  the  connections  of  the  nerves  with  the  brain  are  to  be  regarded  as 
less  intimate  than  in  the  case,  for  instance,  of  the  cutaneous  nerves.  I 
would,  in  addition,  call  attention  to  the  remarkable  occurrence  of  nerves 
in  the  cartilage  of  the  septum  narium  in  the  Calf,  although  I  am  unable 
to  say  anything  more  with  respect  to  their  nature  than  with  regard  to 
that  of  the  nerves  of  bone. 

On  the  subject  of  the  numerous  pathological  changes  which  occur  in 
the  bones,  only  some  brief  remarks  can  here  be  made.  Fractures  readily 
unite,  under  but  moderately  favorable  circumstances,  by  true  bone-sub- 
stance, which,  in  the  cylindrical  bones  of  animals  is  preceded  by  the 
formation  of  a  true  cartilage,  a  fact  of  which  I  and  others  are  satisfied ; 
whilst,  according  to  Paget,  this  rarely  appears  to  be  the  case  in  man. 
In  the  spongy  bones,  in  fractures  within  the  articular  capsules,  and 
under  unfavorable  circumstances,  the  fractured  ends  frequently  unite 
merely  by  a  fibrous  callus,  a  sort  of  articulation  being  formed  between 
them.  After  loss  of  substance  the  osseous  tissue  is  readily  regene- 
rated ;  and  it  is  the  periosteum  especially,  which,  in  this  case,  as  in 


THE  OSSEOUS  SYSTEM.  341 

the  growth  of  a  bone  in  thickness,  plays  the  principal  part  in  the  resto- 
ration ;  of  course  by  means  of  the  exudation  poured  out  from  its  vessels. 
In  animals,  entire  bones  of  the  extremities,  and  ribs  are  regenerated, 
pretty  nearly  in  their  original  figure,  not  only  when  the  periosteum  has 
been  saved,  of  which  many  examples  are  exhibited  in  Heine's  collec- 
tion in  Wurzburg,  but  even  after  entire  excision  with  the  periosteum,  a 
rudiment  of  the  bone  is  reproduced  (Heine).  In  man  also,  a  good  many 
instances  have  been  afforded  of  the  reproduction  of  entire  bones,  such 
as  the  lower  jaw,  the  ribs,  the  scapula  (Chopart) ;  and  the  cases  of 
isolated, — in  some  instances  large,  portions  of  bone  being  so  regene- 
rated are  very  numerous.  It  is  especially  the  diaphyses,  which  are 
readily  replaced,  when  they  have  been  lost  in  one  way  or  another,  less 
frequently  the  spongy  bones  and  spongy  parts  of  bones,  and  those  of 
the  cranium ;  in  the  latter,  however,  openings  made  by  the  trephine 
are  in  many  cases  filled  up,  instead  of  fibrous  membrane,  with  isolated 
patches  of  bone,  or  even  with  an  entire  piece  of  bone  ;  in  fact,  trephined 
portions  of  bone  have  united  exactly  in  the  same  way  as  has  been  ob- 
served to  take  place  with  portions  of  bone  half  cut  off  (Pauli).  Hyper- 
trophy of  bone  assumes  the  most  various  forms,  all  of  which  may  be 
reduced  under  two  principal  types :  1,  deposits  on  the  surface,  or  ex- 
ternal Iiyperostoses,  which  are  formed  chiefly  from  the  periosteum  ;  and 
2,  internal  or  scleroses,  which  consist  in  the  filling  up  of  the  medullary 
cavities  and  Haversian  canals  with  new  bone,  and  these  two  forms  may 
occur  either  separately  or  combined.  The  former  takes  place  in  inflam- 
mations of  the  periosteum,  either  idiopathic  or  in  connection  with  cancer, 
arthritis,  syphilis,  &c.,  the  latter  not  only  consecutively  in  old  age,  but 
also  in  rachitis,  osteomalacia,  and  syphilis.  With  respect  to  the  micro- 
scopic conditions  of  these  growths,  Virchow  deserves  the  credit  of  hav- 
ing distinctly  indicated  ("Archiv,  f.  Pathol.  Anat.  I.,"  p.  135),  that 
the  bony  growths  or  osteophytes  on  the  cranium  are  formed  by  a  direct 
ossification  of  connective  tissue  without  any  preliminary  development 
of  cartilage,  which  is  also  undoubtedly  the  case  in  the  filling  up  of  the 
losses  of  substance  in  the  cranium,  in  regeneration  proceeding  from 
the  periosteum,  and  in  most  cases  of  sclerosis.  The  newly  formed  os- 
seous substance  is  sometimes  like  the  normal  (many  exostoses),  some- 
times more  dense,  with  small  vascular  spaces  and  large  irregular  lacunae. 
Atrophy  of  the  bones  is  shown  in  their  disappearance  in  totality  in 
consequence  of  chronic  diseases,  paralysis,  anchylosis  ;  or  in  rarefaction 
of  the  osseous  tissue  analogous  to  senile  atrophy,  in  syphilis,  lepra, 
mercurial  cachexy,  paralysis,  &c.  Death  of  bone  (necrosis)  is  observed 
in  cases  where  the  periosteum  has  been  destroyed ;  in  inflammations  of 
that  membrane  and  of  the  bone,  &c.,  for  the  most  part  attended  with 
an  excessive  growth  of  the  remaining  sound  parts.*  Peculiar  morbid 
conditions  exist  in  osteomalacia  and  rachitis,  but  in  neither  of  these 

*  [In  necrosed  bone,  the  bone-corpuscles  are  generally  but  little  changed;  the  inter-cor- 
puscular structure  is  granular  and  of  a  dark  color. — DaC.] 


342  SPECIAL     HISTOLOGY. 

diseases  have  microscopical  researches  afforded  anything  worth  men- 
tion here,  except  what  has  been  made  known  by  H.  Meyer  and  myself 
(11.  cc.)  with  respect  to  ossification  in  rachitis.  In  this  case  I  have 
found :  1,  that  in  the  disproportionately  large  epiphysal  cartilages, 
the  layer  of  the  ossifying  cartilage-cells  (those  disposed  in  rows),  mea- 
sured, instead  of  J,  2  to  5  lines  ;  2,  that  the  ossifying  border  is  toothed, 
owing  to  the  circumstance  that  the  cartilage  and  bone  interlace  in 
various  ways ;  3,  and  lastly,  that  in  decidedly  rachitic  bones,  the  de- 
position of  calcareous  granular  particles  is  wanting,  and  the  cartilage- 
cells  almost  invariably,  shortly  before  the  matrix,  and  also  without 
any  appearance  of  calcareous  granules,  are  metamorphosed  into  bone- 
cells,  on  which  account  the  formation  of  the  latter  can,  in  no  case,  be 
so  well  studied  as  in  these  bones  (vid.  supra}.  Accidental  cartilage- 
and  bone-formations  are  very  frequent.  The  former  tissue  is  met  with, 
notwithstanding  that  it  is  incapable  of  regeneration,  and  that  wounds 
of  it  heal  only  with  a  fibrous  tissue,  more  rarely  with  bone  (ribs),  in 
very  many  organs  (bones,  mammary  glands,  parotid,  testicles,  lungs, 
and  skin)  forming  what  is  termed  enchondroma  ;  moreover,  as  a  new 
covering  on  the  osseous  growths,  at  the  border  of  the  worn  articular 
ends  of  bones  (Ecker).  The  latter  is  seen  in  ossifications  of  the  per- 
manent cartilages  (ribs,  larynx,  epiglottis,  very  rarely)  of  tendons 
(exercir-knochen,  for  example),  in  the  dura  mater  and  arachnoid  (Mies- 
cher,  Rokitansky),  in  the  eye  (Valentin),  in  the  ovary,  in  fibrous 
membranes  (membrana  obturatoria),  in  enchondroma,  in  fibrous  and 
carcinornatous  growths,  and  in  the  lungs  (Mohr's  cysts  containing  hair). 
Even  in  these  cases  the  osseous  tissue  does  not  essentially  differ  from  the 
normal,  and  it  is  formed,  sometimes  from  a  cartilaginous,  sometimes, 
and  in  fact  mostly,  from  a  soft  blastema  (Yirchow,  1.  c.  p.  137). 

In  investigations  relating  to  the  structure  of  bone,  good  sections  are, 
above  all  things,  requisite.  With  a  fine  saw,  thin  slices  are  made,  which 
are  ground  with  water  upon  a  smooth  stone  with  the  finger,  or  with  a 
second  smaller  stone,  for  some  minutes  (5-10),  until  they  are  rendered 
uniformly  transparent.  The  sections  are  then  cleaned,  and  (the  fat,  if 
they  contain  any,  being  removed  by  ether)  may  be  employed,  being 
wetted  with  water,  for  the  study  of  the  Haversian  canals  and  disposition 
of  the  lacunae  ;  and  with  turpentine,  for  that  of  the  various  lamellar 
systems.  The  lacunae  and  their  prolongations,  which,  in  sections,  are 
dark  and  very  distinct,  owing  to  their  being  filled  with  air,  are  com- 
pletely filled  by  thin  turpentine,  so  that  the  latter  in  great  part,  and 
also  the  former,  are  very  frequently  rendered  invisible ;  the  same  thing 
happens  in  water  and  thicker  turpentine,  though  less  rapidly,  whence, 
before  these  agents  have  produced  their  effect  throughout,  many  of  the 
lacunae  and  canaliculi  are  beautifully  shown.  If  it  be  desired  to  pre- 
serve the  lacunae  and  canaliculi  permanently  visible,  it  is  best  to  polish 
a  thin  section,  by  rubbing  it  between  two  glass  plates.  It  may  then  be 


THE     OSSEOUS     SYSTEM.  343 

examined  without  the  addition  of  fluid,  and  presents  as  perfect  figures 
as  those  represented  in  Figs.  115-117.  The  grinding  of  the  bone  with 
oil  is  not  to  be  recommended,  because  the  lacunae,  then  become  filled 
with  the  oil,  and  even  after  thorough  treatment  with  ether  can  seldom 
be  rendered  distinct.  Next  to  sections  of  bone,  the  investigation  of  the 
bone-cartilage  is  the  most  worth  while.  This  tissue  is  prepared  by  the 
treating  of  bone  in  the  cold,  with  diluted  hydrochloric  acid  (1  part  acid, 
10-20  water),  until  the  fluid,  which  is  to  be  frequently  changed,  no 
longer  affords  any  precipitate  with  ammonia  ;  for  which  purpose,  in 
small  fragments  of  bone,  some  hours,  in  entire  bones  several  days,  are 
required.  From  the  cartilage  thus  obtained,  sections  are  now  to  be 
made  with  a  sharp  knife  in  all  directions,  suitable  chiefly  for  the  study 
of  the  Haversian  canals  and  lamellae,  which  may  even  be  raised  from 
the  surface.  The  lacunae,  also,  are  still  visible ;  their  prolongations  or 
canaliculi  appear  as  fine  streaks,  and  their  nuclei  are  seen  without  fur- 
ther trouble,  especially  also  after  treatment  with  potassa,  or  in  cartilage 
which  has  been  half  dissolved  by  boiling  in  water.  After  long  macera- 
tion in  hydrochloric  acid,  the  lacunae  even  become  isolated,  as  stellate 
bodies  with  delicate  walls,  or,  in  the  cementum  of  the  horse's  tooth,  as 
structures  corresponding  to  the  former  cartilage-cells.  After  long 
softening  of  bone-cartilage  in  water,  the  lamellar  systems  of  the  Haver- 
sian canals  become  more  or  less  completely  separated,  presenting  the 
appearance  of  short,  coarse  fibres  among  the  larger  lamellae  (Gagliardi's 
claviculi).  If  bone  be  exposed  in  a  platinum  capsule  to  a  strong  white 
heat,  the  organic  parts  burn  away,  the  bone  becoming  at  first  black, 
and  ultimately  perfectly  white  ;  and,  if  due  care  be  taken,  the  earthy 
constituents  are  left,  completely  retaining  the  original  figure  of  the 
bone.  Preparations  of  this  kind  are  proper  for  the  study  of  the  lami- 
nated structure  of  the  compact  substance  and  of  the  lamellar  systems 
of  the  Haversian  canals,  which,  in  this  case  also,  sometimes  appear 
isolated,  as  in  macerated  bone.  For  the  microscopic  examination  of 
the  inorganic  constituents  of  bone,  sections  are  subjected  to  heat  on 
platinum  foil,  but  they  must  be  very  thin,  as  they  afterwards  become 
more  opaque,  and,  on  account  of  their  fragility,  except  in  minute  frag- 
ments, do  not  admit  of  being  ground  thinner  (Bruns) ;  or  sections  may 
be  boiled  in  caustic  potassa.  In  either  case,  the  lacunae  are  seen  dis- 
tinct, and  empty,  with  the  beginnings  of  the  canaliculi,  in  a  finely 
granular  matrix.  The  natural  condition  of  the  lacunae  is  readily  seen 
in  perfectly  recent  bone,  in  thin  sections  or  laminae ;  as,  for  instance, 
in  many  parts  of  the  bones  of  the  face.  In  recent  bone,  also,  the 
vessels  may  be  studied,  naturally  injected,  and  with  the  microscope, 
being  thus,  far  fitter  for  the  purpose  than  when  injections,  which  often 
fail,  have  been  practised,  and  for  the  closer  examination  of  which,  more- 
over, the  bones  must  afterwards  be  macerated  in  hydrochloric  acid,  and 
preserved  in  oil  of  turpentine.  The  nerves  of  the  bones  may  be  seen 


344  SPECIAL    HISTOLOGY. 

by  the  naked  eye,  on  the  nutritious  arteries  of  the  larger  cylindrical 
bones,  and  readily,  by  the  microscope,  on  the  smaller  vessels  ;  those  of 
the  periosteum  must  be  studied  after  the  membrane  has  been  rendered 
transparent  by  caustic  soda  or  acetic  acid.  The  costal  and  articular 
cartilages  are  the  most  suitable  for  the  study  of  cartilage,  the  membranes 
of  the  cartilage-cells  being  evident,  sometimes  without  any  addition, 
sometimes  after  that  of  acetic  acid  or  soda,  which  render  the  matrix 
transparent.  The  development  of  bone  may  be  investigated  in  a  cylin- 
drical bone,  and  in  the  parietal  bone  ;  the  formation  of  the  lacunae,  in 
specie,  in  rachitic  bones,  and  in  the  osseous  surfaces  of  the  symphyses 

and  synclwndroses. 

* 

Literature. — Besides  the  works  cited  in  §§  22  and  25,  are  to  be 
noticed,  F.  Bidder,  "  Zur  Histogenese  der  Knochen"  ("  On  the  Histo- 
genesis  of  Bone"),  in  Muller's  "Arch."  1849,  p.  292;  E.  v.  Bibra, 
"  Chemische  Untersuchungen  Ub.  die  Knochen  und  Zahne  des  Menschen 
und  der  Wirbelthiere"  ("Chemical  Researches  on  the  Bones  and  Teeth 
of  Man  and  the  Vertebrata") ;  Schweinfurt,  1844;  Votsch,  "Die  Hei- 
lung  der  Knochenbriiche  per  primam  intentionem"  ("  Union  of  Frac- 
tures, &c.") ;  Heidelberg,  1847;  Kolliker,  "  Ueber  Verknocherung  bei 
Rachitis,  u.  Ub.  den  Bau  der  Synovialhaute"  ("  On  Ossification  in 
Rachitis,  and  on  the  Structure  of  the  Synovia!  Membranes");  "Mitth. 
der  Zurich,  nat.  Gesellsch.,"  1847,  p.  93;  Rokitansky,  "Beitrage 
zur  Kenntniss  des  Verknocherungsprocesses"  ("  Contributions  to  a 
knowledge  of  the  process  of  Ossification"),  in  the  "  Zeitschrift  der 
Wiener  Aerzte,"  1848,  p.  1 ;  A.  Krukenberg,  "  Zur  Lehre  vom 
Rohrensysteme  der  Zahne  und  Knochen"  ("  On  the  Tubular  Sys- 
tem of  the  Teeth  and  Bones"),  in  Muller's  "  Archiv.,"  1849,  p.  403; 
H.  Meyer,  "Der  Knorpel  u.  seine  Verknocherung"  ("Cartilage  and  its 
Ossification"),  in  Mull.  "Archiv.,"  1849,  p.  292;  Virchow,  in  "Ver- 
handl.  der  Wurzb.  phys.  med.  Ges.,"  vol.  i.  No.  13;  Robin,  "  Observa- 
tions sur  le  developpement  de  la  substance  et  du  tissu  des  os,"  in  "  Me'm. 
de  la  Societd  de  Biologie,"  1850,  p.  179;  Brulle  and  Hugwe'ny,  "Ex- 
pediences sur  la  developpement  des  os  dans  les  mammiferes  et  les 
oiseaux,  Ann.  d.  Sc.  Nat.,"  1845,  Nov.  p.  283  ;  Flourens,  in  "Ann.  d. 
Sc.  Nat.,"  2  serie  XIII.  103,  ibid.  XV.  p.  202,  ibid.  1845  ;  Aout,  p. 
105,  and  D^c.  p.  358  ;  "  Compt.  rend.,"  T.  XIX.  p.  621 ;  all  his  ob- 
servations collected  in  "  Th^orie  exp^rimentale  de  la  formation  des  os," 
Paris,  1847-8,  avec  7  pi. ;  Beck,  "  Abb.  Ub.  ein.  in  Knochen  verlau- 
fende  Nerven,"  Freiburg,  1846;  Kolliker,  "Ueber  die  Nerven  der 
Knocken"  ("On  the  Nerves  of  Bone"),  in  Wurzb.  "Verhandl.,"  I.; 
Luschka,  "Die  Nerven  in  der  harten  Hirnhaut"  ("The  Nerves  in  the 
Dura  mater"),  Tubingen,  1850:  and  "  Die  Nerven  des  Wirbelcanales 
und  der  Wirbel"  ("Nerves  of  the  vertebral  Canal  and  of  the  Verte- 
brae"), Tub.  1850. 


THE    NERVOUS    SYSTEM.  345 


OF  THE  NERVOUS  SYSTEM. 

§  109.  The  nervous  system,  regarded  in  the  more  general  anatomical 
sense,  constitutes  a  connected  whole,  consisting  of  two  principal  masses — 
the  spinal  cord  and  brain,  and  of  numerous  cords — nerves — extending 
from  them  to  almost  all  the  organs  of  the  body.  The  two  former — or 
the  central  nervous  system,  the  central  organs,  are  to  be  regarded  not 
merely  from  an  anatomical  point  of  view,  as  affording  origin  to  the 
nerves,  but,  also,  in  a  physiological  sense,  as  exciters  of  the  movements, 
and  seat  of  the  sensations,  as  well  as  of  the  mental  or  psychical  actions, 
and  consequently  as  belonging  to  a  higher  or  governing  order  of  parts, 
whilst  to  the  latter  must  be  ascribed  more  of  a  ministerial  office — the 
communication  of  the  contractions  and  sensations.  This  mode  of  regard- 
ing the  two  divisions  of  the  nervous  system,  however,  is  only  partially 
correct,  because,  in  the  first  place,  in  the  central  organs,  as  in  the 
nerves,  very  many  subordinate  parts  exist ;  and,  secondly,  because  in 
the  peripheral  nervous  system,  the  so-termed  ganglia,  physiologically 
and  anatomically,  represent  central  organs.  The  older  division  also  of 
the  nervous  system  into  animal  and  vegetative,  after  the  observations  of 
recent  times,  can  no  longer  be  maintained  ;  and  the  latter, — the  sym- 
pathetic or  ganglionic  nervous  system,  can  only  be  regarded  as  a  por- 
tion of  the  peripheral  system,  though  undoubtedly  peculiarly  consti- 
tuted. 

ELEMENTS  OF  THE  NERVOUS  SYSTEM. 

§  110.  The  nerve-tubes  or  fibres  (Figs.  137-139),  also  termed,  primi- 
tive tubes,  or  primitive  fibres  of  the  nerves,  are  soft,  fine,  cylindrical 
filaments  having  a  diameter  of  0-0005-0-01  of  a  line ;  they  constitute 
the  principal  part  of  the  nerves  and  of  the  white  substance  of  the  central 
organs,  although  they  are  not  wanting  in  the  greater  part  of  the  gray 
substance  of  the  latter  and  in  the  ganglia.  When  examined  in  the  re- 
cent state  and  by  transmitted  light  (Fig.  137)  they  appear  as  clear  as 
water,  transparent,  and  with  simple  dark  contours ;  by  reflected  light — 
glistening,  opaline,  like  fat,  in  larger  quantities  together,  white,  and  for 
the  most  part  their  appearance  does  not  indicate  that  they  are  composed 
of  different  constituent  parts.  But  it  is  readily  seen  upon  the  applica- 
tion of  various  methods,  that  they  consist  of  three,  entirely  distinct, 
component  structures,  viz. :  of  a  delicate  coat,  and  a  viscid  fluid,  in  the 
centre  of  which  is  a  soft  but  elastic  fibre.  The  coat,  or  sheath  of  the 
nerve-fibres  (limitary  membrane,  Valentin)  (Fig.  139,  1,  2,  3,  4,  a)  is 
an  excessively  delicate,  flexible,  but  elastic,  perfectly  structureless,  and 
transparent  membrane,  which,  in  quite  unaltered  nerve-fibres,  except  in 
certain  situations,  is  altogether  invisible.  But  on  the  application  of 


346 


SPECIAL     HISTOLOGY. 


suitable  reagents,  at  least  in  the  thicker  fibres  of  the  nerves  and  of  the 
central  organs,  it  comes  readily  into  view,  corresponding  in  its  chemical 
characters,  in  all  essential  particulars,  with  the  sarcolemma  of  the  mus- 
cular fibres.  In  the  finest  fibres  of  the  peripheral,  as  well  as  of  the 
central  nervous  system,  the  existence  of  this  membrane  has  not  yet  been 


Fig.  138. 


demonstrated,  and  it  must  consequently  for  the  present  be  left  undecided 
whether  these  fibres  possess  sheaths  or  not. 

Within  the  structureless  sheath,  lies  the  nerve-medulla,  or  pulp, 
("medullary  sheath,"  Rosenthal  and  Purkinje,  "white  substance," 
Schwann),  (Fig.  137,  3,  6,  Fig.  139,  3,  4,  b)  in  the  form  of  a  cylin- 
drical tube,  closely  and  exactly  surrounding  the  central  fibre.  In  the 
recent  nerve-fibre  this  substance  is  perfectly  homogeneous,  fluid,  but 
viscid  like  a  thick  oil,  and,  according  to  the  light  by  which  it  may  be 

FiG.  137. — Nerve-fibres,  magnified  350  diameters.  1,  from  the  Dog  and  Rabbit,  in  their 
natural  condition;  a,  fine;  6,  of  medium  thickness;  c,  coarse  fibre  from  the  peripheral 
nerves :  2,  from  the  Frog,  with  the  addition  of  serum  ;  a,  drop  of  the  contents  expressed  ;  6, 
axis-cylinder  within  the  drop,  continued  into  the  tube :  3,  from  the  spinal  cord  of  Man,  re- 
cent, with  serum  added;  a,  sheath;  6,  medullary  sheath  with  double  contour;  c,  axis-cylin- 
der :  4,  double-contoured  fibre  from  the  fourth  ventricle  in  Man  ;  the  axis-cylinder,  a,  pro- 
jecting and  visible  within  the  fibre  :  5,  two  isolated  axis-cylinders  from  the  cord,  one  undu- 
lated, the  other  of  unequal  thickness,  with  some  medullary  substance  attached  to  it. 

FJG.  138. — Nerve-tubes  of  Man,  magnified  300  diameters:  four  fine,  two  of  which  are 
varicose ;  one  of  medium  size  with  simple  contours ;  and  four  thick,  two  of  which  have 
double  contours,  and  two,  grumous  contents. 


THE     NERVOUS     SYSTEM.  347 

viewed,  transparent  and  clear,  or  whitish  and  pearly,  and  it  is  obviously 
to  it  that  the  peculiar  glistening  appearance  of  the  nerves  is  due.  The 
nerve  pulp  is  rapidly  and  invariably  altered  by  the  application  of  cold 
water,  of  most  acids,  and  of  many  other  reagents,  the  change  consist- 
ing principally  in  a  coagulation  of  it,  which  takes  place  gradually  from 
without  to  within,  sometimes  involving  the  entire  thickness,  sometimes 
only  its  outermost  layer.  In  the  latter  case,  are  produced  the  well- 
known  nerve-fibres  with  double  contour  lines  (Fig.  137,  2,  3,  4),  or  in 
which  the  medullary  sheath  is,  externally,  coagulated  to  a  greater  or  less 
extent,  remaining  fluid  internally ;  in  the  former  case,  with  the  contents 
apparently  wholly  grumous  and  opaque  (Fig.  138).  The  coagulated  nerve- 
medulla,  in  fact,  seldom  appears  homogeneous,  but  most  generally  gru- 
mous, granular,  and  as  if  composed  of  separate,  irregular,  larger  and 
smaller  masses,  and,  upon  the  application  of  acetic  acid,  as  if  formed  of 
minute,  separate,  or  reticularly  united  rods.  The  nerve-pulp  is  also 
altered  very  readily  by  pressure.  It  sometimes  escapes  from  the  ends 
of  the  tubes,  or  from  hernial  protrusions  or  ruptures  of  the  sheath,  form- 
ing larger  or  smaller  drops  of  every  imaginable  shape,  regularly  spherical, 
clavate,  fusiform,  cylindrical,  filamentary,  or  of  the  most  bizarre  figures, 
which  likewise  coagulate  either  on  the  surface  merely,  or  throughout, 
and  thence,  like  the  nerves,  appear  with  a  double  contour,  or  half  or 
wholly  grumous.  But,  within  the  fibres  also,  its  structural  conditions 
alter,  for,  instead  of  being  continued  through  them  as  before, — as  a 
cylinder  of  uniform  size, — it  accumulates  in  places  into  larger  masses. 
In  this  way  are  produced  the  frequently  described,  varicose  nerve-fibres 
(Fig.  138),  in  which  the  medullary  sheath  presents  sometimes,  minute 
moniliform  enlargements,  sometimes,  various  sized,  irregularly  distri- 
buted nodosities,  or  even,  in  places,  complete  interruptions.  All  these 
forms,  in  which  the  sheath  frequently  participates,  but  in  which  the  cen- 
tral fibre  takes  no  part,  arise  artificially,  and  are  developed  most  readily 
in  the  finer  fibres  with  more  delicate  sheaths,  such  as  are  found  in  the 
central  organs. 

The  central  or  axis-fibre  of  the  nerve-tubes  ("primitive  band,"  Re- 
mak,  cylinder  axis,  Purkinje,  Fig.  137,  2,  3,  4,  5 ;  139,  1),  is  a  cylin- 
drical or  slightly  flattened  filament,  which,  in  entire  and  unaltered  nerve- 
fibres,  is  as  little  recognizable  as  the  sheath,  being  surrounded  by  the  pulp, 
and  possessing  the  same  refractive  power,  whilst  it  comes  readily  into 
view  when  the  fibre  is  torn  or  treated  with  various  reagents ;  and  it  may 
thus  be  recognized  as  a  constant  structure,  sometimes  in  the  interior 
of  the  fibre,  arid  sometimes  isolated.  Under  natural  circumstances  it 
is  pale,  most  generally  homogeneous,  more  rarely,  finely  granular  or 
striated,  bordered  by  straight  or  occasionally  by  irregular,  pale  contour 
lines,  and  it  is,  generally,  everywhere  of  uniform  thickness :  it  is  distin- 
guished from  the  medullary  sheath,  especially  by  the  circumstance,  that 


348 


SPECIAL    HISTOLOGY. 


Fig.  139. 


although  soft  and  flexible,  it  is  still,  not  fluid  and  viscous,  but  elastic 
and  solid,  something  like  coagulated  albumen,  with  which  it  also  ap- 
pears to  agree  in  most  of  its  chemical 
characters.  This  axis-cylinder  exists 
in  all  nerve-fibres  without  exception, 
even  in  the  finest,  and  invariably  pre- 
i  sents  the  same  characters,  except 
only,  that  it  is  sometimes  thicker, 
sometimes  more  slender,  according 
to  the  size  of  the  fibre  itself. 

The  nerve-fibres,  in  which  the 
three  structures  above  described  can 
be  distinguished,  and  which  we  would 
designate  as  the  medullated  or  dark- 
bordered,  constitute,  it  is  true,  the 
greater  proportion  of  those  existing 

in  the  body,  but  besides  these  there  are  still  some  forms  requiring 
more  particular  description.  These  are  the  nerve-fibres  in  which  there 
exists  no  trace  of  a  medullary  sheath  ;  whilst  they  have  an  outer  sheath 
and  contents,  sometimes  identical  with  the  axis-fibre  of  the  other  kind 
of  nerves,  sometimes  similar  but  more  clear.  These  non-medullated 
nerve-tubes  occur,  in  the  first  place,  as  continuations  to  the  other  sort, 
where  the  latter  are  in  connection  with  nerve-cells  ;  and  also  as  more 
elongated,  independent  fibres,  representing  the  so-termed  processes  of 
the  nerve-cells  of  authors ;  and  lastly,  at  the  terminations  of  the  dark- 
bordered  nerves.  They  may  again  be  arranged  in  several  subdivisions, 
distinguished  respectively  by  their  having  or  not  having  nuclei,  and 
more  or  less  transparent,  more  or  less  consistent  contents.  It  must 
also  be  added,  that  the  dark-bordered  fibres  differ  extremely — partly  in 
respect  to  the  delicacy  or  firmness  of  their  structure,  and  partly  in  their 
diameter,  which  varies  from  0-0005  to  0-01  of  a  line,  or  more,  so  that 
they  may  be  distinguished  into  fine  and  coarse,  delicate  or  firm  fibres  ; 
from  which  it  is  evident  that  the  nerve-fibres,  notwithstanding  their 
general  tubular  character,  still  differ  pretty  widely  from  each  other  in 
various  respects. 

The  tunic  or  sheath  of  the  nerve-fibres,  discovered  by  Schwann,  in 
most  nerves  is  brought  into  view  with  some  difficulty.     It  is  only  rarely, 

FIG.  139. — Nerve-fibres,  magnified  350  diameters.  1,  from  the  Frog,  boiled  with  alco- 
hol and  acetic  acid  ;  a,  sheath ;  6,  axis-cylinder  ;  c,  crystals  (fat  T)  :  2,  isolated  sheath  of  a 
Frog's  nerve,  boiled  with  soda :  3,  from  the  floor  of  the  fourth  ventricle  in  Man,  after  treat- 
ment with  soda ;  o,  sheath  ;  6,  medulla  flowing  out  in  drops,  the  axis-cylinder  is  wanting 
(having  been  drawn  out  in  the  preparation),  and  the  pale  streak  is  medulla :  4,  from  the 
root  of  the  n.  abducens  of  Man,  treated  with  soda  ;  a,  sheath ;  b,  medulla,  axis-cylinder  not 
visible. 


THE     NERVOUS    SYSTEM.  349 

as  in  the  roots  of  certain  cerebral  nerves  (those  of  the  muscles  of  the 
eye  for  instance),  and  of  the  spinal  nerves  that  it  appears  distinct  from 
the  contents ;  its  presence  however  is,  with  certainty,  and  readily  de- 
monstrated by  the  aid  of  chemical  reagents.  When  the  nerves  are 
boiled  in  absolute  alcohol,  soon  after  the  removal  of  a  considerable 
part  of  the  fatty  matter  of  the  pulp,  the  sheaths  become  tolerably  dis- 
tinct, as  dark  boundary  lines ;  and  they  are  rendered  remarkably  and 
beautifully  so  by  a  short  boiling  in  acetic  acid,  during  which,  the 
remaining  contents  of  the  nerve-sheaths,  with  the  exception  of  the 
central  fibre,  escape  from  them,  whilst  at  the  same  time  numerous  (fat) 
crystals  (Fig.  139,  1)  are  formed.  When  boiled  in  alcohol  and  treated 
in  the  cold  with  caustic  soda,  the  nerve-fibres  also  exhibit  the  sheaths 
very  beautifully,  as  pale,  frequently  undulating  contours  of  the  color- 
less, remaining  contents  ;  and  when  such  fibres  are  boiled  for  a  moment 
in  caustic  soda,  numerous,  elongated  fragments  of  perfectly  empty, 
somewhat  swollen  nerve-sheaths,  are  detached,  which,  from  their  deli- 
cacy, present  a  striking  resemblance  to  the  empty  tubules  of  the  mem- 
brana  propria,  of  the  tubuli  uriniferi  (Fig.  139,  2).  The  sheaths,  how- 
ever, are  rendered  most  distinct  by  means  of  fuming  nitric  acid  and  the 
subsequent  addition  of  caustic  potassa.  In  this  case  the  fatty  matter 
of  the  medullary  sheath  escapes  from  the  tubes  in  the  form  of  color- 
less drops,  the  axis  cylinder  is  dissolved,  and  the  yellow  sheaths  are 
left  empty,  dilated  and  with  swollen  walls  of  0-0004-0-0008  of  a  line 
in  thickness.  In  nerves  treated  with  corrosive  sublimate,  according  to 
Czermaak("  Zeitsch.  f.  wissensch.  Zoologie,"1850),  the  sheaths  are,  also, 
often  very  prettily  shown.  It  has  not  yet  been  determined  whether  the 
finest  nerve-fibres  in  the  central  organs,  and  in  the  peripheral  nerves 
(under  0-001  of  a  line)  possess  a  structureless  sheath.  Analogy  with 
the  coarser  fibres  is  in  favor  of  the  existence  of  such  sheaths,  but  on 
the  other  hand  there  are  some  facts  which  would  seem  to  indicate  that 
there  are  also,  sheathless  primitive  nerve-fibres,  both  of  the  medullated 
and  of  the  non-medullated  kinds.  I  have  already  (in  my  "  Microscopical 
Anatomy,"  II.  1,  396)  remarked,  that  according  to  my  observations  in  the 
Tadpole,  several  dark-bordered  fibres  are  developed  in  one  and  the 
same  structureless  sheath  formed  by  the  coalescence  of  cell-membranes; 
and  that  a  similar  thing  (at  least  from  R.  Wagner's  figures)  occurs  in 
the  electric  organ  of  the  Torpedo :  in  which  cases  special  tunics  can 
scarcely  be  supposed  to  exist  around  each  separate  fibre.  And,  quite 
recently,  Stannius  ("  Gbtt.  Nachr.,"  1850)  has  found,  in  Petromyzon, 
that  the  nerve-fibres  of  the  central  organs  possess  neither  membra- 
nous sheath  nor  pulp,  and  are,  as  it  may  be  expressed,  nothing  more 
than  free  axis-fibres.  When  to  this,  it  is  also  added,  that  the  impossi- 
bility of  demonstrating  membranes,  by  no  means  certainly  proves  their 
non-existence,  still,  the  facts  stated  are  worthy  of  all  consideration, 


350  SPECIAL    HISTOLOGY. 

and  we  must,  in  this  question,  for  the  present,  abstain  from  all  conclu- 
sions drawn  from  analogy. 

[Of  the  chemical  nature  of  the  sheath  of  the  nerve-fibres  but 
little  is  known.  When  boiled  for  about  five  minutes  in  concentra- 
ted acetic  acid,  it  is  not  dissolved,  scarcely  changed.  It  resists 
boiling  in  caustic  soda  for  a  short  time  without  altering,  except  that  it 
swells  up  a  little  ;  longer  boiling  dissolves  it.  It  remains  unchanged  in 
water,  alcohol  or  ether,  even  when  boiled.  Pettenkoffer's  test  for 
bilin  (sugar  and  sulphuric  acid)  which  reddens  protein  and  elein,  but 
according  to  Schulze,  neither  collagenous  substances  nor  elastic  tissue, 
does  not  color  the  nerve-sheath.  Yet  its  action  cannot  be  ascertained 
with  the  most  desirable  accuracy,  since  the  nerve-medulla  is  simultane- 
ously reddened.  Sulphuric  acid  and  potaasa  render  the  nerve-sheath 
yellow  (xantho-proteinic  acid),  producing  the  same  effect  as  they  do,  ac- 
cording to  Paulsen,  on  elastic  tissue.  Hence  it  seems  as  if  the  nerve- 
sheath  agrees  in  composition  with  elastic  tissue,  except  that  it  is  evidently 
less  insoluble  in  alkalies.  From  Kolliker's  Micr.  Anat.  II.  1. — DaC.] 

In  order  to  see  the  medullary  sheath  or  nerve-pulp  in  its  normal  con- 
dition, a  nerve  of  an  animal  just  killed,  without  any  addition,  must  be 
quickly  brought  under  the  microscope  ;  in  which  case  some  isolated  fibres 
will  always  be  seen  quite  unchanged,  although,  as  the  nerve  dries,  they 
are  very  rapidly  altered.  Besides  this  method,  I  would  also  recommend 
the  examination  of  the  nerves  in  the  transparent  parts  of  animals,  either 
alive  or  just  killed  (nictitating  membrane,  mucous  membrane  of  the 
Frog,  tail  of  Tadpole,  &c.),  the  observing  of  them  on  warmed  pieces  of 
glass  (Stark.),  and  after  treatment  with  chromic  acid,  which  frequently 
preserves,  particularly  the  cerebral  fibres,  quite  uninjured.  The  nerve- 
pulp  or  medulla  is  obviously  a  viscid,  fluid,  extensible,  glutinous  sub- 
stance, to  be  compared  in  point  of  consistence  with  thick  oil  of  turpen- 
tine, and  which  under  pressure  assumes  all  possible  figures,  appearing 
in  the  form  of  globules,  filaments,  and  membranous  masses,  of  very  dif- 
ferent aspects,  with  pale  or  dark  borders,  and  opaque  or  clear.  In 
chemical  composition  it  consists  principally  of  fatty  matter. 

The  central  filament  of  the  nerve-fibres,  which  was  perhaps  seen  as 
early  as  by  Fontana,  and  with  which  we  have  become  better  acquainted 
under  the  name  of  "  primitive  band"  given  to  it  by  Remak,  or  "  cylinder- 
axis"  as  it  has  been  termed  by  Rosenthal  and  Purkinje,  is  indisputably 
the  most  difficult  of  investigation,  and  the  least  known  portion  of  the 
nerves.  There  is  no  microscopist  who  has  not  frequently  seen  this  axis- 
fibre,  but  it  may,  without  fear  of  contradiction,  also  be  asserted,  that 
there  is  none,  not  even  excepting  Remak  himself,  its  discoverer,  who  can 
boast  that  he  has  studied  and  learned  its  relations  in  every  particular. 
For  this  reason,  but  few,  as  Hannover  and  J.  Muller,  are  unconditionally 


THE    NERVOUS    SYSTEM.  351 

agreed  with  Remak  and  Purldnje  in  regarding  the  axis-cylinder  as  a 
constant  element  in  recent  nerve,  whilst  most  observers  have  adopted  the 
views  of  Valentin  ("Repert."  1838,  p.  76,  1839,  p.  79),  and  Henle 
("  Allg.  Anat."),  who  regard  it  as  not  always  present,  but  rather  as  a 
secondary  formation,  which  does  not  exist  during  life,  and  as  the  Tin- 
coagulated  central  portion  of  the  contents  of  the  nerve-fibre,  which, 
during  life,  are  homogeneous.  I  have  endeavored  to  the  utmost  of  my 
power  to  investigate  the  relations  of  this  structure,  and  have  arrived  at 
the  following  results : 

1.  The  axis-cylinder  is  constantly  present  in  every  nerve-fibre,  both 
central  and  peripheral,  in  fine  and  in  coarse  fibres,  and  after  death  is 
apparent  before  the  nerves  are  treated  with  any  reagent  whatsoever.    In 
the  human  nerves,  in  the  brain  and  spinal  cord,  as  they  are  commonly 
obtained  for  examination,  the  axis-cylinder,  when  duly  sought  for,  is 
everywhere  and  with  certainty  to  be  recognized ;  and  in  fact  by  far  the 
most  easily  in  the  central  organs,  where  the  absence  of  neurilemma  and 
the  delicacy  of  the  nerve-sheaths  oppose  but   little  hindrance  to  the 
tearing  asunder  of  the  fibres.     In  these  situations  it  may  be  seen  in 
nearly  the  finest  fibres.    It  always  presents  the  aspect  of  a  pale  filament, 
which,  together  with  a  tolerable  degree  of  consistence,  is  still  very  flexible 
and  at  the  same  time  highly  elastic,  as  may  be  readily  observed  on  com- 
pression of  small  portions  of  the  spinal  cord  (in  which  case  very  many 
axis -cylinders    are   stretched    and   torn,    retracting    considerably,  and 
forming  undulating  curves).     On  the  average  it  is  about  one-third  as 
wide  as  its  nerve-fibre,  and  consequently  varies  a  good  deal  in  diameter, 
is  obviously  quite  solid,  most  generally  homogeneous,  but  not  unfre- 
quently  also,  faintly  striated  or  very  finely  granular.     It  most  usually 
follows  a  straight  course,  bordered  by  two  parallel,  pale  contour  lines, 
occasionally,  however,  it  is,  in  parts,  thicker  or  more  slender,  though  it 
never  presents  varicosities  like  the  nerve-fibres ;  and  it  may,  moreover, 
be  curved  or  even  slightly  undulating,  and  also  perhaps  with  an  irre- 
gular, even  jagged  border. 

2.  When  recent  nerve-fibres  of  an  animal  just  killed  are  treated  with 
proper  reagents,  the  axis-fibre  instantaneously  appears.     If  a  thin  cuta- 
neous nerve  of  the  Frog,  whilst  under  examination  with  a  power  mag- 
nifying 100  times — be  touched  with  a  drop  of  glacial  or  concentrated 
acetic  acid,  the  nerve  retracts  and  there  appear  instantaneously,  at  each 
of  the  cut  ends,  large  particles  of  the  grumous  nerve-pulp,  and  pale, 
clear  fibres ;  and  the  same  thing  happens  if  the  nerve  have  been  pre- 
viously teased  out,  and  the  fibres  brought  separately  into  view.     The 
clear  fibres  are  evidently  the  axis-fibres,  as  they  may  readily  be  traced 
into  the  projecting  medullary  sheaths  and  entire  nerve-tubes,  and  in 
other  respects,  also,  present  all  the  characters  of  those  fibres,  only  that 
they  are  much  paler  and  broader  (as  much  as  0*004  of  a  line,  in  the 


352  SPECIAL    HISTOLOGY. 

peripheral  thick  fibres)  and  evidently  swollen  ;  they  frequently,  also, 
appear  convoluted,  or  even  spirally  rolled,  which  is  owing,  simply  to  the 
shortening  of  the  whole  nerve  caused  by  the  acetic  acid.     The  nerve- 
pulp  itself  is  rendered  grumous  by  the  same  reagent ;  the  grumous 
particles  are  sometimes  granules,  sometimes  very  short  rods,  like  fat- 
crystals,  which  latter  may  be  very  often  seen  on  the  nerve-fibres,  forming 
stellate,  acicular  groups  (margaric  acid) ;  alcohol  and  ether  also  render 
the  axis-cylinder  very  distinct,  both,  when  recent  nerves   are  treated 
with  those  reagents  in  the  cold,  in  which  case  their  action  must  be  rather 
more  prolonged,  and  when  they  are  boiled  in  them.     I  can  particularly 
recommend  the  boiling  in  absolute  alcohol,  by  which  means  excellent 
preparations  of  the  axis-fibres  may  be  made,  and  in  the  shortest  time. 
Under  this  treatment  the  nerves  become  firmer,  but  still  admit  of  being 
readily  torn  into  fibres,  and  always  exhibit  very  numerous  isolated  central 
fibres  of  considerable  length,  which,  contrasted  with  those  brought  into 
view  by  means  of  acetic  acid,  are,  as  it  were,  contracted  (at  most  0-002  of 
a  line  wide),  yellowish,  firmer,  and  often  convoluted  or  twisted.     Ether 
acts  in  the  same  manner.     By  both  reagents  the  medullary  sheaths  are 
rendered  paler  and  grumous,  the  grumous  particles  frequently  appearing, 
as  it  were,  to  be  united  into  a  delicate  network.     When  nerve-fibres  are 
boiled,  first  in  ether  and  afterwards  in  alcohol,  they  become  quite  pale, 
but  the  sheath  and  axis-cylinder  perfectly  distinct,  the  latter  presenting 
precisely  the  same  appearance  as  after  treatment  with  alcohol  alone. 
Consequently,  it  would  seem,  that  the  axis-fibres  contain  no  trace  of 
fatty  matter  ;  at  all  events,  except  that  they  shrink  a  little,  they  are 
not  altered  by  the  action  of  ether  and  alcohol,  and  afterwards,  also, 
again  enlarge,  under  acetic  acid,  into  broad  pale  bands.     Besides  the 
reagents  above  mentioned,  the  axis-fibres  are  particularly  well  displayed 
by  chromic  acid  (Hannover),  corrosive  sublimate  (Purkinje,  Czermak), 
and  gallic  acid,  but  less  readily  in  recent  nerves,  in  which,  it  is  true  that 
they  become  instantaneously  manifest,  although  it  is  never,  except  by 
accident,  and  rarely,  that  they  can  be  isolated,  than,  especially  after  a 
more  prolonged  immersion  in  those.     The  nerve-fibres  under  these  cir- 
cumstances appear  contracted,  the  medullary  sheath  grumous,  the  axis- 
cylinder  more  opaque  and  somewhat  diminished,  in  chromic  acid  yellow- 
ish, but  in  other  respects  exactly  as  above  described.     In  the  acoustic 
nerve  of  the  Sturgeon,  Czermak,  by  means  of  corrosive  sublimate,  has 
demonstrated  in  dividing  nerve-fibres,  the  existence,  also,  of  bifurcating 
axis-cylinders.      Iodine  also   or   iodine  combined  with  aqueous  hydri- 
odic  acid  (Lehmann)  act  very  powerfully.     In  quite  recent  nerves  it 
instantaneously  renders  the  medullary  sheath  wholly  grumous,  and  not 
only  isolates  numerous,  somewhat  shrunken  axis- fibres,  for  a  considerable 
length,  but  renders  them  in  many  nerve-fibres  very  distinct  in  situ^  and 
usually  appearing  convoluted  or  serpentine.     Hydrochloric,  sulphuric, 


THE    NERVOUS    SYSTEM.  353 

and  fuming  nitric  acids,  in  certain  cases,  also  render  the  axis- cylinders 
apparent  (Lehmann.)* 

3.  The  axis-cylinder  consists  of  a  solid  protein  compound  differing 
from  common  fibrin,  and  from  the  fibrin  of  the  muscles.  The  chemical 
nature  of  the  axis-cylinder  is  difficult  of  investigation,  because  it  cannot 
be  obtained  in  an  isolated  form  in  large  quantity  ;  something,  neverthe- 
less, may  be  learned  from  microchemical  reaction  as  has  been  shown  by 
Lehmann  and  myself.  In  concentrated  acetic  acid  it  swells  up  conside- 
rably, but  is  dissolved  with  difficulty,  and  even  after  it  has  been  boiled 
continuously  for  several  minutes,  although  pale,  it  always  remains  un- 
changed. When  boiled  for  a  longer  time  in  acetic  acid  it  dissolves, 
exactly  like  coagulated  albumen,  whilst  the  sheaths  and  some  of  the 
contents  remain  undissolved.  Alkalies  (potassa,  soda,  ammonia),  in  the 
cold,  attack  the  axis-cylinder  but  slowly,  though  in  soda  it  instantane- 
ously becomes  very  pale  and  swells  up  to  0'004-0'005  or  even  0*006 
of  a  line.  Longer  immersion  in  soda  dissolves  it,  and  the  same  thing 
takes  place  upon  its  being  boiled,  soon  after  the  commencement  of  ebul- 
lition in  the  fluid.  In  fuming  nitric  acid,  it  disappears  in  a  short  time 
— less  than  half  a  minute, — exactly  as  is  the  case  with  coagulated  albu- 
men. Treated  with  nitric  acid  and  potassa  the  axis-cylinder  is  rendered 
yellow  (xanthoproteinic  acid)  and  may  be  seen  spirally  contracted,  within 
the  nerve-fibres,  which  are  also  shortened,  but  not  to  the  same  extent. 
On  the  other  hand  it  is  not  colored  by  sugar  and  concentrated  sulphuric 
acid,  which  redden  coagulated  albumen,  at  most  acquiring  a  yellowish  or 
pale-reddish  hue.  In  water  the  axis-cylinder  is  unchanged,  even  when 
boiled,  in  which  case  it  is  readily  isolated  and  appears  somewhat  con- 
tracted ;  by  ether  and  alcohol  it  is  undissolved  even  by  boiling,  but 
shrinks  to  some  extent.  The  latter  effect  is  produced  also  by  corrosive 
sublimate,  chromic  acid,  iodine,  and  carbonate  of  potassa.  Viewing  all 
these  reactions  together,  it  might  perhaps  be  stated  with  certainty,  that 
the  axis-cylinder  is  a  coagulated  protein  compound  which,  however,  dif- 
fers from  fibrin,  inasmuch  as  it  is  insoluble  in  carbonate  of  potassa  and 
solution  of  nitre,  and  offers  much  greater  resistance  to  acetic  acid  and 
caustic  alkalies.  On  the  other  hand,  it  agrees  with  the  substance  of 
which  the  muscular  fibres  are  composed,  in  its  elasticity  and  insolubility 
in  carbonate  of  potassa,  differing  from  it  in  its  insolubility  in  dilute 
hydrochloric  acid,  and  difficult  solubility  in  acetic  acid. 

These  are  the  most  important  facts  connected  with  the  axis-cylinder. 
The  conclusion  which  may  be  drawn  from  them,  appears  to  me,  to  be 
simply  this,  that  the  axis-cylinder  is  not  an  artificial  product,  but  that 
it  must  be  regarded  as  an  essential  constituent  of  the  living  nerves. 

*  [I  have  always  obtained  the  best  preparations  by  soaking  a  nerve  for  six  or  twelve  days 
in  concentrated  acetic  acid.  The  axis-fibres  can  then  be  readily  isolated;  but  are  fragile 
and  devoid  of  their  elasticity. — DaC.] 

23 


354  SPECIAL    HISTOLOGY. 

The  only  objection  which  can  be  urged  against  this  opinion  consists  in 
the  circumstance,  that  the  axis-fibre  cannot  be  seen  in  living  fresh 
nerves,  and  that  it  cannot  generally  be  distinguished,  as  a  special 
structure,  in  the  interior  of  the  nerve-tubes  without  the  aid  of  reagents. 
But  it  must  be  remarked  that  it  can  also  be  brought  into  view  in  nerves 
that  are  still  warm.  Thus  I  find  well-marked  projecting  axis-fibres  at 
the  roots  of  the  cerebral  nerves  in  Frogs  just  killed,  which  I  have 
examined  as  quickly  as  possible,  after  the  application  of  a  solution  of 
sugar,  particularly  in  those  of  the  optic,  trigeminal,  and  vagus,  also  in 
the  spinal  nerves,  for  instance  in  the  second.  I  see  them  under  the 
same  conditions  in  the  peripheral  nerves  of  the  Frog  that  have  been 
teased  out,  and,  in  these  nerves,  have  on  several  occasions,  even  dis- 
tinctly noticed  the  axis-fibres  in  the  form  of  convoluted  filaments,  in 
larger  drops  of  the  nerve-pulp  expressed  from  the  tubes  (Fig.  137,  2). 
The  only  fact,  therefore,  that  can  be  adduced  in  opposition,  is  this,  that 
it  is  quite  true  that  the  axis-fibre  cannot,  with  certainty,  be  perceived 
in  the  interior  of  the  recent  nerve-tubes  themselves,  except  upon  the 
application  of  some  reagent ;  but  this  circumstance  obviously  proves 
nothing  at  all,  because  neither  can  it  be  seen  in  the  interior  of  tubes  of 
less  recent  nerve-substance,  all  of  which,  as  innumerable  examples  of 
isolated  axis-fibres  occurring  in  them,  show,  invariably  contain  such  fibres. 
The  axis-cylinder,  possessing  the  same  refractive  power  as  the  still 
fluid  part  of  the  medullary  sheath,  is  necessarily  indistinguishable  from 
it,  but  from  this  circumstance  we  cannot  conclude  that  it  is  absent, 
nor,  equally,  can  such  a  conclusion  be  drawn  from  its  invisibility  in  the 
recent  nerve-fibril.  Taking  all  these  circumstances  together,  I  am 
firmly  convinced  that  a  special,  central  structure  exists  even  in  recent 
nerves,  which  is  distinguished  from  the  more  external  portion, — that  is 
from  the  medullary  sheath, — not  only  by  its  chemical  composition,  as 
appears  to  me  to  have  been  placed  beyond  all  doubt,  but  also  by  its 
consistence  and  elasticity,  as  well  as  by  its  possessing  a  determinate 
form.  The  condition  in  which  we  obtain  the  axis-fibre  in  the  human 
nerves  and  central  organs,  by  the  addition  of  the  serum  of  the  blood, 
albumen,  or  vitreous  humor,  appears  to  me  to  represent  its  natural 
state ;  on  the  other  hand  alcohol,  ether,  iodine,  corrosive  sublimate, 
gallic,  and  chromic  acid  render  it  more  consistent  than  it  is  normally  ; 
whilst  acetic  acid,  dilute  nitric  acid,  and  alkalies  exhibit  it  paler  and 
more  swollen.  The  nerve-pulp  forms  a  semi-fluid  cortex  around  the 
axis-fibre,  and,  though  intimately  connected,  is  not  continuous  with  it. 
By  pressure,  therefore,  the  pulp  may  very  frequently  be  expressed,  by 
itself,  from  the  ends  of  the  tubes  or  from  lateral  rents  of  the  sheath. 
The  drops  of  pulp  thus  formed,  usually  coagulate  on  the  surface,  re- 
maining clear  and  transparent  in  the  interior,  like  the  central  portion 
of  the  nerve-tubes.  Many  authors  have  described  these  bodies  as  por- 


THE     NERVOUS     SYSTEM.  355 

tions  of  the  whole  contents  of  the  nerve-tube,  and  have  regarded  their 
formation  as  a  proof  against  the  pre-existence  of  the  axis-fibre,  but 
incorrectly.  They  belong  to  the  medullary  sheath  only,  which,  in  the 
interior  of  all  nerve-fibres  with  only  a  double  contour,  is  still  for  some 
space  perfectly  clear  and  bright.  An  axis-fibre  and  a  clear  space,  in 
fibres  having  a  double  contour,  are  therefore  by  no  means  identical,  and 
it  is  not  at  all  surprising,  nor  opposed  to  the  existence  of  an  axis-cylin- 
der, that  a  multitude  of  drops  with  a  double  contour  and  clear  contents 
should  be  obtained  from  such  fibres.  The  medullary  sheath  may  also 
coagulate  entirely,  and  then  the  axis-fibre  remains  evident,  sometimes  as 
a  transparent  streak  of  uniform  breadth  throughout ;  sometimes,  when 
the  grumous  particles  are  more  numerous,  it  may  be  concealed  by  them, 
so  that  the  entire  contents  of  the  nerve  appear  to  be  coagulated.  They 
are  so,  however,  only  in  appearance,  the  clear  fibre  always  lying  in  the 
interior ;  arid  I  have  never  yet  seen  it  coagulated  or  grumous.  Non- 
medullated  nerve-fibres  occur  in  many  situations.  I  enumerate  among 
them :  1,  the  pale  fibres  in  the  Pacinian  bodies ;  2,  the  nucleated 
pale  fibres  in  the  terminations  of  the  olfactory  nerves  ;  3,  the  per- 
fectly transparent,  non-nucleated  nerve-fibres  in  the  cornea;  4,  the 
pale,  branched,  and  partially  anastomosing  terminations  of  the  nerves 
in  the  electrical  organ  of  the  Torpedo  and  Ray  (R.  Wagner,  Ecker) ; 
5,  the  similarly  constituted  terminations  of  the  nerves  in  the  skin  of 
the  Mouse  (vid.  "  Micr.  Anat."  §  11);  6,  the  pale  processes  of  the 
nerve-cells  in  the  central  organs  and  ganglia,  even  though  they  may 
not  all  pass  into  dark-bordered  fibres.  Of  these  fibres,  those  which 
occur  at  the  extremities  of  nerves  were,  even  by  the  earliest  observers 
of  them,  unconditionally  regarded  as  nerve-fibres ;  and  as  respects  the 
processes  of  the  nerve-cells,  I  described  this  to  be  their  nature  as  early 
as  the  year  1846  ;  but  these  views  could  not  be  considered  as  fully  es 
tablished,  until  the  relation  of  the  fibres  with  the  elements  presenting 
the  dark  borders  was  completely  elucidated.  But  since  it  has  been 
ascertained  by  Schwann,  Ecker,  and  myself,  that  the  nerve-fibres  of 
the  embryo  are  in  precisely  the  same  condition  as  the  pale  fibres  now 
in  question,  and  since,  I,  Wagner,  Robin,  and  Bidder  and  Reichert, 
have  shown  that  the  pale  processes  of  the  nerve-cells  pass  into  dark- 
bordered  fibres,  it  has  become  more  possible  to  arrive  at  positive 
conclusions  on  the  subject.  R.  Wagner  was  the  first  to  broach  the 
supposition,  that  the  pale  fibres  in  the  Pacinian  bodies,  and  in  the  elec- 
tric organs,  were  nerve-sheaths,  with  axis-cylinders,  and  that  the  pro- 
cesses which  pass  into  nerve-fibres,  were  themselves  bare  axis-cylinders, 
and,  moreover,  that  the  entire  granular  contents  of  a  nerve-cell  are 
nothing  but  an  axis-cylinder  enlarged  into  a  globular  form ;  and  after 
I  had  demonstrated  the  constant  existence  of  the  axis- cylinder  in  the 
living  nerve,  and  that  it  was  a  structure  distinct  from  the  medullary 


356  .    SPECIAL    HISTOLOGY. 

sheath,  I  considered  myself  fully  justified  in  asserting  that  the  dark- 
bordered  nerve- fibres  were  in  direct  connection  on  the  one  side  through  the 
axis-cylinder,  with  the  pale  processes  of  the  nerve- cells  and  the  contents 
of  those  cells,  and  on  the  other,  that  they  passed  into  the  pale  terminal 
nerves  in  the  situations  above  mentioned.  But  this,  by  itself  as  I  believe, 
affords  no  ground  for  the  identification  of  the  pale  fibres  in  question,  or 
the  contents  of  the  nerve-cells,  with  the  axis-cylinders.  This  could 
only  be  established,  if  we  knew  with  certainty  that  the  medullary  sheath 
of  the  dark-bordered  nerve-fibres  is  superadded  from  without  to  the 
contents  of  the  pale  embryonic  fibres  during  the  development  of  the 
nerves,  and  is  an  entirely  new  formation  between  those  contents  and 
the  membranous  sheath.  This  is  not  the  case,  however,  it  being  on  the 
contrary  more  probable  that  the  medullary  sheath,  which  is  also  albu- 
minous, is  developed  merely  from  a  metamorphosis  of  the  outermost 
part  of  the  embryonic  nerve-contents,  that  is  to  say  from  the  develop- 
ment of  fat  in  it,  and  that  the  axis-cylinder  is  the  unaltered  innermost 
part  of  those  contents.  In  this  case  all  the  structures,  the  nature  of 
which  we  are  now  discussing,  would  represent,  not  bare  axis-cylinders, 
but  an  entire  embryonic  nerve-tube,  the  contents  of  which  were  still 
homogeneous,  or  had  not  undergone  differentiation,  and  would  also  be 
in  continuous  connection  with  all  the  parts  of  the  dark-bordered  fibres, — 
a  mode  of  explaining  them  to  which,  at  all  events  at  present,  I  am  dis- 
posed to  give  the  preference.  In  addition  I  would  remark,  that  the  pale 
nerve-fibres  are  also  met  ivith  in  different  stages  of  development.  The 
nucleated  fibres  in  the  olfactory  membrane  remain  altogether  in  the 
stage  of  embryonic  fibres,  as  also,  to  all  appearance,  do  the  pale  rami- 
fications in  the  electric  organ,  and  the  contents  of  both  these  kinds  of 
nerve-tubes  would  appear  to  have  little  agreement,  in  their  consistence, 
with  an  axis-fibre ;  in  the  Pacinian  bodies  the  contents  of  the  pale  fibres 
in  all  respects,  represent  an  axis-fibre,  for  it  is  probable  that  a  sheath  also 
exists  in  this  situation  ;  in  the  cornea,  the  contents  of  the  transparent 
terminal  nerve-tubules  are  apparently  more  fluid ;  and,  lastly,  with 
respect  to  the  processes  of  the  nerve-cells,  they  consist,  whether  they 
have  a  delicate  sheath  or  not,  of  a  substance  often  exactly  resembling 
an  axis-cylinder,  but  which  is  also  frequently  of  softer  consistence,  cor- 
responding with  the  contents  of  the  nerve-cell.  The  contents  of  the 
pale,  non-medullated  nerve-tubes,  therefore,  although  genetically  com- 
prehending more  than  an  axis-fibre,  still  in  all  probability  are  capable 
pretty  nearly  of  assuming  its  nature. 

§  111.  The  nerve-cells  (accessory  corpuscles  (Belegungskorper),  nerve- 
corpuscles,  Valentin),  (Fig.  140),  are  nucleated  cells,  occurring  in  great 
numbers  in  the  gray  or  colored  substance  of  the  central  organs,  in  the 
ganglia,  and  occasionally  also  in  the  trunks,  and  peripheral  expansions 
of  the  nerves  (retina,  cochlea,  vestibule).  The  nerve-cells  are  covered 


THE     NERVOUS    SYSTEM. 


357 


externally  by  a  delicate,  structureless  membrane,  which  in  the  cells  of 
the  ganglia  (ganglion-cells,  -globules,  -corpuscles),  may  be  demonstrated 
easily,  but  with  great  difficulty  in  those  of  the  central  organs ;  the 


Fig.  140. 


application  of  reagents,  however,  will  suffice  to  show,  pretty  distinctly, 
that  the  membrane  exists  around  the  larger  cells,  even  in  these  situa- 
tions, whilst  in  the  smallest,  just  as  in  the  finest  nerve-fibres,  no  mem- 
brane has  yet  been  observed,  although  one  probably  exists.  The  contents 
of  the  nerve-cells  are  a  soft,  but  tenacious,  elastic  substance,  which  be- 
sides the  nucleus  consists  of  two  elements ;  firstly,  of  a  clear,  homoge- 
neous, light-yellowish,  or  colorless  matrix,  upon  which  the  physical 
properties  of  the  contents  depend,  and  which  is  a  protein-compound ; 
and,  secondly,  of  minute  granules  of  different  kinds.  In  the  colorless  nerve- 
cells  these  present  the  form  of  uniform,  roundish,  for  the  most  part, 
minute  and  pale,  more  rarely,  darker  and  larger  corpuscles  dispersed 
throughout  the  entire  contents  of  the  cells,  and  imbedded  in  the  tena- 
cious matrix  ;  whilst  in  the  colored  cells,  instead  of  these  granules,  more 
or  less  yellowish,  brown  or  blackish  corpuscles  occur.  The  latter  are 
most  usually  of  a  larger  size,  and  are  placed,  closely  aggregated,  in  a 
mass  near  the  nucleus;  in  other  instances,  they  nearly  fill  the  entire 
cell,  giving  it  the  aspect,  in  all  respects,  of  a  brown  or  blackish  pigment- 
cell.  In  the  midst  of  these  contents  lies  the  nucleus,  for  the  most  part 
as  a  very  clear,  spherical  vesicle  with  distinct  walls,  perfectly  transpa- 

FIG.  140. — Nerve  cells,  from  the  acoustic  nerve,  magnified  350  diameters :  1,  nerve-cells 
with  the  origin  of  a  fibre,  from  the  anastomosis  between  the  facial  and  auditory  nerves,  in 
the  meatus  audit,  int.  of  the  Ox ;  a,  membrane  of  the  cell ;  i,  contents  ;  c,  pigment ;  rf,  nucleus  ; 
«,  continuation  of  the  sheath  upon  the  nerve-fibre;  /,  nerve-fibre  :  2,  two  nerve-cells  with 
fibres,  from  the  n.  ampull.  infer,  of  the  Ox  ;  a,  sheath  with  nuclei ;  6,  membrane  of  the  cell  j 
c,  nucleus  ;  rf,  the  origin  of  a  fibre  with  nucleated  sheath  :  3,  isolated  contents  of  a  nerve- 
cell,  with  nucleus  and  two  nucleoli.  For  these  drawings  I  am  indebted  to  Dr.  Corti. 


358  SPECIAL    HISTOLOGY. 

rent  contents,  and  one,  or  more  rarely  several,  large  opaque  nucleoli, 
which  occasionally  exhibit  a  cavity. 

The  size  of  the  nerve-cells  varies  very  much;  like  the  fibres,  they 
occur  as  large,  small,  and  middle-sized.  The  extreme  dimensions  of  the 
cells  are  0-002-0-003,  and  0-05-0-06  of  a  line.  The  nuclei,  which  for 
the  most  part  are  in  proportion  to  the  cells,  measure  from  0-0015—0-008 
of  a  line;  the  nucleoli  0-0005-0-003  of  a  line.  The  nerve-cells,  more- 
over, are  distinguished  according  as  they  are :  1,  thin  or  thick-walled, 
of  which  the  former  are  found  almost  wholly  in  the  spinal  cord  and 
brain ;  and  2,  as  they  are  independent  cells,  or  are  furnished  with  pale 
processes,  of  which  they  may  have  one,  two,  or  several  (uni-,  bi-,  multi- 
polar  cells),  and  which  are  frequently  ramified,  and  the  former,  in  many 
situations,  continuous  with  dark-bordered  nerve-fibres,  and  even  having 
the  nature  of  non-medullated  nerve-fibres.  Besides  the  nerve-cells, 
there  also  exist  in  the  gray-substance  of  the  higher  central  organs,  as 
constant  constituents,  a  finely  granular  pale  substance,  which  has  the 
greatest  resemblance  to  the  contents  of  the  cells,  and  besides  this,  in 
places,  large  accumulations  of  free  cell-nuclei.  Similar  elements  are 
contained  in  the  retina,  and  according  to  Wagner  and  Robin  in  the 
ganglia  of  the  Plagiostomata. 

The  nerve-cells  are  simple  cells,  as  which  they  were  understood  even 
by  Schwann ;  this  is  clearly  and  manifestly  shown  by  their  form,  their 
chemical  composition,  and  their  development.  When  Bidder,  more 
lately  (1.  c.),  relying  upon  the  fact  that  the  nerve-cells  in  many  situa- 
tions are  in  connection  at  each  end  with  dark-bordered  nerve-fibres,  pro- 
pounds the  opinion  that  they  are  membraneless  masses,  imbedded  in 
dilatations  of  the  nerve-tubes,  he  has  overlooked  those  cells  from  which 
no  fibres  are  given  off,  which  possess  exactly  the  same  membrane  as 
those  with  processes  ;  and  has  not  considered  that  there  also  exist  nerve- 
cells  with  a  single,  and  others  with  numerous  processes,  as  applied  to 
which,  his  view  would  be  altogether  unnatural ;  and  lastly,  that  the 
development  of  these  bodies  indicates  that  the  nerve-cell  is  formed  in 
toto,  whether  it  possess  processes  or  not,  from  a  simple  cell.  It  has  not 
yet  been  determined  whether  the  nerve-cells  of  the  large  central  organs 
have  membranes  or  not ;  Stannius  was  unable  to  detect  them  in  the 
Lamprey,  and  R.  Wagner  says  the  same  of  the  nerve-corpuscles  of  the 
electric  lobes  of  the  Ray.  I  think  I  have  seen  a  membrane  in  the  large, 
many-rayed  corpuscles  in  the  spinal-cord  and  cerebellum  of  man,  and 
occasionally,  also,  in  others,  but  I  freely  acknowledge  that  no  membrane 
can  be  detected  in  all  the  smaller  cells,  nor  in  the  processes  of  the  cen- 
tral cells  in  general.  This  does  not,  however,  appear  sufficient  to  justify 
the  denial  of  the  existence  of  membranes  in  these  instances,  and  I 
believe,  that  in  this  case,  as  in  that  of  the  finest  nerve-tubes,  we  must 


THE    NERVOUS     SYSTEM.  359 

for  the  present  abstain  from  any  definite  opinion.  The  processes  of  the 
nerve-cells,  in  the  brain  and  spinal  cord,  which  were  first  noticed  by 
Purkinje,  will  be  more  minutely  described  when  we  come  to  speak  of 
the  central  organs,  and  the  question  will  there  be  discussed  as  to  their 
relation  to  the  central  fibres.  In  the  ganglia,  there  are  no  cells  with 
branched  processes,  instead  of  which  we  find  only  those  with  one,  two, 
rarely  three  or  four,  pale  appendages,  which  are  continuous  with  dark- 
bordered  tubes.  The  nerve-cells  consist,  for  the  most  part,  of  a  coagu- 
lated, although  soft  protein-compound,  which  appears  to  correspond  very 
closely  with  that  of  the  axis-fibres.  It  has  not  been  ascertained  whether 
the  membranes  and  nuclei  differ  essentially  from  it.  The  fatty  matter, 
which  has  also  been  found  in  small  quantity  in  the  gray  substance,  con- 
stitutes in  every  case  the  opaque  granules  in  the  cells,  and  appears  to 
exist  in  other  conditions  also,  in  their  contents.  When  isolated  nerve- 
cells  are  compressed,  they  become  much  flattened,  resuming  their  pris- 
tine form  when  the  pressure  is  removed.  Their  processes  also  are  very 
elastic,  and  like  the  axis-fibres  may  be  considerably  extended,  and  after- 
wards again  retract  themselves. 

As  our  knowledge  of  the  chemical  composition  of  the  gray  and  white 
substance  still  leaves  much  to  be  desired,  I  content  myself  with  the  fol- 
lowing statements.  Lassaigne,  in  the  brain  of  a  lunatic,  found — 

Gray  substance.       White  substance. 

Water 85'2  730 

Albuminous  matter 7-5  99 

Colorless  fat I'O  13'9 

Red  fat 3'7  0'9 

Osmazome,  lactates 1'4  I'O 

Phosphates 1'2  1'3 

According  to  Fre*my  (Comptes  rendus,  torn.  ix.  p.  703,  "Ann.  d. 
Chem.  und  Pharm.  1841,"  vol.  xl.  p.  69),  the  brain  (both  substances 
together)  contains — 

Water 80 

Albumen 7 

Fatty  matter 5 

Osmazome  and  salts 8 

100 

Which  almost  exactly  agrees  with  Vauquelin's  analysis,  who  more- 
over estimates  the  osmazome  at  1-12,  and  the  salts  at  6'65;  whilst  it 
differs  from  that  of  Denis,  who  found  much  more  fatty  matter  (12-40 
in  a  man  20  years  old,  13-3  in  one  aged  78),  and  less  water  (78  and  76{j). 

CENTRAL  NERVOUS  SYSTEM. 

§  112.  Spinal  Cord. — The  nervous  elements  are  so  disposed  in  the 
spinal  cord,  that  its  external,  white  substance  is  constituted  almost  ex- 


360  SPECIAL     HISTOLOGY. 

clusively  of  nerve-fibres,  whilst  the  gray  nuclear  portion  with  its  pro- 
longations, the  cornua,  or  horns,  is  formed,  in  almost  equal  proportions, 
of  nerve- fibres  and  cells. 

The  white  substance  of  the  spinal  cord  may,  for  the  purpose  of  de- 
scription, be  most  conveniently,  and  in  accordance  with  usage,  divided 
into  two  halves,  and  each  of  these  into  three  columns.  The  anterior 
columns  (funiculi  anteriores),  are,  towards  the  interior,  almost  com- 
pletely separated  from  each  other  by  the  anterior  fissure  (fissura  ante- 
rior), which  extends  the  whole  length  of  the  cord,  and  into  which  a 
vascular  process  of  the  pia  mater  penetrates.  At  the  bottom  of  the 
fissure,  however,  the  columns  are  united  by  the  anterior  or  white  com- 
missure (com.  alba)',  externally,  they  extend  as  far  as  the  points  of  exit 
of  the  anterior  roots  of  the  nerves,  or  to  the  sulcus  lateralis  anterior, 
but  are  here  inseparably  connected  with  the  lateral  columns  (funiculi 
laterales),  which  again,  at  the  points  of  exit  of  the  posterior  roots,  where 
the  sulcus  lateralis  posterior  is  situate,  are  continuous,  without  any  line 
of  demarcation,  with  the  posterior  columns.  The  latter  (funiculi  pos- 
teriores)  appear  indeed  as  if  they  were  in  contact  in  the  posterior  mesial 
line,  because  the  posterior  longitudinal  fissure  described  by  many  anato- 
mists, does  not  exist  in  man,  except  in  the  lumbar  enlargement  of  the 
cord,  and  in  the  superior  cervical  region ;  but  they  are  nevertheless 
separated,  to  such  a  degree,  throughout  the  whole  length  of  the  cord 
by  very  numerous  vessels,  which  in  the  posterior  mesial  line  penetrate 
as  far  as  the  gray  nuclear  portion,  that  the  columns  in  most  places  are 
not  even  in  contact,  and  even  where  they  are,  they  are  merely  in  juxta- 
position, and  never  by  any  means  continuous  into  each  other.  Thus 
the  white  substance  of  the  cord  represents  two  halves,  united  only  by 
the  anterior  white  commissure,  and  each  of  which  is  divided  more  arti- 
ficially into  three  columns,  which  occupy  the  depressions  left  between. 
the  projecting  processes  of  the  gray  substance. 

The  gray  substance  presents  a  central  portion,  more  of  a  riband-like 
form,  and  four  laminae  projecting  laterally  from  it,  so  that  its  transverse 
section  forms  a  cross.  The  central  portion  or  the  gray  commissure,  in 
the  adult,  does  not,  normally,  contain  any  canal,  such  as  exists  in  the 
foetus,  and  consists  of  a  central,  cylindrical,  or  flattened  tract,  consti- 
tuted principally  of  nerve-cells,  of  a  yellowish  color — the  gray  nucleus 
(subst.  grisea.  centralis),  and  of  nerve-fibres  running  transversely,  con- 
tinued beyond  the  nucleus,  before  and  behind  it — the  gray  or  posterior 
commissures.  Of  the  laminae,  in  a  transverse  section  also  termed  horns, 
the  anterior  are  thicker,  and  shorter,  of  a  uniform  gray  color,  composed 
of  larger  and  smaller  nerve-cells,  and  of  delicate  nerve-fibres  of  me- 
dium fineness ;  the  posterior,  longer  and  thinner,  are  constituted  at 
their  roots  like  the  former,  only  most  usually  of  smaller  cells;  but  at 
the  free  edge  are  invested  with  a  more  transparent  layer,  containing 


THE     NERVOUS     SYSTEM.  861 

a  preponderance  of  smaller   nerve-cells — the  substantia   gelatinosa  of 
Rolando.     Of  the  roots  of  the  spinal  nerves,  the  anterior  penetrate  be- 
tween the  anterior   and  lateral  columns,  di- 
rectly to  the  anterior  horns,  and  the  poste- 
rior are  lost  between   the  lateral  and  pos- 
terior columns,  passing  through  the  substan- 
tia  gelatinosa  into  the  posterior  laminae  or 
horns. 

With  respect  to  the.  intimate  structure  of 
the  spinal  cord,  we  have  to  distinguish  in  the 
white  substance : — 1,  horizontal ;  and  2,  lon- 
gitudinal fibres.  The  latter,  in  all  situations, 
except  in  the  anterior  commissure,  are  in 
great  part  altogether  unmixed  with  horizon- 
tal fibres,  and  everywhere,  both  superficially 

and  deeply,  run  parallel  with  each  other,  but  they  are  never  in- 
terlaced, nor  do  they  ever  constitute  smaller  fasciculi.  The  number 
diminishes  from  above  downwards,  because,  as  will  be  afterwards 
shown,  they  successively  pass  inwards  towards  the  gray  substance, 
presenting  the  general  characters  of  the  central  nerve-fibres  ;  that 
is  to  say,  the  delicacy  of  sheath,  disposition  to  the  formation  of  vari- 
cosities,  and  to  the  breaking  up  into  separate  fragments,  which  are 
constituted  either  of  all  the  elementary  parts  of  the  nerve-tubes,  or 
consist  of  nothing  more  than  an  axis-fibre,  or  of  the  medullary  sheath. 
Their  diameter  amounts  to  0-0012-0-0048,  on  the  average  0-002-0-003 
of  a  linej  and,  in  one  and  the  same  fibre  is,  evidently,  always  nearly 
the  same,  since,  in  the  white  substance,  neither  divisions  nor  any  other 
kind  of  alteration  in  diameter  of  the  fibres  are  found  to  exist.  The 
transverse  fibres  occur : — 1,  in  those  portions  of  the  lateral  and  pos- 
terior columns  which  adjoin  the  horns  of  the  gray  substance,  and  the 
description  of  which  will  be  given  afterwards  with  that  of  the  gray 
substance ;  2,  in  the  white  commissure ;  and,  3,  at  the  points  of 
entrance  of  the  roots  of  the  nerves.  The  white,  or  anterior  commissure 

FIG.  141. — Transverse  section  through  the  spinal  cord  in  the  superior  lumbar  region,  mag- 
nified about  30  diameters,  half  diagrammatic  :  a,  anterior  column  ;  6,  lateral  columns,  motor 
portion;  c,  lateral  columns,  sensitive  portion;  d,  posterior  columns;  e,  anterior  longitudinal 
fissure;  /,  posterior  longitudinal  fissure  ;  g,  motor  roots  ;  A,  their  internal  fasciculus;  i,  their 
external  fasciculus ;  k,  decussation  of  the  anterior  columns  in  the  anterior  commissure  ;  I, 
gray  fibres  of  the  lateral  columns  passing  into  the  anterior  gray  commissure;  w,  gray  cen- 
tral nucleus,  here  internally  with  two  groups  of  somewhat  darker  cells ;  «,  posterior  gray 
commissure,  with  a  vessel  cut  across;  o,  fibres  of  the  posterior  column  passing  into  the  gray 
commissure;  p,  fibres  of  the  sensitive  roots  going  off  to  the  lateral  columns;  <?,  similar  fibres 
entering  the  posterior  column ;  r,  longitudinal  fasciculi  of  fibres  passing  into  the  sensitive 
roots;  s,  substantia  gelatinosa,  with  traversing  bundles  of  the  sensitive  roots,  w ;  t,  sensitive 
radical  fibres  running  horizontally  forwards  to  the  gray  commissure  ;  M,  large  cells  of  the 
anterior  cornua  (the  puricta),  inner  group  ;  v,  the  same,  outer  group. 


362  SPECIAL     HISTOLOGY. 

(Fig.  141,  Jc\  is  not  a  commissure  in  the  common  sense  of  the  word. 
It  is  formed  by  those  nerve-fibres  of  the  anterior  columns,  which  are,  in 
succession,  the  most  deeply  placed,  and  which  bending  obliquely  inwards, 
cross  in  front  of  the  gray  commissure ;  the  fibres  coming  from  the  right 
anterior  column,  passing,  in  a  radiating  manner  and  horizontally,  to  the 
left  anterior  horn  of  the  gray  substance,  and  those  from  the  left  anterior 
column  passing  in  like  manner  to  the  right  anterior  horn.  The  anterior 
commissure,  therefore,  represents  a  decussation,  or  crossing  of  the 
anterior  columns,  and  would  be  better  designated  as  such.  It  varies 
both  in  thickness  and  breadth  ;  it  is  thickest  in  the  region  of  the  two 
enlargements,  and  is  least  so  in  the  middle  of  the  dorsal  portion  of  the 
cord.  Its  breadth  is  regulated  pretty  nearly  by  that  of  the  cord,  and 
of  the  bottom  of  the  anterior  fissure  ;  being  greatest  in  the  cervical 
enlargement,  and  from  this  point  decreasing  pretty  uniformly  in  both 
directions.  The  decussating  fibres  measure  0*0012-0*003  of  a  line, 
and,  as  they  diverge  in  the  anterior  horns,  evidently  in  some  degree 
decrease  in  diameter. 

The  roots  of  the  spinal  nerves  (Fig.  141,  g,  w\  without  any  communi- 
cation with  the  longitudinal  fibres,  are  continued,  in  larger  fasciculi,  from 
the  sulcus  lateralis  anterior  arid  posterior,  either  horizontally  or  slightly 
ascending  between  those  fibres,  in  order,  all  of  them,  to  enter  the  ante- 
rior and  posterior  gray  laminae,  where  we  shall  again  meet  them.  Their 
nerve-fibres  (in  the  posterior  roots,  about  fds  measuring  0'004— 0*008, 
and  Jd  0*0012-0*003  of  a  line,  in  the  anterior  about  Jths  measuring 
from  0-006-0-011,  and  Jth  0-0025-0-003  of  a  line)  present,  as  soon 
as  they  have  entered  the  cord,  all  the  characters  of  the  central  fibres, 
the  largest,  at  their  commencement,  measuring  about  0-004-0-006  of 
a  line,  in  the  sensitive,  up  to  0*008  of  a  line,  in  the  motor  roots. 
They  continue,  however,  distinctly  and  constantly  decreasing  in  size, 
until  ultimately,  the  former,  when  they  enter  the  gray  substance,  have 
a  diameter  scarcely  more  than  0-0012-0-0028  of  a  line,  and  the  latter 
in  like  manner  one  of  not  more  than  0-004,  or  in  some  of  0-006  of  a  line. 

In  the  gray  substance,  the  nerve-cells  and  fibres  deserve  special 
consideration.  The  former  present  very  various  forms,  all,  however, 
corresponding  in  one  respect,  that  they  are  invariably  furnished  with 
processes  or  prolongations,  and,  for  the  most  part,  with  many  such, 
which  repeatedly  branching,  ultimately  terminate  in  extremely  fine, 
pale  fibrils,  like  the  finest  axis-fibres.  I  distinguish : — 1.  The  cells  of 
the  central  gray  substance.  These  (Fig.  142)  are  0-004-0-008  of  a 
line,  in  size,  always  pale  and  finely  granular,  with  multiple  nuclei  and 
branching  pale  processes,  constituting  as  it  would  seem  the  principal 
bulk  of  the  central  gray  substance  ;  but  in  which,  dark,  true  nerve- 
fibres  also  occur  although  of  nearly  the  finest  kind,  which  can  scarcely 
be  recognized  as  such,  and  are  indeed  very  few  in  number,  and  quite 


THE    NERVOUS    SYSTEM. 


363 


Fig.  142. 


isolated ;  besides  these,  there  are  a  good  many  extremely  fine,  pale 
fibrils,  like  the  processes  of  the  cells,  only  more  extended,  and  running 
in  a  transverse  and  longitudinal  direction,  of  which  nothing  more  can 
be  said,  as  to  whether  they  are  nerve-tubes, 
or  are  to  be  referred  to  the  processes  of 
the  cells.  The  gray  central  substance, 
taken  altogether,  is  thickest  in  the  lumbar 
enlargement,  and  on  a  transverse  section  is 
of  a  pyriform,  scutate,  or  cordate  figure ; 
next  to  this  stands  the  cervical  enlarge- 
ment ;  and  lastly,  the  superior  cervical  and 
dorsal  portions,  in  which  latter  parts  its 
transverse  section  presents  an  ellipse,  in 
the  cervical  region,  with  the  longer  dia- 
meter much  developed.  It  occasionally 
exhibits,  especially  in  the  lumbar  region, 
indications  of  its  being  constituted  of  two 
halves,  inasmuch  as  the  middle  appears 
somewhat  clearer,  and  the  lateral  portions, 
owing  to  the  accumulation  of  fatty  gra- 
nules in  the  cells,  more  opaque.  2.  With 
the  above-described  cells,  those  of  the  sub- 
stantia  gelatinosa*  pretty  nearly  agree,  only  that  they  are  of  a  faint, 
yellowish  color,  and  have  1-3  processes  and  simple  nuclei.  Besides 
these  cells,  the  substantia  gelatinosa  also  contains  the  fasciculi  of  fibres 
of  the  posterior  roots  which  pass  through  it,  and  numerous  other  true 
nerve-fibres  (vid.  infra).  3.  Much-developed,  well-marked  nerve-cells 
are  seated  especially  at  the  apex  of  the  anterior  horn,  forming  an  inter- 
nal and  an  external  group  (Fig.  112,  w,  v\  but  occurring  also  in  the  other 
portions  of  the  anterior,  as  well  as,  though  in  less  number,  in  the  poste- 
rior horns,  whilst  they  are  never  met  with  in  the  subst.  gelatinosa,  nor 
in  the  gray  commissure.  All  these  cells  (Fig.  143)  are  0*03— 0*06  of  a 
line,  in  size,  with  nuclei  measuring  0*005— 0*008  of  a  line,  are  fusiform 
or  polygonal,  frequently  containing  brown,  pigmentary  matter,  and  fur- 
nished with  from  2  to  9,  or  even  more  branched  processes,  which  at 
their  origin  are  often  0-004-0*005  of  a  line  thick.  These  processes 
may  be  traced  to  a  length  of  0-1-0*24  of  a  line,  and  ultimately  termi- 
nate in  fine  fibrils,  all  of  which,  scarcely  more  than  0*0004  of  a  line  thick, 
are  contained  within  the  gray  substance.  Besides  these  large  and,  for 
the  most  part,  many-rayed  cells,  there  are  also  found  in  the  gray  sub- 
stance though  more  widely  scattered  among  its  nerve-fibres,  very  numer- 
ous, smaller  cells,  which  constitute  a  complete  series  between  the  large  cells 

FIG.  142. — Cells  from  the  gray  central  nucleus  of  the  cord  in  Man,  magnified  350  diam. 
*  [The  gray  matter  of  the  posterior  horn. — DaC.] 


364 


SPECIAL    HISTOLOGY. 


and  those  of  the  substantia  gelatinosa,  and  consequently  require  no  fur- 
ther description. 

The  nerve-fibres  of  the  gray  substance  are  excessively  numerous,  so 
much  so  as  to  constitute  in  any  case  the  half  of  its  bulk,  if  not  more,  and 
exhibit  the  same  conditions  as  those  of  the  medullary  substance,  except 
that,  on  the  average,  they  are  not  more  than  half  as  thick,  or  even  less 
(not  more  than  0-0008  of  a  line) ;  fibres,  however,  also  occur  of  the  same 

Fig.  143. 


size  as  those  in  the  white  substance  and  in  the  entering  roots  of  the 
nerves,  especially  in  the  anterior  horns,  though  more  widely  scattered, 
and  principally  towards  the  anterior  roots.  The  investigation  of  the 
course  of  these  nerve-fibres  in  the  gray  substance  is  one  of  the  most 
difficult  tasks  in  microscopy.  If  we  observe,  above  all,  the  roots  of  the 
peripheral  nerves  (Figs.  141,  144),  it  is  apparent : — 1.  that  the  motor 
filaments  in  them,  after  they  have  entered  the  sulcus  lateralis  anterior, 
and  the  contiguous  portions  of  the  anterior  and  lateral  columns,  and 
penetrated  horizontally  between  the  longitudinal  fibres  of  the  white  sub- 
stance, are  continued  further  in  the  gray  substance  of  the  anterior 
horns,  principally  in  two  directions.  The  fibres  of  one  bundle,  and 
indeed  of  that  which  enters  the  most  internally  (Fig.  141,  A),  proceed 
directly  backwards  and  a  little,,  in  wards,  without  forming  any  plexus,  or 

FIG.  143. — Large  nerve-cells  with  processes  from  the   anterior  cornua  of  the  spinal  cord 
in  Man  ;   magnified  350  diameters. 


THE    NERVOUS    SYSTEM.  365 

subdividing  to  any  considerable  extent  into  subordinate  fasciculi,  to  the 
innermost  portions  of  the  anterior  horns,  skirting  the  anterior  columns. 
In  this  course  they  pass  through  the  inner  group  of  the  many-rayed, 
large  nerve-cells,  in  perfectly  compact  bundles,  however,  and  having  no 
connection  whatever  with  the  processes  of  the  cells,  as  may  be  readily 
perceived  under  a  strong  magnifying  power,  when  the  individual  nerve- 
fibres  may  be  traced  quite  beyond  these  cells.  Now,  if  these  bundles 
derived  from  the  anterior  roots  are  traced  further  it  will  be  perceived, 
in  favorable  sections,  that  they  extend  to  the  lateral  parts  of  the  anterior 
commissure,  continuing  to  run  in  the  anterior  horns,  and,  that  ultimately, 
forming  more  or  less  well-marked  curves,  they  are  continuous  with  its 
fibres,  and  in  fact  are  disposed  in  such  a  way,  that  the  root-fibres  of  the 
right  side  pass  into  the  left  anterior  column,  and  those  of  the  left  side 
into  the  right.  Consequently  there  is  established  in  the  white  commis- 
sure a  connection  of  the  longitudinal  fibres  of  the  anterior  columns  and 
of  a  part  of  the  motor  roots,  together  with  a  total  decussation. 

A  large  number  of  the  fibres  of  the  motor  roots  take  no  part  in  the 
above-described  decussation,  and  are  wholly  unconnected  with  the 
anterior  fasciculi, — these  are  the  root-fibres  which  enter  the  anterior 
horns  the  most  externally.  Forming,  for  the  most  part,  smaller  fasci- 
culi, or  even  as  separate  fibres,  and  therefore,  less  easily  observable, 
they  run  in  part  directly  backwards,  and  in  part  arch  outwards,  but 
ultimately  bend  towards  the  anterior  half  of  the  lateral  column,  where 
they  pass  between  the  outer  groups  of  the  large,  many-rayed  cells  of 
the  anterior  horns,  and  then  enter  the  lateral  column  in  a  horizontal 
direction.  These  transverse  fibres  now  penetrate  to  various  depths 
(nearly  half,  or  even  more)  into  the  lateral  column,  then  curve  upwards, 
and  after  running  thus  a  short  distance,  appear  as  longitudinal  fibres. 
Consequently,  to  express  the  same  thing  in  other  words,  a  second  por- 
tion of  the  motor  roots  arises  from  the  anterior  half  of  the  lateral  column 
of  the  same  side,  and  quits  the  spinal  cord  without  previously  undergo- 
ing any  decussation. 

It  is,  moreover,  worthy  of  remark,  that  most  of  the  fibres,  perhaps 
all,  which  join  the  motor  roots  from  the  anterior  and  lateral  columns, 
undergo  considerable  changes  in  their  diameter.  Those  of  the  anterior 
column  measure,  as  has  been  observed  before,  at  their  commencement, 
on  the  average,  0-002-0-004  of  a  line,  in  the  anterior  commissure 
scarcely  more  than  0-003,  and  in  the  gray  substance  hardly  more  than 
0-002  of  a  line ;  and  the  same  is  the  case  also  with  those  of  the  lateral 
columns  ;  which,  however,  even  while  still  in  the  interior  of  the  column, 
where  their  direction  is  horizontal,  measure  scarcely  more  than  0-002 
of  a  line.  This  diminution  in  size,  however,  is  again  succeeded  by  an 
increase  in  thickness,  which  takes  place,  in  part,  within  the  gray  sub- 
stance, in  part  at  the  point  where  the  radical  bundles  quit  it,  the  amount 


366 


SPECIAL    HISTOLOGY. 


of  which  increase  has  been  already  stated  in  numbers ;  so  that,  proceed- 
ing from  the  peripheral  nerves,  we  find  them  gradually  diminishing  in 
Fig  144  size  from  their  entrance  into  the  cord 

until  they  reach  the  gray  substance, 
and  again  enlarging  from  the  point 
where  they  join  the  longitudinal  ele- 
ments of  the  white  substance,  but  not 
to  such  an  extent  as  ever  to  attain 
nearly  their  pristine  diameter.  Of 
divisions  in  the  fibres  of  the  anterior 
roots  in  the  anterior  horns,  I  have  seen 
as  little  indication,  as  elsewhere  in  the 
spinal  cord. 

The  posterior  roots  of  the  nerves,  as 
has  been  already  noticed,  penetrate, 
like  the  anterior,  also  horizontally,  or 
in  a  slightly  ascending  direction,  from 
the  sulcus  lateralis  posterior,  through  the  longitudinal  fibres  of  the  white 
substance  as  far  as  the  posterior  horns.  Here  they  divide  into  separate, 
slenderer,  or  thicker  fasciculi  (from  0-01-0-02  of  a  line),  (Figs.  141,  s, 
144,  b),  and  continue,  each  bundle  by  itself,  in  a  straight  course,  and 
without  any  direct  connection  with  nerve-cells,  quite  through  the  sub- 
stantia gelatinosa  into  the  substantia  grisea.  In  this  course  they  follow 
two  directions.  One  portion  of  them  bends  upwards,  in  a  uniform  curve, 
or  nearly  at  a  right  angle,  proceeds  in  the  most  posterior  part  of  the 
substantia  grisea,  close  in  front  of  the  substantia  gelatinosa  in  a  longi- 
tudinal direction,  and  gradually  joins  chiefly  the  posterior  column,  but 
in  part  also  the  posterior  portions  of  the  lateral  column,  being  continued 
further,  as  its  longitudinal  fibres  (Figs.  141,  r,  144,  g).  A  second  por- 
tion of  the  sensitive  roots  (Figs.  141,  t,  144),  penetrates,  always  in  a 
fascicular  form,  between  the  above-mentioned  longitudinal  bundles  fur- 
ther forwards,  losing  itself  in  the  posterior  and  in  the  lateral  columns, 
and  also  entering  the  gray  commissures.  In  horizontal  sections,  the 
former  fibres  are  frequently  very  distinct,  particularly  those  going  off 
to  the  posterior  columns  (Fig.  141,  p,  q).  I  have  seen  them  most  dis- 
tinctly in  the  inferior  extremity  of  the  spinal  cord,  below  the  lumbar 
enlargement,  where  they  ran  towards  the  conus  medullaris,  close  up  to 

FiG.  144. — Vertical  section  through  the  cord,  midway  between  the  gray  cornua  and  the 
point  of  entrance  of  the  roots  of  the  nerves,  magnified  about  25  diameters :  a,  posterior 
column  with  the  sensitive  roots,  A,  traversing  it;  6,  substantia  gelatinosa;  c,  prolongations  of 
the  posterior  roots,  which  bend  round  in  front  of  the  substantia  gelatinosa  and  run  longitudi- 
nally, in  order  there  to  join  more  particularly  the  posterior  column;  c?,  basis  of  the  posterior 
cornua,  with  the  ends  of  the  horizontal  portion  of  the  sensitive  roots  apparent  (owing  to 
their  being  cut  across) ;  e,  anterior  cornua  with  the  large  nerve-cells  (the  spots),  and  the  also 
horizontal  and  divided  continuations  of  the  motor  roots ;/,  anterior  column  traversed  by  the 
motor  roots,  i. 


THE     NERVOUS     SYSTEM.  367 

the  gray  central  nucleus,  and  did  not  bend  backwards  until  they  reached 
the  posterior  columns ;  they  were  also  well  displayed  in  the  lumbar  en- 
largement, between  the  substantia  yelatinosa  and  the  posterior  commis- 
sure. The  horizontal  radical  fibres,  also,  which  proceed  to  the  lateral 
columns,  are  often  exceedingly  numerous,  although  much  less  so,  appa- 
rently, than  those  which  enter  the  posterior  columns.  The  connection 
of  the  gray  commissures  with  a  portion  of  the  sensitive  radical  fibres, 
is,  as  regards  the  posterior  fibres,  not  difficult  to  be  seen,  these  fibres, 
in  part,  at  least,  running  backwards  along  the  posterior  columns,  and 
being  continued  directly  into  the  fasciculi  of  the  substantia  gelatinosa. 
In  the  anterior  gray  commissure,  I  have  also  noticed,  though  not  a  direct 
connection  with  the  sensitive  roots,  still,  fibres  which,  running  horizon- 
tally in  a  direction  towards  the  summits  of  the  posterior  horns,  entered 
those  processes.  The  commissural  fibres  are,  besides,  connected  not 
only  with  the  sensitive  roots,  but  also,  and  indeed  quite  evidently,  with 
the  posterior  columns,  and  less  distinctly  with  the  lateral ;  from  the 
anterior  portions  of  which,  adjoining  the  base  of  the  posterior  horns, 
arched  fasciculi  pass  into  the  commissures  and  become  intermixed  with 
the  other  commissural  fibres  (Fig.  141,  o  and  I).  These  fibres  probably 
pass  over  to  the  opposite  side,  into  the  commissures  connected  with  the 
posterior  roots  ;  in  which  case,  like  the  anterior  halves  of  the  cord,  a 
decussation  of  fibres  also  takes  place  in  the  posterior  commissure.  In 
accordance  with  what  has  been  remarked,  the  sensitive  roots  derive  their 
fibres  principally  from  the  posterior  and  lateral  columns  (the  posterior 
halves)  on  their  own  side,  and  probably  also  through  the  gray  commis- 
sures from  the  same  columns  on  the  other  side. 

The  fibres  of  the  sensitive  roots  also  decrease  in  size  as  they  traverse 
the  gray  substance  of  the  posterior  horns.  In  the  roots  themselves 
they  still  measure  about  0*008  of  a  line  ;  in  the  substantia  gelatinosa, 
never  more  than  0-004,  in  the  substantia  grisea,  0-001-0-003  of  a 
line;  in  the  gray  commissures,  not  more  than  0-0008-0-0012,  in 
the  posterior  and  lateral  columns,  again,  0-0012-0-004  of  a  line;  in 
connection  with  which,  however,  it  should  be  remarked,  that,  in  this 
situation,  the  increase  of  size  in  the  fibres  which  enter  these  columns 
horizontally,  is  not  perceptible  at  their  commencement,  as  is  shown  more 
particularly  in  vertical  sections,  made  in  the  direction  from  within  to 
without,  through  the  posterior  cornua.  The  variation  in  diameter  may 
even  be  directly  observed,  in  many  fibres  in  this  situation ;  as,  for 
instance,  at  the  entrance  of  the  roots  into  the  gelatinous  substance. 

Besides  these  fibres,  belonging  to  the  motory  and  sensitive  roots,  there 
exist,  in  the  gray  substance,  a  considerable  number  of  nerve-fibres  not 
referable  to  the  roots,  and  which  until  more  is  known  about  them  may 
be  termed  special  spinal-medullary  fibres. 

The  filum  terminale  contains,  so  far  as  it  is  hollow,  as  a  continuation 


3G8  SPECIAL    HISTOLOGY. 

of  the  gray  substance  of  the  cord,  a  gray,  soft  substance,  consisting 
chiefly  of  round,  nucleated,  pale  cells,  like  nerve-cells,  and  measuring 
0-005-0-006  of  a  line.  Besides  these  there  occur,  in  its  upper  part 
among  the  cells,  true  dark-bordered  nerve-fibres,  of  various,  and  for  the 
most  part  small  diameter,  and  also  numerous,  fine,  pale  fibres,  the  nature 
of  which  is  not  clear  to  me  ;  that  is  to  say,  whether  they  are  processes 
of  cells  or  belong  to  the  finest  nerve-fibres.  Remak  ("  Observ.,"  p.  18) 
supposes,  that  in  the  Mammalia  the  true  nerve-fibres  of  the  filum  all 
go  off  in  lateral  branches  of  it,  the  existence  of  which  were  detected  by 
him. 

In  the  investigation  of  the  course  of  the  fibres  in  the  spinal  cord, 
chromic  acid,  or  instead  of  it,  chromate  of  potassa,  affords  the  principal 
aid.  It  is  not  easy  to  hit  upon  the  proper  proportion  of  acid,  and  so  to 
harden  the  cord,  previously  stripped  of  its  dura  mater,  and  cut  across 
with  a  sharp  knife  at  the  points  selected,  that  very  thin  transverse  sections 
may  be  taken  from  it.  If  the  solution  be  too  much  diluted,  the  sub- 
stance of  the  cord  remains  soft  in  the  interior  and  spoils,  if  too  concen- 
trated it  becomes  fragile  and  friable,  and  larger  sections  of  it  cannot  be 
obtained.  I  have  unfortunately  neglected  to  estimate  precisely  the 
proper  percentage  of  acid  or  salt  in  the  solution ;  and  can  only  say  this 
much,  that  one  of  a  wine-yellow  color  acted  the  best.  Objects  thus 
properly  hardened  may  be  cut  at  pleasure  with  a  razor,  or  other  very 
sharp  instrument,  if  due  care  be  taken,  particularly  in  the  avoiding  of 
any  sawing  motion  ;  and  sections  suitable  even  for  the  highest  magnify- 
ing powers'  may  be  procured  and  examined,  either  with  or  without 
pressure  or  reagents,  under  various  degrees  of  enlargement.  The  gray 
substance  is  scarcely  altered  by  the  chromic  acid,  except  that  its  ele- 
ments are  more  easily  separated,  and  I  have  in  hardly  any  other  way 
seen  its  nerve-cells,  together  with  their  processes,  and  the  nerve-fibres, 
more  beautifully  displayed.  If  it  be  desired  to  examine  the  former,  the 
gray  substance  is  broken  up  in  water,  which  now  no  longer  produces 
any  change  ;  or,  what  is  best,  in  the  solution  of  chromic  acid  itself;  but 
if  the  examination  of  the  latter  be  wished,  it  is  by  far  the  best  to  employ 
diluted  caustic  soda  or  potassa,  which  renders  all  the  nerve-cells  pale. 
To  those  who  may  consider  the  application  of  these  reagents  as  too 
powerful  for  such  delicate  organs  as  the  spinal  cord,  I  would  remark  : 
1,  that,  as  stated  by  Hannover,  chromic  acid  alters  the  nerve  fibres, 
especially  of  the  gray  substance,  so  little,  that  most  of  them  do  not  even 
become  varicose  ;  and  2d,  that  soda,  added  to  a  preparation  made  with 
chromic  acid,  does  not  act  upon  the  fibres  for  a  long  time,  and  only  so 
far  as  to  render  them  more  transparent  and  their  medullary  contents 
fluid.  I  have  never,  under  any  circumstances,  seen  more  beautiful 
nerve-tubes  of  the  gray  substance,  than  in  preparations  made  with 


THE    NERVOUS    SYSTEM.  369 

chromic  acid,  and  I  think  that  of  all  known  means  this  is  the  best  for 
their  study.  In  employing  pressure,  however,  great  care  is  requisite. 
I  make  use  of  a  compressorium  by  Nachet,  which  allows  extremely  thin 
covering-glass  to  be  employed,  and  consequently  the  highest  magnifying 
powers  ;  if  I  wish  to  apply  more  considerable  pressure  for  the  study  of  the 
coarser  conditions,  the  common  apparatus  suffices,  with  which,  however, 
with  a  shorter  focal  distance  of  the  microscope,  only  lower  powers  can 
be  employed.  I  have  had  entire  transverse  sections  of  the  spinal  cord 
before  me,  in  which  it  might  be  said,  that  no  part  was  disturbed  from  its 
relative  position,  and  yet,  which  admitted  of  the  application  of  a  mag- 
nifying power  of  350  diam.  I  would,  moreover,  remark,  that  the  most 
favorable  place  in  the  cord  for  the  first  investigation,  is  the  lumbar 
enlargement.  In  this  situation  the  cord  is  not  so  thick,  but  that  entire 
sections  of  it  may  be  obtained,  besides  which  the  white  substance,  which 
is  only  an  impediment,  is  thin,  and  the  roots  and  commissures  large  and 
more  readily  traced. 

Whether  the  nerve-fibres  in  the  cord  divide,  has  not  yet  been  fully 
ascertained,  yet  I  think  that  I  saw  such  an  appearance,  on  one  occa- 
sion, in  a  dark-bordered  fibre,  and  on  another  in  an  isolated  axis-cylin- 
der. In  any  case  such  divisions^cannot  be  frequent,  otherwise  I  must 
have  noticed  them  more  often,  having  examined  innumerable  nerve-fibres 
and  axis-cylinders,  expressly  with  reference  to  this  point.  Anastomoses 
between  the  processes  of  branched  nerve-fibres,  which  Schroder  van  der 
Kolk  thinks  he  has  seen,  I  must,  from  my  experience  so  far,  doubt,  but 
I  am  not  able  to  deny  their  possible  occurrence. 

§  113.  Probable  course  of  the  Fibres  in  the  Cord. — We  have  found 
that  the  motor  and  sensitive  roots  do  not  terminate  at  the  point  where 
they  are  implanted  into  the  gray  substance  of  the  cord,  as  at  first  sight 
appears  to  be  the  case,  but  that  the  greater  proportion  of  them  are  curved 
upwards,  accompanying  the  longitudinal  fibres  of  the  white  substance. 
The  important  question  now  arises,  viz. :  to  ascertain  what  becomes  of 
these  fibres,  whether,  after  running  a  shorter  or  longer  distance,  they 
terminate  in  the  cord,  or  whether  they  all  ascend  to  the  brain.  It  is 
well  known,  that  until  recently,  most  observers  have  been  of  the  latter 
opinion,  which  was  founded  less  upon  direct  observation  than  on  the 
ground  of  probability,  until  Volkmann,  in  his  deservedly  celebrated 
article,  "  Physiology  of  the  Nerves,"  shook  it  to  its  foundations,  carry- 
ing the  greater  number  of  physiologists  with  him.  I  also  was  among 
these,  until  I  had  myself  investigated  the  conditions,  for  there  could  be 
no  doubt  that  Volkmann's  theory  connected,  in  the  most  harmonious 
way,  the  anatomical  facts  and  the  results  of  physiology  as  at  that  time 
exhibited.  When  I  now,  notwithstanding  this,  abandon  Volkmann's 
theory  of  the  termination  of  the  spinal  nerves  in  the  cord,  I  am  induced 

24 


370 


SPECIAL    HISTOLOGY. 


Fig.  145. 


to  do  so  by  weighty  reasons,  and  much  regretting  that  I  am  unable  to 
maintain  a  view,  which  appeared  to  throw  so  much  light  upon  many  diffi- 
cult parts  of  the  physiology  of  the  nerves,  and  to  be  in  accordance  with 
so  many  other  anatomical  conditions  (ganglia,  invertebrate  animals). 

Volkmann,  in  his  hypothesis  of  the  origination  of  the  fibres  in  the 
cord,  relies  upon  the  circumstance  (1.  c.,  p.  482,  et  seq.),  that  the  spinal 
cord  is  not  of  a  pyramidal  form  with  the  base  above,  as  must  have  been 
the  case  had  all  the  fibres  of  the  roots  of  the  nerves  ascended  towards 
the  cerebrum,  but  that  it  rather  presents  a  local  increase  of  the  nervous 
substance  at  the  points  of  origin  of  large  nerves,  which  enlargement  is 
not  confined  to  the  gray  substance,  but  equally  involves  the  white.  That 
this  is  the  case  Volkmann  shows  from  four  transverse  sections  of  the 
spinal  cord  of  the  Horse,  and  from  a  comparison  of  the  diameter  of  the 
cervical  cord  of  Crotalus  horridus,  with  that  of  all  the  nerve-roots  of 
the  same  animal,  which  was  found  to  be  eleven  times  greater  than  the 
former.  He  also  supports  his  view  by  the  consideration :  1,  that  the 
enlargements  of  the  cord  are  always  regulated  by  the  size  of  the  nerves 
of  the  extremities,  being  sometimes  wanting  and  sometimes  enormously 
developed ;  2,  that  the  cord,  at  the  points  of  exit  of  the  largest  nerves, 
instead  of  becoming  suddenly  thinner,  is  in  most  cases 
enlarged  ;  and  3,  that  the  origin  of  the  spinal  acces- 
sory nerve  in  this  case  loses  all  that  is  remarkable  in  it. 
Now,  if  the  spinal  cord  in  man  be  examined  with  refe- 
rence to  the  above  points,  it  will  present,  in  almost  all 
of  them,  exactly  the  contrary  of  what  Volkmann  noticed 
in  animals.  In  the  first  place,  the  white  substance  con- 
stantly increases  in  thickness  from  below  upwards,  and 
the  enlargements  of  the  cord  depend  upon  an  increase  of 
the  gray  substance  more  than  anything  else.  That  this  is 
the  case,  is  evident  at  a  glance,  when  sections,  such  as  are 
represented,  after  nature,  in  Fig.  145,  are  compared  with 
each  other,  and  it  also  admits  of  being  estimated  in 
numbers  (vid.  "  Mikroskop.  Anatomie,"  II.  1,  p.  431). 

This  fact  being  established,  it  remains  to  determine 
the  proportion  borne  by  the  white  substance  in  the 
superior  cervical  region  to  the  peripheral  nerves.  For 
this  purpose  I  instituted  Volkmann's  measurements  in 
man,  and  in  a  male  and  female  body  estimated  all  the  roots  of  the  spinal 
nerves  on  the  left  side ;  I  determined,  from  the  ascertained  diameters, 

FiG.  145. — Five  transverse  sections  through  a  human  spinal  cord,  hardened  by  chromic 
acid,  to  show  the  relative  proportions  of  the  gray  and  white  substances, — of  the  natural  size  : 
j4,  from  the  conus  medullaris,  the  diameter  of  the  cord  being  3|  lines  ;  B,  from  the  lumbar 
enlargement,  transverse  diameter  4^  lines,  antero-posterior  4^  lines;  C,  from  the  dorsal  part 
of  the  cord,  4i  and  3|  lines ;  Z>,  from  the  cervical  enlargement,  6|  and  4|  lines  ;  E,  from 
the  superior  cervical  portion,  level  with  the  second  nerve,  6J  and  4f  lines. 


6 


THE    NERVOUS    SYSTEM.  371 

the  transverse  sectional  surfaces  of  all  the  nerves  in  square  lines,  and 
compared  with  them  the  transverse  sectional  area,  taken  with  the  utmost 
possible  nicety,  of  the  white  substance  of  the  spinal  cord,  at  the  level 
of  the  second  cervical  vertebra. 

It  is  quite  true  that  there  was  now  evident  a  very  considerable  diffe- 
rence against  the  spinal  cord ;  but  when  the  very  great  attenuation  of  the 
nerve-fibres  of  the  roots,  at  their  entrance  and  in  their  further  course  in 
the  cord,  was  brought  into  account,  which  was  not  done  by  Volkmann, 
the  matter  was  entirely  altered,  and  it  became  clear  that  the  cord  in  the 
male  subject  contained  more  than  sufficient  fibres  to  furnish  the  peripheral 
ones,  and  in  the  female  nearly  sufficient,  particularly  when  it  is  consi- 
dered, moreover,  that  in  the  entire  enumeration,  the  numbers  were  stated 
rather  in  favor  of  the  roots  of  the  nerves  (vid.  the  calculation  in  "  Mikro- 
skop.  Anatom.,"  II.  1,  §  116). 

It  appears,  therefore,  scarcely  to  admit  of  doubt,  that  the  notion  of  a 
termination  of  the  peripheral  nerves  in  the  cord,  has  no  support  in  mea- 
surements such  as  those  which,  following  Volkmann,  I  have  adduced  ; 
.  and  that  the  latter,  even  when  all  due  allowance  is  made  for  the  uncer- 
tainty always  incidental  to  such  an  inquiry,  on  the  contrary  indicate,  at 
all  events  the  probability,  that  the  spinal  nerves  ascend  to  the  cerebrum. 
They  give  no  further  information,  however,  and  it  depends  upon  other 
facts,  whether  such  a  central  origin  should  be  admitted  or  not,  because 
it  is  even  conceivable,  that  the  peripheral  nerves  may  end  in  the  cord, 
and  that  the  longitudinal  fibres  in  the  cord  have  a  wholly  different  source. 
Since  it  is  scarcely  probable  that  the  tracing  of  the  nerve-fibres  through 
the  entire  cord  will  be  effected  either  at  present  or  perhaps  at  any  time, 
it  is  necessary  to  look  round  for  other  facts,  which  may  possibly  afford 
conclusive  evidence  on  the  subject ;  and  such  facts  do  exist.  In  the  first 
place,  let  us  consider  the  course  of  the  roots  of  the  nerves  in  the  cord, 
such  as  it  has  been  described  above.  We  found,  that  after  they  had  all 
come,  more  or  less,  into  contact  with  the  gray  substance,  the  greater 
number  of  them  could  be  directly  traced  into  connection  with  the  longi- 
tudinal fibres  of  the  anterior,  lateral,  and  posterior  columns.  From  this 
fact,  together  with  my  measurements,  the  passage  of  the  greater  part  of 
the  peripheral  nerve-fibres  into  the  cerebrum,  will  appear  to  many  to  be 
proved  ;  but,  not  to  overlook  anything,  it  may  be  further  remarked,  that 
the  radical  fibres,  running  longitudinally  in  the  substance  of  the  cord, 
may  terminate  in  it,  or  after  running  in  it  may  again  enter  the  gray 
substance  higher  up.  The  former  supposition  is  now,  it  must  be  con- 
fessed, but  little  probable,  because  in  the  first  place,  no  one  has  yet 
seen  the  terminations  of  nerve-fibres  in  the  white  substance  ;  and  in  the 
second,  because  anything  of  the  sort,  for  other  reasons,  would  be  very 
surprising,  nerve-fibres  being  nowhere  known  to  commence  in  the  white 
substance ;  and  with  respect  to  the  latter,  any  re-entry  of  the  roots  of 


372  SPECIAL    HISTOLOGY. 

the  nerves  into  the  substance  could  not  escape  notice.  Since  the  junction 
of  the  radical  fibres  with  the  anterior,  posterior,  and  lateral  columns, 
can  be  so  well  and  so  directly  observed,  the  relation  in  question  would 
necessarily  be  evident  also ;  and  yet  in  the  course  of  my  perfectly  unpre- 
judiced observations,  I  have  never  seen  anything  of  the  kind.  Nothing, 
therefore,  remains  but  to  assume,  that  the  great  majority  of  the  periphe- 
ral nerves  really  have  a  cerebral  origin.  Whether  they  all  originate  in 
the  brain  (where,  we  shall  afterwards  see)  or  in  part,  though,  from  my 
observations,  but  to  a  small  extent,  from  the  cord,  cannot  be  determined, 
any  more  than  the  question  can  be  decided,  whether  the  white  substance 
of  the  cord,  besides  the  fibres  derived  from  the  peripheral  nerves,  also 
contains  others  passing  from  the  brain  to  the  cord. 

§  114.  The  medulla  oblongata  and  pons  Varolii  belong  to  the  most 
complex  parts  of  the  central  nervous  system,  containing  white  and  gray 
substance,  intermixed  in  very  various  modes.  The  white  substance  is,  in 
part,  a  continuation  of  that  of  the  cord,  in  part  distinct  from  it,  and  is 
disposed  in  the  following  manner :  the  anterior  columns  of  the  spinal 
cord  diverge  from  each  other  at  the  commencement  of  the  medulla  oblon- 
gata, allowing  the  decussating  fibres  of  the  corpora  pyramidalia  to 
appear.  As  they  proceed,  a  smaller  division  joins  the  pyramids,  form- 
ing their  outer  part,  whilst  the  principal  portion  surrounding  the  olivary 
bodies,  internally  and  externally,  whence  they  are  also  termed  the  oli- 
vary columns,  passes  laterally,  and  then,  divided  into  two  bundles, 
proceeds  above  the  second  transverse  layer  of  fibres,  through  the  pons. 
One  of  these  divisions  constitutes  the  fillet  (laqueus),  which  continued 
above  the  crura  cerebelli  ad  cerebrum,  enters  the  posterior  corpora  quad- 
rigemina,  joining,  within  them,  the  corresponding  division  of  the  opposite 
side.  The  second  division,  or  bundle,  lies  externally  and  inferiorly  to 
the  crura  cerebelli,  and  enters  the  tegmentum  of  the  cerebral  peduncle. 
Besides  this,  the  olivary  columns,  corresponding  to  the  anterior  columns 
of  the  cord,  also,  as  it  seems,  give  off  fibres  to  the  pedunculis  cerebelli. 
The  lateral  columns  of  the  spinal  cord  divide,  on  reaching  the  medulla 
oblongata,  into  three  bundles ;  one  of  which,  ascending  in  a  tolerably 
straight  direction,  is  continuous  with  the  fasciculus  lateralis  of  the  resti- 
form  body,  and  with  it  enters  for  the  most  part  into  the  peduncle  of  the 
cerebellum,  and  in  small  part  into  the  tegmentum  ;  a  second  division 
penetrates  forwards  between  the  divergent  anterior  columns,  decussates 
in  two  or  three  fasciculi  with  that  of  the  other  side  (decussatio  pyrami- 
dum),  constituting  the  principal  bulk  of  the  pyramids  ;  a  third  division, 
lastly,  appears  between  the  posterior  columns  at  the  bottom  of  the 
rhomboid  fossa,  or  fourth  ventricle,  as  the  eminentia  teres.  These  latter 
are  continued,  on  the  floor  of  the  fourth  ventricle  and  applied  to  each 
other,  into  the  tegmentum  of  the  cerebral  peduncles,  whilst  the  pyra- 


THE    NERVOUS    SYSTEM. 


373 


mids,  passing  between  the  first  and  second  transverse  layers  of  fibres  of 
the  pons,  are  continued  into  the  base  of  the  cerebral  peduncles.  The 
posterior  columns  of  the  cord,  lastly,  chiefly  constitute  the  fasciculi  gra- 
ciles  and  cuneati,  the  latter  of  which,  in  great  part,  enter  the  pedunculi 
cerebelli,  whilst  the  remainder,  and  the  fasciculi  graciles,  situated  exter- 
nally to  the  eminentice  teretes,  may  be  traced  into  the  tegmentum  of  the 
crura  cerebri.  All  these  fasciculi  consist,  besides  the  gray  substance, 
of  parallel  nerve-fibres  of  the  same  dimensions  as  those  of  the  cord,  that 
is  to  say,  from  0'001-0'004  of  a  line,  seldom  more. 

Besides  this  white  substance,  the  pons  Varolii  and  medulla  oblongata, 
omitting  the  roots  of  the  nerves,  present  a  system  of  mostly  horizontal 


fibres.     This  system  consists :  1,  of  the  well-known  transverse,  arcuate 
fibres,  external  to  the  corpora  pyramidalia  and  olivaria  ;  2,  of  straight 

FIG.  146. — Transverse  section  through  the  medulla  oblongata  in  Man.  P,  pyramids;  O, 
olivary  bodies ;  F.I,  fasciculus  lateralis;  F.c,  fasciculi  cuneati ;  F.g,fasc.graciles;  H,  root  of 
hypoglossal  nerve;  F,  root  of  n.  vagus ;  F.a,fissura  anterior;  F.p,fissura  posterior  in  the  floor 
of  the  fourth  ventricle,  or  rhomboid  fossa;  R,  raphe :  "a,  longitudinal  fibres  of  the  raphe ;  6, 
central  gray  layer  with  transverse  fibres ;  c,  expansion  of  these  fibres  in  the  olivary  column 
and  body ;  d,  accessory  olivary  nucleus  ;  e,  hypoglossal  nucleus  •  /,  decussation  of  the  hypo- 
glossal  nerve ;  g,  nucleus  of  the  vagus  ;  hhh,  larger  nerve-cells  in  the  restiform  bodies ;  t, 
medullary  mass  in  the  interior  of  the  olivary  body,  belonging  to  the  internal  transverse 
fibres;  &,  arcuate  fibres  external  to  the  olivary  body ;  I,  transverse  fibres  external  to  the 
pyramids;  m,  «,  o,  gray  nuclei  in  the  pyramids  and  olivary  columns. — Magnified  15 
diameters. 


374  SPECIAL    HISTOLOGY. 

fibres,  which  extend  from  before  backwards,  in  the  middle,  through  the 
medulla  oblongata,  contributing  to  the  formation  of  the  so-termed  raphe 
(Stilling) ;  3,  and  lastly,  of  very  numerous  fibres  proceeding  from  this 
raphe  into  the  lateral  halves  of  the  medulla,  following  a  more  or  less 
curved  direction.  These  latter,  the  internal  transverse  fibres,  commence 
behind  the  pyramids,  and  the  anterior  of  them  as  a  large  mass,  very 
minutely  broken  up  by  fine  flattened  fasciculi  of  the  pyramidal  and 
olivary  columns,  penetrate  from  within  into  the  corpus  dentatum  olivce, 
the  white  substance  of  which  is  constituted  by  them ;  they  then  expand 
in  a  brush-like  form,  and  are  continued  through  the  gray  substance  of 
the  corpus  dentatum,  ultimately  turning  backwards  towards  the  fasciculus 
cuneatus  [corpus  restiforme]  and  lateralis.  In  this  course,  the  fibres 
describe  larger  or  smaller  curves.  The  latter  is  the  case  with  those 
which  come  out  from  the  posterior  part  of  the  olivary  nucleus  [corpus 
dentatum],  and  which  go  almost  directly  backwards  and  outwards 
through  the  accessory  olivary  nucleus  (Stilling),  and  the  gray  substance, 
containing  large  cells,  situated  on  its  exterior;  the  former  condition 
obtains  in  the  anterior  fibres,  which  spread  out  in  a  radiating  manner, 
passing  at  first  forwards  between  the  pyramids  and  olivary  nucleus,  and 
afterwards  backwards  in  a  sharp  curve,  superficially  round  the  latter, 
into  the  lateral  fasciculi.  A  second  division  of  the  internal  transverse 
fibres  goes  behind  the  olivary  nucleus  with  which  it  has  no  connection, 
directly  from  the  raphe,  through  the  posterior  part  of  the  olivary 
columns  and  the  eminentice  teretes,  outwards  and  backwards,  also  into 
the  restiform  body.  All  these  fibres,  and  most  of  them  obviously  so, 
are  associated  together,  and  appear  to  me  to  be  continued  from  the 
restiform  bodies  and  the  peduncles  of  the  cerebellum,  into  the  anterior 
divisions  of  the  medulla  oblongata.  With  respect,  however,  to  their 
more  intimate  relations,  concerning  which  Stilling's  work  and  my 
"Microscopical  Anatomy"  may  be  consulted,  little  is  as  yet  known. 

The  gray  substance,  in  the  medulla  oblongata,  is  collected  into  larger 
masses,  chiefly  in  three  situations,  viz.,  in  the  olivary  and  restiform 
bodies,  and  on  the  floor  of  the  rhomboid  fossa  (fourth  ventricle) :  1,  the 
gray  substance  of  the  olivary  bodies  forms,  as  is  well  known,  a  folded 
lamella,  constituting  a  capsule  closed  on  all  sides  except  the  inner, 
which,  although  it  occupies  the  situation  of  the  anterior  horns  of  the 
spinal  cord,  which  are  continued  nearly  to  its  inferior  border,  still  has 
no  direct  connection  with  them ;  appearing,  also,  to  be  otherwise  isola- 
ted from  all  other  gray  substance.  Within  it,  besides  the  very  numer- 
ous nerve-fibres  of  the  transverse  fibre-system,  which  traverse  it  for  the 
most  part  in  straight  lines,  there  occur  in  great  numbers  smaller  nerve- 
cells,  measuring  0-008-0-012  of  a  line  in  diameter,  and  of  a  rounded 
form,  with  3—5  branching  processes,  and  containing  in  the  interior  yel- 
lowish granules,  to  which  the  color  of  the  olivary  bodies  is  due.  The 


THE    NERVOUS    SYSTEM.  375 

closest  observation  has  failed  to  afford  me  any  indication  of  a  connection 
between  these  cells  and  the  fibres  which  run  among  them.  On  a  level 
with  the  two  upper  thirds  of  the  olivary  body,  is  placed,  behind  the 
nucleus  and  wholly  isolated  from  it,  the  body  termed  by  Stilling  the 
accessory  olivary  nucleus,  in  the  form  of  a  flattened,  yellowish  band,  of 
exactly  the  same  structure  as  the  gray  substance  of  the  olivary  body, 
and  also  traversed  by  horizontal  nerve-fibres,  and  in  fact  by  fibres  which 
have  for  the  most  part  already  passed  through  the  olivary  body ;  2,  in 
the  restiform  bodies,  the  gray  substance  (corpus  s.  nucleus  cinereus) 
assumes  the  form  of  an  ill-defined,  elongated  mass  intermixed  with  very 
numerous  nerve-fibres,  and  which  occupies  mainly  the  fasciculus  late- 
ralis,  but  also  extends  into  the  fasciculi  cuneatus  and  gracilis.  This 
structure  may  be  described  as  a  continuation  of  the  posterior  horns  of 
the  spinal  cord,  even  presenting,  as  Stilling  correctly  states,  an  indi- 
cation of  the  substantia  gelatinosa  of  those  processes,  of  which  it  may 
moreover  be  observed,  that  it  is  very  remarkably  developed  in  the  upper- 
most portions  of  the  cord,  as  far  as  the  commencement  of  the  decussa- 
tion  of  the  pyramids,  and  has  a  position  entirely  lateral.  The  elements 
of  the  gray  substance  of  the  restiform  bodies  are,  besides,  numerous 
finer  fibres,  which  appear  to  pass  chiefly  into  the  horizontal,  internal 
fibre-system,  and  many,  rather  pale,  but  in  part  brownish  nerve-cells 
with  processes,  pretty  regularly  disposed,  and  most  of  them  of  the  same 
size  as  those  of  the  olivary  bodies  ;  3,  the  gray  substance  on  the  floor  of 
the  fourth  ventricle,  is  the  continuation  of  the  gray  nucleus  of  the  spinal 
cord,  and  forms  a  tolerably  thick  layer,  extending  from  the  calamus 
scriptorius  as  far  as  the  aqueductus  Sylvii.  It  contains  throughout, 
numerous  nerve-fibres,  in  part  of  very  considerable  diameter,  up  to 
0-006,  or  even  0-008  of  a  line,  in  part  of  the  finer  and  finest  kinds,  and 
besides  these,  nothing  but  caudate  nerve-cells  of  all  dimensions  from 
0-006,  up  to  0-03  of  a  line,  and  more.  The  largest  of  these  are  con- 
tained in  the  ala  cinerea  at  the  posterior  extremity  of  the  fourth  ventri- 
cle, and  in  the  subst.  ferruginea  s.  locus  cinereus  (Fig.  147),  in  which 
latter  situation,  the  cells  also  present  well-marked  pigmentary  matter, 
and  very  numerous,  delicately  branched  processes.  The  small  multi- 
nuclear  cells,  which  in  the  gray  nucleus  of  the  cord  occur  in  the  form  of 
a  compact  structure,  are  here  entirely  wanting,  not  being  found  beyond 
the  decussatio  pyramidum.  Besides  these  three  masses  of  gray  sub- 
stance, which  can  in  part  be  referred  to  that  of  the  spinal  cord,  there 
are  found,  in  the  medulla  oUongata,  some  small  collections  of  it,  as  in 
the  pyramids  near  the  olivary  bodies,  and  in  the  olivary  columns,  exter- 
nal to  the  accessory  nucleus,  in  all  of  which,  as  has  been  already  stated 
by  Stilling,  are  also  to  be  seen  in  part  larger  cells,  all  caudate  (in  the 
latter  situation  measuring  as  much  as  0-025  of  a  line),  and  finer  nerve- 
tubes.  One  part  of  the  gray  substance  just  described,  that  namely  of 


376  SPECIAL    HISTOLOGY. 

the  anterior  half  of  the  fourth  ventricle,  belongs  properly  to  the  ports 
VaroliL     It  also  contains,  in  its  interior,  besides  the  just  described 

Fig.  147. 


elements,  above  the  transverse  fibre-layer,  both  in  the  middle  as  well  as 
more  laterally,  many  accumulations  of  gray  substance,  with  larger  and 
smaller  (as  much  as  O02  of  a  line  and  more)  nerve-cells,  all  caudate, 
which  are  so  irregularly  imbedded  among  the  longitudinal  and  transverse 
fibres,  as  to  require  no  detailed  description,  and  are  connected  on  the 
one  side  with  gray  nuclei  of  the  medulla  oblongata,  and  on  the  other 
with  the  substantia  nigra  of  the  crura  cerebri. 

The  relations  of  the  ten  pairs  of  nerves  which  arise  from  the  medulla 
oblongata,  the  pons,  and  the  crura,  constitute  a  very  difficult  question. 
But  few  inquirers  have  endeavored  to  solve  it  by  other  means  than  those 
usually  employed,  that  is  to  say,  by  the  tracing  of  the  fibres,  with  the 
aid  of  the  scalpel,  which  here  goes  no  way  at  all.  Among  the  excep- 
tions are  E.  Weber  (Art.  "  Muscular  Motion,"  in  Wagner's  "  Handw.  d. 
Phys."  III.  2,  pp.  20—22),  who  made  his  examination  in  preparations, 
hardened  by  carbonate  of  potassa ;  and  Stilling,  who  pursued  his  by  the 
microscopical  examination  of  sections,  similarly  hardened  by  means  of 
alcohol.  My  own  results,  obtained  from  preparations  in  chromic  acid, 
which  had  been  for  the  most  part  made  transparent  by  soda,  agree  in 
almost  every  point  with  those  of  Stilling,  which,  at  all  events,  among 
all  observations  on  the  subject,  have  gone  most  deeply  into  the  matter. 

FIG.  147. — Nerve-cells  of  the  substantia  ferruginea  in  the  floor  of  the  fourth  ventricle  or 
rhomboid  fossa,  of  Man  ;  magnified  350  diameters. 


THE     NERVOUS     SYSTEM.  377 

The  nerves  in  question  arise,  without  exception,  not  from  the  columns 
or  fibrous  substance,  out  of  which  they  proceed,  but  all  penetrate  more 
or  less  deeply  into  the  central  parts,  and  all  probably  become  connected, 
some  not  till  they  have  decussated  like  the  trochleares,  with  definite 
parts  of  the  gray  substance,  which  Stilling  not  inappropriately  terms 
nerve  nuclei  (accessory  nucleus,  for  instance).  It  is  the  floor  of  the 
fourth  ventricle,  and  of  the  aqueduct  of  Sylvius,  which  are  more  par- 
ticularly concerned  in  this  respect,  since  all  the  nerves  above  named,  at 
least  in  part,  extend  to  them.  The  more  minute  consideration  of  these 
relations  may  be  seen  in  Stilling's  Work,  and  in  "  Mikroskop.  Anatomic," 
II.  1,  pp.  458-462. 

Although  a  favorable  judgment  cannot  be  given  upon  Stilling  and 
Wallach's  work  on  the  spinal  cord,  I  am  still  very  far  from  disposed  to 
look  down  upon  Stilling's  anatomical  writings  in  general,  as  would  seem 
to  have  been  the  fashion  for  some  time  past.  I  am  much  rather  of 
opinion,  in  which  R.  Wagner  also  coincides,  that  we  have  great  reason 
to  thank  this  author  for  his  works  on  the  medulla  oblongata  and  pons 
Varolii ;  for  although  there  are  some  thfngs  in  them  which  cannot  be 
maintained,  and  sufficient  attention  is  not  paid  to  the  elementary  con- 
stituents, still  it  cannot  be  denied  that  they  contain  a  mass  of  important 
facts.  I  have  tested,  if  not  all,  still  the  most  important  of  Stilling's 
statements,  and  have  found  them  almost  all  fully  confirmed,  and  am, 
therefore,  glad  to  take  this  opportunity  of  naming  him,  as  the  observer 
to  whom  we  are  indebted  for  the  first  accurate  investigation  of  the 
course  of  the  fibres  in  the  central  organs.  I  would  also  here,  add  :  1, 
that  in  further  investigations  of  this  kind,  chromic  acid,  or  chromate 
of  potassa,  is  to  be  preferred  to  alcohol,  particularly  also  when  caustic 
soda  is  cautiously  employed  for  the  tracing  of  the  course  of  the  nerve- 
fibres  in  the  gray  substance  thus  rendered  transparent;  and,  2,  that  in 
conjunction  with  lower  magnifying  powers,  the  most  powerful  should  be 
employed,  and  the  relations  of  the  elementary  constituents  should  also 
be  otherwise  accurately  investigated. 

The  question  as  to  the  origin  of  the  nerves  in  the  medulla  oblongata, 
presents  itself  as  one  of  the  most  difficult  nature.  Most  anatomists 
have  hitherto  been  content  to  trace  the  roots  of  the  nerves  as  far  as  one 
or  the  other  column  ;  but  this  is  not  sufficient.  All  the  nerves  enter  at 
least  once,  or  even  several  times,  into  gray  substance,  in  which,  and  no- 
where else,  are  their  origins  to  be  sought  for.  Now,  it  must  be  con- 
fessed, that  through  Stilling's  great  pains,  the  fruits  of  which  I  can,  as 
it  may  be  said,  fully  confirm — all  the  ten  pairs  of  nerves  at  present 
under  consideration  have  been  traced  in  their  roots,  as  far  as  perfectly 
definite  points  of  the  gray  substance  ;  but  now  comes  for  the  first  time 
the  further  question :  do  they  commence  in  these  situations,  or  do  they 


378  SPECIAL    HISTOLOGY. 

proceed  beyond  them  ?  As  true  origins  in  the  brain  have  never  yet 
been  seen  with  certainty  by  any  one,  there  remains  nothing  but  physio- 
logical analogies  and  reasons.  As  regards  the  former,  we  see  in  all  the 
spinal  nerves,  that  they  first  penetrate  transversely  as  far  as  the  gray 
substance,  and  then,  only  passing  through  this,  join  the  white  columns, 
and  we  may  thence  suppose  that  the  cerebral  nerves,  which,  in  general, 
so  closely  resemble  them,  are  in  the  same  condition,  and  the  more  so, 
because  these  also  at  first  penetrate  transversely  into  the  interior  of  the 
medulla,  and  the  gray  substance,  with  which  they  come  in  contact, 
corresponds  with  that  of  the  cord.  To  this  may  be  added  also,  that  if 
we  make  the  ten  last  cerebral  nerves  terminate  in  the  gray  substance, 
into  which  they  may  so  readily  be  traced,  the  decussated  influence  of 
the  parts  above,  upon  them,  which  appears  to  be  established  by  patho- 
logical phenomena,  cannot  be  explained  in  the  case  of  any  one  of  them 
except  the  trochlearis,  which  decussates  before  it  reaches  its  gray  sub- 
stance. Now,  in  the  accessorius  and  hypoglossus  it  is  actually  possible 
to  see  that  the  fibres  come  out  from  the  gray  substance,  reached  by 
them  in  the  first  instance,  and  afterwards  decussate  ;  and  the  same 
thing  is  also  at  least  probable*  in  the  oculo-motorius ;  so  that  I  think  it 
may  be,  that  all  the  nerves  now  in  question  undergo  decussation,  and 
do  not  terminate  in  the  so-termed  nuclei  of  Stilling.  Further  investiga- 
tion will  have  to  show  whether  this  [decussation]  takes  place  in  the 
floor  of  the  fourth  ventricle,  as  would  appear  to  be  the  case ;  whether 
all  the  fibres  of  these  nerves  take  part  in  it ;  and  where  the  fibres  pro- 
ceed to  after  decussation.  With  respect  to  the  latter,  it  may  be  sup- 
posed from  analogy  with  the  spinal  nerves,  that  the  true  origin  of  the 
cerebral  nerves  is  probably  not  in  the  medulla  oblongata,  but  in  the 
corpora  striata  and  optic  thalami.  Of  that  portion  of  the  portio  major 
n.  trigemini,  which  is  continued  into  the  restiform  body,  this  may  espe- 
cially be  remarked,  that  it  certainly  does  not  originate  in  that  part,  but 
winds  round  it  to  somewhere  above,  as  is  the  case  also  with  the  n.  acces- 
sorius. 

However,  in  stating,  in  accordance  with  what  has  been  said,  that  I 
do  not  consider  it  directly  probable,  that  the  sensitive  and  motor  cere- 
bral nerves  originate  in  the  medulla  oblongata  and  pons,  it  is  by  no  means 
intended  to  imply  that  these  parts  may  not,  as  central  organs,  exert 
some  influence  upon  them  and  the  more  deeply  placed  nerves.  If  the 
medulla  oblongata  preside  over  the  respiratory  movements,  if  it  and 
the  pons  be  the  agents  of  multiplied  reflex  motions,  this  may  be  the 
case,  without  its  following  that  all  the  nerves  called  into  action  should 
terminate  in  them,  and  simply  for  the  reason  that  the  gray  substance, 
so  abundantly  contained  in  them,  influences  the  nerves  which  traverse 
it,  exactly  as  must  be  supposed  to  be  the  case  in  the  spinal  cord. 


THE    NERVOUS    SYSTEM.  379 

§  115.  The  cerebellum,  with  respect  to  the  distribution  of  the  ele- 
mentary tissues,  exhibits  tolerably  simple  conditions,  gray  substance 
occurring  only  on  the  surface  of  the  convolutions,  in  the  nucleus*  den- 
tatus,  and  in  the  roof  of  the  fourth  ventricle  ;  all  the  remainder  con- 
sists of  white  substance.  The  latter  is  wholly  constituted  of  parallel, 
probably  unbranched,  dark-bordered  nerve-fibres,  possessing  all  the 
characters  of  central  fibres  (softness,  proneness  to  become  varicose,  easy 
isolation  of  the  axis-cylinder,  &c.),  are  essentially  alike  in  all  situations, 
as  far  as  their  condition  can  be  observed,  and  present  a  diameter  of 
0-0012-0-004  of  a  line  in  the  extremes,  and  of  0.002  of  a  line  in  the 
mean.  The  gray  substance  occurs,  in  the  first  place,  very  scantily  in 
the  roof  of  the  fourth  ventricle  above  the  velum  medullare  inferius,  in 
the  form  of  brown  nerve-cells,  measuring  0-02-0-03  of  a  line,  scattered 
in  the  white  substance,  and  recognizable  by  a  sharp  eye  without  further 
aid  (the  substantia  ferruginea  superior) ;  and,  secondly,  in  the  nucleus 
dentatus,  the  grayish-red  lamella  of  which  contains  a  considerable 
number  of  yellowish  pigment  nerve-cells  of  a  medium,  size  (0-008- 
0-016  of  a  line)  with  four  or  five  processes,  and  which  have  no  direct 
connection  with  numerous  nerve-fibres  proceeding  from  the  nucleus 
dentatus  into  the  medullary  substance  of  the  hemispheres,  which  pass 
through  among  them. 

The  relations  of  the  gray  substance  on  the  surface  of  the  convolutions 
of  the  cerebellum  are  more  complex  (vide  "  Mikr.  Anat.,"  PL  IV.  fig.  4). 
It  consists  everywhere,  as  is  well  known,  of  a  layer,  internally  of  a 
rusty  color,  externally  gray,  which,  except  in  the  fissures,  where  the 
internal  layer  is  most  usually  thicker,  presents  pretty  nearly  the  same, 
but  not  everywhere  an  equal  thickness. 

The  internal  ferruginous  layer  Contains  nerve-fibres  and  large  masses 
of  free  nuclei.  The  former  arise,  without  exception,  from  the  white 
substance,  and  run,  in  general,  parallel  to  each  other,  although  on  a 
transverse  section  of  any  convolution  slightly  diverging  in  a  penicillar 
manner,  directly  into  the  ferrugineous  layer.  Within  this  layer  they 
also  run  from  within  to  without  as  far  as  the  gray  layer,  but  are  broken 
up  into  numerous,  for  the  most  part,  fine  fasciculi,  which  are  much  inter- 
laced, so  that  the  whole  ferrugineous  layer  is  penetrated  by  a  close  but 
delicate  network  of  nerve-fibres,  which  recalls  in  appearance  the  ter- 
minal plexuses  in  peripheral  parts,  as  for  instance,  in  the  n.  acusticus, 
in  the  follicles  of  the  vibrissw,  &c.  In  the  meshes  formed  by  these 
nerve-fibres  lie  a  vast  number  of  opaque,  round  corpuscles,  measuring 
0-002-0-004,  in  the  mean  0-003  of  a  line,  which  are  nothing  else  than 
free  nuclei,  and  which  frequently  also  exhibit  a  distinct  nucleolus,  and 
not  unfrequently  other  granules. 

In  their  passage  through  the  ferrugineous  layer,  the  nerve-fibres  of 
the  white  substance  become  gradually  attenuated,  most  of  them  to  a 


380 


SPECIAL    HISTOLOGY. 


diameter  of  0-0012  of  a  line,  and  in  this  state  enter  the  external  gray 
layer.  This  layer,  although  to  outward  appearance  everywhere  per- 
fectly homogeneous,  consists  of  two  not  well-defined  laminae,  the  inner 
of  which  contains  nerve-fibres  and  very  well-marked,  large  nerve-cells, 
whilst  the  outer  presents  nothing  but  a  finely- granular,  pale,  light-yel- 
lowish substance,  which  is  distributed  generally  throughout  this  gray 
layer,  and  contains  no  nerve-cells.  The  granular  substance  agrees 
chemically,  morphologically,  and  physically  in  all  respects  with  the 
already-described  contents  of  the  nerve-cell ;  it  is  tenacious,  elastic, 
rendered  more  opaque  by  acetic  acid,  and  more  transparent  in  caustic 
soda,  in  which  it  is,  for  the  most  part,  dissolved,  and  exists  in  the  purest 
form  in  the  outer  half  of  the  gray  layer,  that  is  to  say,  next  to  the  pia 
mater.  The  small  nerve-cells,  speaking  generally,  are  very  few  in 
number  and  indistinct.  They  occur  scattered  throughout  the  gray  layer, 
having  a  diameter  of  0-004-0-008  of  a  line,  more  frequent  towards  the 
ferrugineous  layer  than  more  externally,  and  when  successfully  prepared, 
particularly  by  means  of  chromic  acid,  most  of  them  exhibit  delicate 
processes,  which,  however,  can  never  be  traced  to  any  distance,  and  are 
frequently  torn  off  close  to  the  cells.  Besides  these  cells,  there  also 
occur  here  and  there,  but  on  the  whole  rarely,  nuclei  of  0-002-0-0048 

Fig.  148. 


of  a  line,  which,  to  all  appearance,  are  free,  as  they  are  met  with  even 
in  the  most  carefully -made  preparations.  Entirely  different  from  these 
smaller  elements,  and  very  peculiar,  are  the  large  cells  of  the  gray  layer 
(Fig.  148)  discovered  by  Purkinje.  These  cells,  measuring  0-016-0-03 
of  a  line,  and  of  a  round  pyriform  or  oval  figure,  with  finely-granular, 
colorless  contents,  occur  only  in  the  innermost  portions  of  the  gray, 

FIG.  148. — Large  cells  of  the  gray  layer  of  the  cortical  substance  of  the  human  cere- 
bellum, magnified  350  diameters. 


THE    NERVOUS    SYSTEM.  381 

close  to  the  ferrugineous  layer,  and  they  are,  not  unfrequently,  at  least 
some  of  them,  partly  imbedded  in  its  nuclei,  in  single  or  multiple  layers, 
and  presenting  2-3,  rarely  1-4,  long  and  much  branched  processes, 
directed  particularly  towards  the  outer  surface  of  the  convolutions,  which 
are,  almost  without  exception,  at  all  events  the  strongest  of  them,  given 
off  from  the  sides  of  the  cells  which  look  from  the  ferrugineous  layer. 
At  their  origin  these  processes  are  even  0-007,  or  as  much  as  0-008  of 
a  line  thick,  and  extremely  finely  granular  or  very  delicately  striped. 
As  they  proceed  they  become  more  homogeneous,  and  at  the  same  time 
divide  into  very  numerous  and  extremely  slender  branches,  so  that  at 
last,  from  each  process  a  large  bundle  of  very  fine  filaments,  having  a 
diameter,  in  the  finest,  of  scarcely  0-0002  of  a  line,  is  produced.  A 
portion  of  these  fibrils  penetrate  more  horizontally  into  the  gray  layer, 
although  most  of  them  stretch  directly  outwards,  and  appear  to  extend 
nearly  to  the  outer  surface  of  the  gray  layer.  That  they  extend  very 
far  is  certain,  for  in  preparations  made  with  chromic  acid,  I  have  iso- 
lated some  measuring  0*15-0-2  of  a  line,  which  were  still  not  the  finest ; 
and  in  successful  perpendicular  sections  through  the  cortical  layers  of 
the  convolutions,  their  principal  branches  appear  as  parallel,  slightly 
undulating  fibres  in  close  contiguity,  extending  through  more  than  two- 
thirds,  or  even  three-fourths,  of  the  gray  layer,  to  which  they  give  a 
peculiar  striated  aspect.  Whilst  the  principal  prolongations  of  the  pro- 
cesses are,  in  this  way,  continued  through  the  gray  layer,  they  give  off 
their  branches  at  acute  or  right  angles,  whence  not  unfrequently  a 
second  striation  is  produced,  crossing  the  one  just  described  at  a  greater 
or  less  angle. 

In  the  innermost  portion  of  the  gray  layer,  among  the  large  cells, 
there  moreover  exists  some  nerve-fibres ;  but  which,  owing  to  their  deli- 
cacy and  the  ease  with  which  they  are  destroyed,  it  is  very  difficult  to 
trace.  Quitting  the  ferrugineous  layer,  and  forming  a  continuous  plexus, 
they  are  distributed  in  the  inner  third  of  the  gray  lamina  among  the 
large  cells  and  their  processes  ;  there  mode  of  termination  has  escaped 
my  observation,  the  result  of  which  amounts  only  to  this  :  1,  that  they 
become  finer  and  paler,  decreasing  from  their  original  thickness  of 
0-0012,  ultimately  to  one  of  0-0006  and  0-0004  of  a  line,  their  dark 
outlines  also  being  replaced  by  a  paler  contour  ;  2,  that  they  certainly 
do  riot  form  terminal  loops,  such  as  Valentin  and  Hyrtl,  who  have  pro- 
bably mistaken  a  fine  plexus  for  such,  think  they  have  noticed  ;  but  be- 
coming isolated,  and  running  in  a  more  straight  direction,  and  almost 
as  pale  as  the  processes  of  the  nerve-cells  at  the  border  of  the  inner 
third  of  the  gray  lamina,  are  lost  towards  the  middle  of  it. 

The  crura  cerelelli  are  composed  of  nothing  but  parallel  nerve-fibres, 
without  any  admixture  of  gray  substance,  corresponding  with  those  of 


382  SPECIAL    HISTOLOGY. 

the  medullary  substance  of  the  cerebellum  itself,  as  a  continuation  of 
which  they  are  to  be  regarded. 

§  116.  G-anglia  of  the  Cerebrum. — The  three  pairs  of  cerebral  gan- 
glia, the  corpora  quadrigemina,  optic  thalami,  and  corpora  siriata,  all  con- 
sist of  bulky  collections  of  gray  substance,  and  of  nerve-fibres  ;  the  former 
of  which  are  in  part  quite  isolated  (corpus  striatum),  in  part  mutually  con- 
nected, and  with  more  deeply  lying  portions  of  gray  substance  (thalami 
opticij  corp.  guadrigemind) ;  the  latter  connect  the  ganglia,  on  the  one 
hand  with  the  cerebellum  and  medulla  oblongata,  and  on  the  other  with 
the  hemispheres  of  the  cerebrum. 

The  corpus  striatum  contains  two  large  gray  nuclei,  the  nucleus 
caudatus  anteriorly  and  superiorly,  and  the  n.  lenticularis  posteriorly 
and  inferiorly,  which  are,  however,  connected  in  front,  constituting  a 
single  mass ;  and  besides  these,  the  slender  n.  tceniceformis,  with  the 
amygdalce  external  to  the  lenticular  nucleus,  and  is  in  connection  prin- 
cipally with  the  basis  of  the  cerebral  peduncle  or  continuation  of  the 
pyramid  which  expands  in  it,  forming  numerous  white  fasciculi.  The 
gray  substance  presents,  as  almost  universally,  nerve-cells  and  fine  nerve- 
fibres.  The  former,  which  measure  from  0-006-0-018  of  a  line,  are,  in 
part,  colorless,  and  in  part,  contain  pigment,  as,  especially,  in  the  cau- 
date nucleus  and  third  segment  of  the  lenticular  nucleus ;  they  are  fur- 
nished with  from  two  to  five  processes,  and  occur  in  greater  numbers 
according  to  the  depth  of  color  of  the  gray  substance. 

The  nerve-fibres  may  be  referred  for  the  most  part  to  those  of  the 
basis  of  the  crura  cerebri.  They  present  the  form  of  dark-bordered 
tubes  from  0-0012-0-005,  most  of  them  from  0-002-0-004  of  a  line 
in  size,  which,  running  parallel  and  close  together  in  a  straight  direc- 
tion, enter  the  first  division  of  the  lenticular  nucleus,  and  the  most 
anterior,  thickest  portion  of  the  caudate  nucleus.  When  traced  further 
in  the  lenticular  nucleus,  it  will  be  seen  that  they  form  larger  and 
smaller  fasciculi,  decreasing  somewhat  in  size  (most  of  them  measuring 
from  0-0012-0-003  of  a  line)  and  that,  passing  straight  through  the 
more  scanty  gray  substance  of  the  first  divisions  of  the  lenticular 
nucleus,  they  are  all  ultimately  lost,  spreading  out  in  a  penicillar  form  in 
its  outermost  and  largest  division.  That  is  to  say,  white  fasciculi  mea- 
suring from  0-04-014  of  a  line,  with  fibres  of  0-0012-0-002 'of  a  line, 
enter  this  division  of  the  nucleus  from  the  second ;  and  these  fasciculi 
in  close  contiguity,  slightly  diverging  and  subdividing  into  smaller  bun- 
dles, are  continued  further  in  a  direction  towards  the  outer  border  of 
the  lenticular  nucleus,  before  reaching  which  they  disappear  to  the 
naked  eye.  If  traced  microscopically  in  preparations  made  with 
chromic  acid,  it  is  apparent,  that  the  fasciculi  proceed  nearly  to  the 
outermost  part  of  the  lenticular  nucleus,  though  gradually  broken  up 


THE    NERVOUS     SYSTEM.  383 

into  smaller  bundles  and  separate  fibres,  and  most  intricately  interlaced 
with  each  other.  That  these  fibres  terminate  here,  and  do  not  proceed 
any  further  into  the  medullary  substance  of  the  hemispheres,  may  be 
considered  as  made  out,  not  the  faintest  indication  of  any  further  con- 
tinuation being  afforded,  which,  if  it  existed,  could  not  escape  being 
seen :  on  the  other  hand  it  is  doubtful  how  they  terminate  here.  All 
I  have  to  state  on  the  point  is  this  :  that  the  fibres  of  the  nerve-fasciculi, 
entering  the  third  division  of  the  lenticular  nucleus,  as  may  be  directly 
observed  in  a  very  great  many  instances,  gradually  become  so  much 
attenuated,  as  ultimately  to  measure  not  more  than  0-0008,  0-0006,  or 
even  hardly  0-0004  of  a  line,  and  present  an  almost  entirely  pale  aspect, 
so  that  they  can  scarcely  any  longer  be  distinguished  from  the  finer 
processes  of  the  nerve-cells  ;  with  which  in  fact,  unless  everything  is 
deceptive,  they  most  probably  are  actually  connected.  All  the  fibres, 
also,  which  enter  the  caudate  nucleus,  present  exactly  the  same  condi- 
tions ;  some  of  these  enter  the  nucleus  directly  from  the  basis  of  the 
cerebral  peduncle,  others,  which  appear  in  its  thinner  portion,  are 
manifestly  derived  from  the  lenticular  nucleus,  the  first  two  divisions  of 
which  they  traverse  in  the  first  instance  ;  in  this  case,  also,  there  is  no 
transition  of  the  fibres  into  the  medullary  substance  of  the  hemispheres, 
but  a  separation  of  the  fasciculi  into  a  plexus  of  the  finest,  almost  non- 
medullated  fibres  takes  place,  and  probably  a  connection  between  them 
and  the  cells. 

Besides  the  above  described,  in  any  case  very  numerous,  nerve-fibres 
derived  from  the  cerebral  peduncles  and  terminating  in  the  corpora 
striata,  the  nuclei  of  those  bodies  contain  a  considerable  number  of 
other  fibres,  whose  origin  it  is,  in  part,  difficult,  and,  in  part,  impossi- 
ble to  assign.  I  think  I  can  trace  one  set  of  these  fibres  to  their 
source.  In  the  most  external  part  of  the  large  nucleus  of  the  corpus 
striatum,  we  find,  on  making  various  sections,  a  considerable  number  of 
moderately  strong  fasciculi,  though  not  visible  to  the  naked  eye,  which 
in  their  relative  thickness  and  the  diameter  of  their  tubes  (0-0012-0-002 
of  a  line)  differ  from  the  fibres  derived  from  the  crus  cerebri,  which  in 
this  situation  are  reduced  to  the  most  extreme  attenuation  and  dispersed 
in  a  plexiform  manner.  It  is  easily  seen  that  all  these  fasciculi  proceed 
from  the  medullary  substance  of  the  hemispheres ;  and,  as  it  appears, 
after  they  have  run  a  certain  distance  parallel  with  the  surface  on  the 
border  of  the  nucleus  of  the  corpus  striatum,  that  they  enter  it.  Many 
of  these  fibres  are  continued  directly  from  the  medullary  substance 
into  the  ganglia,  and,  in  this  way,  decussate,  at  right  angles,  with  the 
former  fibres.  Assembled  in  fasciculi,  these  fibres  penetrate  more  or 
less  deeply  into  the  gray  substance  of  the  corpus  striatum,  and  of  the 
third  division  of  the  lenticular  nucleus ;  and  these  terminate,  as  I  think 
I  have  observed,  without  any  considerable  expansion,  the  formation  of 


384  SPECIAL     HISTOLOGY. 

a  plexus,  or  undergoing  any  farther  decrease  in  size,  their  fibres  form- 
ing loops  with  closely  approximated  sides. 

Although,  speaking  relatively,  it  is  not  difficult  to  make  out  the  struc- 
ture of  the  corpus  striatum,  at  all  events,  in  its  principal  features,  it  is 
quite  otherwise  with  the  optic  thalami  and  corpora  quadrigemina,  chiefly 
because  the  nerve-fibres  in  these  situations  are  not  so  much  assembled 
into  fasciculi,  but  are  more  isolated  and  most  intimately  intermixed  with 
the  gray  substance,  on  which  account  they  cannot  be  traced  to  any 
great  distance.  The  examination  of  the  gray  substance  itself,  however, 
is  perfectly  easy  even  in  these  bodies,  arid  its  elements — the  nerve-cells — 
present  nothing  peculiar,  except  that,  in  the  optic  thalami,  they  are  for 
the  most  part  more  deeply  colored,  whilst  those  in  the  corpora  quadrige- 
mina  are  paler.  With  respect  to  the  nerve-fibres,  it  is  quite  certain 
that  the  superior  portion  of  the  crura  cerebri,  that  is  to  say,  the  crura 
cerebelli  ad  corpora  quadrigemina^  the  continuations  of  the  olivary 
columns,  portions  of  the  corpora  restiformia,  and  the  eminentice  teretes, 
pass  into  the  ganglia  now  under  consideration,  although  I  have  not  as 
yet  succeeded  in  eliciting  anything  determinate  as  to  the  course  they 
take.  But  I  think  it  may  be  stated,  that  the  fibrous  masses  above 
named,  in  great  part  at  least,  are  not  continued  into  the  medullary  sub- 
stance of  the  hemispheres,  because,  on  the  one  hand,  most  of  their  fibres 
decrease  from  the  original  diameter  of  0*0012— 0'004  of  a  line  down  to 
the  smallest,  or  less  than  0-001  of  a  line ;  and  on  the  other,  because  no 
such  passage  of  the  fibres  can  be  perceived  on  that  side  of  the  optic 
thalamus,  which  looks  towards  the  medullary  substance  of  the  hemi- 
spheres. The  superficial  white  investment,  however,  of  the  ganglia  in 
question,  must  be  excepted,  which  in  any  case  may  eifect  a  relation 
between  them  and  the  hemispheres,  as  its  fibres,  measuring  0'001-0'003 
of  a  line,  or  even  more,  disposed  in  fasciculi,  and  crossing  each  other 
'  horizontally  in  various  directions,  do  not  appear  to  terminate  in  it. 
Neither  is  the  relation  of  the  optic  thalami  to  the  corpora  quadrigemina, 
and  that  of  the  fornix  to  the  latter,  by  any  means  clear,  so  that  it  is 
pleasing,  at  all  events,  to  find  that  another  important  question  admits  of 
a  more  satisfactory  solution.  When  the  external  portion  of  the  optic 
thalamus  is  examined,  it  will  be  found  that  it  adjoins  a  considerable  mass  of 
white  substance,  which  at  first  sight  appears  to  be  a  continuation  of  the 
basis  of  the  cerebral  peduncles  passing  below  and  external  to  the  optic 
thalamus,  between  the  lenticular  and  caudate  nuclei  of  the  corpus  stria- 
turn,  to  enter  directly  into  the  medullary  substance  of  the  hemispheres. 
Closer  observation  renders  it  obvious,  that  this  white  substance,  as  has 
been  said  before,  in  part  enters  the  corpus  striatum,  particularly  the 
lenticular  nucleus,  and  in  part  radiates  from  without  inwards,  from  the 
hemisphere  into  the  optic  thalamus.  That  is  to  say,  very  numerous 
white  fasciculi,  visible  even  to  the  naked  eye,  coming  from  the  hemi- 


THE    NERVOUS    SYSTEM.  385 

sphere  throughout  the  entire  height  of  the  thalamus,  enter  the  latter, 
run  towards  the  superior  surface  to  the  superior  and  internal  border, 
and  the  pulvinar,  being  ultimately  lost  exactly  in  the  same  way  as  are 
the  fibres  continued  from  the  cms  cerebri  into  the  corpus  striatum  ;  that 
is,  these  fasciculi,  the  elementary  fibres  of  which  originally  measure 
0-0012-0-0025  of  a  line,  ultimately  subdivide  into  extremely  close  plex- 
uses composed  of  fibres  of  the  most  extreme  fineness,  0-0004-0-0008  of 
a  line,  the  terminations  of  which  cannot  be  traced. 

I  will  just  notice  the  constitution  of  some  structures  connected  with 
the  above-described  ganglia.  The  substantia  nigra  of  the  cms  cerebri 
presents  pigment-cells  precisely  similar  to  those  of  the  substantia  fer~ 
ruginea,  except  that  they  are  for  the  most  part  rather  smaller,  and 
have  fewer  processes,  surrounded  with  nerve-fibres  of  the  finest,  and 
also  of  the  stronger  kind.  The  commissura  mollis  contains  smaller  cells, 
with  1,  2,  3,  and  more  processes,  and  light-colored  pigmentary  contents; 
and  besides  these,  very  many,  plexiform,  vertical,  and  horizontal,  fine 
fibres  of  0-0012-0-0016  of  a  line,  with  some  still  finer,  less  than  0-001, 
and  a  few  stronger  measuring  as  much  as  0-004  of  a  line.  The  pineal 
gland  exhibits  pale,  rounded  cells,  without  any  processes,  and  scattered 
nerve-fibres  of  0-001-0*002  of  a  line,  and  also,  generally,  a  considerable 
quantity  of  sabulous  matter  (brain-sand)  (vid.  §  118).  Its  peduncles, 
their  anterior  prolongations,  and  the  commissura  posterior,  contain  fibres 
measuring  0-001-0-003  of  a  line,  and  are  composed  in  part  also  of  the 
finest  fibres.  The  floor  of  the  third  ventricle  presents,  immediately 
beneath  and  behind  the  anterior  commissure,  extremely  large,  and 
smaller,  colorless  cells,  with  from  one  to  four,  occasionally  very  thick 
processes.  These  are  lodged  in  great  number  in  a  close  plexus  of  fine 
fibres  of  0-0004-0-0012  of  a  line;  and  cells,  in  other  respects  exactly 
similar,  though  not  quite  of  the  same  size,  also  exist  in  the  corpus  mam- 
millare,  likewise  intermixed  with  very  numerous  fibres  of  the  finest  sort; 
there  are  other  still  smaller  cells  of  0-008-0-012  of  a  line,  for  the  most 
part  with  only  two  processes,  in  the  tuber  cinereum.  The  hypophysis 
cerebri  contains,  in  its  anterior,  reddish  lobe,  no  nervous  elements  ;  but 
rather,  according  to  Ecker  (art.  "  Blood-vascular  Glands,"  in  Wagner, 
"  Handw.  d.  Physiol."),  the  elementary  tissues  of  blood-vascular  glands ; 
that  is  to  say,  a  vascular  stroma  of  connective  tissue,  in  the  interstices 
of  which,  lie  vesicles  (cells?)  measuring  0-030-0*090mm,  containing 
sometimes  only  nuclei,  and  a  fine  granular  substance,  sometimes  distinct 
cells,  in  older  persons  also  colloid-like  masses.  The  posterior,  smaller 
lobe  consists  of  a  fine  granular  substance,  with  nuclei  and  bloodvessels, 
and  also  contains  fine,  varicose  nerve-fibres,  which,  like  the  vessels, 
descend  from  the  infundibulum. 

§  117.  Hemispheres  of  the   Cerebrum. — The  white  substance  of  the 

25 


SPECIAL    HISTOLOGY. 

hemispheres  of  the  brain  consists  entirely  of  nerve-fibres,  of  0-00012- 
0-003,  on  the  average  0-002  of  a  line  in  size,  without  any  admixture 
of  gray  substance.  These  fibres,  of  whose  special  course,  we,  as  yet, 
know  extremely  little,  never  form  plexiform  interlacements  or  fasci- 
culi, but  all  run  in  parallel,  and  most  generally,  straight  lines,  and 
undoubtedly  proceed  from  the  corpus  callosum  and  ganglia  of  the  cere- 
brum as  far  as  the  superficial  gray  substance,  whilst  it  must  remain 
undetermined  whether,  in  their  course,  they  divide  or  not.  But  besides 
these  fibres,  omitting  also  the  commissura  anterior,  ihefornix,  and  the 
origin  of  the  optic  nerves,  the  hemispheres  contain  others  crossing  the 
former  at  right  angles.  I  have  found  these  fibres,  in  the  first  place,  on 
the  outer  side  of  the  corpus  striatum,  in  which  situation  they  are  to  be 
referred,  in  part,  to  the  fibres  which  enter  the  corpus  striatum  from  the 
hemispheres  and  terminate  in  it ;  perhaps,  also,  in  part,  to  the  expan- 
sion of  the  corpus  callosum  in  the  inferior  lobes  ;  and  secondly,  in  the 
most  superficial  layer  of  the  white  substance,  near  the  gray  cortical  sub- 
stance, where  they  occur  in  not  inconsiderable  numbers,  and  running,  in 
part,  obliquely  ;  but  of  their  origin  nothing  satisfactory  could  be  ascer- 
tained. Whether  there  are  still  other,  and  what  traces  of  fibres,  the 
future  must  show. 

The  more  intimate  structure  of  the  gray  substance  of  the  convolutions 
is  tolerably  manifest  (vid.  "Mikroskop.  Anatomie,"  PL  IV.  fig.  2).  It 
is  most  conveniently  divided  into  three  layers,  an  external,  white ;  a 
middle,  pure  gray  ;  and  an  internal,  yellowish  red.  The  latter,  in  thick- 
ness almost  equal  to  the  other  two,  usually  presents,  on  its  outermost 
border,  a  clear,  frequently  white  streak,  and  occasionally,  more  inter- 
nally, a  second,  thinner  and  less  white  layer,  so  that  there  are  in  fact 
four  or  even  six  successive  laminse ;  1,  a  yellowish-red  layer  (inner  part) ; 
2,  the  first  white  streak ;  3,  yellowish-red  layer  (outer  part) ;  4,  second 
white  streak  ;  5,  the  gray  layer ;  6,  superficial  white  layer.  The  gray 
substance  contains,  in  its  whole  thickness,  both  nerve-cells  and  nerve- 
fibres  ;  and  besides  these,  much  granular  matrix-substance,  exactly  like 
that  of  the  cerebellum.  The  nerve-cells  are  not  easily  investigated, 
except  in  preparations  in  chromic  acid,  and  in  all  the  three  layers  they 
agree  in  this  respect,  that  by  far  the  greater  number  of  them  are  fur- 
nished with  from  one  to  six  processes,  which  give  off  numerous  branches, 
and  ultimately  form  extremely  fine,  pale  fibrils  of  about  0-0004  of  a  line 
in  diameter,  differing,  however,  in  respect  of  size,  number,  &c.  In  the 
superficial  white  layer  the  cells  are  few,  small  (0-004-0-008  of  a  line), 
with  one  or  two  processes,  and  scattered  in  an  abundant,  finely  granular 
matrix.  The  middle  or  pure  gray  layer,  most  abounds  in  cells,  which 
in  it,  are  closely  aggregated  also  in  a  granular  matrix.  Their  size 
varies  very  considerably,  some  being  very  small  (0-003—0*005  of  a  line), 
frequently  appearing  as  little  more  than  nuclei,  whilst  there  are  many 


THE    NERVOUS    SYSTEM. 


387 


others  of  larger  dimensions,  up  to  0-016  and  0-02  of  a  line  (Fig.  149). 
Their  figure  is  pyriform  or  fusiform,  tri-  or  multangular,  also  perhaps 
more  rounded,  by  far  the  greater  number  having  from  one  to  six  pro- 
cesses, usually  three,  four,  or  five  ;  and  where  this  is  not  the  case,  they 
may  have  been  torn  off  in  the  preparation,  since  stumps  of  them  may 
be  very  readily  noticed  in  the  cells,  which  are  altogether  very  delicate. 
In  the  innermost  yellowish-red  layer,  lastly,  the  cells  are  again  rather 
more  scanty,  though  still  extremely  abundant,  otherwise  presenting  the 
same  characters  as  those  in  the  gray  substance,  having  sometimes  pale, 
sometimes  pigmentary  contents ;  the  latter  in  the  inner  layers  more 
particularly,  and  in  old  persons. 

The  nerve-fibres  of  the  gray  substance  of  the  convolutions,  arise,  as  it 
is  easy  to  demonstrate,  from  the  medullary  substance  of  the  hemispheres, 

Fig.  149. 


and  penetrate,  bundle  after  bundle,  directly,  and  all  parallel,  into  the 
yellowish-red  layer.  Arrived  here,  many  fibres  separate  from  the  rest, 
and  penetrate  the  yellowish-red  layer  in  all  directions,  but  more  espe- 
cially parallel  to  the  surface,  and  consequently  crossing  the  main  fasci- 
culi. When  these  horizontal  fibres  are  more  closely  aggregated,  they 
produce  the  above-described  whiter  or  clearer  streaks  in  this  layer,  the 
outer  of  which  streaks  is  situated  exactly  at  the  point,  where  the  fasciculi 
which  enter  the  gray  substance,  are  lost.  In  fact,  as  these  proceed  more 
outwardly,  they  constantly  decrease  in  size,  owing  to  their  giving  off  lateral 

FIG.  149. — From  the  internal  portions  of  the  gray  layer  of  the  convolutions  of  the  human 
cerebrum,  magnified  350  diameters.  Nerve-cells:  a,  larger;  6,  smaller;  c,  nerve-fibres  with 
axis-cylinder.  . 


388 


SPECIAL    HISTOLOGY. 


fibres,  and  to  the  attenuation  and  separation  of  their  elements,  until,  when 
they  have  reached  the  gray  layer,  they  become  lost  to  sight,  although  if 
more  closely  traced  they  may  still  be  perceived  as  intricately  interlaced 
fibrils  of  the  utmost  fineness,  and  with  scarcely  any  appearance  of  dark 
contours,  only  that  there  are  a  certain,  though  smaller  number  of  fibres, 
which,  upon  reaching  the  gray  layer,  do  not  lose  their  breadth  and 
dark  contours,  but  are  continued  in  a  straight  or  oblique  course  through 
it,  extending  horizontally  to  a  further  distance,  in  the  outer  white 
layer.  In  this  layer,  consequently,  we  find  a  considerable  number  of 
finer,  and  of  the  very  finest  fibres  (Fig.  150),  crossing  each  other  in 

various    directions,    and    in 

- 15°-  several  superimposed  layers, 

which,  are  obviously,  as  to 
their  origin,  to  be  referred 
to  those  arising  from  the 
reddish-gray  layer ;  and 
which  probably  also,  as 
Remak  has  assumed,  are 
derived,  at  the  basis  of  the 
cerebrum,  from  the  anterior 
extremity  (knee)  of  the  cor- 
pus callosum.  How  these 
fibres  are  related  to  the  cells 
in  the  white  layer  is  doubt- 
ful, although  this  much  is 
certain,  that  many  of  them 
return  into  the  gray-red 
substance  from  which  they 
arose,  or  in  other  words  from  loops,  which  were  first  described  by 
Valentin,  and  which  I  have  very  frequently  and  distinctly  noticed  in 
chromic  acid  preparations  treated  with  caustic  soda.  I  have  also 
observed,  in  the  gray-red  substance,  isolated  loops  with  closely  ap- 
proximated sides,  and  also  with  their  convexity  looking  towards  the 
surface  of  the  brain.  The  fasciculi  of  the  gray-red  substance  contain 
fibres  which,  at  first,  measure  00012-0-003  of  a  line,  but  almost  all 
of  which  ultimately  decrease  in  size  down  to  0-001,  and,  in  the  gray 
substance,  acquire  the  diameter  of  the  smallest  nerve-tubes,  0'0004— 
O'OOOS  of  a  line.  The  fibres  given  off  from  these  fasciculi,  within 
the  gray-red  layer  are,  in  part,  of  the  same  size  as  those  in  the 
fasciculi, — which  is  the  case  particularly  with  those  of  the  thicker  white 
streak, — in  part  finer.  The  fibres  which  proceed  from  these  fasciculi 
into  the  superficial  white  substance,  are  also,  usually,  of  greater  size,  up 

FIG.  150. — Finest  nerve-tubes  of  the  superficial  white  substance  of  the  human  cerebrum; 
magnified  350  diameters. 


THE    NERVOUS    SYSTEM.  389 

to  0*003  of  a  line,  many  of  which  form  loops  ;  there  are,  however,  in 
this  layer  together  with  these,  some  of  the  finest  fibrils,  measuring 
0*0004  of  a  line.  Notwithstanding  all  my  endeavors,  I  have  been  unable 
to  discover  any  connection  between  the  nerve-cells  and  fibres,  in  the 
cortical  portion  of  the  cerebrum  ;  but  the  existence  of  such  a  connection 
would  appear  to  me  to  be  nowhere  so  probable  as  here,  where  the  nerve- 
fibres,  especially  in  the  pure  gray  layer,  assume  so  much  the  appearance 
of  processes  of  the  cells,  as  almost  to  deceive  the  observer,  and  where,  in 
any  case,  they  terminate.  There  are  in  this  situation  an  immense 
number  of  nerve-fibres,  so  fine  and  pale  that  they  could  scarcely  be 
regarded  as  such,  were  they  not  straighter  than  the  processes,  and  did 
they  not,  particularly  when  treated  with  soda,  exhibit  minute  varicosi- 
ties.  If  anywhere  in  the  central  organs,  an  origination  of  nerve-fibres 
exists  here,  although  it  is  quite  intelligible  that  it  should  not  yet  have 
been  observed,  when  we  consider  the  delicacies  of  the  structures  con- 
cerned. 

The  corpus  callosum  presents,  in  the  anterior  portions  of  its  body 
above  the  septum  pellucidum,  the  fornix,  and  the  corpora  striata,  dull 
gray  streaks,  scattered  in  the  white  substance,  in  which  the  microscope 
discovers  no  cells,  but  only  clear  vesicles  of  0-003-0-004  of  a  line,  with 
nuclei,  in  the  midst  of  numerous  nerve-tubes,  similar  to  what  are  met 
with  in  certain  fasciculi  of  fibres  of  the  corpus  striatum.  Besides  this, 
Valentin  ("  Nervenl.,"  p.  244)  occasionally  noticed  on  the  surface  of  the 
corpus  callosum,  between  the  raphe  and  the  strice  obtectce,  a  delicate 
gray  investment  with  clear  nerve-cells,  which  appears  to  be  identical 
with  the  fasciola  cinerea,  which  is  continued  into  the  fascia  dentata  of  the 
pes  hippocampi  major  (vid.  Arnold.  "  Bemerk,"  p.  87) ;  otherwise  the 
corpus  callosum  is  wholly  composed  of  white  medullary  substance  with 
parallel  nerve-fibres  of  exactly  the  same  aspect  and  diameter  as  those 
of  the  medullary  substance  of  the  hemispheres.  The  same  may  be  said, 
also,  of  the  commissura  anterior  and  fornix,  which  latter,  however, 
comes  in  contact  with  gray  substance  in  very  many  ways,  as  in  the  optic 
thalamus,  from  the  tuberculum  anterius  of  which  its  radix  descendens 
arises  ;  in  the  corpus  mammillare  (vid.  sup.  §  116) ;  at  the  commence- 
ment of  the  radix  ascendens  ;  in  the  floor  of  the  third  ventricle,  to- 
wards which  some  delicate  fasciculi  of  the  radix  ascendens  are  given  off; 
and  at  its  point  of  junction  with  the  septum  pellucidum,  which  latter, 
together  with  a  common  thick  coat  presenting  much  connective  tissue 
and  corpuscula  am.ylacea  (vid.  §  118),  exhibits  numerous  plexuses  of  the 
finest  kind  of  nerve-fibres  and  nerve-cells,  exactly  as  does  the  tuber 
cinereum.  The  fibres  of  the  fornix  measure,  in  its  white  portions 
0-0008-0-005,  mostly  0-002-0-003  of  a  line;  in  the  optic  thalamus  (upper 
part),  and  in  the  corpus  mammillare^  the  fibres  are  only  of  the  finest  sort, 
measuring  0-0004-0-001  of  a  line.  The  cornu  ammonis,  and  the  calcar 


890  SPECIAL    HISTOLOGY. 

avis  (pes  hippocampi  minor),  present  nearly  the  same  conditions  as 
those  of  the  cerebral  convolutions  ;  in  the  gray  substance  of  the  former, 
however,  there  is  a  peculiar  sort  of  streak,  containing  chiefly  round  cells 
•without  processes,  and  closely  aggregated. 

Lastly,  we  have  to  consider  the  origin  of  the  first  two  pairs  of  nerves. 
The  olfactory  nerve  contains,  in  the  white  portion  of  the  tractus  olfacto- 
rius,  fine  nerve-fibres,  of  0-0004,  or  at  most  0-002  of  a  line,  the  finest, 
pale-bordered,  and  apparently  non-meclullated  ;  and  besides  these,  also 
some  gray  substance,  with  fine  granular  structure,  and  cells  of  0-007- 
0-008  of  a  line.  These  cells,  with  some  still  smaller,  down  to  a  diameter 
of  0-003  of  a  line,  many  with  branched  processes,  constitute  the 
bulbus  n.  olfactorii,  intermixed  with  numerous  fine  fibres,  the  relation  of 
which  to  the  cells  and  to  the  true  nerves  of  smell  cannot  be  made  out. 
The  optic  nerve  arises,  with  its  tractus  divided  into  two  crura,  from  the 
corpora  geniculata,  and  the  corpora  quadrigemina  and  optic  thalami ; 
besides  which,  it  is  also  in  connection  with  the  crura  cerebri,  the  sub- 
stantia  perforata  antica,  the  tuber  cinereum,  and  the  lamina  terminalis. 
The  precise  origin  of  its  fibres,  dark-bordered  tubes  of  0-002  of  a  line, 
is  in  Man  unknown,  but  to  draw  conclusions  from  experiments  in  ani- 
mals, it  exists  principally  in  the  corpora  quadrigemina,  whilst  we  know 
that  they  partially  decussate  in  the  chiasma  (commissure).  In  this  body, 
however,  there  are,  as  stated  by  Arnold,  Todd  and  Bowman,  &c. :  1, 
fibres  which  do  not  decussate,  but  are  continued  from  the  tractus  into 
the  optic  nerve  of  the  same  side ;  and  2,  commissural  fibres,  which  may 
indeed  be  divided  into  an  anterior  and  posterior  set,  the  latter  constituting 
a  commissure  between  the  two  points  of  origin  of  the  optic  nerves,  whilst 
the  anterior  could  only  unite  the  two  retince.  The  existence  of  the 
first-named  fibres  is  certain,  although  they  are  much  more  scanty  than 
the  decussating  elements;  but  that  of  the  others  also  can  hardly  be 
denied.  Speaking  physiologically,  a  commissure  of  the  optic  thalami 
and  corpora  quadrigemina  may  perhaps  be  explained,  but  a  commissure 
also  of  the  retince  does  not  appear  to  be  altogether  impossible,  because 
we  know  that  the  retina  contains  gray  substance,  and  in  it,  nerve-cells 
with  branched  processes. 

With  respect  to  the  origin  of  the  nerve-fibres  in  the  brain  and  higher 
central  organs,  in  general,  it  is  several  years  since  I  first  observed  the 
origin  of  dark-bordered  fine  fibres  from  the  processes  of  the  nerve-cells 
in  the  spinal  cord  of  the  Frog  ("Zeitsch.  f.  wiss.  Zool.,"  vol.  I.  p.  144, 
tab.  xi.  Fig.  7).  In  man  I  have  not  as  yet  been  so  fortunate  as  to  per- 
ceive anything  of  the  sort  with  certainty,  though  I  do  not  myself  doubt 
that  similar  conditions  obtain  in  this  case  also.  In  fact,  R.  Wagner  and 
Leuckart  think  they  have  seen,  in  man,  the  processes  of  the  many-rayed 
cells  in  the  substantia  ferruginea,  passing  into  nerve-tubes  ("  Gott.  An- 


THE  NERVOUS  SYSTEM.  391 

zeig.,"  1850,  No.  43);  as  has  Prof.  Domrich,  in  the  cortical  substance 
of  the  cerebellum,  according  to  a  communication  to  me  by  letter.  R. 
Wagner  again  ("  Grb'tt.  Nachr.,"  Oct.  1851),  has,  recently,  also  found  in 
the  electric  lobes  of  the  Ray,  that  from  the  many-rayed  ganglion-globules 
or  nerve-cells,  one  or  more,  rarely  two,  unbranched  processes  are  con- 
tinued into  dark-bordered  fibres.  He  now  explains  this  transition,  in 
the  same  way  as  before,  saying  that  the  processes  were  continued  as 
axis-cylinders  into  the  dark-bordered  tubes,  in  which  Leydig,  who  has 
observed  the  same  transition  in  the  cerebellum  of  the  "Hammer-headed 
Shark,"  agrees  with  him,  as  does  Stannius,  in  the  case  of  Petromyzon. 
Nevertheless,  it  is  still  not  quite  evident  to  me,  that  any  condition  should 
exist  in  this  case,  different  from  that  which  obtains  in  the  ganglia,  where 
the  processes  of  the  nerve-cells  are  not  simply  axis-cylinders,  but  also 
have  a  coat,  which  investing  the  medullary  matter  of  the  nerve,  is  con- 
tinuous with  the  sheath  of  the  dark-bordered  tubes ;  although,  seeing 
that  the  presence  of  tunics  on  the  nerve-corpuscles  of  the  central  organs, 
and  their  processes,  in  general,  is  still  a  disputed  point,  I  am  prepared 
to  admit  that  the  fact  may  be  otherwise.  These  researches  have  opened 
the  way,  and  I  have  no  doubt,  as  I  have  already  said  in  rny  Microsco- 
pical Anatomy,  that  in  time  we  shall  succeed  in  demonstrating  the  origin 
of  dark-bordered  tubes  in  many  other  situations  in  the  central  organs, 
in  man,  and  other  animals.  On  the  other  hand,  however,  supported  by 
repeated  investigation  of  the  human  brain,  I  must  assert,  that  it  is  in 
the  highest  degree  probable  that  in  many  places  it  will  be  altogether 
impossible  to  demonstrate  the  origin  of  fibres  from  nerve-cells,  because 
very  many  nerve-tubes,  particularly  those  of  the  cortical  substance  of 
the  cerebellum  and  cerebrum,  ultimately  become  so  pale  and  slender,  as 
not  to  allow  of  their  being  distinguished  from  the  processes  of  nerve- 
cells.  Whether  the  loops  which  distinctly  exist  in  the  convolutions  of 
the  cerebrum,  and  which  I  have  also  seen  in  the  corpora  striata,  are  ter- 
minations, or  whether  free  prolongations  of  nerve-tubes  exist,  we  know 
not,  and  the  less  so  because  it  cannot  even  be  asserted  that  certain  fibres 
really  so  terminate.  It  may  fairly  be  assumed  that  the  fibres  of  the 
corpus  callosum  and  the  commissural  fibres  in  general,  commence  in  the 
one  hemisphere  in  connection  with  cells  and  terminate  in  the  other,  and 
that  the  fibres  which  proceed  from  the  surface  of  the  convolutions  to  the 
optic  thalami  and  corpora  striata  terminate  in  the  latter,  but  to  assert, 
that  it  is  so,  is  impossible,  notwithstanding  the  visible  loops,  for  it  may 
be  that  these  latter  are  not  terminations  at  all,  and  that  the  fibres  in 
question  are  all  in  the  one  place  and  the  other  in  connection  with  nerve- 
cells.  That  nerve-fibres  should  originate  independently  of  any  connec- 
tion with  cells  would  be  contrary  to  all  analogy,  but  in  such  an  obscure 
subject  we  must  always  be  prepared  for  much  that  is  new,  and  be  careful 
not  wholly  to  reject  any  possibility,  simply  from  d  priori  considerations. 


392  SPECIAL    HISTOLOGY. 

Several  authors  have  noticed  divisions  of  the  nerve-tubes  in  the  central 
organs,  such  as,  among  the  older  ones,  Ehrenberg,  Volkmann,  E.  H. 
Weber,  and  more  lately  also,  Hessling  (uFror.  N.  Notiz.,"  Ap.  1849, 
Jenaische,  Ann.  I.  p.  283),  E.  Earless  (ibid.,  p.  284),  and  Schaffner 
("  Zeits.  f.  rat.  Med.,"  IX.)  in  the  brain  of  various  vertebrate  animals, 
especially  at  the  junction  of  the  white  and  gray  substance.  I  am  not 
inclined  to  doubt  these  statements,  especially  the  latter,  but  I  cannot 
avoid  the  remark,  that  in  the  human  brain,  I  have,  hitherto,  in  vain 
sought  for  divisions  of  this  kind,  and  have  had  many  hundreds  of  fibres 
from  the  gray  substance  before  me,  under  the  most  favorable  circum- 
stances, which  presented  no  indications  of  the  sort,  whilst  I  have  inva- 
riably found  such  divisions  in  the  spinal  cord  (vid.  supra).  The  many- 
rayed  nerve-cells  with  branched  processes  are  not  as  yet  fully  known  in 
all  their  relations.  I  have  described  their  processes  (as  will  be  univer- 
sally allowed,  correctly),  as  a  sort  of  pale,  non-medullated  nerve-tubes, 
and  have  isolated  them  occasionally  to  the  extent  of  J  and  J  of  a 
line,  without  being  able  to  notice  anything  more  with  regard  to  their 
termination,  than  the  fact  of  their  ultimately  assuming  an  extreme  de- 
gree of  fineness.  R.  Wagner  states,  that  those  processes,  which  do  not 
pass  into  dark-bordered  nerve-tubes,  serve  to  connect  the  separate  nerve- 
cells  together,  but  in  so  doing  he  manifestly  says  more  than  actual 
observation  warrants,  as  he  has,  hitherto,  seen  such  a  connection,  only 
in  the  electric  lobes  of  the  Ray.  In  the  present  state  of  neural  Anatomy 
there  is  nothing  which  should  be  more  carefully  avoided  than  the  general 
application  of  isolated  observations,  and  I  am  therefore  of  opinion  that 
this  question  must  as  yet  be  regarded  as  an  open  one.  It  may  indeed 
be  very  consonant  with  physiological  considerations,  to  explain  the  reflex 
and  alternating  actions  of  separate  sections  of  nerves  by  such  connec- 
tions between  the  cells,  but  it  is  precisely  for  that  reason,  that  we  should 
be  the  more  careful,  and  the  more  so  because  less  obvious  theories  explain 
the  conditions  just  as  well.  I  conclude,  therefore,  from  the  observations 
hitherto  made,  only  this  much,  that  nerve-cells  may  anastomose,  leaving 
it  to  future  inquiries  to  decide,  whether  they  do  so  universally  and  with 
all  their  processes,  or  whether  in  certain  situations  the  latter  do  not 
stretch  out  without  any  attachment,  exerting  a  mutual  influence  and 
affecting  the  nerve-fibres  simply  by  juxtaposition,  as  appears  to  be  the 
case  in  the  large  nerve-cells  of  the  cord  and  the  roots  of  the  spinal 
nerves. 

§  118.  Membranes  and  Vessels  of  the  central  Nervous  System. — 
A.  MEMBRANES.  1.  Spinal  cord.  The  dura  mater  *.  meninx  fibrosa  is  a 
whitish  yellow,  occasionally  glistening,  firm,  tolerably  elastic  membrane, 
consisting  of  parallel  and  mostly  longitudinal  fasciculi  of  connective  tis- 
sue, and  of  a  fine,  elastic,  fibrous  network  in  almost  equal  proportions. 


THE    NERVOUS    SYSTEM.  393 

The  outer  surface  of  the  dura  mater  is,  in  front,  where  the  membrane  is 
always  at  least  as  thin  again  as  behind,  pretty  closely  united  to  the  fas- 
cia longitudinalis  posterior  of  the  spinal  column,  free  posteriorly  and  on 
the  sides,  and  separated  from  the  arches  of  the  vertebrae  and  their  peri- 
osteum by  a  space,  occupied  by  a  lax  connective  tissue  with  anastomosing 
fasciculi  scarcely  more  than  0-004-0-005  of  a  line  thick  (reticular  con- 
nective tissue),  containing  a  few  elastic  fibrils  (convoluted  and  longitu- 
dinal), and  round,  fusiform  and  stellate  nucleated  cells,  similar  to  the 
formative  cells  of  the  connective  tissue,  and  besides  these  with  larger  or 
smaller  aggregations  of  frequently  gelatiniform,  transparent  fat  with 
cells  containing  serous  fluid.  The  vessels  of  this  space  are  in  part  the 
well-known  plexus  venosi,  in  part  finer  vessels,  and  also  a  network  of  the 
finest  capillaries  in  the  lax  connective  tissue  itself.  The  internal  sur- 
face of  the  dura  mater  would  appear,  from  what  is  generally  stated,  to 
be  lined  with  an  outer  lamella  of  the  arachnoid ;  nothing,  however,  is 
to  be  seen  but  an  epithelium,  composed  of  polygonal,  flattened,  nucleated 
cells,  on  the  innermost  layer  of  the  dura  mater,  and  not  a  trace  of  any 
special  substratum.  The  ligamentum  denticulatum  has  no  epithelium, 
and  like  the  thickened  processes  of  the  pia  mater,  to  which  it  is  attached, 
presents,  in  all  respects,  a  structure  similar  to  that  of  the  dura  mater. 

The  arachnoid  membrane  is  constituted,  not  of  an  external  and  inter- 
nal lamella,  the  former  of  which  is  united  to  the  dura  mater,  the  latter 
free,  but  of  a  single  layer  corresponding  to  the  internal  lamella  of  authors. 
It  is  an  extremely  delicate,  transparent  membrane,  exactly  correspond- 
ing in  extent  and  relations  to  the  dura  mater.  Its  outer  surface,  in  the 
posterior  mesial  line  of  the  cervical  portion,  is  connected  with  the  dura 
mater,  above,  by  tolerably  strong  processes,  lower  down,  by  delicate 
fibrils,  elsewhere  it  is  perfectly  smooth  and  glistening,  which  appearance 
depends  upon  an  epithelium  precisely  like  that  of  the  dura  mater,  and 
it  is  merely  in  apposition  with  that  membrane,  as  the  pulmonary  pleura 
is  with  the  costal.  The  internal  surface  of  the  arachnoid  is  also  smooth, 
though  without  epithelium ;  it  is  separated  from  the  spinal  cord,  and 
cauda  equina  by  a  large  interspace,  the  subaracJmoid  space,  affording, 
however,  numerous  slender  processes  to  the  pia  mater  and  the  roots  of 
the  nerves,  which  processes  not  only  accompany  the  vessels  and  nerves, 
but  occur,  especially  in  the  posterior  mesial  line,  arranged  in  a  consecu- 
tive series,  and  occasionally,  particularly  in  the  cervical  region,  form  a 
perforated  or  complete  septum.  As  regards  its  intimate  structure,  the 
arachnoid  contains,  chiefly,  reticularly  anastomosing  bundles  of  con- 
nective tissue  of  0-001-0-004  of  a  line,  which  are  so  united  as  to  form 
lamellae,  some  external  with  more  slender,  and  some  internal  with 
stronger  fasciculi,  and  which  are  usually  so  surrounded  by  fine  elastic 
fibres,  as  to  present  a  moniliform  appearance  when  swollen  by  the  appli- 
cation of  acetic  acid  (Fig.  23).  In  many  fasciculi,  these  fibres  are  very 


394  SPECIAL    HISTOLOGY. 

fine  or  wanting,  others  again,  in  addition,  contain  elastic  fibres  also  in 
the  interior. 

The  vascular  membrane,  pia  mater,  very  closely  invests  the  spinal 
cord  and  the  gray  substance  of  the  filum  terminale,  penetrating  on  the 
one  hand  into  the  anterior  and  posterior  fissures,  where  it  appears  within 
the  spinal  cord  in  the  form  of  slender  processes,  and  affording,  on  the 
other,  delicate  sheaths  to  the  roots  of  the  nerves.  It  contains  for  the 
most  part  common  connective  tissue  with  straight  fibres,  and,  more  rarely, 
anastomosing  bundles  ;  and  besides  these  a  good  many  nuclei  often  of  a 
lenticular  form,  with  a  few  elastic  fibrils.  Here  and  there  are  met  with 
in  the  pia  mater  bright  yellow  or  brown  pigment-cells,  of  an  irregular, 
fusiform  figure  with  fine  prolonged  ends  and  measuring  0-04-0-05  of  a 
line  in  length,  which  in  the  cervical  region,  owing  to  their  greater  num- 
ber, give  the  membrane,  not  unfrequently,  a  brown  or  even  blackish  color. 

2.  Brain. — The  membranes  of  the  brain,  though  corresponding,  in. 
general,  with  those  of  the  spinal  cord,  yet  present  some  differences.  The 
dura  mater,  in  this  situation,  consisting  of  the  true  fibrous  membrane  of 
that  name  and  of  the  internal  periosteum  of  the  cranial  bones,  which,  as 
the  immediate  continuations  of  the  corresponding  membranes  of  the 
spinal  canal,  become  consolidated  together  at  the  level  of  the  atlas,  is, 
in  general,  thicker  and  also  whiter  than  in  the  spinal  cord.  Its  external 
or  periosteal  lamella,  of  a  whitish-yellow  color  and  rough,  is  attached 
more  or  less  firmly  to  the  bones,  supports  the  larger  vasa  meningea,  and 
is  also  otherwise  more  richly  supplied  with  vessels  than  the  internal 
proper  dura  mater,  with  which,  at  an  earlier  period,  it  was  more  laxly 
united,  and  from  which,  except  where  the  sinuses  are  contained,  it  may 
not  unfrequently  be  separated  even  in  the  adult.  The  internal  lamella 
is  less  vascular,  whiter,  presenting  in  many  places  a  glistening  tendinous 
aspect,  and  on  its  surface  is  quite  smooth  and  for  the  most  part  even. 
The  processes  of  the  dura  mater,  the  greater  and  less  falciform  processes, 
and  the  tentorium,  appear  as  prolongations  of  this  internal  lamella ; 
and  between  the  two  lamellge  are  situated,  with  few  exceptions,  the 
venous  canals  or  sinuses  of  the  dura  mater.  Both  lamellae  contain  con- 
nective tissue  of  the  same  form  as  that  in  the  tendons  and  ligaments, 
with,  for  the  most  part,  indistinct  bundles,  and  parallel  fibrils,  which 
either  extend  of  a  uniform  size  for  considerable  distances  in  it,  or,  espe- 
cially as  in  the  sinuses,  form  small,  tendinous  bands,  crossing  each  other 
in  various  directions,  and  containing  among  them  a  good  many  fine  elastic 
fibres.  The  internal  surface  of  the  dura  mater  is  lined  with  a  single 
(according  to  Henle  with  more  than  one)  layer  of  tessellated  epithelial 
cells,  of  0-005-0-006  of  a  line  in  size,  with  rounded  or  elongated  nuclei 
measuring  0-002— 0*004  of  a  line  ;  possessing  no  other  covering  which 
might  be  described  as  a  parietal  lamella  of  the  arachnoid  (vid.  Luschka, 
Serose  Haute,  p.  64). 


THE    NERVOUS     SYSTEM.  395 

The  arachnoid  membrane  of  the  brain  differs  from  that  of  the  spinal 
cord,  not  so  much  in  its  structure  as  in  its  disposition.  It  is  true,  that 
in  this  situation  also,  there  is  but  one  lamella  demonstrable  as  a  mem- 
brane composed  of  connective  tissue,  which  corresponds  with  the  so- 
termed  visceral  layer  of  the  arachnoid  of  authors,  and  is  also  very  closely 
applied  to  the  inner  surface  of  the  dura  mater,  but  the  arachnoid  mem- 
brane here  is  in  much  more  intimate  relation  to  the  pia  mater.  That  is 
to  say,  instead  of  its  being  united  with  the  latter,  as  in  the  cord,  by  scat- 
tered fibres  and  lamellae,  it  is,  in  the  brain,  in  many  situations,  as  on  all 
the  convolutions,  and  the  projecting  parts  at  the  base  of  the  brain, 
adherent  to  and  coalescent  with  it,  and,  elsewhere,  where  this  is  not  the 
case,  united  to  it  by  numerous  processes.  For  this  reason,  there  exists, 
in  the  brain,  no  continuous  subarachnoid  space,  but  numerous,  larger 
and  smaller  spaces,  which  only  partially  communicate.  The  larger  of 
these  spaces  between  the  cerebellum  and  medulla  oblongata,  and  under 
the  pons  Varolii,  the  crura  cerebri,  the  fossa  Sylvii,  &c.,  open  directly 
into  the  subarachnoid  space  of  the  spinal  cord,  whilst  the  smaller,  corre- 
sponding to  the  sulci,  and  over  which  the  membrane  composed  of  connec- 
tive tissue  is  stretched,  are  perhaps  partially  in  communication  with  each 
other,  but,  at  all  events  most  of  them,  not  with  the  larger  spaces  just 
mentioned.  The  arachnoid,  as  has  been  correctly  stated  by  Henle,  is 
nowhere  in  connection  with  the  lining  membranes  of  the  cerebral  ven- 
tricles. The  structure  of  the  membrane  is  the  same  as  in  the  spinal 
cord,  except  that  the  anastomosing  fasciculi  and  spiral  elastic  fibres  are 
for  the  most  part  thicker,  measuring  as  much  as  0*01  or  even  0-02  of  a 
line ;  and  the  former  frequently  present,  as  it  were,  special  and  more 
homogeneous  sheaths  of  connective  tissue,  beneath  which,  fat-  and  pig- 
ment-granules are  often  deposited.  The  outer  surface  is  covered  with 
an  epithelium  in  all  respects  like  that  of  the  dura  mater. 

The  pia  mater  cerebri  is  more  vascular  but  more  delicate  than  that  of 
the  spinal  cord,  and  covers  all  the  elevations  and  depressions  on  the 
surface  of  the  brain,  if  not  very  closely  yet  quite  exactly,  with  the 
single  exception  of  the  floor  of  the  fourth  ventricle,  above  which  it  is 
stretched  across  from  the  calamus  scriptorius,  as  far  as  the  nodulus,  the 
free  border  of  the  vela  medullaria  inferiora  and  the  flocculi,  forming 
the  tela  chorioidea  inferior,  from  which  points  it  proceeds  to  invest  the 
under  surface  of  the  inferior  vermiform  process  and  of  the  tonsillce. 
The  pia  mater  penetrates  into  the  interior  of  the  brain  only  at  one 
point,  viz.,  at  the  transverse  fissure  of  the  cerebrum,  where  it  passes 
beneath  the  splenium  corporis  callosi,  investing  the  vena  maana  G-aleni, 
as  well  as  the  pineal  gland,  forming  the  tela  chorioidea  superior,  with 
the  plexus  chorioideus  ventriculi  tertii;  and  passing  beneath  thefornix, 
also  constitutes  the  vascular  plexuses  of  the  lateral  ventricles,  which 


396  SPECIAL    HISTOLOGY. 

are  continuous  with  the  pia  mater  at  the  base  of  the  brain,  between  the 
cms  cerebri  and  the  inferior  lobe.  With  respect  to  its  intimate  struc- 
ture, the  cerebral  pia  mater  contains  so  many  vessels,  that  in  parts  the 
connective  tissue  which  forms  the  matrix  appears  as  a  subordinate  con- 
stituent. It  is  rarely,  as  in  the  spinal  cord,  distinctly  fibrous,  for  the 
most  part  more  homogeneous,  approaching  in  character  "  Reichert's  mem- 
branes," or  immature  connective  tissue,  with  a  few  nuclei  and  without 
elastic  fibres.  Occasionally,  however,  the  pia  mater  also  contains 
reticular  connective  tissue,  as  around  the  vena  Craleni,  the  pineal  gland, 
the  larger  vessels,  and  also  on  the  cerebellum.  Fusiform  pigment-cells 
also  occur  here,  as  in  the  spinal  cord,  particularly  on  the  medulla  ob- 
longata,  arid  pons  Varolii,  but  also,  more  anteriorly,  at  the  base  of  the 
brain  as  far  as  within  the  fissure  of  Sylvius,  in  which  situation  I  have 
noticed  them  even  in  the  m.  adventitia  of  smaller  arteries. 

Those  portions  of  the  pia  mater  which  are  in  relation  with  the  ven- 
tricles, the  telce  chorioidece  and  plexus  chorioidei,  do  not  differ  in  their 
structure  from  other  portions  of  the  membrane,  except  that,  especially 
in  the  plexus,  they  are  composed  almost  wholly  of  vessels,  and  are  fur- 
nished with  an  epithelium  at  those  points  where  they  are  not  adherent 
to  the  walls  of  the  ventricles.  This  epithelium  consists  of  a  single 
layer  of  roundish  polygonal  cells,  0-008-0-01  of  a  line  in  diameter,  and 
0-003-0-004  of  a  line  in  thickness,  and  usually  containing  together  with 
the  rounded  nucleus,  yellowish  granules,  often  in  great  numbers,  and 
one  or  two,  dark,  round  oil-drops  of  0'001-0*002  of  a  line  in  size.  Ac- 
cording to  Henle,  almost  all  these  cells  send  out,  from  the  angles  towards 
the  layer  of  connective  tissue  of  the  plexus,  short,  slender,  acuminate, 
transparent,  -and  colorless  processes,  like  spines ;  and  according  to 
Valentin  ("Physiol.,"  2d  ed.,  part  2,  p.  22),  in  the  Mammalia  they  also 
support  cilia.  The  epithelium  is  succeeded  by  a  thin  layer  of  apparently 
homogeneous,  connective  tissue,  beneath  which  is  a  very  close  inter- 
lacement of  larger  and  smaller  vessels,  between  which  no  formed  con- 
nective tissue  can  be  perceived,  but  only  a  clear,  homogeneous,  inter- 
stitial substance. 

All  the  portions  of  the  ventricles  which  are  not  lined  by  the  con- 
tinuations of  the  pia  mater,  that  is  to  say,  the  floor  of  the  fourth 
ventricle,  the  aqueductus  Sylvii,  the  floor  and  the  sides  of  the  third 
ventricle,  the  ventriculus  septi  lucidi,  the  roof  of  the  lateral  ventricles, 
the  anterior  and  the  posterior  cornua,  and  a  considerable  part  of  the 
descending  cornu,  in  the  embryo  also  the  cavity  in  the  olfactory  bulb, 
and  the  canal  in  the  spinal  cord,  have  a  special  lining  membrane,  the 
so-termed  ependyma  ventriculorum  (Fig.  151).  This  is  a  simple  tessel- 
lated epithelium,  which,  according  to  Purkinje  and  Valentin  (Mull. 
"Arch.,"  1836;  Val.  "Repert.,"  1836,  p.  156),  is  said  to  exhibit  ciliary 


THE    NERVOUS    SYSTEM.  397 

motion,  a  statement,  however,  which  Virchow  and  I  have  not  been  able 
to  confirm  in  the  case  of  an  executed  criminal. 
It  lies,  normally,  immediately  upon  the  nerve- 
substance,  but  there  is  so  frequently  developed 
beneath  it,  especially  in  the  for  nix,  the  stria 
cornea,  and  the  septum  lucidum,  a  filamentous 
layer,  resembling  connective  tissue,  0-01-0-05 
of  a  line  thick,  that  its  occurrence  at  a  certain 
age  might  almost  be  described  as  constant,  as  a 


in  fact  it  is  by  Virchow.  The  epithelium 
sometimes  presents,  particularly  as  in  the  third  ventricle,  large  cells  of 
0-008-0-012  of  a  line,  with  pigment-granules  and  masses,  together  with 
nuclei,  measuring  0*003  of  a  line;  in  other  situations,  as  in  the  lateral 
ventricles,  the  cells  are  not  more  than  0-005-0-007  of  a  line  in  size,  but 
almost  as  thick  as  wide,  with  roundish  nuclei  and  a  good  many  yellowish 
granules,  which  are  generally  crowded  in  the  interior.* 

The  vessels  of  the  membranes  just  described  present  very  various 
conditions.  In  the  first  place,  in  the  dura  mater  of  the  cord,  if  we  ex- 
cept those  on  the  external  surface  and  the  numerous  arteries  and  veins 
of  the  cord  by  which  it  is  perforated — the  vessels  are  very  few  in  num- 
ber, and  in  this  respect  the  membrane  presents  more  of  the  conditions 
of  a  muscular  fascia  or  tendinous  expansion.  On  the  other  hand,  there 
exist  in  this  situation,  between  the  dura  mater  and  periosteum  of  the 
vertebral  canal,  the  well-known  venous  plexuses,  as  well  as  finer  ramifi- 
cations in  the  adipose  tissue,  which  do  not  demand  any  further  descrip- 
tion. In  the  cranium,  on  the  contrary,  the  entire  dura  mater  is  vascu- 
lar, but  especially  in  its  external  periosteal  layer,  which,  partly  for  its 
own  supply,  partly  for  that  of  the  cranial  bones,  to  which  it  gives  off 
numerous  branches,  supports  the  arterice  meningece,  and  also  conveys 
through  its  veins  a  portion  of  the  blood  returned  from  the  bones. 
Besides  this,  in  the  cerebral  dura  mater  are  lodged  the  venous  sinuses, 

FIG.  151. — Ependyma  in  man.  A,  from  the  cm-pus  striatum  •  1,  from  the  surface:  2,  from 
the  side;  a,  epithelial  cells;  b,  nerve-fibres  lying  beneath  ;  B,  epithelium  cells  from  the  com- 
missura  mollis. — Magnified  350  diameters. 


*  [According  to  the  recent  researches  of  Virchow,  the  spinal  ependyma  differs  some- 
what from  that  lining  the  ventricles  of  the  brain.  It  is  more  gelatinous  and  resistant, 
and  contains  cells  which  are  much  larger  than  those  of  the  cerebral  ependyma.  It  lies  in 
the  middle  of  the  gray  matter,  in  the  exact  situation  where  the  spinal  cord  exists  in  the 
foatus,  and  forms  a  continuous  filament,  extending  to  ihefilum  terminate. 

The  ependyma  is  prolonged  without  distinct  boundaries,  between  the  nervous  elements. 
Virchow  has  found  a  continuous  layer  of  a  similar  substance  in  the  interior  of  the  higher 
nerves  of  sense.  He  has  quite  recently  also  discovered  in  its  deeper  layers  peculiar 
granules,  with  the  chemical  reaction  of  cellulose.  (Vide  §  118,  infra.)— DaC.] 


398  SPECIAL    HISTOLOGY. 

which  are  simple  excavations  in  it,  for  the  conveyance  of  blood  and 
lined  with  an  epithelium ;  and  most  of  which  are  obviously  situated 
between  the  periosteal  lamella  and  the  proper  dura  mater,  thus,  in  their 
position,  corresponding  with  the  plexus  venosi  spinales.  The  arachnoid 
membrane,  either  of  the  spinal  cord  or  of  the  brain,  contains  no  proper 
vessels  (vid.  Luschka,  1.  c.,  p.  71),  whilst  the  pia  mater  in  both  situa- 
tions supports  not  only  the  very  copious  ramifications  of  the  vessels  of 
the  nervous  substance  itself,  but  is  also  supplied,  with  a  tolerably  rich, 
proper  capillary  plexus  of  its  own.  In  one  portion  of  the  pia  mater, 
viz.,  in  the  vascular  plexuses,  the  vessels  are  distributed  solely  in  the 
membrane  itself,  the  branches  entering  the  nervous  substance  being  of 
subordinate  importance.  Lymphatics  it  is  said  have  recently  been  in- 
jected with  air  and  quicksilver  by  Fohmann  and  Arnold,  (vid.  "  Anat." 
II.  p.  618)  both  in  the  pia  mater  on  the  surface  of  the  cerebrum  and 
cerebellum,  as  well  as  in  the  choroid  plexus,  but  this  observation  appears 
to  me  very  much  to  demand  confirmation. 

The  membranes  of  the  central  nervous  system,  also  contain  nerves,  at 
all  events  in  part.  In  the  dura  mater  of  the  cerebrum  they  run  in  the 
periosteal  lamella  of  the  membrane,  following  pretty  nearly  the  course 
of  the  meningeal  arteries,  and  are  especially  distinct  on  the  a.  meningea 
media,  which  is  accompained,  not  only  by  twigs  of  the  nervi  molles,  but 
also  by  a  special  nerve  first  noticed  by  Arnold  (n.  spinosus,  Luschka), 
which,  according  to  Luschka,  is  derived  from  the  third  branch  of  the 
n.  trigeminus,  the  former  of  which  are  distributed  with  the  vessels,  and 
the  latter  appears  to  be  destined  principally  for  the  bones.  Besides 
these,  Purkinje  has  noticed  nerves  on  the  anterior  and  posterior  menin- 
geal arteries,  and  Arnold  long  ago  described  the  well-known  n.  tentorii 
cerebelli,  proceeding  from  the  fifth  pair,  which,  as  has  been  lately  shown, 
particularly  by  Pappenheim  and  Luschka  (1.  c.),  goes  to  the  larger 
sinuses  of  the  dura  mater.  The  elements  of  this  white-looking  nerve 
and  of  the  n.  spinosus  of  Luschka,  are  those  of  the  n.  trigeminus,  those 
of  the  others,  fine  fibres,  and  in  both  situations  they  present  divisions. 
In  the  dura  mater  of  the  spinal  cord,  I,  as  well  as  Purkinje,  have  been 
unable  to  detect  any  nerves ;  they  occur,  however,  as  has  been  already 
mentioned,  in  the  periosteum  of  the  vertebral  canal,  and  on  the  arteries 
going  to  the  vertebrse  and  cord,  as  well  as  in  the  sinuses  and  lax  adipose 
tissue  of  the  canal  (Luschka,  1.  c.). 

In  the  arachnoid  itself  I  have  never  noticed  any  nerves,  but  on  the 
vessels  by  which  it  is  penetrated,  and  in  the  processes  connecting  it  with 
the  pia  mater,  they  may  perhaps  be  seen,  especially  at  the  base  of  the 
brain — to  which  nerves,  those  seen  by  Luschka  (Serose  Haute,  p.  70), 
notwithstanding  the  divisions  observed  in  them,  appear  tome  to  belong. 
Bochdalek  (1.  i.  c.)  has  lately  described  nerves  of  the  cerebral  arachnoid, 


THE    NERVOUS    SYSTEM.  399 

derived  from  the  n.  accessorius,  iheportio  minor  trigemini,  and  the  facial 
nerve,  but  fails  to  show  that  they  terminate  in  the  membrane.  When 
the  same  author  also  finds  extremely  numerous  nerves  in  the  arachnoid 
covering  the  cauda  equina,  he  falls  into  the  same  error,  as  Rainey  had 
previously  encountered  in  regarding  connective  tissue,  disposed  in  the 
more  rare  reticular  form,  as  nerves.  In  the  cauda  equina,  I  am 
acquainted  with  nerves  only  on  the  filum  terminate,  accompanying  the 
vessels,  and  nowhere  else  ;  not  even  in  the  dura  mater,  into  which  Boch- 
dalek  equally  supposes  he  has  traced  them. 

The  nerves  discovered  by  Purkinje  in  the  pia  mater  of  the  Ox,  also 
exist  in  man,  in  whom  the  pia  mater  of  the  cord,  including  the  filum 
terminate,  is  richly  supplied  with  plexuses  of  fine  nerves,  measuring 
0*0015-0-003  of  a  line,  which  throughout  do  little  more  than  accom- 
pany the  vessels.  At  the  base  of  the  brain,  many  similar  plexuses 
occur  on  the  arteries  of  the  circle  of  Willis,  which,  in  twigs,  at  most 
0-03  of  a  line  in  diameter,  are  distributed  through  the  entire  pia  mater 
of  the  brain,  accompanying  and  always  following  the  course  of  the 
various  vessels,  with  the  exception  of  those  of  the  cerebellum ;  their 
terminations,  however,  can  nowhere  be  perceived.  It  is  certain  that 
they  do  not  accompany  the  arteries  into  the  cerebral  substance,  and 
that  no  nerves  exist  in  the  vascular  plexuses  ;  whether  there  are  any 
or  not  on  the  vena  Cf-aleni,  I  have  not  yet  inquired.  The  origin  of  these 
nerves  has  been  ascertained  by  Remak  to  be  in  the  posterior  roots,  each 
of  which,  as  I  have  satisfied  myself,  in  many  situations,  and  as  it  appears 
to  me  more  frequently  in  the  cervical  portion  of  the  cord,  from  the 
fibres  in  closest  contiguity  to  each  other,  sends  out  fine  fibrils  across  the 
subarachnoid  space  into  the  pia  mater.  As  in  this  case,  so  also  in  the 
cerebrum,  besides  the  sympathetic  nerves  (plexus  caroticus  internus, 
plexus  vertebralis),  the  cerebral  nerves  may  participate  in  the  supplying 
of  the  pia  mater,  since  Bochdalek  has  noticed  numerous  fine  twigs, 
given  off  from  the  roots  of  many  of  the  cerebral  nerves,  of  the  same 
structure  as  the  roots  themselves,  joining  the  nervous  plexuses  of  the 
arteries  at  the  base  of  the  brain  and  of  the  pia  mater  of  that  region, 
and  of  the  cerebellum,  as  well  as  in  the  plexus  chorioideus  ventric. 
quart.  (?).  He  also  found  that  isolated  fine  filaments  entered  the  pia 
mater,  directly  from  the  medulla  ollongata,  the  pans  Varolii,  and  crura 
cerebri,  which  were  not  previously  conjoined  with  the  neighboring  ner- 
vous trunks. 

B.  Vessels  of  the  central  nervous  system. — With  respect  to  the  dis- 
tribution and  condition  of  the  bloodvessels — the  brain  and  spinal  cord 
agree  almost  entirely.  After  ramifying  to  a  considerable  extent  in  the 
pia  mater,  the  arteries  enter  the  nervous  substance,  except  in  a  few 
situations  (substantice  perforator,  pons),  as  fine,  though  still  distinct, 


400 


SPECIAL    HISTOLOGY. 


Fig.  152. 


arterial  vessels,  and  ultimately  subdivide,  by  continuous  ramification,  for 

the  most  part  at  acute  angles  into  a 
rather  wide  network  of  very  fine  capil- 
laries, from  which  again  the  venous 
radicles  arise,  joining  so  as  to  form  the 
well-known  trunks,  both  on  the  surface 
and  in  the  interior  (Fig.  152).  The 
gray  substance  is  invariably  much 
more  richly  supplied  with  vessels  than 
the  white,  the  plexus  formed  by  them 
being  closer,  and  the  capillary  vessels 
themselves  of  less  calibre,  to  which  its 
color  is  in  some  respect  due.  Accord- 
ing to  E.  H.  Weber,  the  interstices  of 
the  capillaries  in  the  medullary  sub- 
stance, measure  0*0142  of  a  line  in 
width  and  0-025  of  a  line  in  length  ; 
in  an  injected  preparation  by  Gerlach 
of  the  sheep's  brain,  the  breadth  of  the 
interstices  in  the  gray  substance  was 
three  or  four  times  less  than  in  the  white. 
In  the  spinal  cord,  the  disposition  of  the  entering  trunks  is  sometimes  very 
regularly  in  series.  Two  series  of  vessels  of  this  kind  exist  in  the  bottom 
of  the  anterior  fissure,  which,  from  the  processes  of  the  pia  mater,  pene- 
trate the  gray  substance  on  the  right  and  left;  whilst  a  third  series  corre- 
sponds to  the  posterior  fissure,  and  others  not  unfrequently  also  to  the 
roots  and  the  processes  of  the  ligamentum  denticulum.  All  these  vessels 
enter  the  gray  substance  without  undergoing  any  direct  or  considerable 
decrease  in  size,  and  there  find  their  ultimate  distribution.  In  the  brain 
very  delicate  parallel  vessels  are  met  with  in  the  gray  substance  of  the 
cerebellum,  less  distinctly  in  the  cerebrum  and  other  parts.  The  structure 
of  the  vessels  is,  in  general,  the  same  as  elsewhere.  The  arteries,  upon 
their  entrance  into  the  nervous  substance,  possess  three  coats — the 
tunica  adventitia,  though  resistant,  is  a  thin  and  apparently  quite  homo- 
geneous membrane  ;  the  t.  media  is  purely  muscular ;  and  the  t.  intima 
formed  of  nothing  but  a  very  delicate  elastic  membrane,  with  openings, 
and  well-marked  fusiform  epithelial  cells.  One  after  another  of  these 
coats  is  gradually  lost,  till  before  the  capillaries  are  reached,  we  find 
nothing  but  the  t.  adventitia,  and  scattered,  transversely  placed,  elon- 
gated cells,  with  transverse  nuclei  and  an  epithelium  ;  with  which  class 
of  vessels  are  soon  associated  capillaries  with  a  structureless  membrane 
and  few  or  more  nuclei,  sometimes  of  great  minuteness,  the  finest 

FIG.  152. — Vessels  of  the  cerebral  substance  of  the  Sheep,  from  one  of  Gerlach's  injec- 
tions :  a,  of  the  gray ;  b,  of  the  white  substance. 


THE    NERVOUS    SYSTEM.  401 

measuring  in  the  cord,  0-0022,  in  the  brain  0-002  of  a  line.  Of  the 
veins,  the  largest,  for  the  most  part,  do  not  present  a  trace  of  smooth 
muscle,  exhibiting  nothing  but  connective  tissue  with  nuclei,  or  fine 
elastic  filaments  and  epithelium  ;  in  the  smaller  ones  I  have,  occasion- 
ally, though  very  rarely,  observed  contractile  elements. 

In  the  ventricles  of  the  brain  there  exists,  under  normal  conditions, 
an  extremely  small  quantity  of  clear  serous  fluid,  which  is  manifestly 
secreted  by  the  arterial  plexuses,  and  which,  probably  aided  by  the 
ciliary  movements,  assists  in  the  nutrition  of  the  walls  of  the  cavities. 
A  second  fluid,  the  liquor  cerebro-spinalis  is  contained  in  the  suba- 
rachnoid  spaces  above  described,  which  according  to  Luschka,  are  lined 
by  an  epithelium,  and  from  the  largest  of  which,  extending  from  the 
base  of  the  brain  to  the  termination  of  the  canal  of  the  dura  mater 
medullas,  the  fluid  in  question  may  be  readily  obtained.  It  is  alkaline, 
contains — of  water  98*56 — albumen  and  extractive  matter  0-55 — salts 
0-84  per  cent.,  principally  chloride  of  sodium.  Its  principal  function 
appears  to  be  to  conduce  to  the  more  free  motion  of  the  central  nervous 
system,  and  to  act  as  a  regulator  in  varying  degrees  of  fulness  of  the 
vascular  system. 

A  few  pathological  points  may  here  be  referred  to.     The  ependyma 
ventriculorum  presents  not  only,  as  above  mentioned,  almost  constantly 
in  places,  a  thin  fibrous    substratum,  but  is  frequently,   especially  in 
dropsy  of  the  ventricles,   and  in  old   age,  very   much  thickened  by  a 
layer  of  that  kind.     In  either   case  it  invariably  contains,  as  was  first 
mentioned  by  Purkinje,  yellowish  bodies,  with  con- 
centric striae  of  a  round  or  biscuit  shape,  and  not 
unlike   starch  granules.     They  are  scarcely  affected 
by  acids,  whilst  in   caustic  alkali   they  become  pale 
and   gradually   dissolve.      I  find   these    corpuscula 
amylacea  (Fig.   153),  almost  always   on  the  fornix, 
the  stria  cornea,  and  septum  pellucidum,  and  also 
elsewhere  in   the  walls  of  the  ventricles,  as   well  as 
in  the  cortical  substance  of  the  brain,  in  the  medul- 
lary substance  of  the  cord,  and  in  the  filum  termi- 
nate ;  in  the  first-mentioned  situations  they  frequently 
occur  in  incredible  quantity,  close  together,  in  the 
newly  formed  connective  tissue,  or  between  the  ner- 
vous elements.     That  these  bodies  are  a  pathological 
product  is  certain,  but  not  so  of  what  they  consist, 
or  how  they  are  formed,  although  everything  indicates  a  nitrogenous 

FIG.  153. — 1,  " Brain-sand"  from  the  pineal  gland,  in  bundles   of  connective  tissue:  2f 
corpuscula  amylacea  from  the  ependyma  of  Man  ;  magnified  350  diameters. 

26 


402  SPECIAL    HISTOLOGY. 

substance,  and  a  formation  from  successive  deposits.*     In  the  plexus 
chorioidei,  in  the   pineal   gland,    occasionally   in   the   pia   mater  and 

*  [The  recent  investigations  of  these  corpora  amylacea  by  Virchow,  (see  Archiv.  f.  path. 
Anat.  Sept.  1853)  have  led  him  to  the  important  discovery  of  their  true  nature,  viz. :  that 
they  are  composed  of  a  substance,  resembling  the  cellulose  in  plants.  The  fact  that  in  the 
animal  kingdom,  starchy  substances  had  only  been  found  in  a  low  class  of  the  invertebrated 
animals,  induced  Virchow  to  examine  all  starch-like  bodies  occurring  in  the  higher  classes 
of  the  animal  kingdom,  and  thus  the  exact  composition  of  the  corpora  amylacea  was  ascer- 
tained. As  this  discovery  is  of  great  importance,  I  shall  quote  the  author's  own  words. 

"  In  a  histological  point  of  view,  it  has  often  occurred  to  me,  that  the  umbilical  cord  in 
Man  possessed  a  great  similarity  in  its  structure  to  the  cellulose  in  the  Ascidians.  (See 
Wiirzb.  Verhandl.  1851,  Vol.  II.  p.  161,  note.)  And  I  was  the  more  confirmed  in  this  idea 
by  Schacht's  observations,  so  that  ever  since  my  researches  have  been  more  carefully  directed 
to  this  subject.  But  in  most  instances  I  searched  in  vain,  as  in  the  ova  of  amphibia  and 
fishes,  the  peculiar  yelk-plates  of  which  I  described.  (Zeitschrift  fur  Wiss.  Zoologie.  1852, 
Vol.  IV.  p.  240.)  I  was  more  successful,  however,  recently,  when  I  directed  my  attention 
to  the  so-called  "  corpora  amylacea  "  of  the  brain,  of  the  exact  nature  of  which,  as  compared 
with  the  other  starch-like  bodies  in  man,  I  had  not  been  able  to  form  any  very  definite 
conclusions.  I  soon  found  that  on  the  application  of  iodine,  they  assumed  a  bluish  tint,  and 
upon  subsequently  adding  sulphuric  acid,  the  exquisite  violet  color,  which  is  known  to  be- 
long to  cellulose,  and  which  appeared  the  more  intense,  as  it  formed  a  distinct  contrast  to 
the  surrounding  yellow  or  brown  nitrogenous  substances. 

"  I  have  so  frequently  repeated  these  investigations,  and  with  so  many  precautions,  that  I 
consider  the  results  as  perfectly  certain.  For  I  have  instituted  comparative  researches  not 
only  in  different  human  bodies,  and  in  the  most  different  situations,  but  I  have  allowed  the 
reagents  employed  to  act  under  all  possible  conditions." 

The  best  manner,  Virchow  continues,  to  obtain  this  reaction  is  to  allow  an  hydrated 
solution  of  iodine  to  act  on  the  bodies  in  question,  and  then  to  add  a  little  diluted  sulphu- 
ric acid.  Care  should  be  taken  not  to  add  too  much  iodine  at  once,  and  to  allow  the 
sulphuric  acid  to  act  very  slowly.  The  most  beautiful  preparations  were  obtained  by 
adding  a  drop  of  sulphuric  acid  to  the  edge  of  the  thin  glass  covering  a  preparation,  and 
allowing  it  then  to  remain  undisturbed  from  twelve  to  twenty-four  hours.  Every  precaution 
having  been  taken  against  an  accidental  admixture  of  starch  or  cellulose,  the  following  results 
were  obtained : — 

"The  corpora  amylacea  are  chemically  different  from  the  concentric  spherical  corpuscles 
of  which  the  brain-sand  is  composed,  and  with  which  they  have  hitherto  been  confounded. 
The  organic  basis  of  these  brain  sand-granules,  is  evidently  nitrogenous ;  iodine  and  sul- 
phuric acid  color  it  an  intense  yellow.  The  same  is  true  not  only  of  the  sandy  matter  in 
the  pineal  gland,  and  the  choroid  plexuses,  but  also  of  that  of  the  Pacchionian  granulations 
and  of  the  dura  mater,  as  well  as  of  the  dentated  plates  in  the  spinal  arachnoid.  In  all 
these  parts,  except  in  a  few  spots  in  the  pineal  gland,  I  have  never  obtained  the  characte- 
ristic blue  reaction.  It  would,  therefore,  be  henceforth  advisable  to  restrict  the  term  '  cor- 
pora amylacea'  to  these  cellulose  corpuscles. 

"  The  cellulose  granules  seem  to  be  connected  with  the  presence  of  the  ependyma  sub- 
stance in  certain  quantities,  and  might  not  improperly  be  considered  as  a  part  of  it.  But 
how  they  are  produced  from  it,  it  was  impossible  to  recognize.  They  are  usually  minute, 
scarcely  corresponding  in  size  to  the  nuclei  of  the  ependyma.  Can  they  originate  from 
these1?  The  larger  they  are,  the  more  distinctly  laminated  they  appear.  But  they  do  not 
exhibit  anywhere  a  nitrogenous  admixture,  distinguishable  by  its  yellow  color.  Their 
centre  is  generally  of  a  darker  blue,  and  hence,  perhaps,  denser  than  their  border. 

"  The  supposition,  of  these  bodies  being  introduced  from  without,  is  the  less  probable 
because  a  similar  substance  is  nowhere  else  known.  The  cellulose  in  plants  exhibits  a 
number  of  varieties,  but  this  animal  cellulose  is  distinguishable  above  all  by  its  slight  resis- 
tance towards  reagents;  for  concentrated  acids  and  alkalies  act  on  it  more  powerfully  than 
on  vegetable  cellulose." 


THE    NERVOUS    SYSTEM.  403 

arachnoid  (also  in  the  cord),  and  although  rarely,  also  in  the  walls 
of  the  ventricles,  there  is  furthermore  met  with,  as  a  constant, 
though  pathological  production,  the  gritty  matter  of  the  brain  (brain- 
sand).  It  consists  of  roundish,  simple  or  mulberry-shaped,  opaque, 
mostly  concentrically  striated  globules  of  0*005-0*05  of  a  line,  and 
together  with  them  of  angular  bodies,  of  a  stalactitic,  clavate,  or  other 
irregular  figure,  with  an  uneven,  botryoidal,  scaly  surface  ;  and  also  in  the 
form  of  simple,  cylindrical,  rigid  fibres,  either  branched  or  reticular,  and 
of  fine  particles.  The  brain-sand  contains  principally  carbonate  of  lime, 
but  also  phosphate  of  lime  and  magnesia,  and  an  organic  substance, 
which  after  the  salts  have  been  removed,  for  the  most  part  perfectly 
retains  the  figure  of  the  concretion,  that  is  to  say,  of  a  concentrically 
laminated  pale  body,  or  as  clear  fibres.  It  is  quite  certain  that  this 
brain-sand,  when  it  assumes  the  form  of  elongated,  branched,  reticular 
bodies,  is  simply  developed  in  the  bundles  of  connective  tissue  (Fig. 
153),  as,  not  unfrequently,  in  the  pineal  gland  and  in  the  membranes 
of  the  brain ;  in  other  cases  it  appears  to  be  an  independent  incrusta- 
tion on  fibrinous  concretions.  Whilst  cells  impregnated  with  calcareous 
matter,  which  Remak  ("  Obs.,"  p.  26)  supposed  them  to  be,  according 
to  Harless  (Mull.  "Arch.,"  1845,  p.  354),  do  not  exist.  Lastly,  also, 
may  be  mentioned  the  Pacchionian  granulations  of  the  pia  mater,  and 
ossifications  of  the  membranes.  The  former,  which  are  situated  prin- 
cipally on  both  sides  of  the  falx  major,  on  the  flocculi,  in  the  choroid 
plexuses,  &c.,  consist  chiefly  of  a  tough  fibrous  substance,  not  unlike 
immature  connective  tissue,  containing  also  undeveloped  elastic  tissue, 
and  corpuscula  amylacea.  The  latter,  which  are  true  osseous  plates, 
occur  sometimes  on  the  inner  surface  of  the  cerebral  dura  mater,  some- 
times on  the  arachnoid,  particularly  of  the  cauda  equina. 

The  cellulose  corpuscles  were  found  only  in  the  substance  of  the  ependyma  of  the 
ventricles  and  its  prolongations,  including  the  transparent  substance  in  the  spinal  marrow  de- 
scribed by  KoMliker  as  the  "  substantia  grisea  centralis,"  but  not  in  the  cortical  layer  of  the 
brain,  or  in  the  interior  of  the  cerebral  substance.  Neither  was  Virchow  able  to  detect 
them  in  the  brain  of  a  child,  or,  as  Bernard's  experiments  might  lead  us  to  suppose,  in  the 
brain  of  a  Rabbit,  and  he  is,  therefore,  inclined  to  attribute  to  them  a  pathological  import. 
Similar  bodies  have  been  found,  by  Rokitansky  in  the  optic  nerve,  by  Kolliker  in  the  retina, 
by  Luschka  in  the  ganglion  of  Gasser. 

The  exact  chemical  nature  of  these  bodies  has  not,  as  yet,  been  satisfactorily  ascertained. 
They  have  not  the  pure  reaction  of  vegetable  cellulose,  nor,  as  Donders  supposes  them 
'to  have,  that  of  starch,  and  they  might,  perhaps,  at  present,  be  more  properly  called  "amy- 
loid" corpuscles.  If  boiled  in  water  they  are  dissolved. 

This  discovery  of  Virchow's  is  of  great  importance,  not  only  with  regard  to  the  anatomy 
of  the  corpora  amylacea,  but  as  establishing  as  an  undoubted  fact  the  existence  of  vegetable 
matter  as  a  part  of  the  animal  economy.  Whether  this  be  a  pathological  formation  or 
not,  it  is  at  present  impossible  to  decide,  the  former  is,  however,  highly  probable,  since 
corpuscles  with  the  same  reaction  have  been  found  in  certain  abnormal  conditions  of  the 
spleen.  (Vid.  §  170,  Spleen).— DaC.] 


404  SPECIAL    HISTOLOGY. 

PERIPHERAL  NERVOUS  SYSTEM. 

§  119.  Spinal  nerves. — The  thirty-one  pairs  of  nerves  springing 
from  the  spinal  cord,  arise,  with  few  exceptions,  by  anterior  and  pos- 
terior roots.  Receiving  a  delicate  tunic  from  the  pia  mater,  they  con- 
verge, and  are  continued  across  the  subarachnoid  space,  to  perforate, 
independently  of  each  other,  the  arachnoid  and  dura  mater,  from  the 
latter  of  which  they  obtain  a  firmer  coat.  Proceeding  further,  the  pos- 
terior root  forms  its  ganglion,  by  the  deposition  around  and  among  its 
nerve-fibres,  of  ganglion-cells,  which,  to  all  appearance,  give  origin  to 
special  nerve-tubes,  the  ganglionie  fibres  of  the  spinal-nerves,  each  for 
the  most  part  arising  from  a  cell,  and  which  have  no  further  connection 
with  the  fibres  of  the  posterior  root  passing  through  the  ganglion,  than 
that,  in  their  invariably  peripheral  course,  they  are  in  apposition,  and 
intermingled  with  the  latter.  The  motor  root  never  acquires  ganglion- 
cells,  merely  passing  by  the  ganglion,  in  more  or  less  close  apposition 
with  it.  Beyond  the  ganglion,  the  two  roots  are  united  in  such  a  man- 
ner that  their  elements  are  very  intimately  commingled,  and  a  common 
nervous  trunk  formed,  containing  in  all  its  divisions  sensitive  and  motor 
elements.  It  is  usually  connected  with  the  neighboring  nerves  above 
and  below  it,  in  the  formation  of  the  well-known  plexuses,  afterwards 
giving  off  its  terminal  branches  to  the  muscles,  integument,  vessels  of 
the  trunk  and  extremities,  articular  capsules,  tendons,  and  bones.  As  in 
the  roots,  so  also  in  the  branches  of  the  common  trunk,  it  is  seen  that 
the  motor  twigs  contain  principally  thick  fibres,  and  those  destined  for 
the  integument  and  other  organs  ab.ove  named,  finer  ones ;  ultimately, 
however,  in  the  terminal  ramifications,  all  the  fibres  are  of  uniform  size. 
The  fibres  of  all  the  spinal  nerves  appear  to  run  quite  distinct  from  each 
other,  and  to  present  no  divisions  in  the  trunks  and  branches,  whilst,  in 
the  terminal  ramifications  of  them,  divisions  frequently  occur,  and,  at 
all  events  in  certain  animals  (Mouse,  batrachian  larva),  also  reticular 
anastomoses.  They  terminate  either  in  loops,  or  in  free  prolongations, 
the  latter  being  the  case,  particularly,  in  the  Pacinian  bodies,  which 
are  structures  composed  of  numerous  concentric  capsules  separated  by 
fluid,  of  an  oval  form,  and  measuring  J-2  lines,  found  principally  in 
the  hand  and  foot,  and  which  usually  contain  the  termination  of  a  nerve- 
fibre. 

In  the  first  and  last  pairs  of  spinal  nerves  occasionally  only  a  single 
root  can  be  perceived,  in  the  former  case  the  motor,  and  in  the  latter 
the  sensitive.  I  have  communicated  the  diameters  of  aril  the  anterior 
and  posterior  roots  on  the  left  side  in  a  male  and  female  body,  in  the 
"  Verh.  d.  Wurzb.  phys.  med.,"  Gesellsch.  1850,  Heft  II.  and  the 
transverse  sectional  areas  deduced  from  these  observations  are  given  in 


TUB    NERVOUS    SYSTEM. 


405 


my  "Microscopical  Anatomy,"  §  116.  The  roots  are  furnished  with  a 
delicate  neurilemma,  derived  from  the  pia  mater,  and  presenting  a  simi- 
lar structure,  which  forms  both  an  external  sheath  0-002  of  a  line  in 
diameter,  as  well  as  internal  septa  to  the  individual  fasciculi.  The  con- 
tiguous roots  frequently  anastomose,  and  this  is.  much  more  usually  the 
case  with  the  sensitive  roots ;  in  the  cervical  nerves  in  Man  in  parti- 
cular, it  is  found  to  take  place  constantly  in  one  or  other  of  the  nerves. 

§  120.  The  structure  of  the  spinal  ganglia,  in  the  Mammalia,  is  a 
difficult  subject  of  investigation,  but  I  think  the  following  may  be  stated 
with  certainty  respecting  them.  Fig.  154. 

The  sensitive  roots,  so  far  as  I 
have  hitherto  been  able  to  make 
out,  enter  into  no  connection 
with  the  nerve-cells  in  the  gan- 
glion, but  forming  one,  or,  in  the 
larger  ganglia,  several,  or  even 
numerous  fasciculi,  which  in  the 
latter  case  anastomose,  simply 
traverse  it,  to  be  reunited  be- 
low the  ganglion  into  a  single 
trunk,  which  is  then  immediate- 
ly blended  with  the  motor  root. 
Most  of  the  nerve-cells  them- 
selves appear  to  be  in  connec- 
tion with  the  nerve-fibres,  giv- 
ing off  either  one  or  two,  or 
more  rarely,  several.  These 
fibres,  which  I  term  ganglion- 
fibres,  proceed  in  a  prepon- 
derating majority  perhaps  all 
of  them  peripherally,  joining 
and  strengthening  the  perfora- 
ting root-fibres ;  so  that  each 
ganglion  is  to  be  regarded 
as  a  source  of  new  nerve- 
fibres.* 

FIG.  154. — 'A  lumbar  ganglion  of  a  young  Dog,  treated  with  soda,  and  magnified  45 
diameters:  S,  sensitive  roots;  AT,  motor  roots;  R.a,  anterior  branch  of  the  spinal  nerve;  R.p, 
posterior  branch ;  in  both  their  composition  from  both  roots  is  manifest ;  £r,  ganglion,  with 
the  cells  and  ganglion-fibres,  which  assist  in  the  strengthening  of  the  sensitive  roots  travers- 
ing the  ganglion. 


*  [The  new  "ganglion-fibres"  join  differently  the  nerve-fibres  on  which  the  ganglion  is 
seated,  or   by  which  it  is  perforated.     In  the   large  ganglia  the  new  fibres  penetrate  in 


406  SPECIAL    HISTOLOGY. 

The  structure  of  the  spinal  ganglia  (Fig.  154)  is  a  difficult  subject  for 
investigation,  in  Man.  No  complete  results  can  be  obtained  from  the 
larger  of  them,  but  more  may  be  made  out  in  the  smaller  or  smallest,  as 
in  those  of  the  fifth  sacral  nerve  and  n.  eoccygeus,  which  are  to  be  sought 
within  the  sac  of  the  dura  mater,  also  perhaps  in  the  fourth  sacral  and 
first  cervical  nerves.  If  a  comparative  examination  be  instituted,  of  the 
spinal  ganglia  of  the  smaller  Mammalia  (Rabbit,  Puppy,  Mole,  Mouse, 
Rat),  and  if  not  only  the  scalpel  and  needle  be  employed,  but  if  the 
entire  ganglia  be  examined  after  the  application  of  acetic  acid,  and  above 
all,  of  a  dilute  solution  of  soda,  with  the  aid  of  the  compressorium,  a 
satisfactory  insight  into  their  structure  may  be  obtained.  The  fibres  of 
the  roots  of  the  nerves  while  passing  through  the  ganglia  present  nothing 
at  all  peculiar,  that  is  to  say,  no  change  in  size ;  nor  have  I  ever 
observed  any  divisions  of  them,  and  I  think  it  may  be  positively  asserted, 
that  such  an  occurrence,  if  it  take  place  at  all,  must  be  extremely  rare, 
as,  notwithstanding  that  I  have  specially  sought  for  it,  and  have  been 
able,  in  the  lower  Mammalia,  to  trace  numerous  nerve-fibres  through  the 
entire  ganglion,  I  have  never  noticed  anything  of  the  sort. 

The  principal  constituents  of  the  ganglia — the  ganglion-globules  or 
-cells  [nerve-cells]  (Figs.  155  and  157),  have  a  distinct  outer  coat, 
are  for  the  most  part  roundish,  elongated,  or  pyriform,  usually  a 
little  flattened,and  measure  from  0-012  to  0-036,  or  even  0-04  of  a 
line;  on  the  average  0-02-0  03  of  a  line.  The  contents  are  through- 
out finely  granular,  and  not  unfrequently  exhibit,  in  the  vicinity  of 
the  nucleus,  an  accumulation  of  yellow,  or  yellowish-brown,  larger 
pigment  granules,  which  increases  in  age,  and  to  which  the  gan- 
glia are  chiefly  indebted  for  their  yellow  color.  The  nuclei  measure 

fasciculi  between  the  perforating  nerve-fibres ;  in  the  smaller  ganglia  they  either  wind 
around  the  nerve-fibres,  or  run  along  the  side  of  the  nerve  on  which  the  ganglion  is  situated. 
This  depends  mainly  on  the  exact  position  of  the  ganglion.  If  it  be  placed  in  the  middle  of 
the  nerve,  the  former  occurs,  whilst  if  it  be  situated  on  one  side  of  it,  the  latter  is  the  more 
frequent. 

The  new  ganglion-fibres  mostly  proceed  peripherally,  but  according  to  a  recent  observer, 
Axmann  (Beitrilge  zur  Anatom.  u.  Phys.  des  Gangl.  Syst.,  Berlin,  1853)  this  is  not  the  case  with 
all  of  them.  From  many  careful  dissections  he  satisfied  himself  that  whilst,  as  stated  by 
Kolliker  and  others,  most  of  the  new  fibres,  proceeding  from  every  spinal  ganglion,  run  in  a 
peripheral  direction,  and  are  distributed  along  with  the  cerebro-spinal  nerve-fibres,  to  the 
tissues  subjected  to  will  and  sensation,  some  are  connected  through  the  rami  communic antes 
with  the  sympathetic  system.  He  also  found  that  a  small  number  of  the  ganglion-fibres 
penetrate  through  the  roots  of  the  cerebro-spinal  nerves  into  the  spinal  column  and  brain, 
where,  he  states,  they  have  been  frequently  mistaken  for  attenuated  cerebro-spinal  nerve- 
fibres.  He  adds,  further,  that  he  has  been  able  to  trace  their  connection  with  the  spinal 
ganglia  in  the  Frog,  Mouse,  and  Pike,  and  also  in  a  human  foetus  of  six  months.  It  is,  how- 
ever, difficult  to  understand  how  Axmann  was  able  to  determine  that  these  fibres  proceeded 
from  the  ganglia  to  the  spinal  marrow,  since  they  might  be  as  readily  supposed  to  have  been 
minute  fibres  proceeding  from  the  ganglia  of  the  spinal  marrow  towards  the  external 
ganglia. — DaC.] 


THE    NERVOUS    SYSTEM. 


407 


These  nerve-cells 


Fig.  155. 


0-004-0-008,  the  nucleoli  0-0008-0-002  of  a  line, 
are  situated,  in  the  first  place,  in  larger 
numbers  on  the  surface  of  the  ganglion,  be- 
tween the  neurilemraa  and  the  perforating 
radical  fibres  ;  and  secondly,  at  all  events  in 
Man,  in  the  interior,  where  they  occupy  the 
interstices  of  the  plexus  formed  by  the  nerve- 
fibres.  The  individual  cells  are  retained  in 
their  situations  by  a  special  tissue,  which 
also  separates  them  from  the  contiguous  cells 
and  from  the  nerve-fibres.  This  tissue  ap- 
pears on  isolated  cells,  as  if  it  formed  a  spe- 
cial coat  to  them,  and  is  consequently  termed 
their  external  sheath,  but  in  fact  it  repre- 
sents a  system  of  small  septa,  connected  in  a 
complex  manner,  and  pervading  the  entire 
ganglion,  receiving  the  separate  cells  in  its  meshes,  and  only  more  rarely 
appearing  as  a  definitely  bounded  coat  on  individual  cells.  This 
structure  is  evidently  to  be  referred  to  connective  tissue ;  it  presents, 
however,  several  forms,  which  have  been,  in  part,  already,  properly  dis- 
tinguished by  Valentin  (Mull.  "Arch."  1839,  p.  143),  viz.  1,  in  the  form 
of  a  sometimes  homogeneous,  sometimes  more  fibrous  substance,  with 
scattered,  flattened,  roundish  nuclei  of  0-002-0-003  of  a 
line ;  and,  2,  in  that  of  isolated  elongated,  triangular  or 
fusiform  cells,  measuring  0-003-0-005  of  a  line,  with 
nuclei  as  above,  and  which  sometimes  may  be  supposed 
to  resemble  epithelial  cells,  although,  as  is  evident  from 
a  comparison  of  their  different  forms,  they  rather  cor- 
respond with  the  developmental  cells  of  connective,  or  of 
elastic  tissue  (Fig.  156).  Besides  these  two  forms,  the 
former  of  which  occurs  everywhere,  and  the  latter  principally  in  the 
larger  ganglia,  certain  intermediate  types  are  met  with  in  Man,  which 
consist,  as  it  were,  of  nucleated  "fibres  of  Remak,"  as  they  are  termed 
(vid.  infra),  or,  at  all  events,  in  the  preparation,  break  up  into  such. 

From  by  far  the  greatest  number  of  the  nerve-cells,  in  Man  and  the 
Mammalia,  are  given  off  pale  processes,  0-0015-0-0025  of  a  line,  in  all 
respects  corresponding  to  those  of  the  central  cells,  but  furnished  with  a 
special  sheath,  and  which,  as  I  discovered  in  the  year  1844  ("  Selbst.  u. 

FIG.  155. — Ganglion-globules  (nerve-cells)  from  the  Gasserian  ganglion  of  the  Cat,  mag- 
nified 350  diam. :  1,  cell  with  a  short,  pale  process,  showing  the  origin  of  a  fibre,  a; 
sheath  of  the  cell  and  nerve-tube,  containing  nuclei;  6,  cell-membrane  of  the  nerve-cell; 

2,  cell  with  the  origin  of   a  fibre,  without    sheath;  6,  cell-membrane  of  the  nerve-cell; 

3,  nerve-cell,  deprived,  in  the  preparation  of  it,  of  its  membrane  and  external  sheath. 
FIG.  1 56. — Cells  from  the  sheath  of  the  nerve-cells  of  the  spinal  ganglia  in  Man,  mag- 
nified 350  diameters. 


Fig.  156. 


408 


SPECIAL    HISTOLOGY. 


Fig.157. 


Abh.  des  Symp.  Nerv.,"  Zurich,  1844,  p.  22),  are  each  of  them  con- 
tinued into  a  dark-bordered  nerve  tube  (Figs.  155,  157).     The  cells 

observed  by  me  had  but  one 
process,  the  so-termed  uni- 
polar-cells,  and  I  at  first 
thought  that  such  only  ex- 
isted in  the  spinal  ganglia. 
It  now  appears,  however, 
from  more  recent  re- 
searches, especially  from 
those  of  Stannius,  that  they 
also  contain  cells  with  two 
processes,  one  of  which  may  again  divide  ;  fresh  and  more  extended  in- 
vestigations therefore  are  required  to  show  how  the  matter  really  stands. 
At  present  I  think  the  following  should  be  remarked  :  1,  in  Man  and 
the  Mammalia  I  have  certainly  established  the  fact  of  the  existence  of 
unipolar-cells,  and  think  it  may  also  be  asserted  that  they  are  very  nu- 
merous;  2,  quite  lately  I  have  myself,  although  rarely,  noticed  cells 
with  two,  pale  processes,  and  I  am  willing  to  admit  the  possibility  that 
such  cells  frequently  occur,  as  it  is  certain  that  many  processes  must  be 
torn  off  in  the  comparatively  rude  methods  necessarily  employed  to 
isolate  the  cells  ;  3,  when  Stannius  very  recently  noticed  in  a  human 
foetus,  and  in  a  foetal  Calf,  together  with  unipolar  and  apolar  cells,  in 
the  latter  numerous  bipolar  cells,  it  should  be  inquired  whether  the  lat- 
ter were  not  cells  which  afterwards  divide  ? — because  divisions  of  the 
nerve-cells  undoubtedly  take  place  (vid.  infra), — and  in  this  way  become 
unipolar ;  4,  whether  the  cells  give  off  one  or  two  fibres,  one  of  the 
latter  does  not  go  towards  the  centre  and  the  other  towards  the  peri- 
phery, but  both  proceed  in  the  latter  direction  ;  at  all  events,  in  the 
examination  of  all  small  ganglia,  only  such  ganglion-fibres  are  visible. 
Stannius,  in  bipolar  cells  of  this  kind  from  the  Calf,  also  found  the  two 
processes  closely  approximated  ;  5,  it  is  difficult  to  determine  whether 
cells  without  processes  also  occur  in  the  spinal  ganglia,  seeing  that  the 
processes  are  very  readily  detached,  and  that  cells  thus  truncated  may 
very  easily  be  regarded  as  apolar  cells.  In  small  ganglia  in  the  Mam- 
malia a  fibre  may  be  traced  to  each  cell,  whilst  in  the  smallest  spinal 
ganglia  in  Man,  and  in  the  inconstant  ganglia  of  the  posterior  roots 
(vid.  seq.\  cells  are  not  unfrequently  met  with,  to  which  no  fibre  is  at- 
tached, "and,  consequently,  I  would,  at  present,  merely  state  that,  in  any 
case,  fibres  arise  from  the  majority  of  the  cells.  In  order  to  examine 
these  conditions,  either  the  larger  ganglia  in  Man  are  selected,  which 

FiG.  157. — Twigs  of  the  coccygeal  nerve  within  the  dura  maler,  with  an  adherent,  pedun- 
culated  nerve-cell  in  its  nucleated  sheath,  from  which  the  derivation  of  a  fibre  is  very 
distinctly  seen  ;  magnified  350  diameters.  From  Man. 


THE    NERVOUS    SYSTEM. 


409 


Fig.  158. 


are  torn  into  fibres  as  carefully  as  possible  under  a  simple  microscope, 
until  the  fibres  are  traced  to  their  origin,  which  may  be  done  with  a 
little  trouble  in  almost  every  ganglion,  or  the  small  ganglia  of  the  fifth 
sacral  and  coccygeal  nerves  are  taken  for  the  purpose.  In  these  gan- 
glia, in  almost  every  individual,  solitary  and  completely  isolated,  pedun- 
culated,  ganglion-globules  are  met  with,  close  to  or  in  the  neighborhood 
of  the  ganglia,  each  in  its  special  sheath,  which  in  this  case  appears  to 
be  homogeneous  (Fig.  157),  and  in  many  cases,  the  simple,  dark  nerve- 
fibres  lying  in  the  peduncle  of  the  globule,  and  frequently  also  its  con- 
nection with  the  cell,  by  means  of  a  pale  process,  may  be  distinctly 
perceived.  In  the  ganglia  aberrantia  also  of  Hyrtl,  that  is  to  say  the 
inconstant,  larger  or  smaller  collections  of  nerve-cells,  which  are  found 
in  every  subject  upon  the  posterior  roots  of  the 
larger  nerves,  the  simple  origins  of  fibres  may 
occasionally  be  distinctly  noticed.  The  dark- 
colored  fibres,  arising  from  the  nerve-cells, 
simply  constitute  the  continuation  of  the  pale 
processes  of  the  cells,  so  that  the  membranes 
and  contents  of  each  part  pass  continuously 
into  each  other,  and  thus  also  the  membrane 
and  the  contents  of  the  cells  are  connected  with 
the  sheath  of  the  nerve-tubes,  the  medullary 
sheath,  and  the  axis-cylinder.  In  older  nerve- 
cells,  or  by  the  operation  of  reagents  (ar- 
senious  acid,  chromic  acid,  iodine),  the  con- 
tents of  the  cell  become  detached  from  the 
membrane,  and  the  axis-cylinder  appears 
as  a  direct  continuation  of  the  former  (Fig. 
158),  as  was  first  shown  by  Harting  (vid. 
also  Stannius  in 
and  Leydig,  1.  c. 

is  the  best   proof    that  the  contents   of   the 
nerve-cells  cannot  be  understood  as  contained  in  a  dilated  nerve-tube.* 


e 


"Gott.    Anzeig.,"    1850, 
Tab.  1,    Fig.    9),    which 


FIG.  158. — Nerve-cell  of  the  Pike  (bipolar,  as  they  are  termed),  which  is  continued  at  each 
end  into  dark-bordered  nerve-tubes,  treated  with  arsenious  acid  :  a,  sheath  of  the  nerve-cell  j 
6,  sheath  of  nerve ;  c,  nerve-medulla  ;  rf,  axis-cylinder  continuous  with  the  contents  of  the 
nerve-cell ;  e,  which  have  shrunk  away  from  the  sheath. —  Magnified  350  diameters. 


*  [The  axis-cylinder  is  supposed  by  some  observers  not  to  be,  as  above  stated,  a  continua- 
tion of  the  contents  of  the  cell,  but  rather  of  its  nucleus.  This  continuation  of  the  nucleus 
into  the. axis-cylinder  is  best  seen  in  ganglia,  which  have  been  kept  for  some  days  in  diluted 
acetic  acid.  We  are  thus,  according  to  Axmann  (I.  c.)  not  only  able  to  see  the  connection  of 
the  axis-cylinder  with  the  nucleus,  but  also  to  isolate  the  nucleus  with  a  portion  of  the  axis- 
cylinder  attached  to  it.  This  continuation  of  the  nucleus  of  the  ganglion  cell  into  the  axis- 
cylinder  has  been  observed  in  all  classes  of  animals.  It  was  first  described  by  Harless  in 
the  ganglion  corpuscles  of  the  electric  lobes  of  the  Torpedo  Galvani. — DaC.] 


410  SPECIAL    HISTOLOGY. 

The  nerve-tubes  or  ganglion-fibres  thus  originating,  which  frequently 
arch  round  or  embrace  the  cells  with  several  circular  turns,  are  at  first 
fine,  measuring  0-0015-0-0025  of  a  line,  but  (not  continuing  so  as  I 
formerly  supposed,  when  I  was  acquainted  only  with  their  origin),  they 
all  very  soon  increase  in  size,  as  may  be  very  readily  observed  in  many 
fibres,  whilst  still  within  the  ganglion,  up  to  0*003  arid  0*004,  many  even 
to  as  much  as  0*005  and  0-006  of  a  line;  becoming,  consequently,  medium- 
sized,  and  thick  nerve-fibres.  The  processes  of  the  cells  and  the  nerve-fibres 
springing  from  them  are  also  furnished  with  nucleated  sheaths  like 
the  cells  themselves,  the  vaginal  processes,  as  they  are  termed,  which 
they  lose,  however,  at  the  point  where  they  join  the  emergent  trunk, 
obtaining  instead  of  it,  as  a  coat,  the  common  neurilemma  of  the 
nerves. 

The  description  I  have  above  given  of  the  conditions  observable  in 
the  spinal-ganglia  in  Man  and  the  Mammalia,  differs  very  considerably 
from  what  was  found  by  Bidder,  Reichert,  R.  Wagner,  and  Robin,  to  be 
the  case  in  Fishes.  The  chief  difference  consists  in  this,  that  whilst  in 
the  Mammalia,  from  all  we  know,  the  roots  of  the  nerves  have  no  direct 
connection  with  the  nerve-cells,  and  merely  pass  through  the  ganglion, 
in  Fishes,  all  the  radical  fibres  are  connected  with  the  cells,  so  that  each 
fibre  is  interrupted  by  a  bipolar  cell,  and  independent  ganglion-fibres  are 
wholly  wanting.  R.  Wagner  has  thought,  that  what  obtains  in  the  Fish 
might  be  applied,  unconditionally,  to  all  the  Vertebrata,  and  asserts,  that 
the  occurrence  of  bipolar  cells  in  the  course  of  the  posterior  radical 
fibres  is  in  accordance  with  Bell's  doctrine,  and  a  necessary  contingent 
in  the  mechanism  of  the  sensitive  fibres  ;  and  moreover,  that  in  this  case 
the  highly  important  and  long-sought  distinction  between  sensitive  and 
motor  primitive  fibres,  has  been  discovered.  In  opposition  to  this  I  have 
expressed  the  opinion,  that  it  is  not  a  necessary  postulate,  that  what  is 
found  in  the  Fish  should  be  applied  to  Man,  and  that  the  interruption  of 
a  sensitive  fibre  by  a  nerve-cell  does  not  distinguish  it  from  a  motor 
fibre.  Although  Wagner  has  very  recently  characterized  this  opinion 
of  mine  as  unphysiological,  he  will  not,  at  the  same  time,  convince  any 
one  that  the  spinal  ganglia  of  the  Mammalia  are  constructed  as  he  thinks, 
and  I  shall  therefore  wait  to  see  whether  further  observations  will  con- 
firm my  observations  or  not.  In  order  to  complete  them,  I  will  more- 
over mention,  that  direct  measurement  of  the  sensitive  roots  above  and 
below  the  ganglia,  shows  a  not  inconsiderable  difference  in  favor  of  the 
latter  situation  (vid.  "  Mikroskop.  Anat.,"  II.  p.  509),  which  as  diffe- 
rences in  the  thickness  of  the  entering  and  emergent  nerve-fibres,  and 
divisions  of  them  within  the  ganglion  do  not  exist,  can  only  be  referred 
to  the  fibres  which  originate  in  the  ganglion  and  proceed  towards  the 
periphery,  a  view  which  is  also  confirmed  by  direct  observation  (Fig. 


THE    NERVOUS    SYSTEM.  411 

154).  With  respect  to  the  interesting  observations  on  the  structure  of 
the  spinal  ganglia  of  the  lower  animals,  and  particularly  of  Fishes,  I 
would  refer  especially  to  the  works  of  R.  Wagner,  Bidder,  Robin,  and 
Stannius,  cited  below. 

§  121.  Further  course  and  termination  of  the  Spinal  Nerves. — Below 
the  spinal  ganglion,  the  sensitive  and  motor  roots  unite  to  form  a  common 
trunk,  their  fibres  being  intermixed  in  diverse  ways,  as  may  be  very 
distinctly  perceived  in  small  animals.  All  the  subsequent  branches, 
both  of  the  anterior  and  posterior  main  divisions,  as  well  as  their  fur- 
ther continuations,  are  consequently  of  a  mixed  nature,  formed  of  por- 
tions derived  from  both  roots ;  a  condition  which  they  retain  up  to  their 
ultimate  distribution.  Here,  however,  an  alteration  takes  place,  the 
motor  fibres  going  off  in  by  far  the  larger  proportion  into  the  muscular 
branches,  and  the  sensitive  chiefly  to  the  cutaneous.  Where  the  gan- 
glion-fibres which  arise  in  the  spinal  ganglia  are  distributed,  cannot  be 
ascertained  anatomically.*  When  their  physiological  relations,  how- 
ever, are  considered,  it  would  appear  as  by  far  the  most  probable  sup- 
position, that  they  do  not,  as  at  first  sight  one  would  be  inclined  to 
suppose,  join  the  sympathetic  in  the  rami  communic  antes,  but,  that  ac- 
companying the  spinal  nerves,  they  are  continued  chiefly  into  the  vascular 
branches,  and  consequently  are  distributed  in  the  integuments,  muscles, 
bones,  joints,  tendons,  and  membranes  (periosteum,  pia  mater,  &c.),  but 
also,  perhaps,  to  the  glands  and  involuntary  muscles  of  the  skin.  The 
nerve-fibres  in  the  main  trunks  of  the  spinal  nerves  present  the  same 
diameter  as  in  the  roots,  that  is  to  say,  there  are  finer  and  thicker 
tubes,  and  a  certain  number  of  intermediate  forms ;  but,  as  they  pro- 
ceed, the  fibres  separate,  the  thicker  going  more  to  the  muscular 
branches,  and  the  thinner  into  the  cutaneous  nerves.  According  to  the 
statements  of  Bidder  and  Volkmann,  the  proportion  of  the  fine  to  the 
thick  fibres  is,  in  man,  as  1. 1 :  1,  in  the  muscular  nerves  as  0.  1-0*33  : 1 ; 
statements  which  I  can  but  confirm,  adding  to  them,  that  the  nerves  of 
the  bones  contain,  in  the  trunks,  one-third  of  thick  and  two-thirds  of 
fine,  whilst  those  of  the  articulations,  tendons,  and  membranes,  exhibit 
a  great  preponderance  of  fine  fibres.  In  my  opinion,  most  of  the  fine 
fibres  contained  in  the  branches  of  the  spinal  nerves  must  be  regarded 
as  derived  from  the  spinal  cord,  and  as  being,  in  their  function,  quite  of 
equal  importance  with  the  thick  fibres,  and  at  present,  the  only  thing 
that  remains  unascertained,  is  whether  they  all  ascend  to  the  brain,  or 
perhaps  in  part  arise  in  the  spinal  cord ;  upon  which  point  reference 
may  be  made  to  §  112. 

The  spinal  nerves  are  composed  in  general  of  parallel  tubes,  for  the 

*  [Vid.  note,  §  120.— DaC.] 


412  SPECIAL    HISTOLOGY. 

most  part  undulating,  upon  which  circumstance  their  transversely  banded 
aspect  depends ;  they  exhibit,  however,  in  their  course,  very  frequent 
anastomoses,  in  which  way  the  various  larger  and  smaller  plexuses  with 
decussating  fibres  are  formed.  The  formation  of  these  plexuses  is  due 
to  an  interchange  of  entire  fasciculi  or  fibres,  never  to  a  connection  be- 
tween the  individual  primitive  fibres,  and  in  a  microscopical  point  of 
view  affords  no  point  worthy  of  remark. 

Divisions  of  the  nerve-fibres  do  not  occur,  according  to  our  present 
experience,  in  the  trunks  and  larger  branches  of  the  spinal  nerves  of  the 
Mammalia  [in  Fishes,  Stannius  noticed  numerous  divisions  in  the  trunks 
of  the  motor  and  mixed  nerves  ("  Archiv  fiir  phys.,"  Heilk.  1850,  p. 
77)],  nor  do  they  exhibit  any  considerable  change  in  their  diameter  ; 
but  in  the  ultimate  ramifications,  on  the  other  hand,  it  is  certain  that 
such  divisions  do  take  place,  even  in  Man,  accompanied  by  a  very  con- 
siderable diminution  in  the  size  of  the  fibres  ;*  with  respect  to  which  con- 
ditions, and  the  terminations  in  the  skin,  muscles,  bones,  and  membranes 
in  general,  reference  may  be  made  to  the  detailed  descriptions  given  in 
the  proper  places. 

One  kind,  only,  of  termination  of  the  spinal  nerves,  is  still  to  be 
noticed  here, — that  in  the  Pacinian  bodies.  The  small  bodies,  so  named 
by  Henle  and  myself  ("  Ueber  die  Pacin.  Korperehen  des  Menschen  und 
der  Thiere,"  Zurich,  1844),  were  first  accurately  described  by  the  Italian, 
Pacini  ("Nuovi  organi  scoperti  nel  corpo  umano,"  Pistoja,  1840),  espe- 
cially in  the  nerves  of  the  palm  of  the  hand  and  sole  of  the  foot,  and, 
in  fact,  as  Langer  of  Vienna  afterwards  showed,  had  been  previously 
noticed  by  A.  Yater  (J.G.  Lehmann,  "  De  consensu  partium  corp.  hum.," 
Vitembergse,  1741),  although  their  nature  had  riot  been  recognized. 
These  organs  are  of  an  elliptical  or  pyriform  shape,  of  a  whitish  trans- 
parent color,  with  whiter  streaks  internally,  and  measure  J-2  lines  in 
size ;  in  Man,  they  are  constantly  found  on  the  cutaneous  nerves  of  the 
palm  of  the  hand  and  sole  of  the  foot,  in  the  subcutaneous  connective 
tissue  itself,  and  most  numerously  in  the  fingers  and  toes,  particularly 
on  the  third  phalanx, — according  to  Herbst  ("Die  Pacin.  Korperchen 
und  ihre  Bedeutung,"  Gott.,  1847),  there  are  about  600  in  the  hand  and 
not  quite  so  many  in  the  foot;  besides  which,  it  must  here  also  be 
stated,  that  they  are  invariably  found  on  the  great  sympathetic  plexus, 
in  front  of,  and  close  to  the  abdominal  aorta,  behind  the  peritoneum, 
particularly  near  the  pancreas,  frequently  also  in  the  mesentery,  close 
to  the  intestine ;  and  also  occasionally  on  other  nerves,  such  as  the 

*  [The  ultimate  ramifications  are  supposed  by  Axmann  (I.e.),  to  be  merely  axis-cylinders 
surrounded  by  the  sheaths  of  the  nerves,  the  granular  contents  of  the  nerve-tubes  having 
gradually  disappeared. — DaC.] 


THE    NERVOUS    SYSTEM. 


413 


Fig.  159. 


...0 
...4 


n.  pudendus  communis,  on  the  glans  penis  (Fick)  and  bulb  of  the  ure- 
thra, on  the  intercostal  nerves,  sacral  plexus, 
cutaneous  nerves  of  the  upper-  and  fore- 
arm, on  the  dorsum  of  the  hand  and  foot, 
and  the  cutaneous  nerves  of  the  neck. 

The  structure  of  the  Pacinian  bodies  is, 
upon  the  whole,  simple  (Fig.  159).  Each  of 
them  consists  of  very  numerous  (20-60) 
concentric  layers  of  connective  tissue,  of 
which  layers  the  external  are  separated  by 
wider,  and  the  internal  by  narrower  inter- 
spaces, in  which  is  contained  a  clear  serous 
moisture,  which  is  collected  in  larger  quan- 
tity in  an  elongated  central  cavity,  bounded 
by  the  innermost  lamella.  Each  body  pre- 
sents a  rounded  peduncle,  formed  from  the 
continuation  of  its  lamellae,  and  connected 
with  a  nervous  twig,  and  in  which  a  dark 
nerve-fibre,  0-006-0-068  of  a  line  (in  the 
Cat,  0-0044-0-0077  of  a  line)  thick,  runs  to 
the  Pacinian  body.  This  fibre  enters  the 
central  cavity  from  the  penduncle,  where  it 
becomes  0-006  of  a  line  wide  and  0-004 
of  a  line  thick,  pale,  non-medullated,  almost 
like  an  axis-cylinder,  and  terminates  in  the 
upper  part  of  the  cavity,  in  a  free,  slightly 
granular  tubercle,  the  extremity  being  fre- 
quently bifid  or  trifid.  Further  observa- 
tions, and  comparative  anatomical  details 
with  regard  to  these  bodies,  which  are  also 

found  in  great  number  in  many  Mammalia,  as  well  as  in  Birds,  in  the 
skin,  beak,  and  tongue  (Herbst,  Will),  and  with  respect  to  which  physio- 
logy is  still  wholly  in  the  dark,  will  be  found  in  the  works  above  quoted, 
and  also  in  Reichert  ("  Bindegewebe,"  p.  65),  Herbst  ("  Gott.  gel.  Anz.," 
1848,  Nos.  162,  163,  1850;  "  Nachr.  v.  d.  Univ.,"  p.  204,  1851,  p. 
161),  Will  ("Sitzungsber.  d.  Wiener  Acad.,"  Feb.,  1850),  Osann("Bericht 
ttber  d.  zoot.  Anst.  in  Wurzb.,"  1849),  Strahl  (Miiller's  "  Arch.,"  1848, 
p.  163),  and  Pappenheim  ("  Comptes  rendus,"  xxiii.  p.  68).  [Todd  and 
Bowman,  "  Physiol.  Anatomy,"  Part  II.,  p.  395,  figs.  74,  75,  76;  and 
Bowman,  art.  "Pacinian  Bodies,"  "  Cyc.  of  Anat.  and  Phys."] 

FIG.  159. — A  Pacinian  body  in  Man,  magnified  350  diam. :  a,  its  peduncle ;  b,  nerve- 
fibre  in  it ;  c,  external ;  d,  internal  layer  of  the  sheath ;  e,  pale  nerve-fibre  in  the  cen- 
tral cavity ;  /,  divisions  and  terminations  of  the  same. 


414  SPECIAL    HISTOLOGY. 

The  spinal  nerves,  from  their  point  of  exit  through  the  dura  mater, 
are  enclosed  by  a  firm  sheath  of  connective  tissue — the  nerve-sheath,  or 
neurilemma — which  also  sends  finer  prolongations  into  the  interior  of 
the  nerves,  and,  as  in  the  muscles,  forms  boundaries  to  larger  or  smaller 
fasciculi,  as  well  as  extremely  delicate  septa  between  the  individual 
tubules  (Fig.  160).  In  the  ultimate  ramifications,  where  isolated  primi- 
tive fibres,  or  some  few  of  them,  still  often  re- 
tain an  external  coat,  the  neurilemma  presents 
the  aspect  of  a  homogeneous  membrane,  with 
elongated  nuclei  of  0*003  of  a  line ;  and  it 
presents  this  character  also  in  the  smaller 
twigs  of  the  cutaneous  and  muscular  nerves, 
only  that  gradually  the  substance  begins  to 
split,  in  a  longitudinal  direction,  into  fibres,  the  nuclei  become  longer 
(0-005-0-008  of  a  line),  frequently  almost  like  those  in  smooth  muscles, 
and  elastic  fibres  also  make  their  appearance,  which  are  not  unfre- 
quently  entwined  around  whole  fasciculi.  The  larger  nerves,  lastly 
present  common  connective  tissue,  with  distinct  longitudinal  fibrils,  as 
in  fibrous  membranes,  intermixed  with  numerous  reticulated  elastic  fila- 
ments ;  they  still,  however,  exhibit,  especially  in  the  interior,  immature 
forms  of  connective  tissue. 

All  the  larger  nerves  contain  vessels,  although  not  in  great  number ; 
they  run  principally  in  a  longitudinal  direction,  and  form  a  loose  plexus 
of  minute  capillaries  of  0-002-0*004  of  a  line,  with  elongated  inter- 
stices, which  invests  the  fasciculus,  and,  in  fact,  penetrates  between  its 
elements ;  never,  however,  surrounding  individual  primitive  fibres,  but 
only  entire  divisions  of  them.  The  ganglia  contain  a  delicate  capillary 
plexus,  in  the  form  of  a  network,  so  that  each  nerve-cell  is  surrounded 
by  special  vessels.  The  Pacinian  bodies  also  contain  vessels,  which 
even  penetrate  as  far  as  the  central  cavity  (Todd  and  Bowman,  II.  p. 
397,  Fig.  75,  and  p.  399,  Fig.  76 ;  Herbst,  Tab.  IV.  Figs.  1  and  2). 

On  the  subject  of  the  condition  of  the  cutaneous  nerves  of  animals,  I 
would  here  add  a  few  remarks.  In  the  skin  of  the  tail  of  batrachian 
larvae  (Rana,  Bvifo,  Triton,  Bombinator^  Alytes\  I  have  described  the 
very  delicate  ramifications  and  plexuses  of  the  embryonic  pale  nerve- 
fibres  ;  and  moreover,  quite  evident  loops  of  the  fully  formed  dark  nerve- 
tubes,  and  isolated  divisions  of  the  latter  ("Ann.  des  S.  Nat.,"  1846, 
p.  102,  pi.  6,  7).  In  the  full-grown  Frog,  according  to  Czerm&k  (Mull. 
"Archiv,"  1849,  p.  252),  the  nerves  destined  to  the  skin,  form,  on  its 
inner  aspect,  a  wide  network,  already  described  by  Burdach,  from  which 

FiG.  160. — Transverse  section  of  the  ischiatic  nerve,  magnified  15  diam.:  a,  general 
sheath  of  the  nerve;  b,  neurilemma  of  the  tertiary  fasciculi;  c,  secondary  nervous  fasciculi, 
in  part  with  special  sheaths.  From  the  Calf. 


THE    NERVOUS    SYSTEM.  415 

again  numerous  fasciculi  are  given  off,  penetrate  the  derma  perpendicu- 
larly, and,  having  reached  the  superficial  glandular  layer  of  the  skin, 
form  a  superficial  nervous-plexus  between  the  glands.  With  respect  to 
the  true  termination  of  the  nerve-fibres,  Czermdk  arrived  at  no  definite 
results,  but  made  the  interesting  discovery  that  thick  and  thin  nerve- 
fibres  of  the  deeper  plexus  divide  dichotomously  very  frequently  and 
repeatedly,  and  thus  spread  themselves  over  larger  surfaces;  of  which 
divisions  I  have  most  fully  satisfied  myself  from  preparations  furnished 
by  Czermdk.  Similar  conditions  were  found  by  Leydig  ("  Zeitsch.  f. 
wissen.  Zool.,"  III.)  in  the  skin  of  Fishes;  where  also  exist  superficial 
and  deeper  plexuses,  with  numerous  divisions  of  finer  and  thicker  tubes, 
all  of  which  on  the  surface  ultimately  become  quite  fine,  pale,  and  finally 
invisible.  In  the  Invertebrata,  as  appears  from  Leydig's  researches  in 
Argulus,  and  especially  in  Carinaria,  conditions  are  met  with  perfectly 
analogous  to  those  described  by  me  in  the  nerves  of  the  Tadpole ;  and  I 
cannot  agree  with  Leydig,  when  he  describes  the  nucleated  enlarge- 
ments as  nerve-cells.  On  the  other  hand,  the  conditions  observed  in 
Artemia  and  Corethra  are  perhaps,  peculiar,  because  in  these  instances 
larger  branches  of  the  cutaneous  nerves  are,  at  their  extremities,  in  con- 
nection with  numerous  roundish  vesicles,  which  might  have  the  function 
of  nerve-cells  ("  Zeitsch.  f.  wiss.  Zool.,"  vol.  I.  iii.). 

In  the  integuments  of  the  Mammalia  and  of  Man,  except  in  the  Paci- 
nian  bodies,  until  a  short  time  since,  no  one  had  seen  anything  of  divi- 
sions in  the  nerve-tubes ;  all  observers  rather  agreeing  that  terminal 
loops  existed  there,  especially  in  the  papillae.  But  it  now  appears,  from 
the  researches  of  myself,  J.  N.  Czermdk,  and  C.  Gegenbaur,  that  pro- 
bably loops  and  divisions,  and  occasionally  even  free  terminations,  all 
exist  in  that  situation.  That  in  Man,  terminal  loops  occur  in  the 
papillae,  and  divisions  in  the  terminal  plexuses,  I  have  already  men- 
tioned ;  the  latter  are  especially  well  shown  in  the  conjunctiva  scleroticce, 
where  free  terminations  also  appear  to  exist,  and  where  peculiar  convo- 
lutions of  nerves  (nerven-knauel),  similar  to  those  formerly  described  by 
Gerber*  (vide  "  Micr.  Anat.,"  II.  i.  p.  31,  Fig.  13  J.,  3),  present  them- 
selves. Czermak,  moreover,  observed  divisions  of  the  cutaneous  nerves 
in  the  Mouse,  and  I  myself  a  transition  of  the  dark-bordered  nerves  into 
pale  anastomosing  filaments,  of  0'001-0f0005  of  a  line,  exactly  resem- 
bling the  embryonic  fibres  in  the  Tadpole  ("  Micr.  Anat.,"  II.  i.  p.  24) ; 
lastly,  Gegenbaur  has  noticed  numerous  divisions  in  the  expansion  of  the 
nerves  of  the  tactile  hairs  in  the  Mammalia.  Further  experience  will 
have  to  show  in  what  relative  proportions  the  loops,  divisions,  and  free 
terminations,  stand  with  respect  to  each  other,  and  whether  in  the  diffe- 
rent Mammalia,  notwithstanding  any  apparent  difference,  some  corre- 
spondence obtains  or  not. 

*  ["  General  Anatomy,"  translated  by  G.  Gulliver,  p.  263,  pi.  19,  Figs.  99,  100.— TBS.] 


416  SPECIAL    HISTOLOGY. 

§  122.  Cerebral  Nerves. — The  sensitive  and  motor  nerves  arising  in 
the  brain,  correspond  in  most  particulars  so  closely  with  the  spinal 
nerves,  that  a  short  description  of  them  will  suffice  ;  and  with  respect 
to  the  higher  nerves  of  sense,  they  will  be  afterwards  described,  more 
fully,  in  connection  with  the  organs  to  which  they  belong. 

The  motor  cerebral  nerves,  the  third,  fourth,  sixth,  seventh,  and 
twelfth  pairs,  with  respect  both  to  their  roots  and  to  their  course  and 
distribution,  present  exactly  the  same  conditions  as  the  motor  roots  and 
muscular  branches  of  the  spinal  nerves,  with  the  sole  exception,  that  by 
all  these  nerves,  from  their  anastomosing  with  sensitive  nerves,  some 
sensitive  fibres  are  conveyed  to  the  muscles.  It  deserves  remark  :  1, 
that  according  to  Rosenthal  and  Purkinje,  nerve-cells  exist  in  the  trunk 
of  the  oculo-motorius  in  the  Ox,  which,  however,  Bidder  (p.  32)  was 
unable  to  find ;  2,  that  the  facial  nerve,  in  its  gangliform  enlargement, 
presents  a  number  of  larger  nerve-cells,  through  which,  however,  accord- 
ing to  Remak,  only  part  of  the  fibres  pass  (Mull.  "Archiv."  l%tl); 
3,  that  according  to  Volkmann  (in  Bidder's  "  Ganglien-korper,"  p.  68), 
the  small  root  of  the  hypoglossal  nerve  in  the  Calf,  which  is  furnished 
with  a  ganglion,  produces  motor  effects.  What  is  the  significance  of 
this  occurrence  of  nerve-cells  in  motor  nerves  has  not  been  ascertained. 
Probably  simple  fibres  having  a  peripheral  destination  arise  from  them, 
exactly  as  in  the  spinal  ganglia.  In  any  case  it  shows  that  ganglia  are 
not  necessarily  placed  only  on  sensitive  nerves.  The  fifth,  ninth,  and 
tenth  pairs,  resemble  the  spinal  nerves,  inasmuch  as  that  they  all  con- 
tain motor  and  sensitive  elements.  In  the  irigeminus  the  small  root 
exhibits  a  preponderance  of  thick  fibres ;  the  larger,  numerous  fine 
fibres.  The  Gasserian  ganglion,  as  well  as  the  smaller  ganglionic  body 
seated  upon  it,  contains  many  larger  and  smaller  nerve-cells  of  0-008- 
0-030  of  a  line,  with  nucleated  sheaths,  and  presents  the  same  conditions, 
according  to  my  observations,  in  small  Mammalia  and  in  Man,  as  a  spi- 
nal ganglion,  that  is  to  say,  it  is  simply  traversed  by  the  fibres  of  the 
greater  root,  and,  from  unipolar  cells,  gives  origin  to  numerous  nerve- 
fibres  of  medium  size,  which  go  to  join  the  emergent  branches.  Bipolar 
cells  also  occur,  but,  as  it  appears,  in  less  quantity,  and  anything  that 
can  be  said  about  apolar  cells  is  as  applicable  here  as  in  the  case  of  the 
spinal  ganglia.  The  ultimate  distribution  of  the  n.  trigeminus  is  for  the 
most  part  similar  to  that  of  the  cutaneous  nerves,  and,  in  particular,  the 
existence  of  divisions  of  the  nerve-tubes  may  be  distinctly  demonstrated 
in  the  mucous  membranes,  as  in  the  conjunctiva  at  the  edge  of  the  cor- 
nea, in  the  ciliary  ligament,  in  the  tooth-pulp,  and  in  the  papillae  of  the 
tongue.  Terminal  loops  and  free  terminations  appear  to  exist  in  the 
papillae  of  the  mucous  membrane  of  the  mouth  and  tongue,  and  in  the 
conjunctiva,  whilst  in  the  cornea,  the  extremities  of  the  nerves  are  quite 


THE    NERVOUS    SYSTEM.  417 

transparent  and  pale,  and  constitute  a  wide-meshed  plexus  without  any 
divisions.  With  respect  to  the  ganglia,  which  are  placed  on  the  n. 
trigeminus  (ganglion  ciliare,  oticum,  sphenopalatinum,  linguale,  supra- 
maxillare),  I  find  their  structure  more  to  resemble  that  of  the  sympa- 
thetic ganglia,  only  that  they  contain  a  considerable  number  of  larger 
nerve-cells.  The  glossopharyngeus,  although  endowed  with  motor  pro- 
perties, still,  according  to  Volkmann  (Mull.  "Arch.,"  1840,  p.  488), 
has  no  fibres  which  do  not  pass  through  one  or  other  of  its  ganglia.  In 
its  roots,  which  contain  numerous  fine  fibres,  there  are,  according  to 
Bidder  (1.  c.  p.  30),  in  the  Mammalia,  not  unfrequently,  isolated  nerve- 
cells,  often  placed  free  upon  it,  in  which,  as  in  similar  cells,  on  the  roots 
of  the  n.  vagus,  the  giving  off  of  two  middle-sized  fibres,  it  is  said,  may 
occasionally  be  readily  perceived.  The  ganglia  of  the  glossopharyngeus 
present  the  same  conditions  as  the  spinal  ganglia,  that  is  to  say,  the 
radical  fibres  simply  traverse  them,  and,  within  the  ganglion,  fibres  arise 
from  cells,  which  are  for  the  most  part  unipolar ;  its  ultimate  ramifica- 
tion in  the  tympanic  cavity  and  in  the  tongue,  contains  small  ganglia, 
and  otherwise  corresponds  with  that  of  the  n.  trigeminus  (p.  major).  In 
Man,  all  the  roots  of  the  n.  vagus  enter  the  jugular  ganglion,  whilst  in 
some  of  the  Mammalia — Dog,  Cat,  Rabbit,  according  to  Remak  (in  Fro- 
riep's  "Not.,"  1837,  No.  54),  in  the  Dog  and  Sheep,  according  to  Volk- 
mann (Mailer's  "Arch.,"  1840,  p.  491),  but  not  in  the  Calf,  in  which 
nerve-cells  occur  in  the  apparently  motor  root,  it  has  also  a  primary 
fasciculus,  which  has  no  connection  with  the  ganglion.  In  the  ganglion 
jugulare  and  in  the  intumescentia  ganglioformis  of  the  facial  nerve,  I 
have  not  been  able  to  find  anything  different  from  the  spinal  ganglia, 
only,  that  the  nerve-cells  measure  occasionally  no  more  than  0-009  of  a 
line,  although  it  is  true  that  there  are  also  a  great  many  as  large  as  0-03 
of  a  line.  The  ultimate  distribution  of  the  nerve  exhibits,  as  Bidder 
and  Volkmann  correctly  state,  a  constant  kind  of  separation  of  thicker 
and  more  slender  fibres,  so  that  the  branches  to  the  oesophagus,  heart, 
and  stomach,  are  composed  almost  entirely  of  fine  fibres,  whilst  in  those 
going  to  the  lungs,  and  in  the  laryngeus  superior,  the  fine  are  to  the 
thick  fibres  as  2  to  1 ;  and  in  the  laryngeus  inferior  and  the  rami  pha~ 
ryngei,  as  1  to  6-10.  All  these  fine  fibres  are  very  far  from  being 
derived  from  the  sympathetic,  as  they  occur  in  preponderating  quantity 
even  in  the  roots  of  the  vagus,  and  are  also  numerous  in  the  laryngeus 
superior.  Many  of  them,  moreover,  may  be  nothing  more  than  attenu- 
ated or  originally  finer  ganglion-fibres,  as  they  are  termed,  arising  in  the 
ganglia  of  the  vagus  itself,  and  which  likewise  I  should  not  refer  to  the 
sympathetic.  With  respect  to  the  terminations  of  the  vagus,  reference 
must  be  made  below  to  the  proper  places.  The  n.  accessorius  Willisii, 
although  perhaps  also  in  part  sensitive,  has  no  nerve-cells,  and  in  its 

27 


418  SPECIAL    HISTOLOGY. 

distribution   and  termination,  so   far  as  is   known,  presents    nothing 
peculiar. 

Terminal  loops  within  the  trunks  of  nerves  had  been  already  noticed 
by  Gerber,  and  have  lately  been  described  by  Valentin  in  the  vagus 
(pectoral  portion)  of  the  Mouse  and  Shrew-mouse,  but  without  their 
expressing  any  opinion  with  respect  to  their  signification.  Still  more 
mysterious  are  the  nervous  filaments  seen  by  Remak  and  Bochdalek, 
coming  out  from,  and  again  re-entering  the  brain. 

§  123.  Granglionic  Nerves. — Under  this  name,  perhaps,  is  most 
suitably  designated  the  n.  sympathicus,  as  it  is  termed, — the  sympa- 
thetic or  vegetative  nervous  system, — as  it  presupposes  no  physiological 
hypothesis,  but  simply  expresses  the  fact,  which,  anatomically,  is  most 
apparent  to  the  eye.  The  ganglionic  nerves  are  neither  a  wholly  inde- 
pendent part  of  the  nervous  system  (Reil,  Bichat),  nor  a  mere  section  of 
the  cerebro-spinal  nerves  ;  but  on  the  one  hand,  from  the  very  numerous 
fine  nerve-fibres  originating  in  their  ganglia — ganglion-fibres  of  the  sym- 
pathetic,— form  an  independent  system  ;  whilst  on  the  other,  they  are 
also  connected  with  the  spinal  cord  and  brain,  owing  to  their  receiving  a 
smaller  number  of  fibres  of  the  other  nerves.  Upon  comparing  the 
ganglionic  nerves  with  the  cerebro-spinal,  we  find,  that  the  former,  as 
they  are  constituted  from  a  double  source,  in  a  certain  respect  undoubt- 
edly resemble  the  latter,  which  are  also  formed  from  ganglionic  fibres  of 
the  spinal  ganglia,  and  from  others  proceeding  from  the  cord ;  but  they 
differ,  particularly  in  this  respect,  that  they  possess  a  much  greater 
number  of  independent  elements,  of  ganglia  and  ganglionic  fibres,  and 
enter  into  much  more  numerous  anastomoses  with  each  other.  Conse- 
quently, although  we  appear  to  be  justified  from  an  anatomical  point  of 
view,  in  considering  the  ganglionic  nerves  by  themselves,  still  they  must 
not  be  regarded  as  something  altogether  peculiar,  seeing  that,  essentially, 
every  nerve  exhibits  the  same  principal  elements,  and  some  cerebral 
nerves,  vagus,  glossopharyngeus,  possess  even  numerous  peripheral 
ganglia ;  and  moreover,  because  comparative  Anatomy  shows  that  they 
are  produced  from  the  spinal  nerves,  and  Physiology  the  absence  of 
peculiar  functions  in  them. 

§  124.  The  principal  trunk  of  the  ganglionic  nerves  (nervus  sympa- 
thicus).  The  n.  sympathicus  in  man  appears  as  a  whitish,  or  white 
nerve,  the  dark-bordered  fibres  of  which  usually  run  parallel  with  each 
other,  without  divisions  or  anastomoses,  some  measuring  0-0025-0-006 
of  a  line  or  even  more,  and  others  not  more  than  0-0012-0-0025  of  a 


THE    NERVOUS     SYSTEM.  419 

line.     These  finer  and  coarser  fibres  are  partially  intermixed,  partly 

Fig.  161. 

Vs. 


disposed  more  in  a  fascicular  manner,  the 
latter  being  the  case  near  the  ganglia  of 
the  main  trunk  and  in  that  part  itself. 
The  structure  of  the  ganglia  is,  in  the 
main,  similar  to  that  of  the  spinal  ganglia. 
Each  of  them  consists  :  1,  of  perforating 
nerve-fibres,  proceeding  from  one  part  of 
the  trunk  to  the  other ;  2,  of  a  certain 
number  of  finer  tubules  originating  in  the 
ganglion  ;  and  3,  of  numerous  nerve-cells; 
besides  these  the  rami  communicantes 
also  enter  the  ganglia,  and  a  certain  num- 
ber of  peripheral  branches  are  given  off  from  it.  The  nerve-cells  in  the 
sympathetic  (Fig.  162  B),  present,  in  all  essential  particulars,  precisely 
the  same  conditions  as  those  in  the  spinal  ganglia,  only  that  they  are, 
on  an  average,  smaller,  measuring  0*006-0'018,  0-008-0-01  of  a  line 
in  the  mean,  with  less  and  paler  pigment,  or  even  colorless  and  usually 
pretty  uniformly  rounded.  As  respects  the  origin  of  the  nerve-fibres  of 
the  main  trunk,  it  is,  in  the  first  place,  evident,  that  they  are  in  great 
part  derived  from  the  rami  communicantes  which  arise  immediately 
below  the  spinal  ganglia  from  the  trunks  of  the  spinal  nerves  ;  that  they 
are  in  general  formed  like  the  sensitive  roots  of  those  nerves  (that  is, 
contain  a  preponderance  of  finer  fibres),  and,  whether  simple  or  com- 
pound, that  they  are  manifestly  connected  with  both  roots.  From  all 
that  has  hitherto  been  made  out,  the  fibres  of  these  connecting  branches 
are  derived  chiefly  from  the  spinal  cord  and  from  the  spinal  ganglia, 

FIG.  161.-— Sixth  thoracic  ganglion,  on  the  left  side,  of  the  sympathetic  nerve  of  the  Rabbit, 
viewed  from  behind,  treated  with  soda,  and  magnified  40  diam. :  T.  2,  trunk  of  the  sympa- 
thetic; R.  c.  R.  c,  rami  communicantes,  each  dividing  into  two  branches;  Spl.,  n.  splanc hnicus ; 
S,  twigs  of  the  ganglion  with  two  stronger  fibres  and  finer  filaments,  probably  going  to 
vessels ;  G,  nerve-cells,  and  ganglion-fibres  joining  the  main  trunk. 

FIG.  162. — From  the  sympathetic  in  Man,  magnified  350  diam. :  j$,  a  portion  of  a  gray  nerve 
treated  with  acetic  acid  ;  a,  fine  nerve-tubes ;  6,  nuclei  of  the  fibres  of  Remak.  B+  Three 
nerve-cells,  one  with  a  pale  process. 


420  SPECIAL    HISTOLOGY. 

and  are  consequently  roots  of  the  sympathetic  ;  in  a  smaller  proportion, 
however,  they  might  be  derived  from  the  sympathetic,  and  joining  them- 
selves to  the  spinal  nerves  are  further  distributed  peripherally  together 
•with  them.  Having  entered  the  main  trunk  of  the  sympathetic,  the 
rami  communicantes,  so  far  as  they  are  derived  from  the  spinal  nerves, 
almost  invariably  run,  dividing  into  two  or  several  branches  upwards 
and  downwards  in  it,  towards  its  cephalic  and  pelvic  extremities,  being 
in  apposition  with  the  longitudinal  fibres  of  the  trunk.  In  the  Rabbit, 
the-  fibres  of  a  given  ramus  communicans  may  very  frequently  be  traced 
as  far  as  the  nearest  ganglion  and  beyond  it,  in  separate  peripheral 
branches,  but,  in  general,  the  course  of  the  individual  fasciculi  very 
soon  escapes  the  eye.  It  may  nevertheless  be  asserted  with  great  cer- 
tainty, that  they  all  gradually  go  off  in  the  peripheral  branches  of  the 
main  trunk,  for  in  the  first  place  all  these  branches  frequently  contain, 
in  considerable  quantity,  the  same  dark-bordered  thicker  fibres,  as  those 
•which  are  contained  in  the  rami  communicantes,  and  secondly  their  ter- 
mination or  origin  is  never  observed  in  the  main  trunk  itself;  which 
circumstance  is  also  the  principal  reason  why  the  rami  communic antes 
can  be  regarded  not  as  branches  of  the  sympathetic,  but  only  as  its 
roots. 

Besides  the  fine  and  coarser  fibres  of  the  rami  communicantes,  the 
main  trunk  of  the  sympathetic  contains  other  fibres  in  very  great 
numbers,  which  are  dark-bordered,  but  pale,  finest  nerve-tubes  measur- 
ing 0'0012-0*002  of  a  line,  with  respect  to  which  I  unhesitatingly  assert, 
that  they  originate  in  it,  and  are  in  no  way  continuations  of  the  rami 
communicanteSj  as  has  been  quite  recently  supposed,  since  the  discovery 
of  the  bipolar  ganglion-cells  in  Fishes.  In  the  Mammalia  it  is,  in  fact, 
extremely  easy  to  prove,  by  the  examination  of  entire  sympathetic 
ganglia  under  the  careful  application  of  dilute  soda  and  compression, 
that  the  great  majority  of  the  fibres  of  the  rami  communicantes  have 
not  the  slightest  connection  with  the  ganglion-cells,  but  much  rather 
that  they  simply  pass  through  the  ganglia,  and  ultimately  go  off  in  the 
peripheral  branches.  Now,  as,  besides  these  fibres  in  the  main  trunk, 
numerous  other  fibres  of  the  finest  kind  exist,  which  can  in  no  way  be 
assigned  to  the  rami  communic  antes  ^  it  is  clear,  that  they  must  be  struc- 
tures of  entirely  new  formation.  This  conclusion  appears  to  be  the 
more  legitimate,  when  it  is  added,  that  it  is  not,  as  I  first  and  many 
since  have  shown,  by  any  means  so  difficult  to  demonstrate  simple 
origins  of  fibres  in  the  sympathetic  ganglia  of  the  Mammalia  and 
Amphibia,  and  that,  in  the  ganglia  a  considerable  portion  of  fine  fibres 
assume  the  aspect  of  so-called  convoluted  fibres,  that  is  to  say,  of  fibres 
•winding  about  in  various  directions  through  the  mass  of  cells.  From 
•what  I  have  seen  in  the  Mammalia  and  man,  the  sympathetic  ganglia 
correspond  so  far  with  those  of  the  spinal  nerves,  that  they  contain  a 


THE    NERVOUS    SYSTEM.  421 

preponderance  of  unipolar,  rarely  of  bipolar  cells,  differing,  however,  in 
this  respect,  that  apolar  cells  certainly  exist  in  them  in  more  consider- 
able quantity,  and  the  ganglion  fibres  arising  in  them  are  invariably  of 
the  finest  kind,  occurring  in  the  peripheral  nerves,  and  probably  in  most 
cases,  quit  the  ganglia  in  various  directions.  As  for  a  topographical 
tracing  of  the  various  fibres  in  the  main  trunk  of  the  sympathetic,  with 
reference  to  their  origin  from  particular  rami  communic antes  and 
ganglia,  and  their  continuation  into  particular  peripheral  branches, — 
if  more  be  required  than  what  has  already  been  stated — it  is  not  by  any 
means  at  present  to  be  thought  of,  but  must  be  reserved  for  future  in- 
vestigation. 

It  has-been  asserted,  that  the  smaller  cells  in  the  ganglia  of  the 
sympathetic  are  different  from  the  larger  cells  in  the  spinal  ganglia,  for 
instance ;  and  also  that  they  are  connected  only  with  fine  nerve-tubes 
(Robin),  but  this  is  not  correct,  as  is  apparent  in  part  from  the  observa- 
tions of  Wagner  and  Stannius ;  for  we  find :  1,  in  the  ganglia  of  the 
cerebral  and  spinal  nerves  of  the  Mammalia  and  of  man,  all  intermediate 
sizes  between  larger  and  smaller  nerve-cells,  and  also,  occasionally, 
though  rarely,  larger  cells,  measuring  as  much  as  0-03  of  a  line  in  the 
sympathetic  ganglia ;  and  we  may  also  be  convinced,  2,  that  the  diame- 
ter of  the  nerve-fibres  originating  in  the  first-named  ganglia,  is  not  at 
all  regulated  by  that  of  the  cells,  all  their  ganglion-fibres  being  pretty 
nearly  of  the  same  size,  and  which  is  confirmed  also  by  the  bipolar  cells 
of  Fishes,  where  the  one  fibre  arising  from  the  cell  is  often  considerably 
thicker  than  the  other ;  in  Petromyzon,  according  to  Stannius,  even 
six  times.  Should  it  be  at  all  supposed  that  the  small  cells  are  peculiar 
to  the  sympathetic  nerve  alone,  I  must,  as  above,  with  respect  to  the 
nerve-fibres,  remark,  that  not  to  mention  the  ganglia  of  the  roots  of  the 
cerebral  and  spinal  nerves,  small  nerve-cells  also  occur  in  situations 
where  there  can  be  no  question  about  the  sympathetic,  as  in  the  spinal 
cord  and  brain,  and, — if  instances  of  the  same  kind  in  the  peripheral 
nerves  be  desired — in  the  retina  and  cochlea.  At  all  events,  this  much  is 
certain,  that  the  ganglia  of  the  ganglionic  system  of  nerves  constantly 
present  smaller  nerve-cells,  and  that  the  fibres  arising  from  them  are 
of  the  fine  kind  only. 

Bidder  and  Volkmann  have  shown,  in  the  Frog,  that  the  greater  part 
of  the  fibres  of  the  rami  communicantes  are  distributed  peripherally, 
with  the  spinal  nerves,  and  that  only  a  small  portion  of  them,  which 
moreover  are  derived  from  the  spinal  ganglia,  should  be  regarded  as 
roots  of  the  sympathetic.  But  I  think  I  have  noticed  in  the  Babbit 
and  in  Man,  that  the  rami  communicantes  have  chiefly  a  central  des- 
tination. Still,  in  man,  fibres  also  occur  very  frequently — according  to 
Luschka  always, — which  must  be  regarded  as  branches  of  the  sympa- 


422  SPECIAL    HISTOLOGY. 

thetic  going  to  the  peripheral  distribution  of  the  spinal  nerves,  from 
•which  again  twigs  are  given  off  to  nerves  of  the  vertebrae ;  with  respect 
to  which  conditions  the  more  detailed  observations  given  in  my  "  Mikr. 
Anat.,"  II.  p.  525,  and  particularly  those  of  Luschka  ("  Nerven  des 
Wirbelcanals,"  p.  10  et  seq.)  may  be  consulted.  With  regard  to  the 
question,  whence  the  fibres  are  derived  which  join  the  main  trunk  of 
the  sympathetic  from  the  spinal  nerves,  it  is  certain  that  that  portion  of 
the  rami  communicantes,  which  arises  from  the  motor  root,  and  which, 
according  to  Luschka,  is  always  a  white  filament,  takes  its  origin  from 
the  cord  (or  brain)  itself,  but  as  regards  the  other,  proceeding  from  the 
sensitive  root,  it  may  be  formed,  in  part  or  wholly,  from  fibres  origi- 
nating in  the  ganglion.  The  latter,  however,  appears  to  be  improbable, 
for  two  reasons :  1,  because  in  that  case,  the  existence  of  conscious 
sensations  from  parts  supplied  by  the  sympathetic  would  scarcely  be 
conceivable ;  and  2,  because  the  fibres  originating  in  the  spinal  ganglia 
are  of  medium  size,  whilst,  in  the  rami  communicantes,  upon  the  whole, 
only  a  few  of  that  kind  occur,  and  these,  moreover,  must  be  referred  to 
the  motor  root. 

We  may  here  offer  a  few  remarks  upon  the  fine  fibres  of  the  gan- 
glionic  nerves.  It  has  been  long  known,  that  the  sympathetic  contains 
a  larger  proportion  of  finer  nerve-fibres  than  the  cerebro-spinal  nerves, 
but  it  was  not  till  1842  that  Bidder  and  Volkmann  labored  to  show, 
that  these  fibres  are  not  only  smaller,  but  also,  in  other  respects,  ana- 
tomically different ;  on  which  account  in  contradistinction  to  the  thick 
fibres  of  the  cerebro-spinal  nerves,  they  termed  them  sympathetic  nerve- 
fibres.  In  opposition  to  this,  Valentin  ("  Rep.,"  1843,  p.  103)  and  I 
("  Sympath.,"  p.  10  et  seq.)  have  endeavored  to  prove,  that  the  fine 
fibres  in  the  sympathetic  do  not  constitute  a  special  class,  and  in  this  I 
think  we  were  tolerably  successful.  The  principal  reasons  are  as  fol- 
lows :  1.  Fine  and  thick  nerve-fibres  do  not  differ  intrinsically  in  any 
essential  respect  except  in  size,  and  present  the  most  numerous  interme- 
diate dimensions.  2.  Fine  nerve-fibres  having  exactly  the  same  charac- 
ters as  those  of  the  so-termed  sympathetic  exist  in  many  other  situations, 
as  for  instance, — in  Man  and  the  Mammalia, — in  the  posterior  roots  of 
the  spinal  nerves  and  of  the  sensitive  cerebral  nerves,  in  which  situations, 
as  I  have  already  shown,  there  can  be  no  question  whatever  as  to  a 
derivation  of  the  fibres  from  the  sympathetic,  and  where  we  have  pre- 
sented to  us,  nothing  but  fine  cerebro-spinal  fibres ;  similar  fibres  are 
contained  by  thousands  in  the  spinal  cord  and  brain,  as  well  as  in  the 
two  higher  nerves  of  sense.  3.  All  thick  nerve-fibres  decrease  in  size 
in  their  ultimate  ramifications,  owing  to  divisions,  or  direct  diminution, 
so  that  ultimately  they  acquire  the  diameter  and  nature  of  the  fine, 
and  finest  kinds  of  fibres.  4.  All  thick  nerve-fibres  in  the  course  of 
their  development  are,  at  one  time,  exactly  in  the  condition  of  the  so- 


THE    NERVOUS    SYSTEM.  423 

termed  sympathetic  fibres.  From  these  facts  it  would  appear  certainly 
evident,  that  it  is  impossible  to  regard  the  fine  fibres  of  the  sympathetic 
as  altogether  of  a  special  nature,  and  peculiar  to  it  alone,  and  that  it 
will  not  do,  in  the  anatomical  point  of  view,  to  classify  the  fibres  accord- 
ing to  their  size,  very  many  in  fact,  in  their  course,  assuming  all  possi- 
ble degrees  of  thickness.  Allowing  that  the  great  number  of  very  fine 
pale  fibres  in  the  sympathetic  is  a  prominent  anatomical  fact,  as  is  also 
indeed  the  case  in  the  higher  nerves  of  sense  and  in  the  gray  substance, 
still,  speaking  physiologically,  I  am  by  no  means  of  opinion  that  the 
fineness  of  the  fibres  in  the  sympathetic  indicates  anything  of  a  special 
nature  in  them,  and  which  does  not  exist  elsewhere,  but  perhaps,  that 
where  this  condition  does  exist  both  in  them  and  in  other  situations,  it 
is  connected  with  a  distinct  kind  of  function. 

§  125.  Peripheral  distribution  of  the  ganglionic  Nerves. — From  the 
main  trunk  of  the  sympathetic  arise  the  branches  proceeding  to  the 
periphery,  which  without  exception,  receive  finer  and  thick  fibres  from 
it,  but  besides  these,  in  part  at  least,  contain  other  special  elements,  to 
which  is  due  their  varied  aspect.  Some  of  them,  for  instance,  are 
white,  as  is  the  main  trunk  in  most  situations,  such  are  the  n.  splanch- 
nici ;  others  grayish  white,  as  the  nervi  intestinales,  the  nerves  of  the 
unimpregnated  uterus  (Remak,  "Darmnerven  System,"  p.  30);  others 
again  gray,  and  at  the  same  time  less  firm  to  the  feel,  as  the  n.  caroti- 
cus,  internus,  the  nn.  carotid  externi  s.  molles,  the  nn.  cardiaci,  the 
vascular  branches  in  general,  the  branches  connecting  the  large  ganglia 
and  plexuses  in  the  abdomen,  those  which  enter  the  glands,  and  the 
pelvic  plexuses.  The  peculiar  condition  of  the  latter  nerves  depends, 
in  part,  upon  the  paler  color  of  the  fine  fibres  of  the  sympathetic  itself, 
but  in  great  measure  upon  the  presence  of  the  fibres,  named  after  their 
discoverer,  the  fibres  of  Remak  ("gelatinous  fibres  "  of  Henle),  which 
were  at  first  regarded  as  a  kind  of  nerve-tubes,  and  of  which,  even  now, 
some  cannot  be  convinced  that  they  are  only  a  sort  of  connective  tissue. 
They  are  sometimes  more  readily  isolated,  sometimes  more  united  into 
a  compact  substance  resembling  homogeneous  connective  tissue.  In  the 
former  case  they  present  the  aspect  of  flat,  pale  fibres,  0*0015-0-0025 
of  a  line  broad,  and  0-0006  of  a  line  thick,  of  an  indistinctly  striated, 
granular,  or  more  homogeneous  substance ;  and  which,  under  the  action 
of  dilute  organic  acids,  exhibit  precisely  the  same  conditions  as  connec- 
tive tissue,  and  from  point  to  point  are  furnished  with,  mostly  elongated, 
or  fusiform  nuclei,  0-003-0-007  of  a  line  long,  0-002-0-003  of  a  line 
broad.  These  fibres,  again,  are  found  in  almost  all  the  gray  portions 
of  the  ganglionic  nerves — I  cannot  find  them  in  many  parts  of  the 
pelvic  plexuses  in  Man,  where  they  are  replaced  by  a  non-nucleated 
abundant  connective  tissue,  though  they  are  said  by  Remak  to  abound 


424  SPECIAL    HISTOLOGY. 

in  the  nerves  of  the  impregnated  uterus  (u  Darmnervensyst,"  p.  30) 
in  very  great  quantity,  so  that  they  amount  to  from  three  to  ten  times 
the  number  of  the  dark-bordered  true  nerve-fibres.  They  constitute 
the  main  part  of  the  proper  basis  of  these  trunks,  and  the  dark-bor- 
dered tubes  extend  through  them,  sometimes  more  isolated,  sometimes 
assembled  in  larger  or  smaller  fasciculi ;  more  rarely,  and  only  in  the 
neighborhood  of  the  ganglia  themselves,  do  they  appear  to  form  sheaths 
to  individual  tubes  of  the  finest  kind.  Besides  these  "  fibres  of  Remak," 
the  peripheral  ramifications  of  the  sympathetic  are,  above  all,  distin- 
guished by  a  great  number  of  ganglia.  These  bodies,  of  a  larger  or  less 
size,  some  even  microscopic,  are  placed  on  the  branches  or  terminations, 
and,  indeed,  the  microscopic  ganglia,  so  far  as  is  hitherto  known,  on  the 
nervi  carotid,  in  the  pharyngeal  plexus,  in  the  heart,  at  the  root  of  the 
lungs  and  in  the  lungs,  on  the  suprarenal  capsules,  in  the  lymphatic 
glands,  in  the  kidneys  of  Man  occasionally,  on  the  posterior  wall  of  the 
bladder,  in  the  muscular  substance  of  the  neck  of  the  uterus  in  the 
Sow,  in  the  plexus  cavernosi,  and  with  respect  to  their  distribution,  will 
be  further  adverted  to  when  we  come  to  speak  of  the  viscera.  I  will 
here  remark  in  general,  concerning  them  that  with  respect  to  the  size 
and  figure  of  the  nerve-cells,  and  the  origination  of  fine  fibres,  they 
present  precisely  the  same  conditions  as  the  ganglia  of  the  main  trunk. 
As  regards  the  last  point,  it  may  be  especially  noticed,  that  in  one  situa- 
tion the  origin  of  nerve-fibres  from  unipolar  cells,  and  the  rarity  of  the 
double  origin  of  fibres,  is  particularly  well  displayed,  viz.  in  the  septum 
of  the  heart  in  the  Frog  (Fig.  163),  where  R.  Wagner  has  also  described 
their  occurrence.  These  ganglia,  therefore,  are  also 
sources  of  nerve-fibres,  and  the  emergent  branches 
always  contain  more  than  the  roots,  on  the  supposition 
that  the  fibres  come  out  only  in  one  direction,  which 
perhaps  in  most  places  may  be  the  case.  In  the  same 
situation  also,  it  is  most  readily  and  satisfactorily 
seen  that  many  of  the  cells  are  apolar  and  without 
any  processes  (Fig.  163);  as  is  also  most  plainly  shown 
in  the  cardiac  ganglia  and  small  ganglia,  t>n  the  wall 
of  the  urinary  bladder  in  Bombinator,  in  which  ganglia,  as  well  as  in 
the  similar  ganglia  in  the  Frog,  the  conditions  described  are  as  manifest 
as  possible. 

How  the  fibres  arising  from  these  various  localities,  from  the  rami 
communicantes,  the  ganglia  of  the  main  trunk,  and  the  peripheral  gan- 
glia, are  disposed  in  their  ultimate  distribution,  is  as  yet  very  doubtful. 
Many  peripheral  branches  anastomose  with  other  nerves,  and  thus  escape 
all  further  research,  as  the  nn.  carotid  externi  and  internus,  the  latter 
of  which,  containing  scarcely  anything  but  fine  fibres  and  numerous 

FIG.  163. — Nerve-cells  from  the  cardiac  ganglia  of  the  Frog,  magnified  350  diam.:  one 
with  the  origin  of  a  nerve-tube. 


THE    NERVOUS    SYSTEM.  425 

"fibres  of  Remak,"  I  do  not  look  upon  in  the  common  sense  as  a  root, 
but  as  a  branch,  arising  from  the  superior  cervical  ganglion,  and  pro- 
bably the  other  cervical  ganglia ;  as  well  as  the  rami  communicantes, 
seeing  that  individual  fibres  of  them,  actually  join  peripherally  the 
spinal  nerves  ;  and  the  rami  cardiaci,  pulmonales,  &c.  Other  branches 
in  the  parenchyma  of  the  organs  become  so  fine,  that  it  is  impossible  to 
trace  them.  What  has  been  as  yet  established  respecting  their  ultimate 
course,  is  as  follows :  1.  Divisions  occur  in  the  branches  and  terminal 
ramifications  of  the  sympathetic,  as  in  the  nerves  of  the  spleen,  the 
Pacinian  bodies  in  the  mesentery,  in  the  nerves  accompanying  the 
mesenteric  vessels  in  the  Frog,  in  those  which  exist  temporarily  in  the 
uterus  of  the  Rodentia,  of  the  lungs  and  stomach  of  the  Frog  and 
Rabbit,  of  the  dura  mater  on  the  meningeal  arteries,  in  branches  of  the 
sympathetic  of  the  Sturgeon,  in  the  cardiac  nerves  of  the  Amphibia, 
and  in  those  of  the  urinary  bladder  in  the  Rabbit  and  Mouse.  2.  There 
are  free  terminations  of  the  nerves,  as  in  the  Pacinian  bodies  and  on  the 
mesenteric  vessels  in  the  Frog.  3.  The  thicker  fibres  of  the  sympathetic 
ultimately  so  decrease  in  size  as  to  become  of  the  fine  kind;  as  may  be 
readily  seen  in  the  rami  intestinales,  lineales,  and  hepatici,  which,  indeed, 
even  in  the  interior  of  the  organs  in  question,  contain  some  coarser 
nerve-fibres,  but  ultimately  lose  them.  The  actual  terminations,  how- 
ever, in  the  organs  themselves,  in  the  heart,  lungs,  stomach,  intestine, 
kidneys,  spleen,  liver,  uterus,  &c.,  are  as  yet  quite  unknown ;  although 
from  the  impossibility  of  finding  any  dark-bordered  fibres  in  the  ultimate 
ramifications  of  these  nerves,  it  may  be  supposed  that  they  terminate, 
almost  everywhere,  in  non-rnedullated,  embryonic  fibres.  In  fact,  I 
have,  at  all  events  hitherto,  in  vain  endeavored  to  find  a  trace  of  them. 
Schaffner  says,  that  in  the  heart  of  Bombinator  he  has  seen  the  passage 
of  the  dark-bordered  fibres  into  pale,  anastomosing  fibrils  of  the  finest 
kind,  whilst  Pappenheim  (1.  c.)  describes  loops  in  the  nerves  of  the 
kidney. 

As  regards  the  nature  of  the  "fibres  of  Remak,"  most  recent  ob- 
servers incline  to  the  opinion  first  advanced  by  Valentin  ("  Repert.," 
1838,  p.  72;  Muller's  "Archiv,"  1839,  p.  107),  that  they  are  not  nerve- 
fibres  at  all,  but  to  be  referred  to  the  connective  tissue  of  the  nerves ; 
whilst  Remak  still  thinks  himself  obliged  to  adhere  to  his  previous 
opinion,  that  they  are,  or  may  be,  in  part  at  least,  nerve-fibres  ("Darm. 
nervensyst.,"  p.  30).  As  for  myself,  I  freely  acknowledge  the  force  of 
the  reasons  adduced  by  the  latter  observer,  which  are  based  chiefly  upon 
the  similarity  of  the  fibres  in  question  to  the  pale  embryonic  nerve- 
fibres,  inasmuch  as  that  even  in  the  adult,  nucleated  nerve-fibres  are  met 
with  in  the  olfactory  nerve ;  but  I  am  compelled,  nevertheless,  as  before, 
fully  to  concur  with  Valentin,  as  do  also  Bidder  and  Volkmann,  and 


426  SPECIAL    HISTOLOGY. 

many  others.  My  reasons  are  the  following  :  1.  The  "  fibres  of  Remak," 
as  may  be  easily  shown,  arise  from  the  sheath  of  the  nerve-cells  of  the 
sympathetic  ganglia,  and  are  continued  in  the  nervous  trunks,  surround- 
ing the  nerve-fibres  arising  from  the  ganglia.  Now  as  it  is  certain  that 
these  sheaths  are  a  sort  of  connective  tissue,  as  is  apparent  also  from 
the  spinal  ganglia,  where  they  occur  in  precisely  a  similar  way,  only 
more  scantily  and  without  their  being  continued  into  the  nerves,  it  fol- 
lows that  the  "fibres  of  Remak"  can  scarcely  be  anything  else.  2.  The 
finest  twigs  of  the  spinal  nerves  also  exhibit  nucleated  fibres,  in  all  re- 
spects like  those  of  Remak,  as  for  instance,  those  going  to  the  skin,  &c. ; 
with  respect  to  which,  as  they  are  wanting  in  the  trunks  of  the  nerves, 
there  can  be  no  question  at  all  of  their  not  being  nerve-fibres.  3.  The 
quantity  of  the  "fibres  of  Remak"  always  diminishes  towards  the  finest 
ramifications,  which  could  not  be  the  case  were  they  nerves.  It  is  not, 
indeed,  altogether  correct,  as  stated  by  Valentin,  that  they  are  not  to  be 
found  in  the  finer  intestinal  nerves,  for  there  can  be  no  doubt  that  they 
do  exist  there,  though  much  more  rarely  than  in  the  trunks  of  the  nerves, 
and  are  only  to  be  brought  into  view  by  compression.  According  to 
Remak  (Mull.  "  Arch.,"  1844,  p.  464),  they  also  exist  in  the  cardiac 
nerves  of  the  Mammalia ;  although  as  far  as  I  can  perceive,  only  in  the 
immediate  neighborhood  of  the  ganglia.  Relying  upon  these  reasons, 
I  continue  in  the  firm  persuasion  that  the  nucleated  fibres  in  the  sympa- 
thetic nerve  of  adult  Mammalia  are  a  form  of  the  neurilemma;  but  I  will 
not  omit  to  remark,  that  I  consider  it  quite  impossible  to  determine,  in 
undeveloped  nerves,  what  is  neurilemma  and  what  young  nerve-fibres. 
Thus  in  the  Rabbit,  2-6  months  old,  in  the  n.  caroticus  internus,  not  a 
single  developed  nerve-fibre  is  to  be  met  with,  and  apparently  nothing 
but  "fibres  of  Remak,"  although  it  is  quite  certain  thattogether  with 
them,  there  must  also  exist  the  rudiments  of  numerous  dark-bordered 
fibres.  In  the  nerves  of  the  spleen,  in  the  Calf,  in  like  manner,  nume- 
rous nucleated  fibres  are  met  with,  though  in  the  terminations  (vide 
"  Cyclopaedia  of  Anatomy,"  III.  p.  795,  figs.  539  and  540),  which,  pro- 
bably, afterwards  become  nerve-fibres.  In  young  animals,  consequently, 
we  must  not  look  for  a  decision  of  the  question;  whilst  in  older  ones,  it  is 
quite  otherwise.  In  them,  a  nucleated  fibre  can  only  be  regarded  as 
a  nerve  when  it  can  be  traced  into  a  dark-bordered  fibre,  or  to  a  true 
process  of  a  nerve-cell ;  and  this,  as  we  have  seen,  is  not  the  case  in 
those  of  the  sympathetic  system.  It  may,  however,  be  remarked,  that 
"  fibres  of  Remak"  also  occur  in  the  ganglia  of  the  main  sympathetic 
trunk,  but  that  they  do  not,  for  the  most  part,  extend  to  any  distance 
beyond  them,  so  that  usually  but  few  are  contained  in  the  trunk  of  the 
nerve  itself, 

§  126.  Development  of  the  elements  of  the  Nervous  System. — The 


THE    NERVOUS    SYSTEM. 


427 


nerve-cells,  wherever  they  may  occur,  are  nothing  else  than  transforma- 
tions of  the  so-called  embryonic-cells;  some  of  which  simply  enlarge, 
whilst  others  throw  out  a  varying  number  of  processes,  and  are,  at  all 
events  in  part,  connected  with  nerve-fibres. 

Many  nerve-cells  also  appear,  at  a  subsequent  period,  to  increase  by 
division ;  at  all  events,  I  do  not  know  how  otherwise  to  explain  the  fre- 
quent occurrence  of  two  nuclei  in  the  nerve-cells  of  young  animals, 
especially  in  the  ganglia ;  and  the  cells  connected  by  communicating 
filaments,  which  have  been  noticed  by  various  observers. 

Fig.  164. 


The  peripheral  nerve-fibres  all  originate  on  the  spot,  but  their  subse- 
quent development  proceeds  in  such  a  way  that  the  central  extremities 
always  precede  the  peripheral.  With  the  exception  of  the  extremi- 
ties of  the  nerves,  they  are  developed  from  fusiform  nucleated  cells, 
which  are  nothing  else  than  modifications  of  the  primordial  formative 
cells  of  the  embryo,  and  are  conjoined  into  pale,  flattened,  elongated, 
nucleated  tubules  or  fibres  0-001-0-003  of  a  line,  broad.  Now,  at  first 
the  nerves  consist  only  of  fibres  of  this  kind,  and  of  the  rudiment  of 
the  neurilemma,  being  gray  or  dull  white,  like  the  sympathetic  filaments  ; 
subsequently,  in  the  human  embryo  at  the  fourth  or  fifth  month,  they 
always  assume  a  whiter  color,  and  the  proper  white  or  medullary  sub- 
stance continues  to  be  more  and  more  developed  in  them.  Of  the  three 
possible  modes  of  development  of  this  substance  propounded  by  Schwann, 
one  only,  in  the  present  state  of  things,  can  come  into  question,  that 
namely,  as  to  whether  the  medullary  sheath  is  a  structure  deposited 
between  the  membrane  and  the  contents  of  the  embryonic  nucleated 
fibres;  in  which  case  the  contents  of  the  latter  would  become  the  axis- 
fibre.  But  besides  this,  the  medullary  sheath  may  originate  in  what  did 

FIG.  164. — Nerve-cell  from  a  spinal  ganglion  of  a  sixteen  weeks'  human  embryo :  a,  nucleus 
in  the  pale  process  of  the  cell;  2,  self-developing  nerve-tubes  from  the  brain  of  a  two-months' 
human  embryo ;  3,  cells  from  the  gray  cerebral  substance  of  the  same  embryo. 

FIG.  165. — 1,  two  nerve-fibres  from  the  ischiatic  nerve  of  a  sixteen- weeks'  embryo;  2, 
nerve-tubes  from  a  newly-littered  Rabbit;  a,  their  sheath  ;  6,  nucleus;  c,  medullary  sheath  ; 
3,  nerve-fibre  from  the  tail  of  the  Tadpole ;  a,  6,  c,  as  before ;  at  </,  the  fibre  retains  its 
embryonic  character ;  the  dark-bordered  fibre  shows  a  division. 


428 


SPECIAL    HISTOLOGY. 


Fig.  166. 


not  occur  to  Schwann,  viz.,  a  chemical  metamorphosis  of  the  external 
portion  of  the  contents  of  the  embryonic  fibres  ;  arid  the  axis-fibre  may 
be  only  the  remainder  of  those  contents  which  has  not  undergone  a  fatty 
metamorphosis.  It  is  difficult  to  determine  which  of  these  two  views  is 
correct.  Direct  observation  shows  only  this  much,  that  the  contents  of 
the  pale  embryonic  fibres  invariably,  by  degrees,  obtain  dark  contours, 
and  ultimately  present  the  aspect  of  a  true  dark-bordered  fibre,  whilst 
it  teaches  nothing  with  respect  to  the  proper  origin  of  the  white  sub- 
stance. Since,  however,  it  can  be  proved,  that  the  fibres,  whilst  they 
undergo  this  change,  do  not  alter  in  size,  the  supposition  I  have  expressed 
would  still  appear  the  more  correct. 

The  development  of  the  terminations  of  the  nerves,  which  appears 

in  some  respects  to  present  condi- 
tions different  from  those  exhibited 
in  the  trunks,  may,  as  I  have 
shown  ("  Annal.  d.  sc.  nat.," 
1846,  p.  102,  tab.  6,  7),  be  readily 
traced  in  the  tails  of  the  larvse  of 
the  naked  Amphibia  (Fig.  165,  3; 
Fig.  166).  We  there  find,  as  is 
mentioned  by  Schwann  (p.  177), 
the  primary  rudiments  of  the 
nerves  to  be  pale  branched  fibres, 
measuring  0-001-0-002  of  a  line, 
which  here  and  there  anastomose, 
all  finally  terminating  in  free 
fibrils  of  the  finest  kind,  measur- 
ing 0-0002-0-0004  of  aline.  There 
is  no  difficulty  in  showing  that 
these  fibres  arise  from  the  coa- 
lescence of  fusiform  or  stellate 
cells,  for,  in  the  first  place,  such 
cells  may  be  seen,  in  part,  still  in 
close  apposition  with,  but  inde- 
pendent of  them;  in  part  more  or 
less  connected  by  means  of  their 
processes ;  and,  secondly,  cell-nu- 
clei occur  at  the  divisions  of  the 
fibres,  which  are  there  somewhat 
dilated;  and,  at  all  events,  in 
young  larvae,  with  them  are  asso- 

Fm.  166.— Nerves  from  the  tail  of  a  Tadpole,  magnified  350  diameters:  1,  embryonic 
nerve-fibres,  in  which  more  than  one  dark-bordered  tube  has  become  developed  ;  2,  similar 
fibres  containing  but  one  tube,  which  in  one  fibre  ceases  at  b  ;  3,  embryonic  pale  fibres  ; 
4,  fusiform  cells  connected  together,  and  with  a  complete  nerve-fibre. 


THE    NERVOUS     SYSTEM.  429 

ciated  the  well-known  angular  vitelline  corpuscles,  with  which  at  first, 
all  the  cells  of  the  embryo  are  filled.  At  first  the  number  of  pale 
embryonic  nerves  is  very  small,  and  limited  to  a  few  short  trunks  closely 
applied  to  the  muscular  structures  in  the  tail ;  but  they  are  gradually 
developed,  in  the  direction  from  the  centre  towards  the  periphery,  fur- 
ther into  the  transparent  portion  of  the  tail,  new  cells  being  continually 
added  in  connection  with  the  existing  trunks,  whilst  the  latter  them- 
selves, almost  in  the  same  manner  as  the  capillaries  of  these  larvae, 
unite  directly  by  delicate  offsets.  When  these  fine  ramifications — with 
respect  to  the  nervous  nature  of  which  no  doubt  can  be  entertained,  as 
it  is  evident  that  the  larvse  in  which  they  exist  already  possess  very 
acute  sensibility — are  once  formed,  the  following  further  changes  then 
take  place.  Whilst  the  fibres  gradually  enlarge  to  twice  or  four  times 
their  orginal  diameter,  there  are  by  degrees  developed  in  them,  and  in 
fact  from  the  trunk  towards  the  branches,  dark-bordered,  fine  primitive 
fibres,  which  in  no  case  owe  their  origin  to  newly  added  medullary 
sheaths,  but  are  certainly  formed  solely  from  a  metamorphosis  of  a  part 
of  the  contents  of  the  pale  fibres.  In  connection  with  this,  however, 
the  following  conditions,  which  have  not  yet  been  observed  in  the  higher 
animals,  are  to  be  remarked:  1,  where  a  pale  embryonic  fibre  bifurcates, 
there  occasionally,  though  not  always,  also  takes  place  a  division  of  the 
dark-bordered  tube  developed  within  it ;  2,  the  dark-bordered  tubes 
scarcely  ever  completely  fill  the  pale  fibres  in  which  they  are  formed, 
but  a  space,  frequently  of  the  same  diameter  as  that  of  the  tubes,  is 
most  usually  left  between  them  and  the  membranes  of  the  embryonic 
fibres,  in  which  space  occasionally  the  nuclei  of  the  primordial  formative 
cells  may  be  perceived  ;  3,  in  the  trunks  and  main  branches  of  the 
embryonic  fibres,  several  (2-4)  dark-bordered  tubules  are  undoubtedly 
developed  within  one  and  the  same  embryonic  fibre  ;  a  very  remarkable 
condition,  which  shows  that  there  are  even  dark-bordered  fibres  which  do 
not  possess  a  structureless  sheath  (vid.  note  to  §  110),  and  resembling 
what  exists  in  the  muscular  fasciculus,  in  which,  in  like  manner,  within  a 
single  tubule,  numerous  finer  elements  are  produced.  As  the  tail  of 
the  Tadpole  is  afterwards  thrown  off,  it  is  to  be  regretted  that  its  in- 
teresting nerves  cannot  be  traced  to  the  same  state  of  completion,  as 
can  be  done  in  those  of  other  situations.  It  is  obvious,  however,  in  the 
oldest  Tadpoles,  that  the  nerves  are  somewhat  thicker  than  they  are 
originally,  and  that  they  extend  towards  the  periphery  sometimes  in 
loops,  sometimes  with  free  ends,  but  in  such  a  way  that  the  primary 
pale  fibres  continue  to  exist,  and  proceeding  from  the  dark-bordered 
fibres,  constitute  a  very  fine  terminal  nervous  plexus,  with  anastomoses 
and  free  ends. 

I  should  not  have  delayed  so  long  on  the  subject  of  the  nerves  in  the 


430  SPECIAL    HISTOLOGY. 

Tadpole,  did  not  similar  conditions  most  probably  also  obtain  in  many 
other  terminations  of  nerves.  This  is  certain  as  regards  those  of  the 
electric  organ  of  the  Ray,  which,  even  when  developed,  agree  in  many 
respects  with  those  of  the  more  advanced  Tadpole,  and  as  Ecker  has 
lately  shown  ("  Zeitsch.  fiir  wissensch.  Zoologie,"  1849,  p.  38),  are  de- 
veloped in  precisely  the  same  manner.  The  nerves,  also,  in  the  skin  of 
the  Mouse  (vid.  note  to  §  121),  evidently  belong  to  the  same  category  ; 
and  consequently  it  may  hereafter  be  shown,  that  wherever  peripheral 
divisions  of  nerves  occur,  their  development  proceeds  essentially  as  it  is 
here  described. 

With  respect  to  the  development  of  the  nerve-fibres  in  the  central 
organs,  we  possess  but  few  researches.  Of  the  fibres  in  the  ganglia,  I 
can  only  observe,  that  they  are  developed  subsequently  to  those  of  the 
nerves,  and  probably  from  smaller  fusiform  cells,  which  may  be  noticed 
in  association  with  the  nerve-cells.  On  one  occasion,  in  a  spinal  gan- 
glion of  a  four  months'  human  embryo,  I  noticed  a  cell  of  this  kind  in 
connection  with  the  process  of  a  nerve-cell  (Fig.  164).  The  formation  of 
the  fibres  in  the  cord  and  brain  is  extremely  difficult  of  investigation, 
and  is  best  studied  with  the  aid  of  chromic  acid.  In  the  human  embryo, 
I  find,  as  early  as  the  end  of  the  second  month,  the  commencement  of 
the  formation  of  the  tubules  in  question,  the  white  substance  being  dis- 
tinctly finely  striated,  and  manifestly  containing,  in  places,  very  delicate 
fusiform  cells,  which  are  sometimes  independent  or  isolated,  sometimes 
connected,  two  or  three,  or  several  together  (Fig.  164).  All  these  cells 
are  at  first  pale,  investing  the  nucleus,  which  measures  0-002-0-003  of  a 
line  quite  closely,  and  having  processes  almost  as  fine  as  the  fibrils  of 
connective  tissue.  In  the  fourth  month,  when  the  two  kinds  of  sub- 
stance are  quite  distinct,  nuclei  are  still  occasionally  to  be  seen  in  the 
now  wider  fibres,  but  in  some  they  have  disappeared,  although  the  fibres 
are  without  dark  contours ;  which  are  not  developed  before  the  middle 
period  of  foetal  life  (in  the  foetal  Calf,  when  more  than  12  inches  long, 
according  to  Valentin),  and,  indeed,  first  in  the  spinal  cord. 

As  regards  the  subsequent  changes  in  the  nerve-fibres,  it  has  already 
been  remarked,  that  they  occasionally  increase  very  considerably  in 
thickness.  According  to  Harting  (1.  c.  p.  75),  the  fibres  of  the  median 
nerve  which  have  not  yet  acquired  dark  contours,  measure  in  a  four 
months'  human  embryo,  on  the  average  3'4mm,  in  a  new-born  child 
10-4mm,  in  the  adult  166mm.  The  increased  thickness  of  the  nerves 
themselves  appears,  according  to  Harting,  from  the  fourth  month 
onwards,  to  depend  solely  upon  the  enlargement  of  the  already  existing 
elements,  the  foetus  and  new-born  child  already  possessing  the  same 
number  of  primitive-fibres  as  the  adult. 

It  remains  to  be  observed,  that  extremely  iw  pathological  changes  of 


THE    NEKVOUS    SYSTEM.  431 

the  nervous  elements  are  known.  In  the  nerve-cells  of  the  brain,  the 
deposition  of  pigmentary  matter  becomes  excessive,  particularly  in  old 
age  ;  and  fatty  deposition  also  takes  place  (Virchow,  "  Archiv,"  I.  1). 
Valentin  thinks  that  he  has  observed  a  regeneration  of  nerve-cells  in  the 
superior  cervical  ganglion  of  the  Rabbit.  Nerve-fibres  are  readily  de- 
stroyed, as  in  consequence  of  extravasation  of  blood,  tumors,  softening, 
fibroid  growths,  &c.,  in  which  cases  the  medullary  substance  breaks  up 
into  larger  or  smaller,  coagulated  or  fluid  masses,  of  very  various  con- 
figuration, whilst  the  axis-fibres  seem  to  disappear.  In  atrophied  nerves, 
the  fibres  are  observed  to  be  thinner,  easily  broken  up,  and,  instead  of 
the  medullary  matter,  are  frequently,  in  parts,  entirely  occupied  by 
minute  fatty  molecules,  as  was  seen  on  one  occasion  by  Virchow,  in  a 
human  optic  nerve,  and  by  myself  in  the  nerves  of  a  Frog.  Nerves 
that  have  been  cut  across,  readily  unite ;  portions  of  peripheral  nerves 
from  8-12  lines  even  are  restored  by  true  nervous  tissue  (Bidder,  1.  c., 
p.  65;  Valentin  "  de  funct.  nerv."  p.  159,  §  323;  and  "  P %s.,"  2 
Aufl.  I.  2,  716).  Should  the  union  of  a  divided  nerve  not  take  place, 
the  peripheral  end  undergoes  a  gradual  change  in  a  particular  way, 
with  a  simultaneous  extinction  of  the  nervous  activity.  The  nerve- 
fibres  generally  become  yellowish,  soft,  lacerable,  and  lose  their  trans- 
versely banded  and  glistening  aspect.  They  no  longer  present  any 
trace  of  a  double  contour,  their  medullary  substance  is  wholly  coagu- 
lated, and  their  breadth  frequently  very  various  (Stannius  in  Mull. 
"  Arch.,"  1817,  p.  452).  Whether  the  axis-fibres  undergo  change,  we 
are,  unfortunately,  not  informed.  According  to  Brown-Sequard,  incised 
•wounds,  even  of  the  spinal  cord,  in  the  Rabbit,  united.  Hypertrophies 
of  the  nerve-substance  itself  are  unknown,  although  probably  such  a 
condition  occurs  in  the  neurilemma.  Virchow  noticed  a  new  formation 
of  fine  nerves  in  pleuritic  and  peritoneal  adhesions,  and,  according  to 
the  same  observer,  it  would  appear  that  gray  nerve-substance  may  be 
formed  on  the  walls  of  the  cerebral  ventricles. 

§  127.  With  respect  to  the  functions  of  the  nervous  system,  the  follow- 
ing remarks,  which  are  immediately  "pertinent  to  the  anatomical  facts,  may 
suffice.  As  regards  the  two  elementary  portions  of  the  nervous  system, 
anatomical  investigation  shows,  that  all  its  divisions,  which  preside  over 
the  higher  functions,  contain  gray  substance  in  greater  or  less  quantity, 
as  in  the  sympathetic,  the  ganglia  of  the  spinal  and  cerebral  nerves, 
and  in  the  spinal  cord  and  brain ;  whilst  the  nerves  which  act  only  as  a 
conducting  apparatus,  contain  nothing  but  nerve-fibres.  This  being 
admitted  to  be  the  attribute  of  the  gray  substance,  it  may  further  be 
inquired  whether  it  presents  differences  in  its  structure,  as  it  does  in  its 
functions.  With  respect  to  this  I  would  remark  as  follows  :  the  largest 
nerve-cells  are  met  with  in  situations  from  which  motory  effects  proceed, 


432  SPECIAL    HISTOLOGY. 

as  in  the  anterior  horns  of  the  spinal  cord,  amongst  the  fibres  of  the 
anterior  roots,  in  the  medulla  oblongata,  at  the  points  of  origin  of  the 
motor  cerebral  nerves,  in  the  cortical  substance  of  the  cerebellum,  the 
pons  Varolii  and  crura  cerebri  ;  whilst  the  smallest  cells  are  found  in  the 
sensitive  regions,  as  in  the  posterior  horns  of  the  spinal  cord,  the  corpora 
restiformia,  and  quadrigemina.  There  does  not,  however,  appear  to  be 
any  constant  relation  between  the  size  of  the  cells  and  the  existence  of 
sensitive  or  motor  functions,  for,  in  the  ganglia  of  the  cerebro-spinal 
nerves  and  of  the  sympathetic,  and  in  the  optic  tlialami,  both  sorts  of 
fibres  arise,  in  one  place,  from  small,  and  in  another  from  large  cells. 
It  seems,  therefore,  as  in  the  case  of  the  nerve-fibres,  that  there  are  large 
and  small  motor  cells,  as  well  as  sensitive  cells  of  various  dimensions,  a 
fact  which  is  confirmed  by  comparative  anatomy,  as  the  large  bipolar 
cells  in  Fishes  are  manifestly  sensitive.  No  essential  difference  can  be 
pointed  out  between  sensitive  and  motor  cells,  whether  the  latter  be  of 
uniform  or  of  different  size,  and  in  particular  the  variations  existing 
between  such  cells  are  not  greater  than  those  between  the  motor  cells  in 
different  localities.  Even  the  cells  in  the  cortical  substance  of  the  brain, 
to  which  physiologists  assign  the  mental  manifestations,  with  our  present 
means  of  research,  exhibit  no  perceptible  peculiarities.  The  nerve-cells, 
however,  may  be  divided  into  those  which  are  in  direct  connection  with 
nerve-fibres,  and  those  which  are  not  thus  connected,  but  independent. 
The  former,  of  course,  are  to  be  especially  regarded  as  sensitive  and 
motor;  with  respect  to  the  latter,  anatomy  to  some  extent  affords  no 
information,  inasmuch  as,  that  they  present  no  processes,  as  in  the  sym- 
pathetic ganglia,  and  in  some  situations  in  the  brain  ;  as  regards  those 
furnished  with  processes,  particularly  the  many-rayed  cells,  which  in 
many  situations  undoubtedly  are  not  prolonged  into  nerve-fibres,  it 
might  be  considered  certain  that  they, — both  larger  and  smaller,  by 
means  of  their  processes  which  fulfil  the  functions  of  nerves,  and  whether 
the  latter  anastomose  or  not, — bring  different  regions  of  the  central 
organs  into  mutual  connection,  and  participate  in  the  reflex  phenomena, 
the  sympathies,  and  other  modes  of  association  of  the  functions.  Cells 
of  this  kind  exist  in  the  spinal  cord  and  brain  everywhere  in  very  large 
quantity,  but  not  in  the  ganglia,  although  it  is  not,  from  this,  intended 
to  imply  that  no  reflex  actions  are  performed  in  those  bodies. 

Respecting  the  nerve-fibres,  anatomy  is  not  in  a  condition  to  point  out 
any  difference  in  them,  between  the  sensitive  and  motor  nerves ;  a  cir- 
cumstance, however,  which,  physiologically,  can  afford  no  reason  to 
ascribe  identical  functions  to  them.  As  regards  the  various  sizes  of  the 
nerve-fibres,  the  numerous  changes  in  diameter,  undergone  in  their 
course  by  all  the  cerebro-spinal  nerves,  very  obviously  indicate  that 
these  proportions  have  no  relation  to  the  functions  of  the  fibres  in  gene- 
ral. Nevertheless,  I  do  not  look  upon  these  relations  of  size  as  alto- 


THE    NERVOUS    SYSTEM.  433 

gether  of  little  consequence,  and  in  particular  does  the  attenuation  of  the 
fibres,  where  they  extend  through  gray  substance  (vid.  sup..,  §  112), 
appear  to  me  to  be  important,  as  also  their  diminution  at  their  origins 
and  terminations.  It  is,  however,  difficult  to  perceive  the  physiological 
import  of  these  facts.  Were  it  the  case,  that  in  the  nerve-fibres  the  axis- 
cylinder  alone  was  the  conducting,  and  the  medullary-sheath,  an  insu- 
lating substance,  and  could  it  be  proved  that  the  medullary  sheaths  were 
wanting  in  the  attenuated  portions,  the  peculiar  activity  of  the  nerve- 
fibres  in  these  situations  (the  transverse  conduction  in  the  spinal  cord, 
the  acuteness  of  sensibility  at  the  terminations,  &c.)  would  be  satisfac- 
torily explained.  It  is  well  known  that  such  a  notion  has  already  been 
entertained  by  various  writers,  and  its  conception  has  usually  proceeded 
upon  the  idea  that  a  close  alliance  or  identity  exists  between  electricity 
and  the  nervous  force,  and  the  medullary  sheath  abounding  in  fatty 
matter,  has  from  this  point  of  view  been  regarded  as  an  insulator.  But 
(1)  it  is  anything  but  demonstrated,  that  the  nerves  possess  no  other 
active  force  but  electricity ;  and  (2)  there  is  nothing  to  indicate  an 
absence  of  the  medullary  sheath,  and  a  free  condition  of  the  axis-fibres 
in  many  peripheral  extremities  of  the  nerves  (skin,  muscles),  and  in 
those  portions  of  the  central  organs  (spinal  cord)  in  which  a  transverse 
conduction  is  evident.  The  question  always  remains,  whether  the  medul- 
lary sheath,  although  not  altogether,  yet  at  all  events  partially,  may  not 
insulate  more  or  less,  according  to  its  thickness.  Since,  however,  this 
membrane  is  wanting  not  only  in  many  terminations  of  nerves,  where  an 
insulated  conducting  faculty  might  not  be  required,  but  also  in  other 
situations,  as  in  the  Invertebrata  and  the  nerves  of  Petromyzon  gene- 
rally, as  well  as  in  the  processes  of  the  nerve-cells  which  certainly  act  as 
nerves,  in  the  central  organs  of  the  higher  animals,  and  in  the  finest 
nerve-fibres  in  those  situations  (brain),  the  notion  that  such  is  its  effect 
in  the  dark-borderved  nerves  loses  all  ground  of  support.  It  would 
seem  to  me,  that  the  medullary  sheath  represents  nothing  more  than  a 
protective  soft  envelope  for  the  tender  central  fibre.  This  mode  of  expla- 
nation also,  renders  it  intelligible,  why  it  is,  that  in  dark-bordered 
nerves,  where  the  medullary  sheath  is  thin  or  wanting,  and  the  central 
fibre  is  in  a  more  free  condition,  the  nerve-fibres  are  more  readily  excited 
and  able  to  communicate  their  conditions  ;  and  as  regards  the  pale  nerve- 
fibres,  in  this  case  they  would  essentially  have  the  same  functions  as  the 
others,  and  the  absence  of  the  medullary  sheath  in  them  could  either  be 
explained  on  the  supposition,  that  they  are  less  readily  excitable,  as  in 
the  invertebrate  animals,  and  the  Cf/clostomata,  or  because  they  occur 
in  situations  where  a  protective  tunic  to  the  nerve-fibres  is  no  longer 
required,  as  in  the  retina,  in  the  nasal  mucous  membrane,  in  the  gray 
substance,  and  in  the  electric  organs,  or  even  where  its  refractive  power 
upon  light  would  be  prejudicial  to  a  certain  object,  as  in  the  cornea.  A 

28 


434  SPECIAL    HISTOLOGY. 

similar  mechanical  function  appears  to  me  to  be  performed  by  the  fine 
granular  substance,  which  in  the  higher  central  organs  is  found  in  so 
many  situations  supporting  the  most  delicate  nerve-fibres,  cells,  and 
processes. 

With  respect  to  the  methods  to  be  employed  in  investigations  of  the 
nervous  system,  the  principal  have  been  noticed  in  the  preceding  sec- 
tions. I  will,  here,  once  more  advert  to  the  importance  of  preparations 
made  with  chromic  acid  in  the  investigation  of  the  course  of  the  fibres, 
and  in  the  examination  of  the  central  nerve-cells ;  and  direct  attention 
to  the  dilute  solution  of  caustic  soda  for  the  detecting  of  nerve-fibres  in 
non-transparent  tissues, — without  which  two  means  very  many  points 
would  remain  in  the  dark.  In  this  way  also  the  extreme  proneness  to 
become  changed,  of  the  gray  and  white  substances,  and  particularly  the 
ready  disruption  of  the  processes  of  the  nerve-cells,  and  the  varicosity, 
coagulation,  and  destruction  of  the  nerve-fibres,  are  at  once  removed  or 
avoided.  The  brain  and  spinal  cord,  as  well  as  the  elements  of  the 
ganglia,  are  best  studied  in  the  human  subject,  but  the  course  of  the 
fibres  in  them,  and,  above  all,  the  terminations  of  the  nerves,  are  best 
investigated  in  the  smaller  Mammalia,  and  only  in  the  second  place  in 
Man.  In  the  searching  for  the  minute  ganglia  in  the  heart,  Ludwig 
recommends  the  treatment  with  phosphoric  acid  and  the  solution  of  iodine 
in  hydriodic  acid,  the  latter  so  diluted  that  it  has  only  a  tinge  of  brown. 
For  the  development  of  the  nerves,  the  human  and  mammalian  embryo 
are  quite  suitable ;  but  the  batrachian  larvae,  and  if  opportunity  offer, 
the  electric  organs  of  the  embryo  Ray,  in  which  the  conditions  are  by 
far  the  most  clearly  displayed,  should  not  be  overlooked. 

Literature  of  the  Nervous  System. — C.  G.  Ehrenberg,  "Beobachtung 
einer  bisher  unbekannten  Structur  des  Seelenorgans  des  Menschen" 
(Observation  of  a  hitherto  unknown  structure  in  the  Human  Brain), 
Berlin,  1836;  G.  Valentin,  in  Mull.  "Archiv,"  1839,  p.  139,  1840,  p. 
218,  in  Valentin's  "  Repertorium,"  1838,  p.  77,  1840,  p.  79,  1841,  p. 
96,  1843,  p.  96,  and:  "  Hirn-  und  Nervenlehre"  (Treatise  on  the  Brain 
and  Nerves),  Leipzic,  1841 ;  J.  E.  Purkinje,  in  the  "  Bericht  uber  die 
Versammlung  deutscher  Naturforscher,"  in  Prague,  for  the  year  1837, 
Prague,  1838,  p.  177,  and  in  Mull.  "  Archiv,"  1845,  p.  281 ;  R.  Remak, 
in  Mull.  "  Archiv,"  1841,  p.  506, 1844,  p.  461,  "  Ueb.  ein  selbstandiges 
Darmnervensystem"  (On  an  independent  system  of  intestinal  nerves), 
Berlin,  1847;  J.  F.  Rosenthal,  "  De  formatione  granulosa  in  nervis 
aliisque  partibus  organismi  animalis"  Vratisl.,  1839 ;  A.  W.  Volk- 
mann,  in  Mull.  "Archiv,"  1838,  p.  274,  and  1840,  p.  510;  Artie. 
"Nervenphysiologie,"  in  Wagner's  "  Handw.  der  Phys.,"  II. ;  F.  H. 
Bidder  and  A.  W.  Volkmann,  "  Die  Selbstandigkeit  des  sympathischen 
Nervensystems  durch  anatomische  Untersuchungen  nachgewiesen"  (The 


THE    NERVOUS    SYSTEM.  435 

independence  of  the  sympathetic  Nervous  System,  proved  by  anatomical 
Researches),  Leipzic,  1842;  Stilling  and  Wallach,  "  Untersuchungen 
iiber  die  Textur  des  Riickenmarks"  (Researches  on  the  Texture  of  the 
Spinal  Cord),  Leipzig,  1842;  Stilling,  "Ueber  die  Medulla  oblongata" 
Erlangen,  1843;  "Researches  on  the  Structure  and  Functions  of  the 
Brain.  I.  On  the  Structure  of  the  pons  Varolii"  Jena,  1846;  A. 
Kolliker,  "  Die  Selbstandigkeit  u.  Abhangigkeit  des  sympathischen  Ner- 
vensystems,  durch  anatomische  Untersuchungen  bewiesen"  (The  inde- 
pendence and  dependence  of  the  Sympathetic  Nervous  System,  shown 
by  anatomical  researches),  Zurich,  1844  ;  P.  Savi,  "  Etudes  anatomiques 
sur  le  systeme  nerveux  de  la  Torpille,"  Paris,  1843.  As  an  appendix 
to  Matteucci,  "  Traitd  des  phe'nome'nes  electro-physiques  des  animaux," 
Paris,  1844  ;  R.  Wagner,  "  Ueber  d.  innern  Bau  der  electrischen  Organe 
im  Zitterrochen"  (On  the  intimate  Structure  of  the  Electric  Organ  in 
the  Ray),  Gottingen,  1847.  With  a  plate;  "Sympathetic  Nerve," 
"Structure  of  Ganglia,"  and  "Terminations  of  Nerves,"  in  Wagner's 
"  Handw.  d.  Physiol.,"  part  III.  p.  360  ;  "  Sympathetic  Ganglia  of  the 
Heart,"  ibid.,  p.  452;  "Neurological  Researches,"  in  Getting.  "Nach- 
richt  v.  d.  Universit.,  &c.,"  Feb.  1851,  No.  14;  H.  Stannius,  "Das 
peripherische  Nervensystem  der  Fische"  (Peripheral  Nervous  System  of 
Fish),  Rostock,  1849.  Moreover,  in  the  "  Archiv  diir  phys.,"  Heilk. 
1850,  and  in  Gott.  "  Nachricht,  &c.,"  1850,  Nos.  6-16,  1851,  No.  17 ; 
J.  N.  Czermak,  "  Ueber  die  Hautnerven  der  Frosche"  (On  the  Cuta- 
neous Nerves  of  the  Frog),  Mull.  "Archiv,"  1849,  p.  252;  "  Veraste- 
lung  der  Primitivfasern  des  N.  acusticus"  (Ramifications  of  the  primitive 
Fibres  of  the  Acoustic  Nerve),  in  "  Zeitsch.  f.  wissen.  Zoologie,"  II. 
1850,  p.  105.  [To  these  should  be  added:  Robin,  "Memoires  sur  la 
Structure  des  Ganglions,"  in  the  Journal  de  1'Institut,  1847,  N.  687, 
and  1848,  N.  733,  also  in  the  Comptes  Rendus,  xxiv.  p.  1019  ;  Axmann, 
Beitrage  zur  Microscopischen  Anatomic  des  Ganglien  Nervensystems 
des  Menschen  und  der  Wirbelthiere,  Berlin,  1853  ;  Virchow,  Uebereine 
im  Gehirn  und  Ruckenmark  des  Menschen  aufgefundene  substanz  mit 
der  chemischen  reaction  der  cellulose.  (On  a  substance  found  in  the 
brain  and  spinal  marrow  of  Man,  presenting  the  chemical  reaction  of 
cellulose),  in  "Archiv"  f.  Path.  Anat.  vi.  I,  1853.— ED.]  Besides" 
these,  should  be  consulted  the  general  works  of  Schwann,  Henle,  Valen- 
tin, Todd  and  Bowman,  Bruns,  and  myself,  which  also  give  figures ;  the 
Reports  of  Henle  and  Reichert;  and  the  memoirs  cited  under  the 
descriptions  of  the  nerves  of  the  different  organs,  and  in  the  various 
sections. 


436  SPECIAL     HISTOLOGY. 

OF  THE  DIGESTIVE  ORGANS. 


I.— OF  THE  INTESTINAL  CANAL. 

§  128.  THE  intestinal  canal  is  composed  fundamentally  of  the  so- 
called  membranes  of  the  intestine.  The  innermost  of  these,  the  mucous 
membrane,  membrana  mucosa,  corresponds  in  its  structure  with  the  skin, 
and  like  it  possesses,  (1)  a  non-vascular  investment  composed  of  cells — 
the  epithelium;  (2)  the  mucous  membrane,  more  strictly  speaking,  com- 
posed of  connecting  and  elastic  tissues ;  containing  vessels,  nerves, 
smooth  muscular  fibres,  and  different  forms  of  minute  glands,  and  often 
presenting  peculiar  processes  (papilla?,  villi)',  and  (3)  an  external  layer 
of  loose  connective  tissue,  the  submucous  cellular  tissue.  The  second 
intestinal  tunic,  the  muscular  membrane,  tunica  muscidaris,  is  provided, 
for  a  certain  distance  at  the  commencement  and  at  the  termination  of 
the  intestine,  with  striated  fibres,  but  in  the  remainder  of  its  extent  the 
muscles  are  everywhere  of  the  smooth  kind,  and  form  in  general  two 
distinct  layers  ;  an  external,  with  longitudinal,  and  an  internal,  with 
transverse  fibres  ;  more  rarely  there  are  three  separate  layers.  The 
third  membrane,  the  serous,  tunica  serosa,  exists  only  upon  those  por- 
tions of  the  intestine  which  occupy  the  cavities  of  the  abdomen  and 
pelvis  ;  it  is  a  delicate,  transparent  membrane,  poor  in  nerves  and  ves- 
sels, and  provided  with  an  epithelium  ;  it  invests  the  intestinal  canal,  and 
connects  it  with  the  walls  of  the  abdominal  cavity  and  with  the  other 
viscera. 

OF  THE  ORAL  CAVITY. 
A.  OF  THE  MUCOUS  MEMBRANE  OF  THE  OKAL  CAVITY. 

§  129.  The  commencement  of  the  intestine  may  be  said  to  have  only 
one  tunic,  the  mucous  membrane,  which  is  applied  more  or  less  closely 
to  the  bones  and  muscles  bounding  the  oral  cavity  ;  and  is  distin- 
guished by  its  not  inconsiderable  thickness,  by  its  red  color,  arising  from 
the  abundance  of  its  vessels,  and  by  its  numerous  nerves  and  papillae. 

The  proper  mucous  membrane,  although  it  is  continuous  with,  and 
gradually  passes  into,  the  cutis  upon  the  lips,  is  more  transparent  and 
softer  than  the  corium  ;  however,  it  possesses  considerable  firmness  and 
is  still  more  extensible.  Like  the  thinnest  portions  of  the  cutis,  it  con- 
sists of  a  single  layer,  0-1-0-2  of  a  line  in  thickness,  and  presents  a 
great  number  of  papillae,  like  those  of  the  skin,  upon  its  outer  surface; 
they  are  in  general  simple  but  occasionally  bifurcated  (when  hypertro- 
phied  they  may  possess  even  more  processes),  are  conical  or  filiform, 


THE    ORAL    CAVITY.  437 

0-10-0-18  of  a  line  in  length,  0-02-0-04  of  a  line  in  breadth  (extremes, 
0-024-0-28  of  a  line  in  length,  0-004-0-05  of  a  line  in  breadth),  and 
stand,  without  any  very  regular  distribution,  so  close- together,  that  their 
bases  are  almost  in  contact  and  are  rarely  more  than  their  own  breadth 
apart. 

Besides  these  papillae,  the  mucous  membrane  presents  upon  its  free 
surface  the  orifice  of  the  naso-palatine  duct,  and  a  great  number  of 
glandular  apertures,  a  few  of  which  are  situated  at  the  extremities  of 
large  papillary  elevations. 

The  submucous  cellular  tissue  of  the  mouth  varies  in  its  structure. 
On  the  floor  of  the  oral  cavity,  on  the  anterior  surface  of  the  epiglottis, 
and  especially  upon  the  frcena  of  the  lips,  of  the  tongue,  and  of  the 
epiglottis,  it  is  thin  and  yielding  ;  and  therefore,  in  these  localities,  the 
mucous  membrane  is  very  movable  upon  the  subjacent  parts.  Where 
glands  occur  in  the  submucous  tissue,  it  is  more  solid,  as  in  the  lips  and 
cheeks ;  at  the  root  of  the  tongue,  and  on  the  soft  palate,  it  may  be 
said  to  be  firmly  fixed,  and  here,  especially  in  the  last-named  localities, 
we  find  large  masses  of  fat  in  it.  The  submucous  tissue  is  very  dense, 
firm  and  of  a  whitish  color,  upon  the  alveolar  processes  ;  where,  united 
into  one  mass  with  the  proper  mucous  membrane  and  the  periosteum,  it 
forms  the  gums  ;  upon  the  hard  palate,  to  which  the  mucous  membrane 
is  attached  by  an  immovable  thick  fibrous  layer,  which  in  some  parts 
contains  glands ;  and  finally  upon  the  tongue,  where  the  papillae  are  situ- 
ated. In  the  latter  case,  there  is  a  very  close  union  between  the  mucous 
membrane  and  the  muscular  tissue,  the  processes  of  many  muscular 
fibres  extending  into  it  and  terminating  especially  in  a  white,  very  solid, 
and  dense,  tendinous  layer,  which  is  in  immediate  contiguity  with  the 
upper  longitudinal  muscular  fibres,  and  has  been  described  as  the  fascia 
linguce  (Zaglas). 

With  respect  to  the  minute  structure  of  the  mucous  membrane  of  the 
mouth,  connective  tissue  is  the  predominant  constituent  of  the  submu- 
cous cellular  tissue,  while  throughout  the  proper  mucous  membrane,  verj 
numerous  elastic  elements  are  everywhere  found.  In  both  localities,  the 
former  usually  presents  itself  in  bundles  of  0-002-0-005  of  a  line  in 
breadth,  not  united  into  a  network,  but  while  they  cross  one  another  in 
the  most  various  directions,  presenting  a  certain  indistinct -lamination. 
The  felted  mass  of  connective  fibrils  becomes  densest  towards  the  epi- 
thelium, and  finally  passes  into  a  more  structureless  layer,  which  in  my 
opinion  is  here,  as  little  as  in  the  corium,  to  be  considered  a  special  mem- 
brane.* In  the  interior  of  the  papillce  also,  with  the  exception  of  those 
of  the  tongue,  a  fibrous  structure  is  usually  very  indistinct,  the  whole 
more  resembling  a  homogeneous  substance,  slightly  granular.  The 

*  [This  structureless  layer  is  the  "  basement  membrane"  of  Todd  and  Bowman,  who 
describe  it  as  a  separate  membrane. — DaC.j 


438 


SPECIAL    HISTOLOGY. 


Fiff.187. 


elastic  element  in  the  subcutaneous  cellular  tissue  has  generally  the  form 
of  scattered,  interstitial,  and  occasionally,  though  more  rarely,  of  spi- 
rally convoluted,  fine  fibres;  here  and  there,  as  in  thefrenulum  epiglot- 
tidis,  they  are  not  only  more  abundant,  but  thicker.  The  latter  is  inva- 
riably the  case  in  the  proper  mucous  membrane,  which,  even  close  to  the 
epithelium,  contains  in  the  midst  of  its  connective  tissue,  very  close  and 
intimately  connected  networks  of  elastic  fibrils,  or  (and  this  is  the 
general  rule)  of  moderately  thick  elastic  fibres  of  0*001-0'0015  of  a  line. 
Spirally  convoluted  elastic  fibres  exist  here  also,  though  rarely.  In 
addition,  the  mucous  membrane  contains  common  fat-cells,  sometimes  in 
groups,  sometimes  more  isolated,  and  especially  in  the  submucous  layer. 
The  vessels  of  the  mucous  membrane  are  very  numerous,  and  present 
essentially  the  same  arrangement  as  in  the  skin.  The  smaller  papillce 

contain  only  a  single  capillary  loop, 
•whilst  in  the  larger,  either  simple  or 
branched,  a  network  of  capillaries 
may  be  observed  (Fig.  167) ;  this  is 
especially  the  case  in  the  gums,  the 
palate,  the  glandular  region  of  the 
root  of  the  tongue,  the  lips,  and  the 
lower  surface  of  the  tongue.  The 
investigation  of  the  nerves  presents 
many  difficulties.  If  caustic  alkalies 
be  added,  a  wide  network  of  the  finer 
and  finest  branches  is  rendered  dis- 
tinct in  the  outermost  layers  of  the 
mucous  membrane,  in  which  also, 
divisions  of  the  nervous  fibrils  may 
be  observed  in  some  localities,  par- 
ticularly upon  the  anterior  surface  of  the  epiglottis  ;  on  the  other  hand, 
it  is  often  impossible  to  detect  so  much  as  a  trace  of  nerves  in  the 
papillce.  Sometimes,  however,  even  in  these,  especially  in  the  larger, 
one  or  two,  often  twisted,  nerve-fibrils  of  0*02  of  a  line  in  diameter, 
diminishing  to  0-0012  of  a  line,  may  be  detected,  without  its  being 
possible  to  make  out  their  ultimate  destination  ;  upon  the  lip  the  papillce 
possess  axile-corpuscles  similar  to,  but  smaller  than,  those  of  the  hand, 
though  not  in  all  individuals.  I  found  here,  also,  the  nerve-coils 
described  by  Gerber  (see  §  37).  Of  the  origin  and  relation,  in  the 
t.  mucosa  itself,  of  the  abundant  lymphatic  vessels  of  the  oral  mucous 
membrane,  nothing  is  known. 

§  130.     The  epithelium  of  the  cavity  of  the  mouth  (Fig.  167),  is  a 
so- called  pavement  epithelium,  consisting  of  many  superimposed  layers 

FIG.  167. — A  simple  papilla  with  manifold  vessels  and  epithelium,  from  the  gum  of  a 
child;  magnified  250  diameters. 


THE     ORAL    CAVITY. 


439 


of  roundish,  polygonal,  more  or  less  flattened  cells.  Taken  altogether, 
this  epithelium  is  a  transparent,  whitish,  pellicle,  0-1-0-2  of  a  line  thick 
on  the  average,  very  flexible,  but  possessing  little  elasticity  or  firmness  ; 
it  may  be  detached  in  considerable  flakes  by  macerating  and  scraping 
the  mucous  membrane,  and  also  by  the  use  of  acetic  acid.  Its  elements 
are,  throughout,  nucleated  cells,  whose  arrangement  and  structure, 
strongly  recall  those  of  the  epidermis  ;  they  are  not,  as  in  the  latter 
case,  distinguishable  into  two  sharply  defined  laminae,  but  constitute  one 
connected  layer,  more  resembling  the  mucous  layer,  but  representing  the 
horny  layer  also.  The  cells  are  thus  disposed,  from  within  outwards : 
immediately  upon  the  free  surface  of  the  mucous  membrane,  and  upon 
the  papillce,  rest  many  layers  of  small  vesicles  of  0-004-0'005  of  a  line 
(Fig.  167),  the  deepest  of  which  are,  almost  without  exception,  elongated 
and  larger  (0-006-0-009  of  a  line),  and  disposed  perpendicularly.  To 
these  succeed  many  layers  of  roundish,  angular,  flattened  cells,  which 
gradually  increase  in  size,  become  flatter  from  within  outwards,  and 
assume  a  more  and  more  distinctly  polygonal  form  (Fig.  168,  5). 

Fig.  168. 


On  the  outer  surface,  finally,  we  meet,  gradually  proceeding  from  the 
deeper  cells,  with  a  few  layers  of  the  so-called  epithelial  plates  (Fig. 
168,  «),  that  is,  large  (0-02-0-036  of  a  line)  bodies  with  rounded  cor- 
ners, in  which  the  flattening  has  gone  so  far  that  they  no  longer  de- 
serve the  title  of  vesicles. 

All  these  cells  possess  a  delicate  membrane,  easily  demonstrable  by 
alkalies  and  acetic  acid ;  clear  contents,  present  in  greater  or  smaller 
quantity,  according  to  the  amount  of  flattening,  with  frequently  a  few 
fatty  granules,  and  invariably  a  nucleus.  In  the  smallest  cells  the 
nuclei  measure  from  0-002-0-003  of  a  line,  they  are  elongated  or  round, 
and  usually  without  any  distinct  nucleolus ;  in  the  polygonal  cells  there 
are  invariably  one  or  two  beautiful,  clearly  vesicular,  usually  spherical 
nuclei,  of  0-004-0-005  of  a  line,  with  clear  contents,  and  1-2  nucleoli; 

FIG.  168. — Epithelial  cells  in  the  oral  cavity  of  Man:  a,  large;  b,  middle-sized;  c,  the 
same  with  two  nuclei ;  magnified  350  diameters. 


440  SPECIAL    HISTOLOGY. 

finally,  in  the  plates,  the  nuclei  have  begun  to  retrograde,  are  smaller, 
0-004-0-006  of  a  line  long,  0-002-0-0015  of  a  line  broad,  generally  flat- 
tened and  more  homogeneous,  without  any  distinct  cavity  or  nucleolus,  or 
containing  instead  several  granules.  With  respect  to  its  chemical  rela- 
tions, the  pavement-epithelium  of  the  mouth  agrees,  so  far  as  we  know, 
in  all  essential  points  with  the  mucous  layer  of  the  epidermis,  and 
with  the  deepest  layer  of  the  horny  lamina,  particularly  in  the  circum- 
stance, that  even  the  plates  readily  swell  up  in  alkalies ;  the  reader 
may  therefore  be  referred  to  §  45. 

The  most  essential  physiological  characters  of  the  epithelium  of  the 
oral  cavity  are,  the  continual  change  to  which  it  is  subjected,  and  its 
relations  as  regards  absorption  and  secretion.  With  respect  to  the  for- 
mer, it  may  be  said  that  the  epithelium  undergoes  a  continual  desqua- 
mation,  which,  however,  does  not  here,  any  more  than  in  the  epidermis, 
appear  to  be  the  effect  of  special  vital  energies  in  the  mucous  membrane, 
or  in  the  epithelial  cells,  but  rather  to  result  from  the  manifold  mecha- 
nical disturbances  to  which  the  surface  of  the  oral  mucous  membrane  is 
subjected  during  mastication  and  speaking.  On  the  one  hand,  these 
disturbances  give  rise  to  a  constant  detachment  of  the  uppermost  plates  ; 
and  on  the  other,  an  uninterrupted  regeneration  of  the  lost  parts  takes 
place,  a  process  which  I  am  disposed  to  interpret  in  this  case  exactly  as 
I  have  done  in  §  46,  for  the  epidermis,  and  in  §  64,  for  the  hairs.  As 
regards  the  exact  mode  of  that  growth  of  the  oral  epithelium,  which, 
from  what  has  been  said,  must  perhaps,  always  be  going  on  in  one  part 
or  another,  we  invariably  find,  upon  the  surface  of  the  epithelium, 
during  and  after  very  copious  desquamation,  large,  completely  flattened 
cells  (which,  of  course,  possess  no  power  of  multiplication),  never 
younger  and  smaller  structures,  and,  therefore,  the  reparation  of  any 
loss  cannot  take  place  by  the  formation  of  new  cells  at  the  surface  of 
the  epithelium ;  on  the  contrary,  everything  indicates  that  the  renewal 
occurs  in  the  layers  of  smallest  cells,  for  although  no  new  development 
of  cells  can  here  be  directly  observed,  yet  the  analogy  with  other  epi- 
dermic structures,  and  the  frequent  occurrence  of  two  nuclei  in  the  cells 
of  these  layers,  nay,  even  of  constricted  cells  (Bowman,  compare  §  46), 
are  striking  facts  in  favor  of  the  multiplication  of  the  cells  which  al- 
ready exist  (by  division)  and  against  their  actual  new  formation. 

The  epithelium  of  the  oral  cavity,  although  thick,  is  yet  readily  per- 
meable, differing  widely  in  this  respect  from  the  epidermis,  which  pre- 
sents similar  relations,  only  in  the  stratum  Malpighii.  Fluids  of  the 
most  different  description  permeate  it  from  without,  and  once  in  contact 
with  the  mucous  membrane,  may  either  be  absorbed  by  its  vessels,  or 
perceived  by  its  nerves.  Other  conditions  remaining  the  same,  the 
activity  of  the  sensitive  and  absorbent  powers  will  depend  upon  the 


THE    TONGUE.  441 

thinness  of  the  epithelial  layer,  particularly  of  the  plates,  which  must 
always  be  least  permeable,  and  upon  the  abundance  and  superficiality 
of  the  vessels  and  nerves  ;  and  these  considerations  readily  explain  why 
the'lips,  in  which  the  papillce  are  very  nnmerous,  and  nearly  reach  the 
surface  of  the  epidermis,  possess  a  more  delicate  sensibility  than  the 
gums  ;  and  why  the  point  of  the  tongue,  whose  papillce  even  project 
with  a  thinner  covering,  is  still  more  sensitive  (compare,  also,  on  the 
import  of  the  axile  Corpuscles,  §  39).  The  epithelium  is  permeable 
outwards,  as  well  as  inwards,  and  permits  of  the  passage  of  plasma 
from  the  vessels  of  the  mucous  membrane  into  the  cavity  of  the  mouth. 
In  this  manner,  like  the  epidermis  in  relation  to  the  cutaneous  perspira- 
tion, it  participates  in  the  formation  of  the  mucous  fluid,  which  is 
yielded,  not  only  by  the  glands  which  open  into  the  oral  cavity,  but 
also  by  the  whole  surface  of  the  mucous  membrane. 

B.  OF  THE  TONGUE. 

§  131.  The  Tongue  is  a  mass  of  muscles  attached  to  a  particular 
bone,  the  os  hyoides,  and  covered  by  the  mucous  membrane  of  the  cavity 
of  the  mouth  ;  its  muscular  elements,  0-009-0-023  of  a  line  in  breadth, 
are  distinguished  from  those  of  the  external  transversely  striated  mus- 
cles, only  by  being  interwoven  in  the  most  complex  manner,  so  that  in 
the  interior  of  the  tongue  the  lingual  muscles  cannot  be  separately 
demonstrated  as  such,  but  only  as  secondary  bundles  and  fibres. 

The  framework  of  the  tongue  may  be  said  to  be  formed  by  the  two 
genio-glossi,  the  musculus  transversus  linguce,  and  the  fibro-cartilage  of 
the  tongue.  The  latter,  which  is  also  called  the  lingual  cartilage  (Fig. 
170,  e),  is  a  dense,  whitish-yellow,  fibrous  lamella,  placed  perpendicu- 
larly in  the  middle  of  the  tongue,  between  the  two  genio-glossi,  extending 
through  the  whole  length  of  the  organ,  and  is  not  very  appropriately 
named,  inasmuch  as  it  is  composed  of  common  tendinous  or  ligamentous 
tissue.  It  commences,  low  down,  upon  the  body  of  the  hyoid  bone,  in 
connection  with  a  broad  fibrous  lamella,  membrana  hypoglossa  (Blandin), 
which  stretches  from  the  hyoid  bone  to  the  root  of  the  tongue,  and 
covers  the  extremity  of  the  genio-glossus,  very  soon  attains  the  level  of 
the  musculus  transversus,  and,  upon  the  anterior  third  of  the  tongue, 
gradually  diminishes,  as  far  as  its  point,  where  it  terminates  very  low 
down.  Superiorly,  the  septum  linguce,  as  this  fibrous  mass,  0-12  of  a 
line  thick,  might  well  be  termed,  ascends  to  within  1J-2  lines  distance 
from  the  dorsum  of  the  tongue  ;  inferiorly,  it  extends  to  where  the 
genio-glossi,  become  lost  in  the  fleshy  mass  of  the  tongue,  and  termi- 
nates here,  not  with  a  defined  border,  but  by  passing  into  the  perimy- 
sium,  between  the  two  genio-glossi.  On  each  side  of  this  septum,  the 
genio-glossi  spread  out,  fan-like,  into  the  tongue  (Fig.  169,  g,  170,  g, 
171, /),  so  that  they  occupy  the  middle  of  the  organ  from  its  point  to 


442 


SPECIAL    HISTOLOGY. 


its  root,  forming  a  long,  moderately  broad,  fleshy  mass,  which,  however, 
is  anything  but  compact.  The  genio-glossi,  in  fact,  when  they  have 
entered  the  tongue,  exchange  a  few  bundles  here  and  there,  along  the 
lower  edge  of  the  septum,  and  then  break  up  on  each  side  into  a  great 
number  of  lamellce,  which  lie  one  behind  the  other,  separated  by  small 
interspaces,  in  which  are  the  transverse  muscular  fibres  of  the  tongue  ; 
the  lamellce  are,  for  the  most  part,  perpendicular,  but  some  curve  for- 
wards and  backwards,  towards  the  dorsuin  of  the  tongue. 

The  fibres  of  the  genio-glossus,  thus  separated  into  distinct  lamellce, 
•which  have,  on  the  average,  a  thickness  of  0-06-0-14  of  a  line,  extend 
as  far  as  the  septum,  and  then  gradually  take  a  new  arrangement,  so  as 
to  be  directed  from  behind  forwards.  For  whilst,  previously,  the  genio- 
glossi  were  broken  up  into  transverse  lamellae,  by  the  bands  of  the 

Fig.  169. 

*• 


transversus,  they  are  now  separated  longitudinally  by  the  interposition 
of  the  bundles  of  the  superior  longitudinal  muscle  of  the  tongue,  between 
their  fibres.  These  perpendicular  longitudinal  lamellce  are  very  distinct 
in  the  two  anterior  thirds  of  the  tongue,  less  so  in  the  vicinity  of  the 
papillce  circumvallatce,  where,  especially  in  the  middle  of  the  tongue, 
the  genio-glossus  passes,  in  more  isolated  bundles  to  the  mucous  mem- 
brane ;  in  the  root  of  the  tongue,  finally,  they  cannot  be  demonstrated 
at  all.  The  genio-glossus  ends  upon  the  upper  surface  of  the  tongue, 
in  such  a  manner,  that  its  primitive  bundles,  immediately  beneath  the 
mucous  membrane,  are  continuous,  in  groups,  with  little  tendinous 
streaks  of  connective  tissue,  which  then  partly  become  lost  in  the 

FIG.  1G9. — Longitudinal  section  of  the  human  tongue,  natural  size;  the  outlines  after 
Arnold  Icon.  org.  (sens.)  ;  g.h,  genio-hyoideus  ;  h,  hyoid  bone  ;  g,  genio-glossus  •  g\  glosso-epi- 
glotticus  •  tr,  transversus  lingua  •  Is.  longitudinalis  superior  •  e,  epiglottis  :  m,  maxilla  inferior ; 
d,  incisor  tooth ;  o,  orbicularis  oris  •  l.m,  levator  menti  •  1.  glandules  labialis  •  folliculi  linguales  ; 
gl,  glandula  linguales  cum  ductibus. 


THE    TONGUE. 


443 


deeper,  very  firm  layer  of  the  mucous  membrane,  to  be  described  pre- 
sently, and  partly  run  as  far  as  the  bases  of  the  papillce.  At  the  root 
of  the  tongue,  the  genio-glossus  does  not  reach  so  far  as  the  mucous 
membrane,  which  may  here  be  easily  dissected  away,  with  its  mucous 
sacs,  from  the  more  deeply  situated  racemose  glands,  but  ends  upon  and 
between  the  latter,  uniting  with  them,  or  with  a  dense  fibrous  tissue 
between  them,  by  means  of  tendinous  striae. 

The  transverse  muscle  or  the  transverse  fibres  of  the  tongue  (trans- 
versus  linguce  sive  fibrce  transversales,  Pig.  169,  tr.,  170,  tr.,  171,  g\ 
consists  of  very  numerous  lamellae  belonging  to  each  half  of  the  tongue, 
which  penetrate  with  great 
regularity  between  the 
transverse  lamellce  of  the 
genio-glossus,  and  are  to 
be  found  in  all  sections  of 
the  organ.  Each  lamella 
is  0-1-0-16  of  a  line  thick, 
and  in  the  middle  of  the 
tongue  f  ths  of  a  line  deep ; 
it  is  usually  perpendicu- 
lar and  its  muscular  fibres 
extend  from  the  septum 
linguce  to  the  lateral  bor- 
der of  the  tongue.  They  arise,  so  to  say,  directly  from  the  whole  surface 
of  the  septum,  by  the  intermediation  of  a  small  quantity  of  a  transverse 
tendinous  tissue,  distinct  from  its  longitudinal  fibres,  and  pass,  united 
into  small  flat  bundles,  at  first,  directly  outwards.  In  their  further 
course,  they  curve  upwards,  and  finally,  the  uppermost  shortest  fibres 
reach  the  sides  of  the  dorsum  of  the  tongue,  the  inferior  longer  ones, 
its  proper  lateral  margin,  where  they  also  become  attached  to  the 
mucous  membrane  by  means  of  short  bands  of  connective  tissue.  The 
other  lingual  muscles  form,  in  a  manner,  the  sheath  of  the  organ  and, 
in  their  course,  partly  follow  the  above,  partly  take  their  own  special 
direction. 

The  hyo-glossus  (baseo-  and  cerato-glossus  of  authors),  has,  at  the 
sides  of  the  tongue,  nearly  the  same  relations  as  the  genio-glossus,  in 
the  middle.  Its  coarser  bundles,  in  fact,  break  up  when  they  have 

FIG.  170. — Transverse  section  of  the  human  tongue,  a  little  in  front  of  the  papilla  circumval- 
lata:  g,  genio-glossus ;  Li,  longitudinalis  inferior  (hngualis)  with  the  arteria  ranina ;  tr,  trans- 
versus,  visible  in  its  whole  extent  on  the  left  side,  on  the  right  only  at  the  edge  and  between 
the  divaricating  bundles  of  the  genio-glossus  ;'g,  termination  of  the  genio-glossus  upon  the 
mucous  membrane ;  /i,  termination  of  the  hyo-glossus ;  Is,  longitudinalis  superior,  with  flat 
bundles  interposed  between  the  perpendicular  fibres ;  rf,  glands  of  the  margin  of  the  tongue ; 
st.gl,  stylo- glossus. 


444  SPECIAL    HISTOLOGY. 

reached  the  lower  surface  of  the  margin  of  the  tongue,  into  a  great 
number  of  thin  transverse  lamella?,  which,  more  or  less  curved,  pene- 
trate superiorly  between  the  lamellae  of  the  transverse  muscle  and  in 
their  further  course,  present  exactly  the  same  relations  as  those  of  the 
genio-glossus,  to  which  they  are  applied  externally,  except,  that  as  their 
fibres  ascend  towards  the  dorsum  of  the  tongue,  they  take  a  slightly 
oblique  direction  inwards.  Upon  the  dorsum  of  the  tongue,  the  Jiyo- 
glossus  lies  between  the  genio-glossus  and  the  upper  edge  of  the  trans- 
versus;  it  presents,  like  the  former,  longitudinal  plates,  with  perpendi- 
cular fibres,  between  which  the  upper  longitudinal  fibres  lie,  and  it 
finally,  also,  terminates  in  the  mucous  membrane.  The  expansion  of 
the  Jiyo-glossus  is  most  distinct  and  strongest,  in  the  middle  of  the 
tongue,  where  the  chief  mass  of  the  baseo-glossus  lies ;  it  is  only  behind 
that  it  becomes  more  indistinct,  the  lamellae  of  the  cerato-glossus  being 
here  very  delicate,  and  lying  more  horizontally ;  however,  they  still  pene- 
trate between  those  of  the  transversus  and  terminate  upon  the  dorsum 
of  the  tongue. 

The  stylo-glossus  (Fig.  170,  st.  gl.},  in  general,  divides  into  two 
bundles,  which  have  totally  different  relations ;  the  posterior,  smaller 
one,  passes  between  the  cerato-glossus  and  baseo-glossus,  and  between 
the  fasciculi  of  the  latter,  directly  inwards,  penetrating,  in  a  few 
bundles,  between  the  lamella?  of  the  lingualis  and  genio-glossus,  as  far 
as  the  septum  linguce,  where  it  becomes  attached,  in  common  with  the 
somewhat  superior  fibres  of  the  transverse  muscle.  The  principal  mass 
of  the  stylo-glossus  passes  inwards  and  downwards  at  the  margin  of  the 
tongue,  unites  in  front  of  the  Jiyo-glossus  with  the  lingualis  inferior,  and 
terminates  in  the  mucous  membrane  of  the  lower  surface  of  the  apex  of 
the  tongue  and  of  the  point  itself;  the  anterior  bundles  of  the  two 
muscles  becoming  united  in  an  arch. 

The  lingualis  of  authors,  which  I  shall  call  lingualis  or  longitudinalis 
inferior  (Fig.  170,  1.  i),  is  a  tolerably  strong,  longitudinal  bundle  of 
muscular  fibres  placed  upon  the  lower  surface  of  the  tongue,  between 
the  genio-glossus  and  hyo-glossus,  but  whose  commencement  and  termi- 
nation are  not  readily  discoverable.  The  posterior  portion  of  the  lin- 
gualis inferior  appears  at  first  to  become  lost  in  numerous  superimposed 
flat  bundles  between  the  transverse  fibres  of  the  genio-glossus  (glosso- 
pliaryngeus),  of  the  stylo-glossus,  and  of  the  transversus,  at  the  root  of 
the  tongue  ;  more  carefully  traced,  however,  it  is  found  that  these,  like 
the  posterior  portions  of  the  genio-glossus,  break  up  into  many  lamellce, 
which  ascend,  slightly  curved,  between  the  transverse  fibres,  as  far  as 
the  outer  portions  of  the  glandular  layer  of  the  root  of  the  tongue ;  and 
finally,  like  the  plates  of  the  genio-glossus,  which  lie  internal  to  them, 
end  in  it.  Anteriorly  the  lingualis  inferior  unites  with  the  larger 
bundles  of  the  stylo-glossus ;  ending  at  the  point  of  the  tongue  with 


THE    TONGUE. 


445 


them,  and  also,  applying  itself  anteriorly  to  the  hyo-glossus,  it  sends 
many  delicate  lamellae  between  the  transverse  muscles  as  far  as  the 
dorsum  of  the  tongue,  presenting,  in  fact,  at  the  border  of  the  anterior 
third  of  the  tongue,  the  same  relations  as  the  hyo-glossus  further  back- 
wards. 

Finally,  there  exist  in  man  yet  another  longitudinalis,  or  lingualis 
superior,  and  isolated  perpendicular  fibres.  The  longitudinalis  superior 
(Figs.  169,  170,  Is,  171,  e\  constitutes  a  longitudi- 
nally fibrous  layer  placed  between  the  uppermost  fibres 
of  the  transversus  and  the  mucous  membrane,  which 
occupies  the  whole  breadth  and  length  of  the  tongue 
and  proceeds  from  the  clwndro-glossus  (overlooked  by 
most  anatomists),  which  arises  from  the  smaller  cornu 
of  the  hyoid  bone  as  a  moderately  large  bundle,  sepa- 
rated from  the  baseo-  and  cerato-glossus  by  the  lingual 
artery  and  the  glosso-pharyngeal  nerve.  It  passes 
forwards,  under  the  deep  glandular  layer  of  the  root 
of  the  tongue,  and  in  part  through  the  midst  of  the 
termination  of  the  genio-glossus  and  lingualis  inferior ; 
occupies,  a  little  in  front  of  the  papillce  cireumvallatce, 
almost  the  entire  half  of  the  tongue,  and  thence  passes 
forwards  in  the  form  of  narrow  bundles,  united  here 
and  there  at  acute  angles,  immediately  under  the  mu- 
cous membrane,  between  the  ends  of  the  genio-glossi 
and  liyo-glossi,  as  far  as  the  point  of  the  tongue,  here  to 
become  lost  in  the  integument  on  its  upper  surface. 
Since  these  longitudinal  fibres  become  thicker  anteriorly,  it  is  probable 
that  independent,  superior  longitudinal  fibres,  arising  from  the  mucous 
membrane  of  the  dorsum  of  the  tongue,  and  ending  upon  it,  become 
associated  with  them.  I  find  perpendicular  fibres,  which  do  notarise 
from  without,  only  in  the  apex  of  the  tongue,  where  delicate  bundles  of 
them  are  stretched  between  the  upper  and  lower  layers  of  mucous 
membrane. 

The  lamellae  of  the  most  anterior  part  of  the  transversus  pass  be- 
tween the  inner  portions  of  these  bundles,  whilst  between  their  extre- 
mities the  longitudinalis  superior  and  inferior  and  stylo-glossus  pene- 
trate with  tolerable  regularity,  so  that  transverse  sections  exhibit  an 
alternation  of  perpendicular  and  longitudinal  fibres,  such  as  that  which 
appears  in  the  dorsal  part  of  the  tongue  in  Fig.  170. 

It  remains  to  be  added,  that  the  palato-glossus  muscle  becomes  in 
part  lost,  together  with  the  cerato-glossus,  in  the  mucous  membrane  of 

FIG.  171 — Portion  of  a  longitudinal  section  through  the  side  of  the  human  tongue:  a, 
papilla  fungifwmis ;  6,  papillce  filiformis ;  c,  mucous  membrane;  d,  fibrous  layer  below  it  j 
e,  longitudinalis  superior  •  f,  genio-glossus ;  g,  transversus,  cut  across. 


446 


SPECIAL    HISTOLOGY. 


the  lateral  borders  of  the  tongue,  and  in  part  seems  to  unite  with  the 
larger  bundles  of  the  stylo-glossus. 

If,  after  thus  describing  the  separate  muscles  of  the  tongue,  both  ex- 
ternal and  internal,  we  consider  the  general  structure  of  the  organ,  it 
appears  that  its  proper  substance  presents  essentially  only  three  sets  of 
muscular  fibres,  which  may  be  denominated  perpendicular,  transverse, 
and  longitudinal.  The  perpendicular  fibres  arise  from  the  genio-glossi 
in  the  middle;  from  the  lingualis  and  hyo-glossus  laterally;  at  the 
apex,  also,  from  the  perpendicular  is  ;  and  they  form  from  the  point  to 
the  root,  a  great  number  of  transverse  lamellce,  occupying  nearly  the 
entire  breadth  of  the  halves  of  the  tongue,  whose  fibres  pass  in  general 
from  the  lower  surface  to  the  upper.  The  transverse  fibres,  derived 
from  the  transversus  and  in  part  from  the  stylo-glossus,  are  inserted  in 
so  many,  usually  somewhat  thicker,  lamellce,  between  the  above  named, 
commencing  at  the  septum  and  ending  at  the  lateral  edges  and  partly 
upon  the  surface;  the  longitudinal  fibres,  lastly,  belong  to  the  lingualis 
superior  (chondro-glossus),  the  lingualis  inferior  and  stylo-glossus,  cover 
the  upper  surface,  the  margin,  and  in  part  the  lower  surface,  and  lie  for 
Fig.  172.  the  most  part  immediately  beneath  the  mucous 

membrane.  The  various  layers  of  muscles  of  the 
tongue  are  invariably  separated  from  one  another 
by  a  thin  perijnysium,  and  where  larger  vessels 
and  nerves  run,  by  thicker  masses  of  connective 
tissue ;  besides  which,  there  are  in  many  localities, 
larger  or  smaller  aggregations  of  common  fat- 
cells,  which  especially  abound  between  the  genio- 
glossi  at  the  septum,  at  the  root  of  the  tongue, 
and  under  the  mucous  membrane. 

In  the  tongue  of  the  Frog  very  beautiful  in- 
stances of  division  of  the  transversely  striated 
fibres  occur  (Fig.  172),  of  which  I  have  not  been 
able  to  find  any  certain  trace  in  man.  Occasion- 
ally, however,  it  has  seemed  to  me  that  the  fibres 
of  the  genio-glossus  exhibited  divisions  shortly 
before  their  passage  into  tendinous  bands. 

§  132.  On  the  dorsum  of  the  tongue,  from  the  foramen  ccecum  as  far 
as  its  point,  the  mucous  membrane  differs  from  that  of  the  rest  of  the 
oral  cavity,  in  being  very  closely  united  with  the  subjacent  muscular 
tissue,  and  in  possessing  a  great  number  of  processes,  the  well-known 
lingual  or  gustatory  papillce.  The  6-12  papillce  circumvallatce  consist, 

FIG.  172. — A  branched  primitive  muscular  bundle,  of  0*018  of  a  line,  from  the  tongue  of 
the  Frog ;  magnified  350  diameters. 


THE    TONGUE.  447 

when  they  are  well  developed,  of  a  central  round  papilla,  flattened 
at  the  end,  having  a  diameter  of  J-l  line,  and  J-J  or  even  f  of  a 
line  high ;  and  of  a  lower  uniform  wall  J— J  of  a  line  broad,  which 
closely  surrounds  the  papilla,  particularly  at  its  base.  These  papilla, 
however,  vary  much  in  number,  size,  and  position,  and  occasionally  pass 
into  the  fungiform  kind ;  which  is  especially  true  of  the  posterior  ones 
lying  in  the  foramen  ccecum,  or  Morgagnii.  The  papillae  anterior  to 
the  circumvallatce,  are  arranged  in  more  or  less  regular  rows,  which  in 
general  run  parallel  to  the  latter,  and  pass,  upon  the  border  of  the 
tongue,  into  laminated,  sometimes  not  even  notched  folds,  which  can  no 
longer  be  considered  as  papillce.  The  papillce  fungiformes  or  clavatce 
are  0-3-0-8  of  a  line  in  length,  0-2-0-5  of  a  line  in  breadth;  they  have 
smooth  surfaces  and,  during  life,  are  readily  recognised  by  their  red 
color ;  they  abound  particularly  upon  the  anterior  half  of  the  tongue, 
scattered  over  its  surface  at  tolerably  regular  intervals  of  J-l  line  and 
more ;  and  at  the  point,  indeed,  they  are  often  so  thickly  crowded  as  to 
be  in  contact ;  they  are  not  absent,  however,  upon  the  posterior  half,  as 
far  back  as  the  papillce  circumvallatce.  The  papillce  filiformes  or  conicce 
are  J-l  J  lines  in  length,  and  0-1-0-2  of  a  line  in  breadth,  and  rendered 
very  obvious  by  their  number  and  whitish  color ;  they  occupy,  in  close 
contact  with  one  another,  the  intervals  between  the  fungiform  kind,  and 
invariably  appear  most  densely  crowded  and  best  developed,  with  brush- 
like  ends,  in  the  concave  side  of  the  V  of  the  circumvallate  papillce,  and 
in  the  middle  line  of  the  centre  of  the  tongue.  Towards  the  edges  and 
the  point,  the  papillce  themselves,  as  well  as  their  processes,  become 
shorter,  and  to  some  extent  more  scanty,  so  that  they  gradually  pass 
into  the  laminct  to  which  we  have  referred,  and  also  in  many  respects 
approximate  the  fungiform  papillce ;  from  which,  in  fact,  so  far  as  the 
structure  of  their  surface  is  concerned,  they  become  hardly  distinguish- 
able. 

Besides  these  papilla;  which  project  freely,  there  may  also  be  observed 
over  the  whole  gustatory  region  of  the  tongue,  smaller  ones  completely 
buried  in  the  epithelium,  which  are  perfectly  similar  to  those  of  the  non- 
gustatory  parts  of  the  organ. 

With  respect  to  the  minuter  structure  of  the  mucous  membrane  of  the 
tongue,  that  part  of  it  which  presents  no  projecting  papillce,  differs  in 
no  respect  from  the  mucous  membrane  of  the  oral  cavity,  and  possesses, 
in  fact,  a  laminated  pavement  epithelium  of  0-045  of  a  line  in  thickness  at 
the  root  of  the  tongue,  of  O-06-O'l  of  a  line  on  the  lower  surface  of  its 
apex,  with  simple  small  imbedded  papillse  of  0-024-0-05  of  a  line  in  length, 
0-004-0-02  of  a  line  in  breadth,  which  are  not  absent  even  upon  the  ante- 
rior surface  of  the  epiglottis,  and  between  it  and  the  papillce  circumvallatce. 
In  the  proper  gustatory  region  of  the  tongue  the  submucous  tissue  is 
wholly  absent,  the  mucous  membrane  being  united  with  the  muscular 


448 


SPECIAL    HISTOLOGY. 


substance  by  means  of  a  dense  layer  of  connective  tissue  (see  above 
§  181) ;  it  has  itself  a  dense  and  solid  appearance,  though  in  conse- 
quence of  the  presence  of  a  considerable  quantity  of  elastic  tissue,  of 
common  fat  cells  of  0'016-0'024  of  a  line,  and  of  its  abundant  vascular 
supply,  it  is  tolerably  elastic. 

The  papillce  filiformes  or  conicce  (Fig.  173),  are  conical  processes  of 
mucous  membrane  beset  either  at  their  extremities  only,  or  over  their 
whole  surface,  with  a  certain  number  (5-20)  of  smaller  secondary 
papillce  of  0-1-0-14  of  a  line  in  length.  The  whole  is  invested  with  a 


Fig.  173. 


Fig.  174. 


thick  epithelial  coat  drawn  out  at  its  extremity  into  a  number  of  long, 
thin  (0-01-0-02  of  a  line),  fine  and  often  subdivided,  processes  (Fig.  173,/), 

FIG.  173. — Two  papilla  filiformes  of  man,  one  with  its  epithelium  magnified  35  diameters. 
After  Todd  and  Bowman:  p,  the  papilla  themselves;  a,  v,  arterial  and  venous  vessels  of 
papilla,  together  with  the  capillary  loops,  which,  however,  ought  to  enter  the  secondary 
papilla. 

FiG.  174. — Jl, papilla  fungiformis,  with  its  secondary  or  simple  papillae, p,  on  one  side  still 
covered  with  epithelium,  e  ;  magnified  30  diameters.  JB,  the  same,  with  only  the  outlines 
of  the  epithelium,  e,  and  the  vessels;  a,  artery;  v,  vein;  d,  capillary  loops  of  the  simple 
papilla? ;  «,  capillaries  in  the  simple  papillae  of  the  mucous  membrane  at  the  base  of  the  p. 
fungiformis ;  magnified  18  diameters.  After  Todd  and  Bowman. 


THE    TONGUE.  449 

which  give  the  papilla  the  aspect  of  a  fine  brush,  and  may  attain  a 
length  of  as  much  as  0-5-0-6-0-7  of  a  line,  with  a  breadth  of  0-02-0-028 
of  a  line  at  their  base.  The  superficial  layers  of  this  epithelium  resemble 
the  epidermic  plates  in  their  long  resistance  to  the  action  of  acids  and 
alkalies,  and  consist,  especially  the  epithelial  processes,  only  of  solid 
horny  scales  of  0-022  to  0-028  of  a  line,  which  frequently  form  a  more 
solid  axis,  and  of  an  external  cortex  composed  of  overlapping  plates,  so 
that  the  whole  mass  may,  with  some  justice,  be  compared  to  a  hair. 

The  primary  papilla  of  the  p.  filiformes  contains  distinct  connective 
tissue,  and  a  very  considerable  number  of  elastic  fibrils,  which  as  10-20 
wavy  threads  of  0-0004-0*0008  of  a  line,  penetrate  even  to  the  points  of 
the  simple  papillae,  and  give  to  the  whole  cone  and  its  processes  a  cer- 
tain solidity  and  firmness  which  are  not  possessed  by  the  simple  papillae  of 
the  mucous  membrane.  A  minute  artery  ramifies  in  each  filiform  papilla, 
in  such  a  manner,  that  every  simple  papilla  contains  a  capillary  loop  of 
0-004-0-005  of  a  line,  from  whose  reunion  a  small  vein  arises.  It  is  dif- 
ficult to  discover  the  nerves,  on  account  of  the  abundant  elastic  tissue  ; 
and  in  many  papillae  they  may  be  sought  in  vain.  In  the  majority,  how- 
ever, at  least  at  the  base  of  the  papillae,  they  are  quite  distinct,  in  the 
form  of  one  or  two  delicate  trunks,  with  5—10,  dark-edged  primitive 
fibrils  of  0-002-0-003  of  a  line,  which  gradually  become  finer  as  they 
run  towards  the  point.  I  have  been  unable  to  make  out  with  certainty 
how  the  nerves  terminate,  yet  everything  appeared  to  indicate  the  exist- 
ence of  loops,  not,  however,  in  the  simple  papillae,  but  at  their  base.  In 
animals  these  loops  are  more  distinct,  as  for  example,  in  the  calf,  where 
every  filiform  papilla  receives  10-12  primitive  fibrils,  of  0-002-0-003  of 
a  line,  which  diminish  to  0*001  of  a  line,  and  do  not  enter  the  simple 
papillae. 

The  papilloe  fungiformes  consist  of  a  clavate  primary  papilla,  whose 
entire  surface  is  beset  with  closely  placed,  conical,  secondary  papillae, 
0-1-0*12  of  a  line  in  length,  and  invested  with  a  simple  epithelium, 
such  as  is  met  with  elsewhere  in  the  oral  cavity,  without  filiform  pro- 
cesses,  or  any  very  horny  cells,  and  which,  measured  from  their  points, 
has  a  thickness  of  0*04-0-05  of  a  line.  The  primary  papilla  contains 
far  less  elastic  tissue  than  the  papillce  filiformes,  and  it  is  almost  wholly 
wanting  in  the  secondary  papillae  ;  on  the  other  hand,  a  network  of 
bundles  of  connective  tissue  of  0*002-0-003  of  a  line  in  breadth,  is 
very  distinct.  The  vessels  present  the  same  arrangement  as  in  the  p^ 
filiformes,  only  that  they  are  much  more  numerous  ;  and  as  regards  the 
nerves,  one  or  two  larger  trunks  of  0-04-0-08  of  a  line,  enter  into 
every  fungiform  papilla,  together  with  many  minute  filaments,  which,, 
spreading  out  in  the  form  of  a  brush,  and  repeatedly  anastomosing  (see 
Zeitschrift  fur  Wiss.  Zool.,  B.  IV.  Tab.  IV.),  finally  diverge  in  all  direc- 

29 


450  SPECIAL    HISTOLOGY. 

tions  towards  the  secondary  papillae,  and  their  axile  corpuscles  (see 
§37). 

The  nerves,  which  in  the  trunks  measured  0-002-0-004,  *  on  the 
average  0-003  of  a  line,  diminish  in  size  during  their  course,  so  that  at 
the  base  of  the  papillae,  their  diameter  is  not  more  than  0-001-0-0015 
of  a  line,  and  they  also  exhibit  distinct  divisions ;  I  have  not  yet 
observed  their  terminations  with  certainty,  but  have  thought  that  in 
some  cases  I  could  detect  loops,  in  others,  free  ends,  without,  however, 
pledging  myself  either  to  the  one  or  the  other. 

In  the  papillce  circumvallatce  the  central  papilla,  which  may  be  re- 
garded as  a  depressed  papilla  fungiformis,  is  closely  covered  upon  its 

plane  terminal  surface  with 
simple  conical  elevations,  and 
is  invested  externally  by  an 
epithelium  of  uniform  thick- 
ness, without  any  special 
processes  and  prolongations. 
The  ivall  is  a  simple  elevation 
of  the  mucous  membrane, 
possessing  a  smooth  epithelial  investment,  beneath  which  its  upper  bor- 
der is  produced  into  many  rows  of  simple  conical  secondary  papillae. 
The  elastic  tissue  is  usually  absent  in  the  papillae,  otherwise,  they  have 
the  same  structure  as  the  fungiform  kind,  only  they  are  still  more  abun- 
dantly provided  with  nerves.  Every  proper  papilla  circumvallata  con- 
tains in  its  lowest  portions  several  nervous  trunks  of  0-05-0-08  of  a  line 
in  diameter,  which  as  they  ascend,  subdivide  into  a  very  elegant  plexus, 
from  which  the  nerves  of  the  secondary  papillae  radiate  upon  all  sides. 
In  other  respects,  they  resemble  the  p.  fungiformes,  except  that  the 
nerve-tubules,  even  in  the  trunks,  have  not  a  greater  average  diameter 
than  0-002,  and  the  largest  not  more  than  0-003  of  a  line,  while  at  the 
base  of  the  secondary  papillae  it  is  not  more  than  0-001-0-0015  of  a  line. 
The  walls  of  these  papillae  also  contain  many  nerves,  whose  ultimate 
disposition  appears  to  be  exactly  the  same  as  in  the  papillae  themselves. 

The  lingual  papillae  present  many  varieties,  the  following  of  which  are 
the  most  important:  1.  The  papillce  filiformes  are  all  elongated,  and 
provided  with  very  considerable  epithelial  processes.  The  appearance 
of  what  is  commonly  called  a  gastric  furred  tongue,  depends  principally 
upon  the  growth  of  the  epithelial  processes  of  the  papillce  filiformes, 
which,  all  directed  backwards  and  in  close  apposition,  form  apparently 
a  peculiar  white  coating.  If  the  processes  become  longer,  so  that  the 

FIG.  175. — Papilla  circumvallata  of  Man  in  section:  ./#,  proper  papilla;  B,  wall;  a,  epithe- 
lium ;  c.  secondary  papilla  :  bb,  nerves  of  the  papilla  and  of  the  wall. — Magnified  about  10 
diameters. 


THE    TONGUE. 


451 


papillae  filiformes  measure  1J-2  lines,  we  have  the  lingua  hirsuta  or 
villosa,  which  is  not  uncommon  in  various  disorders;  and  at  length  forms 
may  be  produced,  in  which  the  tongue  looks  as  if  it  were  covered  with 
hairs,  4-6  lines  long.  2.  The  papillse  filiformes  possess  very  small 
epithelial  processes,  or  none  at  all,  and  are  hardly  distinguishable  from 
the  smaller  p.  fungiformes.  3.  The  papillce  filiformes  do  not  exist  as 
special  elevations,  but  are  imbedded  in  a  general  epithelial  investment  of 
the  dorsum  of  the  tongue.  Tongues  may  be  observed,  particularly  in 
old  people,  which,  without  being  furred,  in  some  spots  or  over  a  large 
extent,  present  no  papilla  at  all,  but  have  either  a  perfectly  smooth 
surface,  or  exhibit  only  a  few  linear  elevations,  corresponding  with  the 
rows  of  papillae  which  would,  otherwise,  exist  there.  In  these  places  we 
find  the  epithelium  more  developed,  and  beneath  it  small  papillae,  more 
of  the  ordinary  form.  Tongues  which,  with  better  developed  papillae 
present  a  smooth  surface,  are  again  different  from  these  ;  here  the  smooth 
or  cracked  surface  is  produced  by  the  papillae  being  glued  together  by 
superabundant  epithelium,  mucus,  blood,  pus-corpuscles,  and  mucedi- 
nous  or  yeast-like  fungi.  4.  The  epithelial  processes  of  the  filiform 
papillce  are  covered  with  mucedinous  fungi.  Every  microscopist  is 
doubtless  acquainted  with  brownish,  elongated  bodies  (0-12-0-24  of  a 
line  in  length,  0-04-0-08  of  a  line  in  breadth),  consisting  of  a  dark  axis 


Fig.  176. 


and  a  finely  granular  cortex,  from  the  coating  of  the  tongue.     The 
centre  of  these  bodies  only  is  composed  of  cornified  epithelial  cells, 

FIG.  176. — A  mass  of  epithelial  cells  covered  with  the  granular  matrix  of  the  fungus,  6, 
from  which  a  luxuriant  growth  of  mucedinous  filaments,  c,  proceeds;  magnified  350  dia- 
meters. From  Man. 


452  SPECIAL    HISTOLOGY. 

which  become  isolated  and  swell  up  by  the  action  of  caustic  potassa  and 
Fi(r  m  soda,'  especially  with  heat,  and  are  derived 

from  the  epithelial  processes  of  the  papillce 
filiformes ;  the  granular  cortex  again,  is 
nothing  but  the  matrix  of  a  mucedinous 
fungus  of  only  0-0006  of  a  line  in  diameter, 
which,  agreeing  completely  with  the  well- 
known  filaments  upon  the  teeth,  is  often 
rooted  in  immense  quantities  in  it.  In  the 
dead  subject  we  readily  recognise  the  epi- 
thelial cells,  covered  with  fungi,  either  with 
or  without  projecting  mucedinous  filaments, 
even  in  situ  (Fig.  177) ;  and  in  living  per- 
sons, they  may  be  procured  in  any  quan- 
tity by  scraping  the  tongue.  In  twenty  or  thirty  healthy  young  people, 
I  have  hardly  once  failed  to  find  the  granular  covering  upon  the  epithe- 
lial processes,  even  in  a  perfectly  clean,  red  tongue. 

The  more  fur  there  is,  the  more  abundant  is  the  matrix,  and  the 
mucedinous  filaments  are  also  apparent,  though  they  are  rarely  (three 
or  four  times  in  thirty  cases)  found  so  clear  and  distinct  as  in  Fig.  176, 
and  in  general  are  not  met  with  in  more  than  a  third  of  those  persons 
whose  papillce  filiformes  are  not  altogether  in  a  normal  condition.* 

FIG.  177. — A  papilla  filiformis,  whose,  here,  short  epithelial  processes  are  invested  by  the 
matrix  of  the  fungus,  from  which  also  single  filaments  are  growing  out. 

*[This  vegetable  is  probably  the  one  to  which  Robin  (Hist,  natur.  des  V^getaux  Para- 
sites), has  given  the  name  of  oidium  albicans.  He  has  most  frequently  met  with  it  in 
a  variety  of  aphtha,  the  "muquet"  of  the  French.  In  this  disease  the  irregular  white 
patches  on  the  mucous  membrane  of  the  tongue,  which  were  formerly  supposed  to  be  the 
result  of  a  diphtheritic  inflammation,  are  found  to  consist  of  a  vegetable  growth.  Robin  (loc. 
cit.)  describes  this  vegetableas  formed  by  distinct  tubular  filaments,  which  sometimes  enclose 
granules,  and  which  always  originate  from  spores.  The  spores  are  spherical  and  have  well- 
marked  contours  and  a  brilliant  centre.  They  generally  enclose  numerous  fine  molecules, 
sometimes  one  or  two  larger  movable  granules.  Robin  has  observed  this  vegetable  growth 
whenever  the  mucus  of  the  oral  cavity  was  changed  in  its  character.  He  agrees,  there- 
fore, with  Kolliker  in  considering  it  neither  as  a  constant  symptom  of  any  disease,  nor  as  a 
disease  in  itself. 

In  some  recent  investigations  upon  the  "  fur  "  of  the  tongue,  I  have  satisfied  myself 
of  the  almost  constant  presence  of  these  fungi,  especially  of  the  granular  matrix.  In  acute 
diseases  (as  in  erysipelas  and  peritonitis),  in  which  the  tongue  was  much  coated,  the 
mucedinous  filaments  were  also  always  found  well  developed.  They  were  firmly  adhe- 
rent to  isolated  epithelial  cells,  by  which  they  were  sometimes  concealed,  but  were  easily 
rendered  apparent  by  the  aid  of  a  solution  of  carbonate  of  soda.  In  one  case  of  typhoid 
fever  I  discovered  large  distinct  spores.  Prof.  Clark,  of  New  York,  has  observed  these 
vegetable  growths  in  cases  of  extreme  debility,  especially  in  infants  exhausted  by  diar- 
rhosa  and  dysentery. 

The  main  constituents,  however,  of  the  fur  of  the  tongue  are  layers  of  epithelial 
cells  in  different  stages  of  development.  If  the  tongue  be  much  coated,  the  cells  on  the 


THE    TONGUE.  453 

The  physiological  results  of  the  anatomical  data  which  have  been 
communicated,  may  be  thus  summed  up  :  the  papillce  filiformes  are 
neither  gustatory  nor  delicate  tactile  organs,  since  their  thick,  and  what 
is  more  to  the  point,  greatly  cornified  epithelium,  is  very  little  fitted  to 
allow  of  the  passage  of  fluids  capable  of  being  tasted,  or  of  other  in- 
fluences, to  the  scattered  nerves,  which  only  attain  to  the  base  of  the 
simple  papillae.  With  Todd  and  Bowman,  I  consider  that  the  p.  fili- 
form.es  have  a  similar  office  to  the  lingual  spines  of  animals,  which  are 
nothing  but  modified  filiform  papillae,  and  I  therefore  ascribe  to  them 
a  certain  importance  for  the  conveyance  and  retention  of  the  morsels  of 
food,  and  I  consider  that  their  epithelium  serves,  at  the  same  time,  as  a 
protecting  investment  for  the  tongue.  The  two  other  kinds  of  papillae 
subserve  the  sense  of  taste  and  are,  besides,  the  seat  of  ordinary  sensa- 
tion (for  mechanical  irritation,  temperatures,  &c.),  for  which  functions 
they  are  excellently  fitted  by  their  thin,  soft  epithelium,  the  softness 
of  the  tissue  of  their  papillae,  and  by  the  superficial  position  (in  the 
secondary  papillae),  and  the  great  number  of  their  nerves.  The  sensi- 
bility of  the  tongue  is  most  delicate  where  the  papillce  fung  if  or  mes  are 
most  closely  set,  i.  e.,  at  the  apex,  which,  on  that  account,  and  also  per- 
haps by  reason  of  the  solid  axile  corpuscles  in  many  of  the  papillae,  is 
especially  fitted  fop  a  tactile  organ  ;  at  the  root  of  the  tongue  it  is  more 
obtuse,  and  is  accompanied  by  peculiar  sensations ;  the  sense  of  taste  is 
much  more  acute  at  the  root  of  the  tongue  than  in  the  other  regions, 
the  point  not  excepted.  The  reason  of  this  lies  neither  in  the  epithelium, 
nor  in  the  fundamental  structure  of  the  papillae,  which  are  essentially 
similar  in  both  the  papillce  circumvallatce  and  fungiformes,  but  is,  very 
possibly,  to  be  sought  for  in  the  nerves.  In  the  p.  circumvallatce,  the 
nervous  fibres  are  always  finer,  and  not  only  absolutely,  but  also  rela- 
tively, considerably  more  numerous  than  in  the  fungiformes,  so  that  they 
possess  more  papillae  and  nervous  terminations  in  the  same  space.  The 
fineness  of  the  nerves  especially,  together  with  the  smaller  quantity  of 
medullary  sheath  and  the  more  superficial  position  of  the  axis-fibre, 
which  indeed  is  the  case  in  all  the  nerves  of  the  high'er  senses,  may 
perhaps  explain  why  tas table  substances  act  here  not  only  more  power- 
fully, but  when  they  are  no  longer  perceptible  by  more  dense  elements 

surface  are  generally  very  granular,  and  from  being  contracted  and  in  close  apposition,  they 
bear  a  certain  resemblance  to  fibrous  tissue.  The  use  of  reagents,  however,  especially  of 
alkalies,  will  always  render  their  cellular  nature  apparent 

The  dark  color  of  the  fur,  sometimes  seen,  may  be  owing  to  large  accumulations  of  the 
fungi  between  the  cells,  or  else  to  the  presence  of  pigment  granules.  The  latter,  if 
abundant,  may  cause  the  tongue  to  appear  as  if  covered  with  a  thin  layer  of  ink.  A 
case  is  reported  by  Dr.  Eulenberg  (Archiv  f.  phis.  Heilk.  1853),  in  which  the  whole  tongue 
was  covered  by  a  perfectly  black  fur,  which,  when  examined  microscopically,  consisted  of 
distinct,  angular  pigment  corpuscles  lying  between  the  epithelial  cells. — DaC]. 


454  SPECIAL    HISTOLOGY. 

of  the  nerves.  If  this  peculiarity  be  insufficient  to  account  for  the 
differences  in  the  sense  of  taste  possessed  by  the  two  kinds  of  papillae, 
they  can  only  be  referred  to  the  central  organs,  or  ascribed  to  specific 
actions  in  the  nervous  fibres  themselves,  which,  however,  is  only  making 
a  public  confession  of  the  hiatus  in  our  knowledge. 

Remak*  discovered  microscopic  ganglia  upon  the  expansion  of  the 

*[  Remak,  "  Ueber  die  Ganglien  der  Zunge  bei  Saiigethieren  und  beim  Menschen."  The 
author  finds  ganglia  upon  the  branches  of  the  glosso-pharyngeal  and  of  the  gustatory  nerves, 
and  not  upon  those  of  the  ninth  nerve  ;  small  ganglia  were  sometimes  observed  near  branches 
of  the  latter,  but  were  never  actually  connected  with  them,  and  probably  belonged  to  neigh- 
boring branches  of  the  gustatory.  Remak  compares  these  ganglia  with  those  observed  by 
himself  in  the  heart,  contractile  wall  of  the  bronchiae,  posterior  wall  of  the  urinary  bladder, 
and  muscular  wall  of  the  uterus,  and  with  the  ganglia  of  the  cavernous  plexus  described  by 
Miiller;  and  his  reasons  against  their  connection  with  the  nerves  of  sense  appear  to  us 
sufficiently  important  to  be  given  in  his  own  words. 

"  The  terminal  branches  of  both  nerves  (glosso-pharyngeal  and  gustatory  nerves)  form  a 
very  dense  plexus  before  entering  the  papillae.  Neither  in  this  plexus,  nor  within  the  pa- 
pillae themselves,  could  ganglion-globules  ever  be  detected.  It  must  be  remembered,  further, 
that  the  ganglia  upon  the  thicker  branches  of  the  glosso-pharyngeal  and  gustatory  are  always 
hemiganglia,  that  is,  they  do  not  occupy  the  whole  thickness  of  the  nerve — a  bundle  of  tu- 
bules, which  takes  no  share  in  the  formation  of  the  ganglia,  passing  over  them.  Those 
ganglia  which  lie  in  the  neighborhood  of  the  papillae  have  the  same  structure.  Far  more 
numerous  are  the  hologanglia,i.  e.  those  in  which  all  the  nervous  fibres  become  lost  between 
the  ganglion  globules  (probably  pass  into  them),  but  these  are  found  only  in  the  finest  lateral 
branchlets.  They  are  almost  always  multipolar,  i.  e.  they  are  connected  with  more  than 
two  nervous  trunks,  and  these  are  very  widely  different  from  the  nerves  which  constitute 
the  papillary  plexus.  While  the  latter  present  very  delicate  sheaths,  and  consist  of  evident 
dark-edged  fibres,  the  processes  of  the  hohganglia  are  closely  surrounded  and  enveloped  by 
very  dense  sheaths,  and  contain,  particularly  in  the  lingual  branch  of  the  fifth,  both  in  man 
and  in  the  sheep  and  calf,  a  very  large  quantity  of  the  well-known  nucleated  fibres,  so  that 
it  is  at  times  difficult  to  find  a  single  dark  edged  fibre  in  one  of  these  nerves.  In  other  cases, 
the  processes  of  the  ganglia  are  delicate  nerves  (of  ^^  of  a  line),  which  possess  a  solid 
sheath,  and  a  single  dark-edged  nervous  fibre  enclosed  by  it.  The  fine  lateral  branches  of  the 
hemiganglia  upon  the  thicker  branches  of  the  nerves  present  the  same  appearances.  No 
fibres  can  ever  be  traced  from  a  ganglion  to  the  papillae.  Another  circumstance  which 
speaks  against  the  relation  of  the  ganglia  to  those  fibres  of  the  gustatory  nerve  which  are 
distributed  to  the  mucous  membrane  is,  that  I  could  never,  in  spite  of  every  exertion,  find 
ganglia  upon  the  terminal  branches  of  the  gustatory  nerve  of  the  apex  of  the  tongue  of  the 
sheep.  I  believe  that  a  certain  value  may  be  attributed  to  this  negative  result,  as  I  never 
failed  to  find  ganglia  upon  the  other  branches  of  the  gustatory  nerve,  up  to  within  about  an 
inch  of  the  apex  of  the  tongue." 

Remak  gives,  further,  the  following  reasons  for  believing  that  the  ganglia  are  related  to 
the  mucous  glands.  •'  1.  The  lingual  ganglia  always  occur  in  the  neighborhood  of  the 
mucous  glands,  or  of  their  excretory  ducts.  2.  That  the  smaller  number  of  mucous  glands 
in  the  anterior  region  of  the  tongue  (in  the  sheep  or  calf),  corresponds  with  the  smaller 
number  of  ganglia  upon  the  branches  of  the  gustatory  nerve.  3.  That  little  ganglia  exist 
upon  the  branches  of  the  gustatory  nerve  distributed  to  the  maxillary  glands,  and  to  the 
duclus  Whartonianus,  whilst  in  man  there  is  the  well-known  maxillary  ganglion.  4.  That 
in  the  point  of  the  tongue  of  the  sheep,  in  which  he  could  find  no  ganglia  on  the  branches 
of  the  fifth,  there  are  no  mucous  glands.  5.  That  in  the  walls  of  the  pharynx  and  larynx, 
upon  which  he  also  found  small  ganglia  on  the  branches  of  the  glosso-pharyngeal  and  supe- 
rior laryngeal  nerves  (Med.  Zeit.,  1840,  No.  2),  the  mucous  glands  are  very  numerous.  6. 


GLANDS    OF    THE    ORAL    CAVITY.  455 

gloss o-pliaryngeal  nerve  in  the  tongue,  and  these  have  been  recently  sub- 
jected by  myself  (Micr.  Anat.  II,  2,  p.  32),  and  by  Remak  (Mull.  Arch., 
1852)  to  a  more  exact  investigation.  Remak  found  such  ganglia  also 
upon  the  branches  of  the  gustatory  division  of  the  fifth  nerve  in  the 
Sheep  and  Calf,  as  far  as  close  to  the  apex  of  the  tongue,  though  they 
•were  smaller  and  more  scanty  than  those  upon  the  glosso-pharyngeus  ; 
whilst  on  the  other  hand,  in  man,  they  were  wanting  upon  the  thicker 
branches  of  the  gustatory  division  of  the  fifth,  and  were  to  be  found 
only  as  very  minute  ganglia  upon  the  more  delicate  internal  branches. 
Remak  endeavors  to  demonstrate  some  relation  between  these  ganglia 
and  the  lingual  glands,  and  draws  a  functional  parallel  between  them 
and  the  ganglion  linguale,  a  view  plausible  enough,  and  against  which 
I  only  have  to  remark,  1.  That  ganglia  exist  not  only  upon  the  branches 
distributed  to  the  mucous  membrane,  but  also  upon  those  passing  to  the 
papillae,  and  in  regions  of  the  tongue  (the  point)  where  no  glands  are 
found  ;  and,  2.  That  the  glandular  region  of  the  root  of  the  tongue, 
also,  possesses  gustatory  sensibility.  Upon  these  grounds,  I  think  it  is 
impossible,  for  the  present,  wholly  to  deny  a  relation  of  the  ganglia  in 
question,  to  the  sensations. 


C.     OF  THE  GLANDS   OF  THE  OKAL  CAVITY. 
I. — MUCOUS    GLANDS. 

§  133.  The  mucous  glands  of  the  oral  cavity  are  yellowish  or  whitish 
racemose  glands,  usually  of  a  rounded  form,  and  tuberculated  surface  of 
J-2  lines  in  diameter,  which  in  general  lie  immediately  external  to  the 
mucous  membrane  and  yield  a  mucous  secretion. 

According  to  the  localities  in  which  they  are  found,  the  mucous  glands 
present  somewhat  different  relations  and  receive  different  names. 

1.  The  labial  glands,  \— 1  \  lines  in  diameter,  lie  between  the  muscular 
layer  and  the  mucous  membrane,  are  very  numerous,  and  form  an  almost 
continuous  glandular  ring  round  the  oral  aperture,  which  commences  at 
3  lines  distance  from  the  red  edge  of  the  lips,  and  possesses  a  breadth  of 
about  \  a  line. 

2.  The  buccal  glands,  lying  further  outwards,  covered  by  the  bucci- 
nator muscle,  are  tolerably  numerous  but  smaller  ;  a  few  large  glands 
appear  at  the  aperture  of  Stenon's  duct  upon  the  buccinator  muscle,  and 
still  further  backwards  in  the  neighborhood   of  the  last  molar  tooth 
(molar  glands). 

3.  The  palatine  glands. — Those  of  the  hard   palate  are  small  and 

That  in  the  sheep  and  calf  he  has  observed  little  ganglia  upon  the  surface  of  the  ductus 
WJiarfonianus,  which  are  connected  with  a  plexus  of  delicate  nerves  investing  the  duct." — 
TBS.] 


456  SPECIAL    HISTOLOGY. 

hardly  pass  beyond  its  middle  anteriorly,  while  on  the  other  hand,  those 
of  the  soft  palate  form  a  considerable  layer  of  glands  upon  its  under 
side,  which  anteriorly  measures  as  much  as  3-4  lineSj  diminishing,  how- 
ever, somewhat  towards  the  free  edge  and  the  uvula.  On  the  posterior 
surface  of  the  soft  palate,  also,  glands  exist,  but  they  are  much  smaller, 
and  do  not  always  form  a  connected  layer. 

4.  The  lingual  glands,  among  which  I  distinguish : — 

a.  The  mucous  glands  of  the  root  of  the  tongue. — These  form  a  stra- 
tum, in  parts  very  thick,  of  glands  J-2  lines  in  diameter,  beneath  the 
simple  mucous  sacs  of  the  root  of  the  tongue,  to  which  we  shall  have  to 
refer  hereafter,  and  the  papillae  circumvallatce ;   it  presents,  especially 
beneath  the  former,  a  thickness  of  as  much  as  4  lines,  and  extends  almost 
continuously  from  one  tonsil  to  the  other.      In  front  of  the  foramen 
ccecum  these  glands  are   smaller   and  more  scattered,  but  a  few  occur 
more  or  less  deep  in  the  muscular  substance  in  front  of  the  most  anterior 
papillae  circumvallatce;  they  are  never  found,  however,  further  forwards 
than  the  middle  of  the  tongue. 

The  excretory  ducts  of  the  glands,  which  are  interwoven  with  the 
extremities  of  the  genio-glossus  and  partly  united  with  them,  are  as  much 
as  6  lines  long  in  the  posterior  glands,  and  open,  as  E.  H.  Weber  first 
showed,  by  a  funnel-shaped  expansion  into  the  simple  mucous  sacs  of 
the  root ;  in  the  neighborhood  of  the  papillce  circumvallatce,  on  the  other 
hand,  they  open  independently  between  the  lingual  papillae,  and  into  the 
clefts  which  surround  the  circumvallate  papillae,  a  few  also  on  the  walls 
of  the  foramen  caecum. 

b.  The  marginal  glands  of  the  root  of  the  tongue. — At  the  borders  of 
the  root  of  the  tongue  we  find,  at  the  level  of  the  papilla?  circumvallatce 
many  perpendicular  laminated  folds,  to  which  reference  has  already  been 
made,  and  between  them  fine  apertures,  which  belong  to  a  special  small 
group  of  glands  lying  in  the  midst  of  the  expansion  of  the  hyo-glossus 
and  transversus.     In  animals,  these  glands,  as  well  as  the  folds  (Mayer's 
organ),  are  often  very  greatly  developed.     (See  Briihl,  1.  c.) 

c.  The  glands  of  the  point  of  the  tongue. — On  the  lower  surface  of  the 
apex  of  the  tongue,  but  still  in  the  substance  of  the  lingualis  inferior 
and  stylo-glossus,  there  lie,  right  and  left,  two  elongated  broad  glandular 
masses  6-10  lines  long,  2-3  lines  thick,  3-4  lines  broad,  where  5  or 
6  excretory  ducts  open  upon  peculiar  lobed  folds  of  mucous  membrane 
close  to  the  frcenulum  linguce  ;  these  glands  were  long  ago  accurately 
described  by  Blandin,  and  have  been  recently  rescued  from  oblivion  by 
Nuhn. 

§  134.  Intimate  structure  of  the  mucous  glands. — All  these  glands 
agree  in  the  essential  characters  of  their  intimate  organization  and  inva- 
riably consist  of  a  certain  number  of  glandular  lobes  with  a  branched 


GLANDS    OF    THE    ORAL    CAVITY. 


457 


excretory  duct.     The  lobes,  of  which  in  the  simplest  glands  (Fig.  178), 
only  a  few  (4-8)  exist,  are  in  their  Fig.  ITS. 

circumference  generally  elonga- 
ted, pyriform,  or  rounded,  not  rare- 
ly flattened,  G'5-0'72  of  a  line 
long,  0-2— Op48  of  a  line  broad,  and 
are  each  seated  upon  a  branch  0-03- 
0*05  of  a  line  thick,  of  the  excre- 
tory duct,  which  measures  0*12- 
0-3,  or  even  0-5  of  a  line  (in  the 
glands  of  the  root  of  the  tongue). 
They  consist  of  a  number  of  coiled 
canals,  presenting  numerous  simple 
or  compound,  vesicular  diverticula 
(Fig.  179),  and  appear  to  be  the 
immediate  continuations  of  the  ex- 
cretory ducts  of  the  lobes,  which, 
as  soon  as  they  have  entered  the 
latter,  usually  without  diminishing 

in  diameter,  breakup  successively  into  a  certain  number  of  them.    What 
have  been  called  the  glandular  vesicles  or  acini,  are  nothing  more  than 


the  dilatations  and  terminations  of  these  canals,  or  ultimate  branches  of 
the  excretory  ducts.  Examined  superficially,  and  under  low  magnifying 
powers,  they  all  appear  uniformly  rounded  or  pyriform;  the  exact  ana- 
lysis of  a  whole  lobe,  or  still  better  of  a  dissected  and  injected  gland, 
shows,  however,  that  their  form  is  very  various,  rounded,  pyriforrn,  or 
elongated.  It  is  impossible  to  describe  at  length  all  the  forms  which 
they  assume  ;  I  will  therefore  only  remark,  that  the  ends  of  the  glandu- 
lar lobes  frequently  repeat,  on  a  small  scale,  the  figure  and  structure  of 
the  seminal  vesicles,  and  refer  to  the  subjoined  diagrammatic  figure. 

FIG.  178. — Racemose  mucous  gland  from  the  floor  of  the  oral  cavity  :  a,  investment  of 
connective  tissue  ;  6,  excretory  duct ;  c,  glandular  vesicles ;  d,  ducts  of  the  lobes  ;  from  Man. — 
Magnified  50  diameters. 

FIG.  179. — Diagram  of  two  ducts  of  a  lobe  of  a  mucous  gland:  a,  excretory  duct  of  the 
lobe  ;  6,  secondary  branch ;  c,  the  glandular  vesicles  upon  it  in  situ  ;  rf,  the  same  separated 
and  the  duct  unfolded. 


458  SPECIAL    HISTOLOGY. 

All  the  finest  glandular  ducts  and  vesicles,  whose  diameter  varies  from 
0-02  to  0-08  of  a  line,  consist  of  a  peculiar,  structureless  coat,  the  mem- 
brana  propria,  of  0-0008— 0*0012  of  a  line  in  thickness,  and  of  an  epi- 
thelium (Fig.  180),  which,  in  fresh  preparations,  appears  as  a  continuous 
investment  of  the  glandular  extremities,  but  is 
Fi£-180-  very  readily  detached,  and  then  fills  the  glan- 

dular vesicles  as  a  granular  mass.  The  epithelial 
cells  constitute  a  simple  layer  upon  the  m&mbrana 
propria,  have  3—6  sides,  are  often  somewhat 
elongated,  0-005-0-006  of  a  line  broad,  0-003- 
0-004  of  a  line  thick,  and  invariably  contain,  be- 
sides a  rounded  or  elongated  nucleus  of  0-002-0-003  of  a  line,  often 
presenting  a  distinct  nucleolus,  a  certain  number  of  larger  or  smaller 
granules,  which  sometimes  simply  resemble  white  fat,  sometimes  are 
colored  yellowish  and  brownish,  and  contribute  to  the  hue  of  the  glands 
themselves. 

The  elements  of  the  glandular  lobes  which  have  been  just  described, 
though  they  are  all  applied  very  closely  together,  so,  indeed,  as  not  un- 
commonly to  be  flattened  against  one  another,  yet  always  present  a 
small  quantity  of  interposed  connective  tissue,  by  which  the  vessels  of 
the  lobes  are  supported.  Besides  this,  the  separate  lobes  and  the  entire 
glands  are  invested  by  dense  coats  of  a  connective  tissue,  with  elastic 
fibres,  which  may,  in  addition,  contain  fat-cells.  In  small  glands,  such 
as  Fig.  178,  the  only  distinguishable  subdivisions  are  the  lobes,  glan- 
dular vesicles,  and  caeca,  which  have  been  described ;  in  the  larger,  on 
the  other  hand,  as  in  the  glands  of  the  lips  and  palate,  the  smallest 
lobes  are  surrounded  in  groups  by  somewhat  stronger  sheaths  of  con- 
nective tissue,  so  that  a  certain  number  of  secondary  lobes  are  formed, 
each  of  which  corresponds  with  a  simple  gland  and  also  has  the  same 
size,  i.  e.j  about  |~1|  lines. 

The  excretory  ducts  of  the*  lobes  have  a  coat  of  connective  tissue, 
with  networks  of  fine  elastic  fibres,  and  a  simple  layer  of  cylindrical 
cells  0-008-0-01  of  a  line  thick.  In -the  principal  excretory  ducts,  the 
wall,  which  is  very  rich  in  elastic  fibres,  measures,  even  in  the  smallest 
glands,  0-02,  in  the  larger  as  much  as  0-03  and  0-04  of  a  line,  the  epi- 
thelium 0-01—0-012  of  a  line.  Of  muscular  fibres  I  saw  no  trace  what- 
soever, either  in  the  glands  themselves  or  in  their  excretory  ducts  ;  on 
the  other  hand,  they  possess  many  minute  vessels,  which  penetrate  with 
the  excretory  duct  or  otherwise  between  the  lobes,  and  form,  in  the  in- 
terior, a  wide  network  of  capillaries  of  0-003  of  a  line,  which  encircle 
the  separate  caeca  and  vesicles,  so  that  each  of  them  is  in  contact  with 

FIG.  180. — Two  glandular  vesicles  of  a  racemose  mucous  gland  of  Man,  magnified  300 
diameters;  a,  membrana  propria ;  6,  epithelium,  as  it  appears  in  the  apparent  section  of  a 
vesicle;  c,  the  same  seen  upon  its  surface. 


GLANDS     OF    THE     OKAL    CAVITY.  459 

at  least  3-4  capillaries.  Nerves  exist  abundantly  upon  the  excretory 
ducts  and,  occasionally,  moderately  fine  tubules  are  found  in  the  glands 
themselves. 

The  secretion  of  the  racemose  glands  is  a  clear,  yellowish  mucus,  with 
only  accidentally  intermingled  granules,  nuclei,  and  remains  of  cells, 
which  coagulates  in  acetic  acid  and  is  insoluble  in  an  excess  of  it,  re- 
maining as  a  viscid  mass,  striated,  or  deceptively  similar  to  a  fibrous 
tissue.  It  fills  the  excretory  ducts  and  the  other  cavities  of  the  gland 
to  their  ultimate  extremities,  being  readily  rendered  obvious  in  them  by 
acetic  acid.  I  have  never  found  the  so-called  mucous  corpuscles,  as  they 
exist  in  the  fluids  of  the  mouth,  in  a  mucous  gland,  and  I  believe  that, 
normally,  the  secretion  of  mucus  goes^on  without  the  production  of  cells. 

II. — FOLLICULAR    GLANDS. 

§  135.  The  follicular  glands  of  the  cavity  of  the  mouth  are:  firstly, 
simple  follicles  at  the  root  of  the  tongue  and,  secondly,  compound  follicles 
at  the  sides  of  the  isthmus  faucium, — the  tonsils.  These  organs  agree  so 
perfectly  in  structure,  that  the  tonsils  may  be  regarded  as  an  aggrega- 
tion of  simple  follicular  glands,  while,  on  the  other  hand,  they  are  so 
widely  different  from  the  mucous  glands  that  they  can  on  no  account  be 
classified  with  them. 

The  simple  follicular  glands  of  the  root  of  the  tongue  (Fig.  169,  /), 
form  an  almost  continuous  layer  from  the  papillce  vallatce  as  far  as  the 
epiglottis  and  from  one  tonsil  to  the  other,  lying  immediately  under  the 
mucous  membrane,  and  above  the  mucous  glands.  Their  position  is  so 
superficial,  that  the  separate  glands  are  visible  from  without,  like  little 
elevations  upon  the  mucous  membrane,  and  allow  their  number  and 
arrangement  to  be  recognized.  When  dissected  out,  we  see  that  each 
follicle  is  a  lenticular  or  globular  mass  of  J— 2  lines  in  diameter,  invested 
upon  its  outer  surface  by  the  mucous  membrane,  which  is  here  very  thin, 
lying  loosely  in  the  submucous  tissue  and  receiving  upon  its  under  sur- 
face the  excretory  duct  of  a  more  deeply  disposed  mucous  gland.  In 
the  midst  of  the  free  surface  a  punctiform  aperture,  often  tolerably  wide 
|— J  a  line,  is  easily  perceived  by  the  naked  eye  ;  it  leads  into  a  funnel- 
shaped  cavity,  which  is  remarkable  on  the  one  hand  for  its  narrowness, 
in  relation  to  the  size  of  the  sac,  and  on  the  other,  for  its  thick  walls, 
and  is  usually  filled  with  a  grayish  mucous  material. 

Each  follicle  (Fig.  181)  is  a  thick-coated  capsule,  externally  surrounded 
by  a  fibrous  investment  connected  with  the  deep  layers  of  the  mucous 
membrane ;  internally,  it  is  lined  by  a  process  of  the  mucous  membrane 
of  the  oral  cavity,  with  its  papillae  and  epithelium,  and  contains  between 
the  two,  imbedded  in  a  delicate,  fibrous,  vascular  matrix,  a  certain 
number  of  large,  completely  closed  capsules,  or  follicles  (Fig.  181,  g\ 
which  are  about  y^-J  of  a  line  in  diameter,  round  or  elongated  in  form 


460 


SPECIAL    HISTOLOGY. 


Fig.  181. 


present  a  whitish   color,  and  closely  resemble  the  capsules  of  Peyer's 
patches,   the  solitary  glands,   the  vesicles  of  the  spleen  and  of   the 

lymphatic  glands.  They  con- 
sist of  a  tolerably  solid  coat, 
about  0-002--003  of  a  line 
thick,  composed  of  more  ho- 
mogeneous connective  tissue, 
without  elastic  fibres,  and 
of  grayish  white  contents, 
which,  when  the  follicle  is 
pricked,  exude  in  the  form  of 
a  drop,  which  becomes  diffused 
through  water,  and  consists  of  a  fluid  with  formed  particles.  The  former, 
alkaline  in  its  reaction,  is  present  in  excessively  small  quantity,  so  that 
it  appears  to  be  merely  the  connecting  medium  of  the  latter,  which 
consist  of  cells  of  0-003-0-005  and  free  nuclei  of  0-002-0-0025  of  a 
line  without  any  determinate  character.  Acetic  acid  renders  the  cells 
granular,  and  thence  communicates  a  whitish  tinge  to  the  contents  ;  but 
it  precipitates  no  mucus,  the  fluid  differing  decidedly  in  this  respect  from 
the  ordinary  mucous  secretion  and  agreeing  with  that  of  the  splenic  cor- 
puscles. The  position  of  the  follicles  is  usually  such,  that  they  form  a 
connected,  almost  simple  layer,  between  the  external  coat  and  the  epi- 
thelium of  the  follicular  glands,  yet  there  are  localities,  at  least  in  ani- 
mals, where  two  follicles  are  found  behind  one  another,  or  at  greater 
intervals. 

The  vessels  of  the  follicular  glands  are  very  numerous,  and  may  often 
be  traced  naturally  injected,  in  man.  Small  arteries  enter  from  without, 
passing  through  the  fibrous  coat  to  the  interior,  ramify  between  the  folli- 
cles, as  they  ascend,  in  an  elegant  arborescent  manner,  and  terminate 
in  the  papillae  and  on  the  follicles.  The  vessels  of  the  former  present 
the  same  relations  as  those  of  the  other  simple  papillae,  and  are  either 
simple  or  complex  loops  ;  around  the  follicles  they  form  an  exceedingly 
elegant  and  abundant  network,  whose  finest  vessels,  0'004-0*006  of  a 
line  in  diameter,  take  a  wavy  course,  forming  a  moderately  close  net- 
work immediately  upon  the  membrane  of  the  follicle.  The  efferent 
veins  converge  from  these  two  localities,  and  are  wide  and  numerous. 
Lymphatic  vessels  also,  according  to  E.  H.  Weber  (Meckel's  Archiv, 
1827,  p.  282),  appear  to  proceed  from  these  glands,  and  I  have  myself 
noticed  nerves  upon  them. 

The  tonsils  are,  according  to  my  investigations,  nothing  but  an  aggre- 

FlG.  181. — Follicular  gland  from  the  root  of  the  tongue  in  Man  :  a,  epithelium  lining  it ;  b, 
papillae  5  c,  external  surface  of  the  follicular  gland,  with  the  coat  of  connective  tissue ;  e, 
cavity  of  the  gland  ;  /,  epithelium  ;  g,  follicle  in  the  thick  wall  of  the  gland.  Magnified  30 
diameters. 


GLANDS    OF    THE     ORAL    CAVITY.  461 

gation  of  a  certain  number  (10  to  20)  of  compound  follicular  glands, 
which,  intimately  united  and  held  together  by  a  common  investment,  form 
a  large  hemispherical  organ ;  the  apertures  of  the  follicles  frequently 
unite,  so  as  ultimately  to  form  only  a  small  number.  Each  section  of 
the  tonsil,  much  as  it  may  vary  in  the  form  of  its  cavity  and  its  external 
appearance,  has  exactly  the  same  structure.  Proceeding  from  the  oral 
cavity,  we  observe  that  its  epithelium  enters  into  the  separate  cavities  of 
the  tonsil  and,  becoming  somewhat  thinner,  completely  lines  all  the 
secondary  cavities.  Beneath  it  we  find  a  grayish,  soft,  very  vascular 
membrane  J-J  of  a  line  thick  ;  and  still  more  externally,  a  dense,  rela- 
tively thick  fibrous  covering,  which,  when  two  lobes  or  sections  of  the 
tonsils  are  in  contact,  belongs  to  them  in  common,  and  is  in  contact  at 
their  outer  extremities  with  the  common  coat  of  the  organ.  The  soft 
thick  layer  between  the  epithelium  and  the  fibrous  investment  has  the 
same  composition  as  the  corresponding  layer  of  the  follicular  glands  of 
the  root  of  the  tongue.  Here  also  we  meet  with  conical  or  filiform,  even 
slightly  branched  papillae,  of  0-06-0-08  of  a  line  in  length,  0-01-0-03 
of  a  line  in  breadth,  directed  towards  the  epithelium  ;  internally  to  these, 
round,  completely  closed  follicles  one  close  to  the  other,  of  the  same  size 
and  possessing  the  same  contents  as  those  previously  described  ;  and 
finally,  a  soft  fibrous  tissue  connecting  them,  and  containing  numerous 
vessels.  The  vessels  are  still  more  numerous  than  in  the  follicles  of  the 
tongue,  though  their  ramifications  are  essentially  similar,  except  that 
the  papillae  frequently  contain  multi- 
ple loops,  and  the  networks  around  Fig.i82. 
the  capsules  are  still  closer  (Fig.  182). 
The  fibrous  investment,  lastly,  con- 
sists of  connective  tissue,  with  elastic 
fibres  and  receives  certain  muscular 
fibres  from  the  superior  constrictor  of 
the  pharynx.  Nerves  may  be  detected 
on  the  external  surface  of  the  tonsil, 
and  in  the  papillae,  but,  as  in  the  case 
of  the  follicular  glands  of  the  root  of 
the  tongue,  I  have  failed  to  observe 
them  in  the  proper  membrane  of  the  follicles. 

Corresponding  with  their  structural  similarity  is  the  resemblance  in 
the  secretion  of  the  tonsils  and  that  of  the  lingual  follicles,  though  the 
former  is  not  easily  obtained  pure  on  account  of  the  tonsils  also  receiv- 
ing the  ducts  of  mucous  glands.  It  is  a  grayish-white  mucous  substance, 
which,  however,  so  far  as  I  have  been  able  to  observe,  contains  no  mucus, 
but  is  composed  either  of  cast-off  epithelial  plates  alone,  or  of  a  mixture 

FIG.  182. — Vessels  of  a  few  follicles  from  a  human  tonsil,  seen  from  the  cavity  of  a  sac, 
and  magnified  60  diameters. 


462  SPECIAL    HISTOLOGY. 

of  these  with  cells  and  nuclei,  perfectly  identical  with  those  contained 
in  the  parietal  follicles  of  the  tonsillar  cavities.  How  these  cells  are 
formed  and  whence  they  arise,  I  know  not.  It  would  seem  probable 
that  they  proceed  from  follicles  which  have  burst,  a  process  which  may 
really  occur  in  man,  though  from  what  is  observed  in  animals  we  can 
hardly  assume  their  dehiscence  to  be  a  normal  process.* 

In  man  it  is  quite  impossible,  in  a  vast  number  of  cases,  to  find  the 
follicles  which  we  have  described  in  the  walls  of  the  tonsils,  a  circum- 
stance which  appears  to  me  to  be  explained  by  the  frequent  morbid 
changes  to  which  these  organs  are  subject.  In  fact,  in  the  course  of 
inflammations  of  the  tonsils  and  their  sequelce,  the  contents  of  the  folli- 
cles appear  to  alter,  the  follicles  themselves  becoming  distended,  and 
finally  bursting.  The  closed  sacs,  filled  with  purulent  or  caseous  masses, 
which  are  described  in  diseased  tonsils,  when  they  do  not  exceed  a  certain 
size,  may  be  nothing  else  than  such  follicles  ;  and  by  their  bursting  they 
may  yield  those  masses  of  secretion  which  are  accumulated  in  the  larger 
cavities.  It  thus  happens,  that  the  normal  structure  is  frequently  no  longer 
recognizable  in  the  walls  of  the  tonsils,  and  thftt  we  find,  at  most,  recently 
opened  follicles,  or  more  usually  nothing  but  a  granular  mass  interpene- 
trated by  fibres  and  vessels,  with  remains  of  papillae  and  of  epithelium. 

On  the  other  hand,  however,  the  frequent  pathological  degenerations 
have  this  advantage,  that  if  we  happen  to  hit  upon  the  right  period,  all 
the  follicles  may  be  seen  enlarged,  but  still  closed  and  beautifully 
injected,  so  that  it  is  quite  impossible  to  overlook  them.  An  instance 
of  such  a  hypersemic  tonsil,  with  distended,  lingual  follicular  glands, 
the  follicles  attaining  a  size  of  0-36-0-48  of  a  line,  was  what  first  led 
me  to  a  conception  of  the  true  structure  of  these  parts,  which  has  been 
only  verified  by  subsequent  investigations.  The  difficulties  attending 
the  investigation  in  man  disappear  in  many  animals,  and  I  can  especially 
recommend  the  tonsils  of  the  Pig  and  Sheep,  the  lingual  follicular  glands 
of  the  Ox  and  the  tonsil-like  organs  at  the  entrance  of  the  larynx  in 
the  Pig,  Sheep,  and  Ox,  in  which  the  structure  may  be  always  readily 
made  out,  both  in  fresh  organs  and  in  those  which  have  been  hardened 
in  strong  alcohol. 

With  respect  to  the  secretion  of  the  tonsils  in  man,  it  is  certainly  ab- 
normal in  many  cases,  in  the  dead  subjects  which  are  accessible  for 
investigation ;  for  instance,  when  the  cavities  contain  considerable  quan- 

*  [In  the  Mikroskopische  Anatomie,  B.  II.  H.  II.,  p.  46,  Professor  Kolliker  adds  a  few 
points  to  the  account  here  given  of  the  structure  of  the  tonsils.  In  man,  racemose  glands 
are  not  unfrequently  met  with  external  to  the  tonsils,  and  probably  open  in  them  ;  and  in 
the  Calf,  a  considerable  number  of  such  glands  may  be  found  between  the  lobes  of  the 
organ.  In  opposition  to  Frerichs  (Wagn.  Handw.  III.,  p.  745),  Kclliker  states  that  he  has 
"  not  yet"'  found  solitary  glands  like  those  of  the  intestine  in  the  mucous  membrane  of  the 
mouth. — TRS.] 


GLANDS     OF    THE    ORAL    CAVITY.  463 

titles  of  a  grayish,  yellowish,  or  greenish,  sometimes  softer,  sometimes 
more  consistent  mucus,  if  it  may  be  so  called,  the  constituents  of  these 
contents  being  larger  and  smaller  cells,  with  a  single  nucleus,  some  of 
which  have  undergone  a  very  obvious  fatty  metamorphosis,  while  others 
have  cavities  and  thickened  membranes  ;  further,  epithelium  (not  ciliated 
cylinders,  as  Valentin  states,  having  probably  confounded  with  such,  the 
deepest,  here  very  much  elongated,  cells  of  the  pavement  epithelium), 
occasionally  abundant  cholesterin  crystals  and  mucedinous  fungi.  The 
secretion  is  more  normal  if  it  consist  only  of  epithelium,  of  small  cells 
without  fat  and  of  free  nuclei,  the  two  latter  elements  being  perfectly 
similar  to  those  in  the  follicles;  such  great  masses  of  them,  however, 
are  often  found,  that  we  must  suppose  they  have  been  developed  in 
excess. 

In  any  case  I  am  disposed  to  consider  such  cells  and  nuclei  as  the 
proper  secretion  of  the  tonsils,  inasmuch  as,  in  animals,  as  for  example, 
the  Sheep,  we  find  similar  contents,  though  their  amount  is  often  small. 
It  is  difficult  to  decide  whether  they  are  afforded  by  the  follicles  or  not ; 
certain  it  is,  that  they  are  identical  with  the  contents  of  the  latter,  and 
that  in  man  the  follicles  burst,  but  the  former  might  be  accidental,  and 
the  latter  only  a  morbid  process. 

In  fact,  however  frequently  the  tonsils  of  animals  are  examined,  no 
ruptured  follicles  are  ever  met  with  ;  they  are  always  entirely  closed, 
and  the  epithelium  extends  them,  so  that  one  is  led  to  the  belief  that  the 
secretion  is  developed  independently,  out  of  a  substance  excreted  into 
the  cavity  of  the  organ.  That  this  is  possible  and  actually  takes  place, 
indeed,  elsewhere  (e.  g.  suppuration  upon  mucous  membranes  which  are 
still  covered  by  their  epithelium),  is  not  to  be  denied  ;  and  the  sole 
difficulty  about  such  a  hypothesis  is,  that  in  this  case  the  import  of  the 
tonsillar  and  lingual  follicular  glands  (for  which,  also,  all  that  has  been 
said,  holds  good),  becomes  highly  problematical.  If  they  do  not  occa- 
sionally burst,  their  function,  as  regards  secretion,  can  only  be  to  elabo- 
rate in  their  interior  a  fluid,  which  when  it  subsequently  enters  the 
cavity  of  the  gland,  is  especially  fitted  to  form  its  proper  secretion. 
For  the  rest,  the  similarity  of  the  follicles  in  question,  especially  with 
those  of  the  solitary  and  Peyerian  glands,  and  also  with  those  of  the 
spleen*  and  lymphatic  glands,  would  indicate  another  series  of  possi- 
bilities, into  which,  however,  I  will  not  enter,  because  in  all  the  organs 
in  question  the  anatomical  facts  and  the  physiological  relations  have 
hitherto  been  by  no  means  completely  determined. 

III. — SALIVARY   GLANDS. 

§  136.  The  salivary  glands,  i.  e.  the  parotid,  the  submaxillary,  the 
sublingual,  and  Rivini  s  glands,  agree  so  closely  in  their  structure  with 

*  [For  some  additional  facts  in  favor  of  these  resemblances,  see  notes  §  Spleen. — Tus.] 


464  SPECIAL    HISTOLOGY. 

the  racemose  mucous  glands,  that  it  would  be  quite  superfluous  to  enter 
into  any  detailed  description  of  them.  They  are  compound  racemose 
glands,  and  they  might  be  regarded  as  aggregations  of  numerous  mucous 
glandules.  In  fact,  the  primary  and  secondary  lobulations  which  are 
observed  in  these  glands  correspond,  the  latter  to  the  entire  mucous 
gland,  the  former  to  its  lobes.  The  secondary  lobulations  then  become 
united  into  still  larger  groups,  and  a  certain  number  of  these  constitute 
the  whole  gland.  The  excretory  ducts  correspond  with  the  number  of 
the  lobulations  of  the  gland ;  they  are  more  or  less  branched,  and  in 
their  final  relations  resemble  those  of  the  mucous  glands. 

The  more  intimate  structure  of  the  salivary  glands  presents  nothing 
remarkable.  The  glandular  vesicles  have  about  the  same  diameter — 
0-016-0-024-O03  of  a  line,  in  all  three  descriptions  of  glands  ;  they  are 
as  variously  formed  as  in  the  mucous  glands,  and  proceed  in  a  similar 
manner  from  the  excretory  ducts.  Their  membrana  propria  frequently 
presents  a  double  contour,  arid  is,  internally,  always  clothed  with  a 
pavement  epithelium,  whose  cells  of  0-005-0-008  of  a  line  have  a  single 
nucleus,  and  may  be  obtained  in  beautiful  series  by  coarsely  crushing 
the  gland ;  they  are  distinguished  by  their  greater  proportion  of  fatty 
granules  and  pigment  granules  from  those  of  most  mucous  glands, 
whence  the  glandular  vesicles  themselves  present  a  somewhat  dark 
appearance.  Here,  also,  acetic  acid  makes  the  contents  of  the  cells 
turbid,  the  addition  of  an  excess  even  not  restoring  their  clearness,  and 
it  is  not  therefore  advisable  to  make  use  of  it  in  our  examinations ;  a 
very  dilute  solution  of  caustic  soda,  which  allows  the  epithelial  cells  to 
be  seen  in  situ,  is  more  to  be  recommended. 

The  excretory  ducts  of  the  salivary  glands  possess  a  single  layer  of 
cylinder  epithelium,  whose  cells  measure  0-016  of  a  line  in  length.  The 
remaining  portion  of  the  wall,  which  is  very  thick  in  Stenons  duct,  but 
much  thinner  in  the  others,  has  a  dense,  solid  structure,  and  consists  of 
connective  tissue,  with  a  very  close  network  of  fine,  and  moderately 
thick,  elastic  fibres.  It  is  only  in  Whartoris  duct  that  we  find,  exter- 
nal to  the  epithelium,  and  to  a  double  layer  of  elastic  membranes  whose 
elements  are  disposed  transversely  and  longitudinally,  a  thin  stratum  of 
smooth  muscles,  which,  however,  can  only  be  demonstrated  and  isolated 
with  very  great  difficulty.  They  are  disposed  longitudinally,  have  short 
nuclei  of  0-004-0-006  of  a  line,  at  most  0-008  of  a  line,  and  are  covered 
externally  by  a  layer  of  connective  tissue  with  elastic  fibres. 

The  vessels  of  the  salivary  glands  are  very  numerous,  and  present  the 
ordinary  structure.  The  capillaries  have  a  diameter  of  0-003-0-004  of 
a  line,  and  form  broad  networks  in  which  the  glandular  vesicles  are  im- 
bedded, so  that  each  vesicle  receives  its  blood  from  several  directions. 
A  considerable  number  of  vessels  are  distributed  also  to  the  excretory 
ducts.  Lymphatics  are  found  in  the  salivary  glands,  but  their  internal 


GLANDS    OF    THE     ORAL    CAVITY.  465 

relations  are  unknown.  Nerves  proceed  from  the  plexus  caroticus  ex- 
ternus,  with  the  vessels,  into  the  interior  of  the  glands;  in  addition,  the 
ganglion  linguale  (lingualis  and  chorda  tympani)  supplies  the  two  smaller 
pair  of  glands,  and  the  facial  nerve,  probably  with  the  anterior  auricular, 
the  parotid.  I  may  remark,  with  regard  to  the  distribution  of  these 
numerous  nerves,  that  here  also  it  is  impossible  to  find  any  in  the  smallest 
lobules  of  the  glands,  while  on  the  other  hand  they  are  readily  discovered 
upon  the  larger  vessels  and  the  excretory  ducts.  In  animals  I  found 
particularly  rich  nervous  networks  upon  Rivinis  ducts,  the  tubules 
having  a  diameter  of  0-001-0-002  of  a  line. 

The  secretion  of  the  salivary  glands  normally  contains  no  formed  ele- 
ments, but  may  accidentally  present  cylindrical  cells  from  the  excretory 
ducts,  or  scattered,  half-disorganized  cells  from  the  glandular  vesicles. 
Its  physical  and  chemical  properties,  in  the  different  salivary  glands, 
appear  to  differ  in  some  respects.  The  parotid  saliva  is  clear  and  fluid, 
and,  like  the  glandular  vesicles  themselves,  contains  no  mucus.  Ber- 
nard and  Jacubowitsch  found  the  secretion  of  the  sub-maxillary  gland  in 
the  dog  to  be  viscid,  and  capable  of  being  drawn  out  into  threads  ;  ac- 
cording to  Bernard  also,  a  watery  extract  of  the  gland  itself  contains 
mucus. 

In  man,  the  ductus  Whartonianus,  if  laid  open,  is  usually  found  to 
contain  a  small  quantity  of  a  kind  of  mucous  fluid,  which,  however,  con- 
sists chiefly  of  cylinder  epithelium  and  broken-up  epithelial  cells  of  the 
glandular  vesicles  themselves,  containing  only  a  very  small  amount  of  a 
substance  which  coagulates  in  acetic  acid,  and  is,  perhaps,  mucus.  The 
glandular  vesicles,  on  the  other  hand,  if  crushed,  usually  yield  a  con- 
siderable quantity  of  mucus,  which  coagulates  into  threads  by  the  action 
of  acetic  acid.  The  vesicles  of  the  proper  sublingual  gland  contain 
still  more  mucus,  and  the  ductus  Bartholinianus  also  commonly  presents 
distinct  evidence  of  it.  With  respect  to  Rivinis  ducts,  they  are  filled, 
in  man  and  animals,  with  the  same  yellowish,  viscid,  amorphous  fluid, 
coagulating  into  threads  by  the  action  of  acetic  acid,  which  is  met  with 
in  the  ducts  of  the  small  mucous  glands,  while  the  glandular  vesicles 
themselves  also  contain  abundant  mucus.  From  all  that  has  been  said, 
it  would  seem  i\&iRivims  glands,  as  I  will  call  them,  must  be  excluded 
from  the  class  of  salivary  glands,  and,  as  regards  the  three  larger  glands, 
their  secretion  does  not  appear  to  be  identical,  but  sometimes  to  contain 
mucus  (submaxillary  and  particularly  the  sublingual),  sometimes  to  want 
it  (parotid). 

We  may  take  this  opportunity  of  making  some  observations  with 
respect  to  the  salivary,  or  mucous  corpuscles,  of  authors  ;  rounded  cells 
of  0*005  of  a  line,  with  one  or  many  nuclei,  which  are  always  to  be  met 

30 


466  SPECIAL    HISTOLOGY. 

with  in  the  fluid  of  the  mouth,  and  are  usually  supposed  to  be  derived 
from  the  mucous  or  salivary  glands,  yet  wrongly,  since  the  examination 
of  both  these  kinds  of  glands,  and  of  their  ducts,  teaches  us  that  they 
excrete  no  formed  elements.  In  my  opinion  the  mucous  corpuscles  are 
nothing  but  products  of  the  mucous  membrane  of  the  oral  cavity — not 
normal,  although  they  are  almost  constant,  but  a  kind  of  exudation-  or 
pus-corpuscles,  with  which  they  have,  as  is  well  known,  the  closest  pos- 
sible resemblance  in  structure.  Many  authors  consider  them  to  be 
abortive  epithelial  cells  of  the  oral  cavity ;  but  in  that  case  the  epithe- 
lium of  the  localities  in  which  they  are  found  must  want  the  outermost 
layer  of  large,  flattened  scales,  which  is  ~by  no  means  the  case.  In  my 
own  person,  at  any  rate,  I  find  mucous  corpuscles  on  the  gums,  the  lips, 
cheeks,  and  tongue,  in  localities  in  which  the  epithelium  is  wholly  un- 
injured ;  and  by  scraping  with  a  knife  I  can  often  obtain  entire 
lamellae  of  epithelial  plates,  covered  with  mucous  corpuscles.  I  do  not 
mean  to  affirm  by  this,  that  in  little  sores,  arising  from  whatever  cause, 
upon  the  gum,  for  instance,  where  the  epithelium  is  wholly  or  partly 
wanting,  or  when  it  is  lost  more  extensively,  in  consequence  of  disease, 
that  mucous-  or  exudation-corpuscles  may  not  be  developed,  as  upon 
other  sore  surfaces,  and  then  might  be  regarded  as  abortive  epithelium- 
cells,  but  only,  that  this  does  not  take  place  in  the  oral  cavity  under 
ordinary  circumstances.  I  consider,  therefore,  that  the  so-called  mucus, 
or  salivary  corpuscles,  are  exudation-corpuscles,  and  consequently  totally 
distinct  from  epithelial  cells ;  and  I  regard  their  formation  to  be  analo- 
gous to  that  of  the  pus-corpuscles  in  catarrh,  which  also  very  often  takes 
place  upon  unbroken  epithelial  surfaces.  It  is  thus  readily  explained 
how  it  is  that  they  are  almost  entirely  absent  in  many  individuals,  while 
in  others  who  are  subject  to  irritation  of  the  mucous  membrane  of  the 
mouth  they  are  very  abundant,  and  that  they  have  been  observed  in 
saliva,  obtained  from  a  fistulous  aperture  (Sebastian,  in  "Van  Setten, 
Diss.  de  Saliva."  1837,  p.  12). 

The  best  mode  of  examining  the  oral  mucous  membrane  is  by  making 
perpendicular  sections  of  portions,  either  fresh,  or  dried,  or  hardened 
in  absolute  alcohol,  in  which  the  papillae  and  epithelium  are  very  dis- 
tinct, and  become  still  more  so  by  the  use  of  very  dilute  caustic  soda  ; 
by  the  aid  of  which  also  the  deepest  perpendicular  epithelial  cells  are 
rendered  readily  visible.  The  papillae  may  be  studied  in  macerated 
portions,  or  if  it  be  only  required  to  ascertain  their  position  and  form, 
in  perpendicular  or  horizontal  sections,  treated  with  concentrated  caustic 
potassa,  on  which  the  epithelium  is  dissolved.  The  lingual  papillae  may 
be  treated  in  the  same  manner ;  the  epithelium  upon  which,  especially 
on  the  filiformes,  moreover,  is  often  entirely  absent.  The  nerves  of  all 
these  parts  are  best  seen  under  the  use  of  dilute  caustic  soda ;  acetic 


THE     TEETH.  467 

acid  is  also  frequently  of  service.  The  muscular  substance  of  the  tongue 
must  be  examined  by  minute  dissection,  a  method  which  may  be  car- 
ried very  far,  especially  in  tongues  which  are  half  macerated  from  hav- 
ing long  lain  in  spirit.  Recent  tongues  are  also  of  use,  but  are  by  no 
means  so  good,  and  it  is  usually  necessary  to  boil  them  until  they  are 
quite  soft ;  and  to  procure  sections  for  the  microscope  the  tongue  may 
be  dried  or  hardened  by  boiling,  or  by  strong  alcohol.  In  all  three 
methods  caustic  soda  is  of  great  service  in  clearing  up  the  tissue, 
although  it  undoubtedly  attacks  the  muscular  fibres  a  little.  Perpen- 
dicular and  longitudinal  sections  in  various  directions  are  to  be  recom- 
mended, especially  in  the  glandular  region.  With  respect  to  the  glands, 
the  most  important  points  have  been  already  stated. 

Literature. — W.  Bowman,  Art.  "  Mucous  Membrane,"  in  Todd's 
"  Cyclopaedia  of  Anatomy,"  April,  1842;  E.  H.  Weber,  "  Ueber  die 
Schleimbalge  und  zusammengesetzten  Drh'sen  der  Zunge  und  Uber  den 
Bau  der  Parotis,"  in  Meckel's  "  Archiv,"  1827,  pp.  276-280  ;  A.  Se- 
bastian, "  Recherches  anatomiques,  physiologiques  et  pathologiques  sur 
les  glandes  labiales,"  Groningue,  1842;  Nuhn,  "Ueber  eine  bis  jetzt 
nicht  naher  beschriebene  Druse  im  Innern  der  Zungenspitze,"  Mann- 
heim, 1845  ;  N.  Ward,  Art.  "  Salivary  Glands,"  in  Todd's  "  Cyc.  of 
Anat.,"  Sept.  1848,  part  xxxiii.  p.  421  ;  C.  Rahn,  "Einiges  Uber  die 
Speichelsecretion,"  Zurich,  1850;  C.  Ludwig,  "  Neue  Versuche  Uber 
die  Beihulfe  der  Nerven  zur  Speichelsecretion,"  in  "Mitth.  der  Zurch. 
nat.  Ges.,"  1850,  Nos.  53  and  54,  and  "  Zeitschr.  f.  rat.  Med.,"  1851  ; 
C.  J.  Baur,  "  Ueber  den  Bau  der  Zunge,"  in  Meckel's  "  Archiv," 
1822,  p.  350 ;  P.  N.  Gerdy,  "  De  la  Structure  de  la  Langue,"  in  "  Re- 
cherches d'Anatornie,  de  Physiologic,  et  de  Pathologic,"  Paris,  1823 ; 
P.  F.  Blandin,  "Sur  la  structure  de  la  Langue,"  in  the  "Archiv. 
gener.  de  Medecine,"  1823;  J.  Zaglas  on  the  "Muscular  Structure  of 
the  Tongue  of  Man  and  certain  Mammalia,"  in  the  "  Annals  of  Anatomy 
and  Physiology,"  ed.  by  J.  Goodsir,  1850,  I.  p.  1 ;  H.  Hyde  Salter, 
Art.  "  Tongue,"  in  Todd's  "  Cycl.  of  Anat.,"  iv.  June  and  September, 
1850  ;  C.  B.  Briihl,  "  Ueber  den  Bau  der  Zunge  der  Haussaugethiere," 
in  "  Kleine  Beitrage  zur  Anatomic  d.  Haussaugethiere,"  Wien,  1850, 
pp.  1-6;  Sappey,  "  Ueber  die  Lymphgefasse  der  Zunge,"  in  "  Comptes 
rendus,"  1847,  p.  26;  and  "Froriep's  Notizen,"  1848,  vi.  p.  88. 
Besides  these,  compare  the  anatomical  works  of  E.  H.  Weber,  Valentin 
(im  Handw.  d.  Phys.),  Todd  and  Bowman,  Henle,  Arnold,  Huschke, 
Krause,  and  myself;  the  figures  of  Berres,  Arnold,  and  Langenbeck. 

D.  OF  THE  TEETH. 

§  137.  The  teeth  are  hard  organs  inserted  into  the  alveolar  processes 
of  the  jaws,  which  although  to  some  extent  identical  in  structure  with 


468 


SPECIAL    HISTOLOGY. 


bone,  and  in  other  respects  clearly  allied  to  it,  must,  from  their  develop- 
ment, be  regarded  as  modifications  of  the  mucous  membrane. 

In  every  tooth  we  must  distinguish  the  tooth  proper,  and  the  soft 
structures;  the  former  consists  of  a  free  part,  the  crown,  and  of  an  im- 
bedded portion,  the  simple  or  multiple  fangs,  whose  special  forms  are 
treated  of  in  anatomical  works ;  they  contain  internally  a  small  cavity, 
the  pulp  cavity,  which  extends  through  each  fang  as  an  elongated  canal 
opening  at  its  point  by  a  simple,  or  more  rarely  double  (Havers,  Rasch- 
kow)  fine  aperture. 

Among  the  soft  parts  we  may  enumerate  first,  the  gum,  gingiva,  a 
dense  mass  formed  by  the  union  of  .the  mucous  membrane  and  of  the 
periosteum  of  the  jaw,  which  surrounds  the  lower  half  of  the  crown  or 
the  neck  of  the  tooth.  Secondly,  the  periosteum  of  the  alveolus,  which 


Fig  183. 


unites  the  tooth  very  closely  with 
the  alveolus.  Finally,  the  pulp,  a 
soft,  vascular  and  nervous  mass, 
which  occupies  the  cavity  of  the 
tooth,  and  is  connected  with  the 
periosteum  of  the  alveolus,  through 
the  aperture  in  the  fang. 

The  proper  tooth  (Fig.  183)  con- 
sists of  three  distinct  structures. 
1.  The  dentine,  which  constitutes  its  principal  mass,  and  determines  its 
general  form.  2.  The  enamel,  which  forms  a  tolerably  thick  invest- 
ment to  the  crown ;  and  3.  The  cement,  which  covers  the  fang  exter- 
nally. 

§  138.  The  dentine  or  ivory  (Fig.  183,  d),  is  yellowish-white  and 
translucent  or  transparent,  in  thin  sections  of  a  recent  tooth ;  when  dry 
it  has  a  silky  or  satiny  aspect,  in  consequence  of  the  reception  of  air 
into  a  special  system  of  canals.  It  is  considerably  harder  and  more 


FiG.  183. — Molar  tooth  (human)  ;  magnified  about  5  diameters:  1,  longitudinal ;  2,  trans- 
verse section:  a,  enamel;  6,  pulp  cavity;  c,  cement;  d,  dentine,  with  its  canals. 


THE    TEETH.  469 

brittle  than  either  the  cement  or  hone,  but,  on  the  other  hand,  yields  in 
these  qualities  to  the  enamel.  With  the  exception  of  a  very  small  spot 
in  the  root,  the  dentine  forms  the  sole  boundary  of  the  pulp  cavity,  and 
in  an  uninjured  tooth  it  is  never  exposed,  inasmuch  as  it  is  covered, 
even  upon  the  neck  of  the  tooth,  by  a  thin  layer  of  enamel,  and  when 
this  ceases,  by  cement. 

The  dentine  consists  of  a  matrix  and  of  a  multitude  of  canals  which 
traverse  it,  the  dentinal  tubules  or  canals.  In  the  recent  tooth,  the  for- 
mer is,  even  in  the  finest  sections,  quite  homogeneous,  without  the 
slightest  trace  of  cells,  fibres,  or  other  elements.  After  the  extraction 
of  the  calcareous  salts  from  the  dentine,  it  exhibits,  however,  a  great 
tendency  to  tear  up  into  coarse  fibres,  parallel  to  the  dentinal  canals ; 
from  these,  finer  fibres  of  0-002-0-003  of  a  line  may  be  detached,  their 
irregular  form,  however,  shows  them  to  be  artificial  products,  and  in 
fact  they  owe  their  existence  simply  to  the  circumstance,  that  the  denti- 
nal canals  run  close  together  arid  parallel  to  one  another  through  the 
dentine.  The  matrix  exists  in  all  parts  of  the  dentine,  but  not  every- 
where to  the  same  amount.  In  general  there  is  less  of  it  in  the  crown 
than  in  the  root,  and  in  the  neighborhood  of  the  pulp  cavity  than  in  that 
of  the  enamel  and  cement. 

The  dentinal  canals  (Figs.  184,  187)  are  microscopic  tubules  of  0-0006- 
0-001  of  a  line  (in  the  root  some  reach  0-002  of  a  line),  which  commence 
by  open  mouths  upon  the  wall  of 
the  pulp  cavity,  and  traverse  the 
whole  thickness  of  the  dentine  to 
the  cement  and  enamel.  Each 
canal  has  a  special  wall,  rather  less 
in  thickness  than  its  diameter, 
which  can  only  be  observed  in  trans- 
verse sections  (and  then  not  al- 
ways), as  a  narrow,  yellowish  ring  surrounding  the  cavity;  in  longi- 
tudinal sections,  on  the  other  hand,  it  is  almost  entirely  invisible. 
During  life  the  canals  contain  a  clear  fluid  and  they  cannot  therefore 
readily  be  detected  in  recent  preparations  ;  it  is  different  in  dry  sections, 
when  they  become  filled  with  air,  and  appear  separately  as  black  lines 
by  transmitted  light,  and  by  reflected,  as  silvery  threads.  On  account 
of  the  immense  numbers  of  the  dentinal  canals,  so  great  in  some  situa- 
tions that  their  walls  are  almost  in  contact,  dry  sections  appear  milk- 
white,  and  if  not  very  thin,  are  quite  unfit  for  microscopic  investigation, 
unless  the  air  has  been  previously  expelled  from  the  canals  by  any  clear 
and  not  viscid  fluid. 

FIG.  184. — Transverse   section  of  dentinal  canals  as  they  are  commonly  seen,  magnified 
450  diameters  :  a,  canals  very  close  together  ;  6,  more  dispersed. 


470 


SPECIAL    HISTOLOGY. 


The  dentinal  canals  present  certain  constant  peculiarities  in  their 
course  which  may  be  best  gathered  from  Figs.  185  and  187 ;  it  is  not 
straight  but  wavy,  and  in  addition,  they  present  numerous  ramifi- 

Fig.  185.  piff.  136. 


cations  and  anastomoses.  Each  canal 
describes,  in  general,  two  or  three  large 
curvatures,  and  a  very  great  number  (as 
many  as  200  in  1  line,  according  to 
Retzius)  of  small  curvatures,  which  are 
sometimes  more  or  less  strongly  marked 
and  occasionally  have  even  the  appear- 
ance of  actual  zigzags,  or  spiral  wind- 
ings. The  ramifications  of  the  canals 
(Figs.  185  and  186),  appear  in  the  first 
place  as  divisions,  and  then  as  true  rami- 
fications ;  the  former  are  very  frequently 
to  be  met  with  close  to  the  origin  of  the 
tubules  from  the  pulp  cavity,  and  are 
almost  always  bifurcations,  of  such  a  kind 
that  one  canal  divides  at  an  acute  angle 
into  two  of  almost  the  original  diameter. 
These  divisions  may  be  repeated  2-5 
times  altogether,  and  even  still  oftener, 
so  that  at  last,  4—8—16,  and  even  more 
canals,  proceed  from  a  single  one.  The 
canals,  already  somewhat  narrowed  after 
division,  then  run  close  together  and  tole- 
rably parallel,  towards  the  surface  of  the 
dentine,  and  excepting  in  the  root,  branch 

FlG.  185. — Dentinal  tubules  from  the  root,  magnified  3"0  diameters:  a,  internal  surface  of 
the  dentine,  with  scattered  canals;  6,  their  divisions;  c,  terminations  with  loops;  rf,  granu- 
lar layer,  consisting  of  small  dentinal  globules  at  the  boundary  of  the  dentine;  e,  bone 
lacunae,  one  anastomosing  with  dentinal  canals.  From  Man. 

FIG.  186. — Transverse  section  through  the  dentinal  canals  of  the  root,  a,  in  order  to  ex- 
hibit their  excessively  numerous  anastomoses  ;  magnified  350  diameters.  From  Man. 


THE    TEETH. 


471 


again  only  in  its  outer  half  or  third  ;  the  ramifications  appearing,  in  the 
root,  as  fine  twigs  given  off  from  the  principal  canal,  while  in  the  crown, 
they  more  resemble  dichotomous  divisions.  In  the  latter  case,  they  are  for 
the  most  part  rare,  in  the  former,  it  is  otherwise ;  the  branches,  which 
are  usually  close  together  and  given  off  at  right  or  acute  angles  from 
the  trunk  canal,  having  sometimes  the  appearance  of  a  feather,  some- 
times that  of  a  brush,  the  latter  being  most  common  when  the  twigs  are 
large  and  undergo  further  branchings.  According  to  their  more  or  less 
frequent  ramification,  are  the  ends  of  the  dentinal  canals  more  or  less 
fine ;  frequently  appearing  merely  as  excessively  fine,  pale  lines,  like 
fibrils  of  connective  tissue,  and  finally  disappear.  When  they  are  dis- 
tinct, they  either  become  lost  upon  the  surface  of  the  dentine  in  a  gra- 
nular layer,  which  we  shall  have  to  consider  presently,  or  they  enter  the 
innermost  portions  of  the  enamel  and  cement,  or  finally  they  are  con- 
nected in  pairs  by  loops  in  the  dentine  (terminal  loops  of  the  dentinal 
canals).  The  branches  of  the  principal  canals  are,  almost  always,  very 
fine  and  usually  simple,  though  sometimes  ramified ;  they  serve,  as  may 
be  best  seen  in  the  root,  where  they  are  excessively  numerous,  to  con- 
nect neighboring  or  even  distant  canals  ;  such  anastomoses  having  either 
the  form  of  simple,  transverse  canals  or  of  loops.  The  ultimate  branches 
present  the  same  relations  as  the  forked  or  simple  terminations  of  the 
principal  canals,  and  end  either  free  or  by  loops,  in  the  dentine,  or  are 
continued  beyond  it. 

The  chemical  composition  of  dried  dentine  is,   according   to   Von 
Bibra :— 


Molar  of  a 
Woman  of  25. 


Phosphate  of  lime,  with  some  fluoride 

of  calcium, 

Carbonate  of  lime,          .... 
Phosphate  of  magnesia. 

Salts, 

Cartilage, 

Fat, 


Organic  substance, 
Inorganic  substance, 


100-00 

21-00 
79-00 


Molar  of  a 
Man. 

66-72 
3-36 
1-08 
0-83 

27-61 
0-40 

100-00 

28-01 
71-99 


Incisor  of  the 
same  Man. 


28-70 
71-30 


In  fresh  teeth,  Pepys  found  28  p.  c.  cartilage,  62  inorganic  matter, 
10  water  and  loss ;  and  according  to  Tomes,  teeth,  after  the  pulp  is 
removed,  lose  in  drying  J— TV  of  their  weight.  The  organic  basis  of 
the  teeth,  which  may  readily  be  obtained  by  treating  them  with  hydro- 
chloric acid,  is  identical  in  all  respects  with  that  of  the  bones,  and  is 
readily  changed  into  gelatin  by  boiling.  This  so-called  cartilage  of 


472  SPECIAL    HISTOLOGY. 

the  tooth  retains  the  exact  form  of  the  dentine  and  its  external  struc- 
ture also ;  the  tubules,  however,  are  seen  with  difficulty.  If  it  be 
macerated  in  acids  or  alkalies  until  quite  soft,  the  matrix  undergoes 
incipient  solution,  but  the  dentinal  tubules,  with  their  walls,  offer  greater 
resistance,  and  may  be  readily  and  abundantly  isolated  (see  "  Mikr. 
Anat."  ii.  2,  p.  61,  fig.  189).  By  still  longer  maceration,  all  is  dis- 
solved. If  teeth  be  heated  to  redness,  or  treated  with  caustic  alkalies, 
the  inorganic  portions  likewise  retain  the  form  of  the  tooth.  It  follows, 
then,  that  the  same  intimate  mixture  of  inorganic  and  organic  parts 
occurs  in  the  teeth,  as  in  the  bones,  with  which  they  so  closely  agree 
in  their  chemical  composition. 

The  apparent  walls  of  the  dentinal  tubuli,  which  are  commonly  visible 
in  transverse  sections  (Fig.  184),  are  not  the  actual  walls  of  the  canals, 
but  rings,  which  result  from  our  invariably  viewing  a  certain  length  of 
the  canals  in  the  always  more  or  less  thick  sections,  their  undulated 
course  giving  the  walls  a  greater  apparent  thickness  than  they  really 
possess.  If  in  any  transverse  section  the  apertures  of  the  canals  be 
exactly  brought  into  focus,  we  perceive,  instead  of  the  dark  ring,  only 
a  very  narrow  yellowish  border,  which  is  what  I  consider  to  be  the 
actual  wall.  That  such  is  the  case,  appears  from  the  examination  of 
transverse  and  oblique  sections  of  canals  filled  with  fluid,  in  which  short, 
yellow  tubules  and  small  rings  of  almost  the  same  diameter  as  that  of 
the  cavities  of  the  canals,  may  be  clearly  recognized. 

The  dentine  occasionally  presents  indications  of  lamination  in  the 
form  of  arched  lines  running  more  or  less  parallel  and  at  different  dis- 
tances, often  quite  close  together  (Fig.  187) ;  which  in  transverse  sec- 
tions appear  as  rings,  and  are  especially  distinct  in  the  crown.  These, 
the  contour  lines  of  Owen,*  are  not  the  same  with  the  glistening, 
indistinctly  defined  striae  observed  by  Schreger,  which  run  exactly 

*  [This  is  not  exactly  correct.  The  term  "  contour  lines,"  as  used  by  Professor  Owen 
("Report  of  British  Association"  for  1838,  p.  135,  and  "  Odontography,"  pp.  460,  464,  611), 
includes  both  descriptions  of  markings  mentioned  in  the  text,  but  is  more  especially  em- 
ployed for  Schreger's.  The  ordinary  contour  lines,  in  fact,  are  stated  by  Professor  Owen  to 
proceed  from  "  a  short  bend"  of  the  tubuli  "parallel  with  the  outer  contour  of  the  crown;" 
from  these,  the  Professor  distinguishes  the  "  strong  contour  lines,"  in  the  ivory  of  the  ele- 
phant's tusk,  as  being  produced  by  "  strata  of  extremely  minute  opaque  cellules."  It  should 
be  observed,  however,  that  Retzius  had  long  before  drawn  attention  to  these  peculiar  striae. 
In  his  admirable  memoir,  published  in  Muller's  Archiv,  for  1837,  he  says,  p.  507,  "In  the 
incisor  teeth  of  the  horse,  also,  many  less  transparent  striae  running  parallel  with  the  cavitas 
pulpa  may  be  seen,  like  the  annual  rings  in  the  trunk  of  a  tree.  They  proceeded  in  this 
case,  however,  not  merely  from  certain  parallel  flexures  of  the  tubes,  but  especially  from 
similar  calcareous  cells,  which  had  accumulated  in  one  zone  for  the  greatest  part  of  the  length 
of  the  tooth.  Tab.  xxii  Fig.  3."  See  also  his  explanation  of  the  zones  in  the  Elephant's 
tooth,  at  pp.  510-11. — TRS.] 


THE    TEETH. 


473 


Fig.  187. 


parallel  to  the  pulp  cavity,  and  arise  from  the  primary  curvatures  of  the 
dentinal  canals,  and  which  are  the  ex- 
pression of  the  laminar  mode  of  de- 
posit of  the  dentine.  In  animals  they 
are  at  times  singularly  beautiful,  espe- 
cially in  the  Cetacea  and  Pachyder- 
mata  (Zeuglodon,  Dugong,  Elephant), 
and  also  in  the  Walrus.  Here,  as  well 
as  in  fossil  teeth,  we  very  frequently 
observe  a  breaking  up  of  the  dentine 
into  lamellae  (Owen),  indications  of 
which  may  be  found  also  in  fresh  human 
teeth  and  in  the  dental  cartilage. 

Upon  the  crown,  the  dentinal  canals 
not  unfrequently  pass  for  some  distance 
into  the  enamel,  and  expand  here  and 
there,  into  larger  cavities  (Fig.  191), 
which  should  perhaps  rather  be  regarded 
as  pathological.  Similar  not  quite  nor- 
mal formations  are  the  interglobular 
spaces  in  the  dentine  itself  (Fig.  188). 
Czermak  has  conferred  this  name  upon 
certain  very  irregular  cavities,  bounded 
by  globular  processes  of  the  dentine, 

which  are,  it  may  be  said,  never  entirely  absent  in  the  teeth.  In  the  crown 
they  are  found  most  frequently  in  the  neighborhood  of  the  enamel,  and 

Fig.  188. 


often  form  a  thin  curved  layer,  extending  along  its  whole  inner  surface, 

FIG.  187. — Perpendicular  section  of  the  apex  of  an  incisor  tooth  (human),  magnified  7 
diameters  :  a,  pulp  cavity;  6,  dentine  ;  c,  arched  contour  lines,  with  interglobular  spaces;  d, 
cement ;  e,  enamel,  the  various  directions  of  the  fibres  being  indicated ;  ff,  lines  of  color  of 
the  enamel. 

FIG.  188. — A  morsel  of  dentine  with  dentinal  globules  and  interglobular  spaces  filled 
with  air  between  them;  magnified  350  diameters. 


474  SPECIAL    HISTOLOGY. 

which,  upon  close  examination,  is  seen  to  be  composed  of  a  multitude 
of  thin  layers,  receiving  the  ends  of  the  contour  lines  (Fig.  187).  They 
also  occur,  however,  more  internally,  but  always  in  longitudinal  sections, 
in  lines  which  correspond  with  the  contour  lines.  The  spaces  are  some- 
times very  wide,  intersecting  or  interrupting  in  their  course  many  den- 
tinal  canals  ;  sometimes  they  are  very  small,  so  that  only  a  few  canals 
are  touched  by  them.  In  the  former  case,  their  limits  are  formed  by 
distinct  globular  projections  of  0-002-0-012  of  a  line,  and  more,  which 
are  pierced  by  dentinal  canals,  and  have  precisely  the  same  aspect  as 
the  dentine,  of  which  they  are  obviously  nothing  but  portions;  whilst 
in  the  latter,  such  dentinal  globules,  as  I  will  term  them,  are  not  always 
distinct.  This  is  especially  true  of  the  smallest  spaces,  which,  on 
account  of  their  notched  form,  and  their  communications  with  dentinal 
canals,  might  be  taken  for  osseous  lacunce,  and  indeed  have  been  so 
regarded ;  yet,  at  least  in  the  crown,  it  is  almost  always  easy  to  recog- 
nize their  identity  with  the  larger  spaces.  Greater  difficulty  is  met 
with  upon  the  fang,  where  small  interglobular  spaces  and  globules  form 
a  zone  (the  granular  layer  of  Tomes),  which  often  appears  like  a  layer 
of  small  osseous  lacunae  or  of  simple  granules.  I  have  but  rarely 
observed  actual  lacunce  in  normal  dentine  ;  they  were,  when  present, 
invariably  situated  at  the  boundary  of  the  cement  (Fig.  185) ;  on  the 
other  hand,  interglobular  spaces  and  dentinal  globules  are  to  be  met 
with  in  the  interior  of  the  dentine  of  the  root,  and  with  especial  dis- 
tinctness on  the  walls  of  the  pulp  cavity,  in  which  latter  locality  the 
globules  often  give  rise  to  irregularities  visible  to  the  naked  eye,  or 
even  to  a  botryoidal  appearance.  The  interglobular  spaces  whose  pre- 
sence is  normal  in  developing  teeth,  contain  during  life,  not  fluid,  as 
might  at  first  sight  be  expected,  but  a  soft  substance  resembling  tooth 
cartilage  and  possessing  a  canaliculated  structure,  like  the  dentine  itself. 
It  is  remarkable  that  this  substance  offers  a  greater  resistance  to  long 
maceration  in  hydrochloric  acid  than  the  matrix  of  the  actually  ossified 
tooth,  and  therefore,  like  the  dentinal  canals,  it  may  be  completely 
isolated.  In  sections,  this  interglobular  substance  usually  dries  up  in 
such  a  manner  that  a  cavity  is  produced,  into  which  air  penetrates  ;  it 
is  properly  only  in  reference  to  these,  that  interglobular  spaces  can  be 
spoken  of.  Many  teeth,  indeed,  exhibit  no  interglobular  substance, 
but  they  occasionally  present  the  outlines  of  dentinal  globules,  in  the 
form  of  delicate  arched  lines. 

Dentine  containing  Haversian  canals,  the  so-called  "  vaso-dentine" 
of  Owen,  which  exists  in  many  animals,  is  rarely  found  in  man,  and  I 
am  only  acquainted  with  one  case,  observed  by  Tomes  (1.  c.  p.  225),  in 
which  the  vascular  canals  were  numerous ;  on  the  other  hand,  in  the 
dentine  with  irregular  tubuli,  which  is  formed  in  obliteration  of  the  pulp 
cavity,  we  occasionally  meet  with  scattered  Haversian  canals  and 


THE    TEETH.  475 

rounded  cavities,  like  osseous  lacunae,  constituting  the  so-called  osteo- 
dentine  of  Owen.* 

*  [Considerable  discrepancies  will  be  met  with  if  we  compare  the  various  statements  of 
authors  who  have  described  the  ultimate  structure  of  the  dentine. 

1.  According  to  Retzius,  the  dentine  contains  cells,  but  these  cells,  in  his  view,  are  cavities 
analogous  to  bone  lacuna,  in  which  the  dentinal  canals  terminate. 

2.  Mr.  Nasmyth  took  a  totally  different  view  from  this.     The  matrix,  or,  as  he  calls  it, 
" interfibrous  substance  of  the  dentine,"  is,  he  says,  composed  entirely  of  cells;  but  these 
cells  are  solid  bodies,  lie  between,  and  form  the  boundaries  of  the  canals.     His  "cells"  and 
those  of  Retzius  had  exactly  as  much, or  as  little  relation  to  one  another, as  the  "osteal  cells" 
of  Tomes  and  De  Morgan  (to  which  we  have  referred  in  the  note  to  §  107,  p.  335),  have 
to  osseous  lacunae. 

3.  Professor  Owen  likewise  affirms  that  the  dentine  is  made  up  of"  cells" — his  "  dentinal 
cells," — which,  however,  can  hardly  be  identical  with  Czermak's  "dentine  globules,'  as 
stated  in  the  text.    We  find  it,  in  fact,  somewhat  difficult  to  understand  what  these  "  dentinal 
cells"  are,  inasmuch  as  we  are  unable  to  reconcile  the  various  definitions  of  their  nature 
which  may  be  found  in  the  "  Odontography."     In  the  first  place,  at  p.  462,  it  is  stated,  in  a 
note,  that  "the  true  dentinal  or  calcigerous  cells  include  many  tubes  and  intertubular  spaces, 
and  it  is  much  more  exact  to  say,  that  those  cells  contain  a  tubular  structure,  than  that  the 
interstitial  space  is  cellular."    In  perfect  accordance  with  this,  we  find,  on  referring  to  plate 
J23,  fig.  1,  which  represents  a  section  of  human  dentine,  that  the  "dentinal  cells"  which 
are  marked  d'd',  are  traversed  by  from  seven  to  eleven  dentinal  tubules. 

But  at  p.  403,  the  passage  in  which  reference  is  made  to  this  figure,  runs  thus:  "  the  den- 
tinal cells  of  the  human  tooth  are  subcircular,  about  ^^th  of  an  inch  in  diameter.  They 
seem  most  numerous  from  being  most  conspicuous  near  the  periphery  of  the  dentine,  as 
originally  described  by  me  in  the  dentine  of  the  Crocodile." 

And  in  the  Introduction,  p.  xlvi.  we  find  :  "The  diameter  of  the  dentinal  or  calcified  pri- 
mary cells  of  the  pulp,  is  usually  one-fourth  or  one-half  larger  than  that  of  the  blood-discs 
manifest  in  them." 

Now,  how  is  it  possible,  that  a  body  s^th  of  an  inch  in  diameter,  can  have  passing 
through  it  seven  tubules,  each  of  which  is  jjj^jj^th  of  an  inch  in  diameter?  To  say  nothing 
of  the  circumstance,  that  these  tubules  are  at  the  very  least  y^^th  of  an  inch  apart. 
Halve  the  actual  diameters  of  the  tubules  and  arrange  them  close  together,  and  they  will 
barely  squeeze  into  j^^th  of  an  inch.  We  conclude,  therefore,  as  the  definitions  and  the 
figures  of  these  dentinal  ceils  are  at  variance,  that  we  are  not  justified  in  making  any  defi- 
nite statement  about  them. 

4.  Mr.  Tomes  asserts  in  his  lectures,  that  the  "  intertubular  tissue  is  itself  made  up  of 
minute  granules  closely  united,"  which  pass  into  those  of  his  "granular  layer  ;''  an  opinion 
which  seems  to  us  to  be  most  nearly  in  accordance  with  fact.     We  may  observe,  that  the 
dentine  globules  and  interglobular  spaces  of  Czermak,  had   been  previously  very  carefully 
figured  and  described  by  Mr.  Tomes,  in  his  lectures,  p.  45. 

5.  The  views  of  Czermak  are  stated  in  the  text.     Mr.  James  A.  Salter  (On  certain  Ap- 
pearances occurring   in  the  Dentine,  dependent  on  its  mode  of  Calcification,  "  Quarterly 
Journ.  of  Mic.  Science,"  vol.  I.,  p.  252,  1853),  has  confirmed  Czermak's  results,  and  has 
added  some  very  interesting  observations  of  his  own.     He  considers  that  the  contour  lines, 
which  he  prefers  to  call  "  contour-markings,"  may  arise  from  various  causes,  not  only  from 
those  pointed  out  by  Czermak — curvings  and  local  enlargements  of  the  canals  and  inter- 
lobular  spaces,  but  also  from  a  difference  in  density  without  alteration  of  structure ;  and  he 
states  as  a  general  law,  that  the  curves  of  the  contour  markings  are  in  proportion  to  the 
primary  curves  of  the  dentinal  tubes  at  any  particular  spot,  and  cross  them  at  right  angles. 
No  markings  are  more  divergent  than  the  outline  of  the  tooth,  and  passing  from  within  out- 
ward, they  abut  in  succession  upon  the  external  surface  of  the  dentine,  under  the  enamel 
and  crusta  petrosa,  in  the  form  of  granular  patches.     The  outer  extremities  of  these  patches 


476  SPECIAL    HISTOLOGY. 

§  139.  The  Enamel,  substantia  vitrea,  forms  a  continuous  layer 
investing  the  crown  of  the  tooth ;  it  is  thickest  upon  the  masticating  sur- 
face, and  gradually  diminishes  towards  the  roots  until  at  last  it  termi- 
nates by  a  sharply-defined  or  sometimes  slightly-notched  border,  ceasing 
sooner  upon  the  contiguous  surfaces  of  the  crowns,  than  upon  their  inner 
and  outer  sides.  The  external  surface  of  the  enamel  appears  smooth, 
but  is  always  marked  by  delicate,  close,  transverse  ridges,  among  which 
more  marked  circular  elevations  may  occur.*  A  delicate  membrane, 
discovered  by  Nasmyth,  and  which  I  will  denominate  the  cuticle  of  the 
enamel  [_NasmytJis  membrane,  TttS.],f  entirely  covers,  but  is  so  closely 

look  like  white  rings  on  the  surface  of  the  tooth.  They  are  composed  of  coarse  globular 
dentine,  and  gradually  thin  out  internally  into  mere  streaks.  When  a  tooth  is  macerated  in 
acid,  it  may  be  broken  up  into  cones  (triangles  in  section),  as  Dr.  Sharpey  first  indicated, 
formed  by  the  normal  dentine  between  the  contour  markings.  In  transverse  sections,  the 
cones  become,  of  course,  rings.  Finally,  Mr.  Salter  points  out  that  the  enamel  is  almost  al- 
ways imperfect  opposite  the  "patches1'  at  the  outer  ends  of  the  contour  lines. — TRS/] 

*  [Czermak  (1.  c.  pp.  4,  5)  states  that  the  fine  regular  annular  ridges  and  furrows  upon  the 
surface  of  the  enamel,  characterize  the  permanent  teeth,  and  are  not  present  upon  the  enamel 
of  the  milk  set.  The  ridges  are  closest  at  the  margin  of  the  crown,  and  most  distant  towards 
its  centre,  where  they  finally  disappear.  In  the  space  of  a  line,  there  were,  at  the  margin 
of  the  enamel,  84-72  ridges;  more  internally,  36-30;  and  where  they  began  to  be  indistinct 
only  18-12.— TRS.] 

t  [We  have  ventured  to  substitute  the  name  "  Nasmyth's  membrane,"  for  that  of  the  "cuti- 
cle of  the  enamel,"  used  by  Professor  Kolliker,  inasmuch  as  the  latter  term  gives  a  false  idea 
of  the  relations  of  this  important  structure,  which  is  much  more  than  a  mere  "  cuticle  of  the 
enamel,"  and  is  in  fact,  as  one  of  us  has  already  shown  (Huxley,  On  the  Development  of 
the  Teeth,  "  Quarterly  Journal  of  Mic.  Science,"  vol.  I.  p.  149,  1853),  the  calcified  membrana 
preformativa  of  the  whole  pulp. 

This  structure  was  first  described,  in  its  true  relation  to  the  dental  tissues,  by  Mr.  Nasmyth, 
in  a  memoir  read  before  the  Medical  and  Chirurgical  Society,  in  January,  1839,  and  which, 
illustrated  with  very  good  figures,  was  published  in  the  twenty-second  volume  of  the  So- 
ciety's Transactions  (p.  310-328).  Mr.  Nasmyth  states,  that  his  attention  had  been  drawn  to 
fragments  of  a  membrane  which  he  found  floating  in  the  acid  in  which  teeth  had  been 
macerated  ;  "  after  a  minute  and  careful  examination,  however,  I  was  able  to  demonstrate 
with  the  greatest  certainty,  that  they  were  derived  from  the  external  surface  of  the  enamel, 
and  that  they  were  continuous  with  the  structure  covering  the  fang,  which  latter  is  itself 
continued  into  the  chamber  of  the  tooth.  1  afterwards  succeeded  in  tracing  this  covering  on 
the  whole  surface  of  the  enamel  and  fang  of  the  tooth  in  one  continuous  envelop  ;  and 
eventually,  I  was  enabled  to  remove  it  from  the  crown  of  the  tooth  in  the  form  of  a  distinct 
coat  or  capsule ;  this  covering,  which  I  proved  to  exist  externally  to  the  enamel,  I  have 
termed  'the  persistent  dental  capsule,'"  p.  312. 

"In  all  cases  where  this  covering  has  been  removed  by  means  of  acid,  it  has,  of  course, 
the  appearance  of  a  simple  membrane,  in  consequence  of  the  earthy  deposits  having  been 
dissolved,  and  of  there  being  only  present  the  animal  tissue.  The  structure  and  appearance 
of  the  covering  detached  in  this  manner  from  the  enamel,  are  the  same  in  every  respect  as 
those  observed  in  the  capsule  of  the  unextruded  tooth ;  consisting,  like  it,  of  two  layers,  fibrous 
externally,  and  having  on  its  internal  surface  the  peculiar  reticulated  appearance  common 
to  both,  and  shown  at  Plate  V.  Fig.  6,"  p.  313. 

"On  examining  carefully  fine  sections  of  .several  teeth  under  the  microscope,  I  perceived 
here  also,  that  the  structure  in  question  was  continuous  with  the  crusta  petrosaof  the  fang  of 
the  tooth,"  p.  313. 


THE    TEETH.  477 

united  with,  the  enamel,  that  it  can  be  demonstrated  only  by  the  use  of 
hydrochloric  acid.  According  to  Berzelius  and  Retzius,*  a  similar  mem- 
brane exists  between  the  internal  usually  irregular  surface  of  the  enamel, 
and  the  dentine,  but  I  have  been  unable  to  find  it.  The  enamel  is  bluish, 
transparent  in  thin  sections  and  much  more  brittle  and  harder  than  the 
other  dental  structures,  so  that  it  is  hardly  touched  by  the  knife,  and 
yields  sparks  with  steel  (Nasmyth).  Chemically,  it  may  be  regarded  as 
osseous  substance,  containing  the  smallest  possible  proportion  of  organic 
matter ;  but  whether  the  latter  belong  to  the  class  of  collagenous  sub- 
stances or  not  is  uncertain.  According  to  Von  Bibra,  the  enamel 
contains: — 
P 

From  a  Molar  of  a  From  a  Molar  of 

Woman  25  years  of  age.         an  adult  Man. 

Phosphate  of  lime,  with  some  fluoride  of  cal- 
cium,   81-63 

Carbonate  of  lime, 888 

Phosphate  of  Magnesia,           ....  2'55 

Salts, 0-97 

Cartilage, 5'97 

Fat, a  trace 

100-00  100-00 


Organic  matters, 5'97  3'59 

Inorganic  matters, 94  03  96'51 

The  enamel,  as  its  fibrous  structure  indicates,  consists  entirely  of  the 
so-called  prisms  or  fibres  of  the  enamel  (Fig.  189) ;  long,  solid  prisms 


Mr.  Nasmyth  does  not  distinguish  quite  clearly  in  the  text,  between  the  proper  capsular 
membrane  on  the  fang  and  the  crusta  petrosa  itself,  though  his  figures  (PI.  5,  Figs,  4,  5)  exhibit 
the  two  structures  as  sufficiently  distinct,  and  he  hesitates,  at  p.  316,  to  decide  what  relation 
the  outer  layer  of  pale  yellowish  or  brown  substance  in  the  cement  of  the  teeth  of  the  Elk, 
Ox,  Bradypus,  &c.,  may  have  to  the  "  persistent  capsule." 

We  have  not  retained  Mr.  Nasmyth's  own  term  for  his  discovery,  because,  as  one  of  us 
has  endeavored  to  show  (Huxley,  1.  c.)  while  he  accurately  described  its  relations  to  the 
other  dental  tissues,  he  mistook  its  true  nature.  (See  Appendix,  §  8,  on  the  Development  of 
the  Teeth.)  But,  on  the  other  hand,  as  no  one  has,  before  or  since,  distinctly  described  his 
"persistent  capsule,"  we  have  thought  it  desirable  that  his  name  should  be  associated  with 
the  structure. — TRS.] 

*  [Berzelius  and  Retzius  obviously  saw  Nasmyth's  membrane  (Retzius,  in  Mull.  Archiv, 
1837,  pp.  53,  54).  The  latter  says,  that  on  macerating  a  large  piece  of  enamel  from  the  fossil 
tooth  of  a  horse  (dug  out  of  a  peat-moss)  in  dilute  acid,  he  found  after  the  enamel  was  dis- 
solved, a  membrane  swimming  in  the  fluid,  "  I  examined  it  immediately  under  a  conside- 
rable magnifying  power;  it  appeared  to  be  pierced  by  a  multitude  of  closely  arranged  little 
holes,  but  exhibited  no  trace  of  fibres."  But  he  states  expressly,  that  this  membrane  was 
"internal  to  the  enamel  fibres,  as  Berzelius  clearly  points  out,"  and  therefore  failed  to  recog- 
nize its  true  relations  with  the  enamel. — TRS.] 


478 


SPECIAL    HISTOLOGY. 


Fig.  189. 


cut  with  a  knife. 


Fig.  190. 


of  0-0015-0*0022  of  a  line  in  breadth,  irregular  in  shape,  but  commonly 
hexagonal  or  pentagonal,  which  usually  occupy  the 
whole  thickness  of  the  enamel,  resting  with  one  ex- 
tremity upon  the  dentine,  and  with  the  other  upon 
Nasmyth's  membrane.  In  adult  teeth,  these  elements 
may  be  very  readily  detected  in  transverse  and  longi- 
tudinal sections,  but  can  hardly  be  isolated  for  any 
great  length;  it  is  otherwise  in  young  or  developing 
teeth,  where  the  enamel  is  much  softer  and  may  be 
In  such  isolated  prisms,  whose  broken  ends  may  by 
accident  appear  pointed,  whence  they  have  been  called  "  enamel 
needles,"  the  surfaces  and  edges  may  be  very  well  seen.  We  may  also 
very  frequently  observe  upon  them,  particularly  after  the  addition  of 
dilute  hydrochloric  acid,  more  or  less  distinct  transverse  striae  0-0014- 
0*002  of  a  line  apart,  which  arise  from  slight  varicosities,  and  give  the 
fibres  a  certain  resemblance  to  muscular  bundles,  or  rather  colossal  mus- 
cular fibrils.  They  certainly  do  not 
indicate  a  cellular  composition.  If 
the  action  of  the  hydrochloric  acid 
be  allowed  to  go  on,  the  fibres  soon 
become  quite  pale,  the  transverse 
striation  disappears,  and  nothing  re- 
mains but  a  delicate  framework  cor- 
responding with  the  previously  solid 
fibres,  and  which  often  presents  cer- 
tain appearances  of  tubes.  In  the 
end  this  also  becomes  almost  com- 
pletely destroyed  by  the  action  of 
the  acid,  so  that  in  teeth  which  have 
been  thus  macerated  hardly  any- 
thing remains  of  the  enamel,  which 
does  not,  like  the  dentine,  retain  its  form. 

The  prisms  of  the  enamel  are  united  very  intricately  without  any  in- 
termediate substance.  I  have  not  been  able  to  convince  myself  that 
canals  constantly  exist  between  the  prisms,*  but  it  is  certain  that  cavi- 

FIG.  189. — Surface  of  the  enamel,  with  the  ends  of  the  enamel  prisms,  magnified  350 
diameters.  From  the  Calf. 

FIG.  190.— Enamel  prisms  isolated,  after  the  slight  action  of  hydrochloric  acid;  magni- 
fied 350  diameters.  From  Man. 

*  [With  respect  to  this  point,  opinions  differ;  Todd  and  Bowman  consider  that  canals 
normally  exist  between  the  enamel  prisms.  Tomes  finds  canals  in  the  enamel  prisms  of 
young  animals,  and  sometimes  in  a  part  or  the  whole  length  of  them  in  old  teeth.  Ktflliker 
(Mikr.  Anat.  77)  has  not  yet  observed  any  such  cases.  Czermdk  (I.e.  p.  13)  believes  that, 
in  a  few  cases,  he  has  observed  "  very  numerous  delicate  enamel  tubules  arranged  in  close 
series."— TKS.] 


THE    TEETH. 


479 


Fig.  191. 


ties  of  various  kinds  may  be  not  nufrequently  found  in  the  enamel.  Such, 
for  instance,  are — 1.  The  continuations  of  the  dentinal  canals  into  the 
enamel,  to  which  reference  has  been  made  above,  with  the  elongated 
cavities  at  the  border  of  the  dentine  which  arise  from  their  expansion 
(Fig.  191,  c);  and  2.  The  cleft-like  gaps  in  the  middle  and  external 
portions  of  the  enamel  (Fig.  191),  which  are  not  in  communication  with 
the  preceding,  are  never  entirely  absent  in  any  enamel,  and  often  occur 
in  very  great  numbers,  as  narrower  or  wider  spaces  which,  however, 
never  contain  air. 

The  general  course  of  the  prisms  of  the  enamel  resembles  that  of  the 
dentinal  canals  of  the  crown  of  the  tooth,  but  extensive  flexures  are 
only  to  be  met  with  towards  the  masticating  surface.  Most  of  the 
prisms  extend  through  the  whole  thickness  of  the 
enamel,  but  this  is  not  the  case  with  all.  They 
also  decussate  in  a  peculiar  manner ;  thus,  in 
some  transverse  sections,  wre  observe  annular 
layers  of  prisms,  0-08-O12  of  a  line  thick, 
extending  from  the  dentine  to  the  surface  of  the 
enamel,  and  corresponding  with  fine  circular  lines 
upon  its  exterior  ;  in  each  layer,  all  the  prisms 
take  a  similar,  direction,  which  is  different  from 
that  of  the  prisms  of  the  contiguous  layers,  so 
that  perpendicular  sections  of  such  enamel,  espe- 
cially when  moistened  with  hydrochloric  acid, 
have  a  very  singular  striated  appearance,  arising 
from  the  dark  transverse,  and  clear  longitudinal 
sections  of  the  prisms  being  alternately  presented 
to  the  eye. 

A  similar  decussntion  of  the  prisms  occurs 
constantly  at  the  masticating  surface,  and  here 
the  layers  of  enamel  take  a  generally  annular 
arrangement,  so  that  they  describe  circles,  in  the 
molars,  and  ellipses  in  the  incisor  teeth  ;  however, 
towards  the  centre  of  the  masticating  surface, 
irregularities  occur  which  we  are  not  yet  in  a  condition  to  explain. 
Care  must  be  taken  not  to  confound  the  colorless  strice  which  indicate 
these  peculiar  arrangements  of  the  enamel  fibres,  with  certain  brownish 
lines  or  colored  streaks  which  cross  the  prisms  in  various  directions,  and 
in  perpendicular  sections  appear  like  oblique  ascending  lines  or  arches 
(Fig.  187) ;  in  transverse  sections,  like  circles  in  the  external  layers  of 

Fig.  191. — Dentine  and  enamel,  magnified  350  diameters;  Man  :  a,  cuticle  of  the  enamel 
(Nasmyth's  membrane);  6,  enamel  prisms  with  transverse  markings  and  interposed  clefts; 
c,  larger  cavities  in  the  enamel ;  d,  dentine. 


480  SPECIAL    HISTOLOGY. 

enamel,  rarely  extending  through  its  whole  thickness.     These  I  regard 
as  the  expression  of  the  lamellated  development  of  the  enamel. 

NasmytJis  membrane  is  a  calcified,  structureless  membrane,  0-0004- 
0-0008  of  a  line  thick,  distinguished  by  the  great  resistance  it  offers  to 
chemical  reagents,  and  its  consequent  appropriateness  as  a  defence  for 
the  crown  of  the  tooth.  It  is  not  altered  by  maceration  in  water,  and 
is  not  dissolved  by  boiling  in  water,  concentrated  acetic  acid,  hydro- 
chloric acid,  sulphuric  acid,  and  nitric  acid ;  the  latter  only  renders  it 
yellow.  In  caustic  alkalies  it  remains  unchanged.  Boiled  with  caustic 
potassa  and  soda,  it  becomes  white  and  somewhat  disintegrated,  but  still 
forms  a  connected  mass ;  the  potassa  is  rendered  slightly  turbid  by  the 
addition  of  hydrochloric  acid,  but  clears  with  an  excess.  The  membrane 
burns  with  an  ammoniacal  odor,  and  yields  a  calcareous  spongy  coal. 

§  140.  The  Cement,  substantia  ostoidea,  cementum  (Fig.  185),  is  a 
cortical  layer  of  true  osseous  tissue,  which  covers  the  fangs,  and  in  the 
many-fanged  teeth,  not  uncommonly  unites  them  all  together.  It  com- 
mences where  the  enamel  ceases,  as  a  very  thin  layer,  either  simply 
abutting  upon,  or  slightly  overlapping  it,  increases  in  thickness  lower 
down,  and  finally  attains  its  maximum  at  the  ends  of  the  fangs,  and  on 
the  alveolar  surface  of  the  molar  teeth  between  the  fangs.  Its  internal 
surface  is,  in  man,  very  intimately  united  with  the  dentine,  but  without 
any  connecting  substance,  so  that  frequently,  at  least  under  high  powers, 
the  limit  of  the  two  structures  is  not  altogether  sharply  defined.  The 
external  surface  is  very  closely  surrounded  by  the  periosteum  of  the 
alveolar  cavity,  but  is  not  so  firmly  united  with  the  gum ;  after  the 
removal  of  these  soft  parts  it  is  usually  irregular,  and  is  frequently 
marked  with  annular  striations.  The  cement  is  the  least  hard  of  the 
three  dental  tissues,  and  is,  chemically,  almost  identical  with  bone. 
Von  Bibra  found : — 

In  Man. 

Organic  matters, 29  42 

Inorganic  matters,      .         .         .         .         .         .     70  58 

100-00  10000 

The  latter,  thus  composed : — 

Phosphate  of  lime  and  fluoride  of  calcium, 58-73 

Carbonate  of  lime, ^'22 

Phosphate  of  magnesia, 0'99 

Salts, 0-82 

Cartilage, 31-31 

Fat, 093 

100-00 
The  earthy  salts  are  readily  extracted  from  the  cement  by  acids,  a 


THE    TEETH. 


481 


white  cartilage  remaining,  which  may  easily  be  separated  from  the  den- 
tine, and  usually,  when  boiled,  yields  gelatin. 

Like  bone,  the  cement  consists  of  matrix  and  of  lacunce,  but  rarely 
contains  Haversian  canals  and  vessels.  Besides  these,  peculiar  canals 
analogous  to  those  of  the  dentine  are  found,  and  other  more  abnormal 
cavities. 

The  matrix  is  sometimes  granular,  sometimes  transversely  striated, 
sometimes  amorphous,  and  frequently  laminated  like  bone.  The  lacunce 

Fig.  192. 


resemble  in  all  essential  characters  those  of  the  bones,  so  that  any  de- 
tailed description  may  be  dispensed  with.  They  are  distinguished  only 
by  the  great  variety  which  they  present  in  number,  form,  and  size  (0-005- 
0-02,  even  to  0-03  of  a  line),  and  the  unusual  number  and  length  (as  much 
as  0*03  of  a  line),  of  their  canaliculi.  The  majority  are  oval,  and  lie 
parallel  to  the  axis  of  the  tooth,  others  are  rounded  and  pyriform.  Those 
are  most  remarkable  which  have  a  very  elongated  form^togefher  with  a 
narrow,  canal-like  cavity  (Fig.  185),  inasmuch  as  their  resemblance  to 
the  dentinal  canals  is  unmistakable.  The  canaliculi  often  resemble 
feathers  and  brushes,  and  unless  the  lacunae  are  altogether  isolated, 
connect  them  with  one  another,  and  anastomose  with  the  ends  of  the 
dentinal  canals.  In  the  thinnest  part  of  the  cement,  towards  the  crown, 
the  lacunce  are  invariably  absent ;  they  are  first  met  with,  as  a  rule, 
about  the  middle  of  the  fang,  but  are  here  scattered  and  solitary ;  towards 
the  extremity  their  number  gradually  increases,  and  they  not  unfre- 
quently  take  on  a  very  regular  arrangement,  as  in  the  external  layer  of 
the  long  bones,  lying  in  series  in  the  layers  of  the  cement,  and  sending 
most  of  their  canaliculi  inwards  and  outwards,  so  as  to  give  rise  to  an 
even,  fine,  transverse  striation  of  the  cement.  The  thicker  layers  of 

FIG.  192. — Dentine  and  cement  from  the  middle  of  the  fang  of  an  incisor  tooth:  a,  dentinal 
canals;  6,  interglobular  spaces,  having  the  appearance  of  osseous  lacunce;  c,  smaller  inter- 
globular  spaces ;  d,  commencement  of  the  cement,  with  many  canals  close  together;  e,  its 
lamella*;  /,  lacuna;  g,  canals;  from  Man.  Magnified  350  diameters. 

31 


482 


SPECIAL    HISTOLOGY. 


cement  which  occur  in  old  teeth,  present  immense  quantities  of  lacunae, 
but  these  are  to  a  great  extent  irregular,  and  have  mostly  the  elongated 
rig.  193.  form.  Many  lacunas  are  bordered,  singly 

or  in  groups,  by  a  very  distinct,  clear, 
yellowish,  slightly  undulated  margin, 
which  partially  or  entirely  surrounds 
them ;  it  has  perhaps  some  relation  to 
the  cells  from  which  the  cavities  are 
developed. 

Haver  sian  canals  do  not  occur  in 
young  teeth,  where  the  cement  has  only 
its  normal  thickness  ;  but  they  are  very 
common  in  old  teeth,  especially  molars, 
and  in  hyperostoses  one,  three,  or  more 
enter  the  cement  from  without,  branch 
out  two  or  three  times,  and  then  termi- 
nate in  blind  extremities.  Their  diameter 
is  too  small  (0-005-0-01  of  a  line),  to 
contain  medulla  as  well  as  bloodvessels,  and  they  are  commonly  like 
those  of  the  bones,  surrounded  by  a  few  connective  lamellae.. 

Besides  these  vacuities,  the  cement  occasionally  presents  peculiar 
sinuous  cavities,  which  are  certainly  pathological  products  (see  "  Mikr. 
Anat."  II.  2,  p.  82,  Fig.  202) ;  and  frequently  canals,  like  dentinal 
canals  (Fig.  192),  which  are  sometimes  closely  set,  at  others  more  iso- 
lated, occasionally  ramified,  and  very  frequently  connected  with  the 
ends  of  the  dentinal  canals,  and  with  the  canaliculi  of  the  osseous 
lacunce. 


In  the  cement  of  the  Solipedia,  the  osseous  lacunae  with  their  canali- 
culi, of  the  innermost  layers,  are  frequently  enclosed  within  actual  cells, 
as  Gerber  first  pointed  out.  If  such  cement  be  macerated  in  hydro- 
chloric acid,  these  cells  maybe  readily  isolated,  and  present  the  following 
characters,  which  are  not  unimportant  in  their  bearing  upon  the  nature 
of  the  lacunae.  1.  The  lacunae  frequently  occur  in  twos  and  threes  in  a 
single  cell,  exactly  as  I  have  seen  in  rickety  bones.  2.  The  substance 
which  immediately  surrounds  the  cavities  and  their  processes,  is  not  so 
readily  soluble  in  hydrochloric  acid  as  the  other  parts  of  the  thickened 
cell.  In  fact,  while  the  cells  appear  generally  pale,  a  dark  notched  body, 
which  often  contains  a  very  distinct  cavity,  is  very  obvious  in  their 
interior  ;  and  as  we  see  by  comparing  it  with  these  lacunae  of  the  cement, 
the  contours  of  whose  cells  are  no  longer  visible,  is  nothing  else  than 
the  innermost  portion  of  the  thickened  wall  of  the  original  cell.  In  the 

FIG.  193. — Cement  and  dentine  of  the  root  of  an  old  tooth  :  a,  pulp  cavity  j  6,  dentine  ;  c, 
cement,  with  lacunae;  c,  Haversian  canals.  From  Man. 


THE    TEETH.  483 

last-mentioned  lacunae,  in  fact,  it  is  easy  to  demonstrate,  by  the  aid  of 
acetic  acid,  a  special  wall,  which  is  at  first  thick,  but  subsequently 
becomes  thinner ;  and  occasionally  such  lacunae,  with  walls  which  give 
off  a  few  processes  externally,  may  be  isolated.  These  lacunae  are  fre- 
quently empty,  but  in  other  cases  they  contain  a  substance  which  at 
first  also  resists  hydrochloric  acid,  wherein,  however,  I  could  discover  no 
nucleus.* 

§  141.  The  soft  parts  of  the  teeth  are :  the  periosteum  of  the  alveolus,  the 
dental  pulp,  and  the  gum.  The  periosteum  of  the  alveolus  is  very  inti- 
mately connected  with  the  fangs  of  the  tooth,  and  has  the  same  structure 
as  any  other  periosteum,  except  that  it  is  softer,  contains  no  elastic  ele- 
ment, and  possesses  an  abundant  nervous  network,  containing  many  thick 
fibres. 

The  dental  pufy — the  remains  of  the  foetal  dental  papilla — arises  from 
the  periosteum  at  the  bottom  of  the  alveolus,  enters  the  fangs,  and,  as  a 
continuous,  soft,  reddish,  very  vascular  and  nervous  substance,  fills  their 
canals  and  the  pulp  cavity  in  such  a  manner  as  to  be  everywhere  in  close 
adherence  to  the  inner  surface  of  the  dentine.  The  pulp  consists  of  an 
indistinctly  fibrous  connective  tissue,  totally  destitute  of  the  elastic  ele- 
ment, but  containing  many  dispersed,  round  and  elongated  nuclei ;  and 
except  that  it  occasionally  contains  narrow  bundles,  almost  like  imper- 
fect foetal  connective  tissue.  A  fluid  may  be  expressed  from  it  which, 
like  mucus,  is  coagulated  by  acetic  acid  and  is  not  dissolved  in  an  excess  ; 
and,  similarly,  the  entire  pulp  is  rendered  whitish  by  acetic  acid,  never 
becoming  transparent  like  perfect  connective  tissue.  This  substance 
constitutes  the  principal  mass  of  the  pulp,  so  far  as  the  vessels  and 
nerves  extend  ;  but  upon  its  surface  we  find,  immediately  beneath  a  deli- 
cate structureless  membrane,  a  layer  of  0-02-0-04  of  a  line  thick,  com- 
posed of  many  series  of  cells,  0-012  of  a  line  long,  0-002-0-003  of  a  line 
broad,  cylindrical  or  pointed  at  one  end,  with  long  narrow  nucleo- 
lated  nuclei  of  0-005  of  a  line,  arranged  perpendicularly  to  the 
surface  of  the  pulp  like  a  cylinder  epithelium.  More  internally  these 
regular  series  are  no  longer  recognizable,  but  the  cells,  without  losing 
their  close  radial  arrangement,  are  more  intermixed,  and  pass,  finally, 

*  [The  structure  of  the  cement  on  the  fang  of  the  still  uncut  molar  of  the  calf,  is  very 
peculiar  and  instructive.  It  is  here  a  white,  friable  substance,  about  Jff  of  an  inch  thick, 
bounded  externally  by  a  delicate  Nasmyth's  membrane.  Its  outer  three-fourths  are  com- 
posed of  straight  parallel  fibres,  resembling  those  of  the  enamel,  but  ^  of  an  inch  long.  The 
inner  fourth  consists  of  similar  fibres  inextricably  interlaced,  cemented  into  a  mass  by  a  cal- 
careous deposit,  and  containing  here  and  there,  spaces  or  lacunae,  y^1^  of  an  inch  in  length, 
as  it  were  left  among  the  fibres.  This  structure  appears  to  become  obliterated  with  age,  as 
the  cement  on  the  fang  of  the  molar  immediately  in  front  of  this,  which  had  cut  the  gum, 
had  the  ordinary  appearance.  (Huxley,  1.  c.) — TRS.] 


484  SPECIAL    HISTOLOGY. 

by  shorter  and  rounder  cells,  without  any  sharp  lines  of  demarcation, 
into  the  vascular  tissue  of  the  pulp.  These  cells  corespond  with  the 
formative  cells  of  the  dentine,  to  be  described  presently,  and  they  afford 
the  materials  for  the  deposits  of  dentine  upon  the  walls  of  the  pulp 
cavity,  which  takes  place  even  in  the  adult. 

The  vessels  of  the  pulp  are  excessively  numerous,  whence  its  red  color. 
3-10  small  arteries  enter  each  pulp  of  a  simple  tooth,  and  ultimately 
form,  as  well  in  its  interior  as  upon  its  surface,  a  loose  plexus  of  capil- 
laries, 0-004-0-006  of  a  line  in  diameter,  which  also  exhibits  here  and 
there  upon  the  surface  distinct  loops  from  which  the  veins  arise.  The 
pulp  appears  to  contain  no  lymphatics,  but  its  nerves*  are  extremely 
abundant.  Arising  from  the  well-known  nervi  dentales,  there  passes 
into  every  fang  a  large  trunk  of  0-03-0-04,  and  besides,  as  many  as  six 
or  more,  fine  branches  of  0-01-0-02  of  a  line,  which  contain  fibres  of 
0-0016-0-003  of  a  line.  They  ascend  at  first  without  any  considerable 
anastomoses  and  only  giving  off  a  few  filaments  ;  but  in  the  thicker  part 
of  the  pulp  they  form  a  rich  plexus,  with  elongated  meshes  and  divisions 
of  the  nerve  tubules,  and  so  gradually  break  up  into  fine  primitive 
fibres  of  0-001-0-0016  of  a  line.  I  am  inclined  to  think  their  final 
termination  is  in  loops,  but  I  grant  that  so  long  as  the  primitive  fibrils 
in  those  loops  which  unquestionably  do  occur,  have  not  been  traced  from 
trunk  to  trunk,  which  no  one  has  yet  done,  the  subject  is  open  to  doubt. 

The  gum,  yingiva,  that  portion  of  the  oral  mucous  membrane  which 
unites  the  alveolar  margins  of  the  jaw  and  the  necks  of  the  teeth,  is  a 
pale  red  vascular  tissue,  which  is  tolerably  soft,  but  feels  firm  on  ac- 
count of  the  subjacent  hard  parts :  it,  attains,  where  it  lies  upon  the 
teeth,  a  thickness  of  J-l  J  lines,  and  possesses  papillae  of  a  considerable 
size  (of  0-15-0-3  of  a  line;  in  old  people  they  even  reach  0-7  of  a  line 
in  length,  and  like  the  papillce  filiformes  are  covered  with  secondary 
papillae),  and  a  pavement  epithelium,  which,  between  the  papillae,  has  a 
thickness  of  0-23-0-4  of  a  line.  I  could  find  no  glands  upon  the  gum, 
but  care  must  be  taken  not  to  confound  with  them  certain  rounded  de- 
pressions of  the  epithelium  of  0'8-0-15  of  a  line  in  diameter,  with 
more  cornified  cells,  which  occur  not  unfrequently  upon  its  upper  por- 
tions. 

§  142.  Development  of  the  Teeth. — The  development  of  the  twenty 
milk  teeth  commences  in  the  sixth  week  of  foetal  life,  by  the  formation 
of  a  groove  in  the  upper  and  lower  margin  of  the  jaws,  in  which, 
up  till  the  tenth  week,  twenty  dental  papillae  gradually  make  their  ap- 

*  [The  nerves  of  the  alveolar  periosteum  and  of  the  pulp,  are  particularly  described  by 
Czermak  (1.  c.  pp.  27,  28).— TBS.] 


THE    TEETH. 


485 


Fig.  194. 


pearance.     Partitions  are  now  developed,  so  that  each  papilla  soon  lies 

in  a  special  cavity.     In  the  course 

of  the  fourth  month,  these  cavities 

gradually    contract,  the  papillae  at 

the  same  time  assuming  the  forms 

of  the  future  teeth,  and  finally  they 

close  up  completely ;  this  takes  place, 

however,  in  such  a  manner  that  a 

little  cavity  is  developed  above  each 

"  tooth-sac,"    and     thus    "  reserve 

sacs,"  in  which  the  pulp  begins  to 

be  developed  in  the  course  of  the 

fifth   month,    are    formed    for    the 

twenty  anterior  permanent  teeth. 

Fig.  195. 


These  "reserve  sacs"  at  first  lie  above  the  milk  sacs,  but  by  degrees 
they  retreat  backwards,  and  are  received  into  hollows  of  the  bony  alveoli 
as  they  are  formed  round  the  milk  teeth  (Fig.  195,  g,  h).  Those  of  the 
incisors  and  canines  eventually  become  completely  separated  from  the 

FIG.  194.— Lower  jaw  of  a  human  foetus,  nine  weeks  old,  magnified  9  diameters:  a, 
the  tongue  thrown  back;  6,  right  half  of  the  lip  depressed;  bf,  left  half  of  the  lip  cut  off; 
c,  outer  alveolar  wall;  d,  inner  alveolar  wall;  e,  papilla  of  the  first  molar;  /,  papilla  of  the 
canine;  g,  of  the  second  ;  A,  of  the  first  incisor;  i,  folds  where  the  ductus  Rimniani  subse- 
quently open. 

FIG.  195. — Diagram  of  the  development  of  a  milk-tooth,  and  of  its  corresponding  perma- 
nent tooth,  after  Goodsir :  a,  dental  furrow;  b,  the  same,  "with  its  papilla;  c,  the  same  begin- 
ning to  close,  with  the  rudiment  of  the  reserve  cavity;  rf,  the  same,  still  more  closed  ;  e,  tooth, 
sac  completed,  with  a  "  reserve  cavity ;"_/",  the  reserve  cavity  moving  backwards;  g.  the  same 
become  quite  posterior,  with  a  pulp;  h,  the  alveoli  of  both  sacs  are  forming,  the  milk-tooth 
has  emerged  ;  i,  the  permanent  tooth  forming,  its  deeper  seated  sac  has  a  gubcrnaculum. 


486  SPECIAL     HISTOLOGY. 

alveoli  of  the  corresponding  milk  teeth,  but  those  of  the  premolars*  open 
into  the  bottom  of  the  alveoli  of  the  deciduous  molars. 

The  sacs  of  all  these  teeth  are  produced  at  their  apices  into  a  solid 
cord,  which  extends  either  to  the  gum,  or,  as  in  the  two  premolars,  to 
the  periosteum  in  the  bottom  of  the  alveoli  of  the  two  deciduous  molars 
(Fig.  195,  i),  and  has  been  erroneously  described  as  a  gubernaculum,  or 
guiding  cord  for  the  teeth  in  their  eruption. 

The  sac  of  the  anterior  of  the  three  permanent  molars,  arises,  together 
with  its  papilla,  in  the  sixteenth  or  seventeenth  week,  quite  indepen- 
dently, from  the  posterior  extremity  of  the  primitive  dental  groove,  and 
closes  in  such  a  manner  that  a  reserve  sac  remains  between  it  and  the 
mucous  membrane  (Mikr.  Anat.  Fig.  206).  It  is  not  till  the  seventh  or 
eighth  month  after  birth  that  the  latter  elongates  behind  the  first  sac, 
arches  into  the  margin  of  the  jaw,  produces  a  papilla  from  its  base,  and 
becomes  constricted  off  into  the  sac  of  the  second  molar.  The  remainder 
of  the  cavity  falls  into  a  line  with  the  other  sacs,  and  forms  that  of  the 
wisdom  tooth. 

The  formation  of  milk  teeth  begins  at  about  the  fifth  month  of  foetal 
life,  and  at  the  seventh,  ossification  has  commenced  in  all  of  them.  The 
first  step  is  the  formation  of  a  little  scale  of  dentine  upon  the  apex  of 
the  pulp ;  in  the  molar  teeth  there  are  at  first  several  of  these  scales, 
corresponding  with  the  several  elevations  of  the  pulp,  but  they  soon  coa- 
lesce. Immediately  after  the  appearance  of  this  dentinal  scale,  a  thin 
layer  of  enamel  is  deposited  from  the  so-called  enamel  organ  upon  the 
roof  of  the  sac,  and  which  coalescing  with  the  dentine,  forms  the  first 
rudiment  of  the  crown  of  the  teeth.  The  scale  of  dentine  extends  over 
the  pulp  and  becomes  thicker,  so  that  it  soon  rests  like  a  cap  upon  the 
pulp,  and  finally  forms  a  sort  of  capsule  for  it,  which,  as  ossification 
proceeds  and  the  pulp  diminishes,  closely  and  completely  embraces  it ; 
the  deposition  of  enamel  goes  on  simultaneously,  so  that  it  soon  proceeds 
from  the  entire  surface  of  the  enamel  organ,  and  becomes  more  and  more 

*  [Instead  of  the  loose  phraseology  "  small  "  and  "  large  "  molars,  £c.,  we  have  adopted 
the  philosophical  nomenclature  of  the  teeth,  introduced  by  Professor  Owen  (see  his  Article 
on  the  Teeth,  in  Todd's  Cyclopaedia),  and  thus  explained  by  him  :  "  Those  teeth  which  are 
implanted  in  the  premaxillary  bones,  and  in  the  corresponding  part  of  the  lower  jaw,  are 
called  '  incisors,'  whatever  be  their  shape  or  size ;  the  tooth  in  the  maxillary  bone,  which  is 
situated  at  or  near  to  the  suture  with  the  premaxillary,  is  the  '  canine,'  as  is  also  that  tooth 
in  the  lower  jaw,  which  in  opposing  it,  passes  in  front  of  its  crown  when  the  mouth  is  closed. 
The  other  teeth  of  the  first  set,  are  the  'deciduous  molars;'  the  teeth  which  displaces  them 
vertically,  are  the  '  premolars  :'  the  more  posterior  teeth  which  are  not  displaced  by  vertical 
successors,  are  the  molars  properly  so  called." 

It  results  from  this,  that  the  so-called  bicuspid  and  "first  molar  "  of  the  permanent  set  in 
man  (Professor  Ko'lliker's  "  small  molars  ")  are  the  premolars  ;  being,  in  fact,  the  third  and 
fourth  of  the  typical  dentition ;  the  first  and  second  premolars  and  the  third  incisor  of  the 
typical  dentition,  not  being  developed  in  man.  The  nomenclature  of  the  teeth,  from  being 
merely  technical  and  arbitrary,  has  thus,  by  Professor  Owen's  recourse  to  development 
become  scientific. — TRS.] 


THE    TEETH.  487 

considerable.  In  this  manner,  the  whole  enamel  is  eventually  deposited 
around  the  dentinal  layer  of  the  crown,  while  the  enamel  organ  and  the 
pulp  gradually  diminish,  until  the  former  is  represented  only  by  a  deli- 
cate membrane  ;  and  the  latter  presents  similar  relations  to  that  of  the 
perfect  tooth.  As  yet  there  exists  no  trace  of  either  fang  or  cement ; 
they  are  not  formed  till  the  crown  is  nearly  complete,  and  the  tooth  is 
about  to  emerge.  About  this  time  the  pulp  undergoes  a  considerable 
longitudinal  growth,  while  the  enamel  organ  becomes  atrophied ;  and 
upon  the  newly  formed  portion  only  dentine,  that  of  the  fang,  is  de- 
veloped. The  tooth,  thus  forced  upwards,  begins  to  press  against  the 
upper  wall  of  its  sac,  and  the  firm  gum  which  is  closely  united  with  it; 
in  which  an  independent  process  of  absorption  also  takes  place,  and  the 
tooth  finally  makes  its  appearance.  The  gum  now  contracts  around  it, 
and  the  rest  of  the  dental  sac  becomes  closely  applied  to  the  fang,  and 
constitutes  the  alveolar  periosteum. 

The  milk-tooth  attains  completeness  :  1,  by  the  addition  of  the 
remainder  of  the  fang,  and  the  constant  elevation  of  the  crown  to  its 
normal  length ;  and  2,  by  a  deposition  which  takes  place  from  the  sac, 
now  united  with  the  alveolar  periosteum,  which  commenced  even  before 
eruption,  and  by  which  the  cement  is  applied  around  the  fang,  while  at 
the  same  time  the  tooth  is  thickened  by  internal  deposition,  the  pulp 
diminishing  to  a  corresponding  extent.  In  teeth  with  several  fangs,  the 
pulp,  which  is  at  first  simple,  divides  as  it  elongates,  near  its  point  of 
attachment,  a  separate  fang  being  developed  around  each  portion.  The 
eruption  of  the  milk  teeth  takes  place  in  the  following  order :  central 
incisors  of  the  lower  jaw  in  the  6th — 8th  month ;  central  incisors  of  the 
upper  jaw  a  few  weeks  later ;  lateral  incisors  in  the  7th — 9th  month, 
those  of  the  lower  jaw  first ;  anterior  molars  in  the  12th — 14th  month, 
those  of  the  lower  jaw  first;  canine  in  the  16th — 20th  month;  second 
molars  between  the  20th  and  30th  months. 

The  permanent  teeth  are  developed  in  precisely  the  same  way  as  the 
milk-teeth.  Their  ossification  begins,  somewhat  antecedent  to  birth, 
in  the  first  molar,  extends,  in  the  first,  second,  and  third  years,  to  the 
incisors,  canines,  and  premolars,  and  finally  reaches  the  second  molar  ; 
so  that  in  the  6th — 7th  year  there  are  48  teeth  co-existing  in  the  two 
jaws,  i.  e.,  twenty  milk  teeth,  and  all  the  permanent  set  with  the  excep- 
tion of  the  wisdom  teeth  (third  molar).  When  the  shedding  of  the 
teeth  takes  place,  the  bony  partitions  which  separate  the  alveoli  of  the 
permanent  from  those  of  the  milk  teeth  are  absorbed,  and  at  the  same 
time  the  fangs  of  the  latter  gradually  disappear  from  below  in  a  manner 
which  is  not  yet  understood.  The  permanent  teeth,  whose  fangs  in  the 
meanwhile  have  elongated,  thus  become  placed  immediately  under  the 
loosened  crowns  of  the  milk  teeth,  which  finally,  as  the  others  protrude, 
fall  out  and  make  way  for  them.  The  permanent  teeth  emerge  in  the 


488 


SPECIAL    HISTOLOGY. 


following  order  :  first  molar  in  the  seventh  year,  inner  incisor  in  the 
eighth  year,  lateral  incisor  in  the  ninth  year,  first  premolar  in  the  tenth 
year,  second  premolar  in  the  eleventh  year,  canine  in  the  twelfth  year, 
second  molar  in  the  thirteenth  year,  third  molar  (wisdom  tooth),  between 
the  seventeenth  and  nineteenth  years. 

The  gum  in  the  foetus,  and  especially  in  newly  born  infants  before 
the  eruption  of  the  milk  teeth,  is  whitish  and  very  firm,  almost  cartila- 
ginous, whence  perhaps  it  has  also  been  called  gum-cartilage,  although 
it  has  not  the  slightest  resemblance  to  cartilage  in  structure,  but  consists 
of  the  ordinary  elements  of  mucous  membrane,  but  with  a  considerable 
admixture  of  a  more  tendinous  tissue.  The  bodies  of  the  size  of  millet- 
seed,  contained  in  it,  described  by  Serres,  the  so-called  glandules 


Fig.  196. 


tartaricce,  which  are  supposed  to  secrete  the  "  tartar  "  of  the  teeth,  are 
aggregations  of  epithelium,  and  are  probably  pathological*  (see  Mikr. 
Anat.  II.  2,  p.  92). 

The  dental  sacs  consist  of  connective  tissue,  in  which  vessels  and  nerves 
are  distributed ;  from  their  base  proceeds  the  dental  pulp,  which,  in 

FIG.  190. — A,  tooth-sac  of  the  second  incisor  of  an  eight-months'  foetus,  from  the  broad 
surface,  magnified  7  diameters:  a,  dental  sac;  6,  enamel  pulp;  c,  enamel  membrane;  c/, 
enamel ;  e,  dentine  ;  /,  dentinal  cells  ;  g,  limits  of  the  cap  of  the  dentine:  h,  dental  pulp  ;  i, 
free  edge  of  the  enamel  organ.  JB,  first  incisor  of  the  same  embryo  from  the  narrow  surface  : 
letters  as  before;  a,  dentinal  cap  in  toto  •  k,  nerves  and  vessels  of  the  pulp. 

*  [They  have  a  diameter  of  from  0  24-0- 30  of  a  line,  and  are  composed  throughout  of 
numerous  concentric  layers  of  ordinary  epithelial  plates,  or  of  softer  scales,  with  cholesterine 
crystals  and  granules.  Besides  these,  microscopic  bodies  of  0'02-0'12  of  a  line,  soft,  and 
with  only  indications  of  lamination,  are  found  in  the  gum  (Ko'lliker,  1.  c.).  The  true  nature 
of  these  glands  was  pointed  out  by  Purkinjeand  Raschkow. — TBS.] 


THE    TEETH. 


489 


Fig.  197. 


form,  resembles  the  tooth  to  which  it  belongs,  and  consists  of  an  internal 
portion  rich  in  vessels,  and  eventually  in  nerves  also,  and  of  a  non- 
vascular  external  portion.  The  latter  is  bounded  by  a  delicate  structure- 
less membrane,  the  membrana  prceformativa  (Raschkow),  which  has  no 
further  relation  to  the  development  of  the  tooth.  Beneath  this,  lie 
cells  of  0-016-0-024  of  a  line  in  length,  and  0-002-0-0045  of  a  line  in 
breadth,  with  very  beautiful,  vesicular  nuclei,  and  distinct,  single  or 
multiple  nucleoli ;  they  are  arranged  close  together  over  the  whole 
surface  of  the  pulp  (Fig.  197),  like  an  epithelium,  though  not  so  sharply 
defined  internally  as  it  would  be,  but 
gradually  passing,  at  least  apparently, 
by  smaller  cells,  into  the  parenchyma. 
In  vascular  pulps  (Fig.  197),  an  addi- 
tional boundary  line  may  be  traced,  inas- 
much as  the  capillary  loops  in  which  the 
vessels  terminate,  do  not  penetrate  be- 
tween the  cylindrical  cells,  but  end  close 
to  one  another  upon  their  inner  surface ; 
so  that,  considering  that  the  dentine  is 
produced  by  the  cells  in  question,  we 
might  be  justified  in  terming  them  the 
dentinal  membrane,  or  membrana  eboris. 
The  internal  portions  of  the  pulp  consist 
throughout  of  an  originally  granular  or  homogeneous,  afterwards  more 
fibrous  matrix,  containing  many  rounded  or  elongated  nuclei,  wrhich 
must  be  regarded  as  a  sort  of  connective  tissue.  Vessels  are  developed 
in  great  numbers  in  the  pulp  at  the  period  when  ossification  commences ; 
the  most  numerous  perpendicular  loops  of  capillaries  of  about  0-006  of 
a  line  existing  in  contiguity  with  the  ossifying  surface.  The  nerves 
accompany  the  vessels,  but  are  developed  later ;  their  number  is  very 
considerable  and  their  distribution  resembles  that  in  the  pulp  of  the 
perfect  tooth. 

The  enamel  organ  (organ  adamantince),  is  applied  to  the  pulp  like  a 
cap  by  its  internal,  concave  surface,  and  is  connected  externally  with 
the  dental  sac,  in  such  a  manner,  however,  that  at  the  base  of  the  pulp 
it  presents  a  very  small  free  edge.  Its  structure  is  very  peculiar.  The 
principal  mass  consists  of  anastomosing  stellate  cells  (Fig.  196,  5),  or 
reticulated  connective  tissue,  containing  in  its  meshes  a  great  quantity 
of  fluid,  rich  in  albumen  and  mucus.  This  gelatinous  connective  tissue 
is  most  abundant  immediately  before  the  commencement  of  ossification, 
and  in  its  earliest  stages.  Thus,  in  the  fifth  and  sixth  months  it  mea- 
sures TV-3  of  a  line ;  in  the  new-born  infant,  on  the  other  hand,  only 

FIG.  197. — Surface  of  the  dentinal  pulp  of  a  newly-born  infant:  a,  dentinal  cells;  6,  their 
appendages;  c,  vascular  part  of  the  pulp  ;  magnified  300  diameters. 


490  SPECIAL    HISTOLOGY. 

0-16-0*2  of  a  line.  At  this  period  it  contains  vessels  in  its  outer  third 
and  its  network  is  metamorphosed  into  true  connective  tissue  (Mikr. 
Anat.  ii.  Fig.  211).  On  the  inner  side  of  the  spongy  tissue  of  the 
enamel  organ,  lies  the  so-called  enamel  membrane,  membrana  adaman- 
tince  (Raschkow),  a  true  cylinder  epithelium,  of  which  it  need  only  be 
said  that  its  cells  measure  0§012  of  a  line  in  length,  and  0-002  of  a  line 
in  breadth,  are  finely  granular  and  delicate,  and  possess  nuclei  fre- 
quently situated  at  the  ends  of  the  cells. 

The  development  of  the  dental  tissues  has,  hitherto,  always  been  re- 
garded as  a  very  difficult  subject.  The  simplest  relations  are  presented 
in  the  enamel,  where  there  can  be  no  doubt  whatever  that  the  enamel- 
cells  become,  by  their  complete  ossification,  the  enamel-fibres.  As  soon 
as  only  a  small  portion  of  the  cells  has  become  ossified  (without  the 
previous  deposit  of  calcareous  matter  in  a  granular  form),  a  little  scale 
of  enamel  is  recognizable  upon  the  somewhat  larger  cap  of  dentine, 
which  has  also  just  been  produced.  The  deposition  of  calcareous  mat- 
ter in  the  cells  constantly  advances  outwards,  until  at  last  they  are  en- 
tirely converted  into  enamel  fibres,  and  extends  at  the  same  time  to 
other  cells,  so  that  the  layer  of  enamel  increases  in  width.  During  this 
process,  the  enamel  membrane  does  not  disappear  in  the  locality  in 
which  ossification  commenced,  but  retains,  there  and  elsewhere,  the 
same  thickness,  so  long  as  the  deposition  of  enamel  continues :  its  ossi- 
fying part,  therefore,  must  be  replaced  by  the  incessant  development  of 
new  substance,  which  takes  place  apparently,  not  by  the  apposition  of 
new  cells,  but  by  the  continual  growth  of  the  old  ones.  The  enamel 
organ  has  assuredly  some  very  important  relation  to  the  development 
of  the  enamel ;  probably  serving  by  the  abundance  of  albumen  and  of 
mucus  in  its  meshes,  as  a  storehouse,  out  of  which  the  enamel  membrane, 
distant  as  it  is  from  bloodvessels,  is  enabled  to  draw  the  materials  for 
its  increase.  In  fact,  the  spongy  tissue  is  seen  to  decrease  more  and 
more  during  the  development  of  the  enamel,  and  finally,  when  the 
enamel  is  complete,  to  disappear. 

In  the  development  of  the  dentine,  as  in  that  of  the  enamel,  it  is  not 
the  whole  pulp  which  shares  in  the  process,  but  only  its  most  external, 
epithelium-like  layer  of  cells,  which  appears  to  maintain  a  constant 
thickness  by  the  elongation  of  the  original  cells,  accompanied  by  a  con- 
tinual multiplication  of  their  nuclei  (Mikr.  Anat.  ii.  2,  p.  103  et  seq.) 
I  by  no  means  intend  to  assert  that  one  and  the  same  cell  suffices  for  the 
whole  duration  of  the  development  of  the  dentine,  although  this  is  not 
at  all  inconceivable;  indeed,  I  consider  it  possible  that  the  dental  cells 
are  from  time  to  time  replaced  by  others,  which  are  formed  upon  their 
inner  surface ;  but  what  I  deny  is,  that  the  whole  pulp  is  simply  changed 
progressively,  from  without  inwards,  into  dentinal  cells  and  ossified,  and 
I  am  of  opinion  that,  like  the  spongy  tissue  of  the  enamel  organ,  the 


THE    TEETH.  491 

only  import  of  the  pulp  in  the  development  of  the  dentine  is  to  sup- 
port the  vessels  which  are  necessary  to  enable  the  dentinal  cells  to  grow 
at  all. 

The  diminution  of  the  pulp,  therefore,  is  very  readily  intelligible 
without  supposing  it  to  be  ossified  from  without  inwards ;  it  takes  place, 
like  the  diminution  of  the  contents  of  the  wide  Haversian  canals  of 
foetal  bones  when  the  lamellae  are  deposited  upon  their  walls,  by  a 
gradual  resorption  of  its  tissue,  which,  as  in  the  latter  case,  is  soft  and 
full  of  juices;  and  it  is  by  no  means  necessary  to  suppose  any  extensive 
retrogressive  metamorphosis  of  its  vessels. 

With  regard  to  the  formation  of  the  dentine  from  the  dentinal  cells, 
it  is  certain  that  no  other  tissue  than  these  cells  contributes  anything  to 
its  development  and  that  they,  like  those  of  the  enamel  membrane,  be- 
come dentine  by  the  gradual  reception  of  calcareous  salts.  The  dentinal 
tubules  are  either  the  remains  of  the  cavities  of  the  dentinal  cells,  whose 
walls,  in  the  course  of  ossification,  thicken  and  harden  into  them,  but 
do  not  quite  close,  or  they  are  developed  from  the  elongated  and  coalesced 
nuclei  of  the  dentinal  cells  whose  cavity  persists ;  or  finally,  they  are 
the  result  of  a  process  of  resorption  in  the  primarily  homogeneous  den- 
tinal tissue,  analogous  to  the  formation  of  the  Haversian  canals,  or  of 
those  in  the  cement.  Of  these  three  hypotheses,  the  second  would,  at 
first  sight,  appear  the  most  probable,  if  we  consider  that  the  dentinal 
tubules  may  be  isolated,  with  distinct  walls,  that  the  dentinal  cells  are 
abundantly  provided  with  nuclei,  and  that  certain  filiform  prolongations 
of  the  dentinal  cells  which  I  have  noticed  (Figs.  9  and  197,  and  Mikr. 
Anat.,  II.,  2,  p.  105),  might  be  regarded  as  elongated  nuclei ;  but  there 
is  one  very  remarkable  fact,  that  no  trace  of  any  elongation  of  the  nuclei 
can  be  discovered  l>y  the  most  careful  investigation.  The  third  hypo- 
thesis is  indeed  conceivable,  but  in  opposition  to  it,  we  find  that  pores 
and  canals  exist  even  in  the  youngest  and  softest  dentine,  when  the  de- 
velopment of  the  tooth  is  at  all  advanced,  and  therefore,  that  they  can 
hardly  be  regarded  as  secondary  formations.  In  favor  of  the  first  sup- 
position, on  the  other  hand,  it  may  be  said,  that  it  would,  if  true,  indi- 
cate a  close  agreement  between  dentine  and  osseous  tissue,  structures 
which  are  in  every  case  nearly  allied,  inasmuch  as  the  dentinal  tubules 
would  be  homologous  with  long  and  narrow,  simple  or  possibly  coalesced, 
osseous  lacunce.  Certain  objections  may  be  urged,  which  are  not,  per- 
haps, so  important  as  they  at  first  appear.  These  are,  in  the  first  place, 
that  the  dentinal  canals  have  special  walls  and  may  be  isolated  as  tubes, 
which  might  be  regarded  as  demonstrative  evidence  that  they  are  deve- 
loped out  of  peculiar  vesicular  structures,  either  nuclei  or  cells;  and 
secondly,  that  upon  this  supposition,  the  filamentous  appendages  to  the 
dentinal  cells  are  not  so  readily  interpreted.  But  as  regards  the  former, 
we  have  recently  learnt  that  the  osseous  lacunce  and  canaliculi  may  also 


492  SPECIAL    HISTOLOGY. 

be  isolated,  with  special  walls  which  are  not  those  of  the  original  cells, 
and  the  same  is  true  of  the  Haversian  canals,  whence  it  would  be  con- 
ceivable that  the  walls  of  the  dentinal  canals  also,  although  originally 
and  genetically  not  special  structures,  might  eventually  become  so. 
Since,  again,  the  processes  of  the  dentinal  cells  may  be  nothing  else 
than  the  still  soft  part  of  the  cells  in  which  ossification  is  commencing, 
this  first  hypothesis  may  be  regarded  as  having  a  certain  claim  to  con- 
sideration, the  more  so  as  the  osseous  lacunce  in  the  teeth  frequently  as- 
sume forms  resembling  those  of  the  dentinal  canals,  often  communicate 
with  them,  and,  at  least  in  animals,  are  interposed  among  them. 

To  sum  up,  it  may  be  said,  that  in  any  case,  the  matrix  of  the  dentine 
proceeds  from  the  cylindrical  cells  investing  the  pulp  of  the  tooth,  which 
undergo  a  greater  or  less  elongation,  coalesce  and  ossify.  The  dentinal 
canals  either  arise  from  the  nuclei  of  these  cells,  or  are,  and  this  at 
present  appears  to  me  to  be  more  probable,  the  remains  of  the  cavities 
of  the  cells,  whose  boundaries  have  undergone  a  greater  consolidation, 
arid  therefore  correspond  with  osseous  lacunce.  The  divisions  of  the 
canals  are  explained,  if  we  conceive,  either  that  the  dentinal  cells  divide 
longitudinally  from  time  to  time,  as  I  believe  I  have  actually  observed, 
or  that  a  cell  coalesces  with  two  of  its  predecessors.  As  to  the  more 
delicate  ramifications,  we  can  only  suppose  that  they  are  formed  by  a 
secondary  process  of  resorption  in  already  formed  dentine,  like  that 
which  must  be  assumed  to  occur  in  the  osseous  lacunce,  to  account  for 
the  anastomoses  of  their  canaliculi,  and  their  communication  with 
Haversian  canals  ;  at  least,  I  see  no  possibility,  whatever  view  we  take, 
of  explaining  their  formation  in  any  other  way,  without  coming  into 
opposition  with  well-ascertained  facts.  No  such  process  as  the  thicken- 
ing and  ossification  of  dentinal  cells  accompanied  by  the  formation  of 
pore-canals  can  be  observed,  so  that  the  fine  lateral  branches  appear  to 
be  entirely  of  secondary  origin. 

In  the  course  of  the  ossification  of  the  dentine,  at  least  in  man,  we 
find  that  the  deposition  of  calcareous  salts  in  the  recently-formed, 
structurally  characterized,  though  only  slightly  hardened  dentine,  takes 
place  in  such  a  manner  that  the  whole  appears  to  consist  of  isolated 
globules.  These  globules,  which  are  visible  not  only  at  later  periods, 
but  in  the  earliest  cap  of  dentine,  and  are  best  seen  at  the  edge  of  the 
root  of  a  large  tooth  viewed  externally,  eventually  disappear  if  develop- 
ment proceed  normally,  calcareous  matter  being  deposited  between 
them,  so  that  the  dentine  becomes  quite  homogeneous  and  clear;  in  the 
opposite  case,  they  persist  in  greater  or  less  number,  and  the  spaces 
between  them,  which  are  nothing  but  the  interglobular  spaces  above 
described,  contain  unossified  dentine. 

According  to  my  observations,  the  development  of  the  cement  takes 
place  from  that  portion  of  the  dental  sac  which  lies  between  the  pulp 


THE    TEETH.  493 

and  the  enamel  organ,  and  commences,  even  before  the  eruption  of  the 
teeth,  contemporaneously  with  the  formation  of  their  fangs.  About 
this  time  the  dental  sac  elongates  inferiorly,  applies  itself  to  the  grow- 
ing fang,  yields,  from  its  abundant  vascular  network,  a  soft  blastema, 
in  which  nucleated  cells  are  developed,  and  then  ossification  takes  place. 
The  cement,  therefore,  is  not  formed  by  the  ossification  of  the  sac  itself. 
I  met  with  the  first  traces  of  it  in  newly-born  infants,  in  the  form  of 
isolated,  elongated,  or  rounded  scales,  which  were  firmly  attached  to 
the  dentine  of  the,  as  yet,  very  short  fang,  and  looked  exactly  like  the 
developing  osseous  substance  in  the  cranial  bones  ;  the  smallest  exhi- 
bited distinct  osseous  lacunce  and  a  faint  yellow  tinge,  but  were  quite 
soft  and  transparent,  passing  at  their  edges  into  a  clear  cellular  blas- 
tema ;  in  the  larger  ones,  the  margins  were  similar,  but  the  centre  was 
darker  and  firmer,  and  in  this  way  every  stage  of  transition  to  actual 
bone  was  presented,  without  any  granular  deposit  of  calcareous  matter. 
With  the  elongation  of  the  fang,  new  osseous  scales  of  this  kind  were 
formed  and  gradually  coalesced  from  above  downwards  into  a  single 
layer,  to  which  continual  additions  were  made  from  without,  until  the 
whole  thickness  of  the  cement  was  produced. 

I  am  unacquainted  with  the  manner  in  which  the  Nasmyth's  mem- 
brane is  produced.  No  structureless  layer  exists  upon  the  enamel 
organ,  by  the  ossification  of  which  it  might  be  supposed  to  be  formed, 
and  therefore  I  should  be  inclined  to  regard  it  as  a  calcified,  amorphous 
exudation  secreted  from  the  enamel  organ  immediately  after  the  ossifi- 
cation of  the  last  enamel  cells,  which  glues  together  and  protects  the 
ends  of  the  prisms  of  the  enamel. 

If  we  now,  in  conclusion,  take  a  general  view  of  the  different  struc- 
tures in  the  teeth  and  their  mutual  relations,  we  perceive  that  although 
they  agree  in  certain  respects,  yet  they  cannot  be  brought  under  one 
class.  Dentine  and  cement  are  much  more  closely  allied  to  one  ano- 
ther, than  to  enamel,  and  should  it  prove  to  be  correct  that  the  den- 
tinal  canals  are  formed  by  the  coalescence  of  the  cavities  of  thickened, 
elongated  cells,  the  dentine  will  correspond  with  an  osseous  tissue, 
whose  matrix  is  constituted  only  by  the  thickened  walls  of  the  original 
cells,  and  whose  lacunce  are  all  directly  connected.  Cement,  or  bone 
and  dentine,  often  have  a  very  close  external  resemblance  to  one  another, 
particularly,  on  the  one  hand,  when  the  latter  is  traversed  by  numerous 
Haversian  canals,  and,  as  Retzius  believes  he  has  observed,  contains 
osseous  lacunse ;  and,  on  the  other  hand,  when,  in  bone,  the  lacunae  are 
either  greatly  elongated,  with  numerous  canaliculi,  vascular  canals  also 
existing ;  or  when  with  few  lacunce,  the  canaliculi  are  numerous  and 
parallel,  like  dentinal  canals.  This  much  is  certain,  that  the  two  sub- 
stances never  become  exactly  alike,  and  it  is  probable  that  their  develop- 
ment is  always  to  a  certain  extent  different. 


494  SPECIAL    HISTOLOGY. 

The  enamel  may  be  best  compared  with  a  dentine  whose  cells  are 
ossified  throughout,  and  which,  therefore  presents  no  canals,  like  that 
in  the  outermost  layers  of  fishes'  teeth;  at  least  the  two  substances 
agree  in  this,  that  they  are  entirely  composed  of  elongated  cells  without 
any  connecting  matrix.  When  canals  occur  in  the  enamel,  it  acquires  a 
very  great  similarity  to  dentine ;  but  these  canals  probably  have  a  to- 
tally different  import  to  those  in  the  dentine,  viz. — that  of  cavities 
which  proceed  from  absorption.  With  the  cement,  the  enamel  has,  in 
general,  no  analogy,  though  there  is  a  kind  of  homogeneous  cement  with 
an  indistinct  transverse  striation  which,  at  least  externally,  looks  some- 
what like  enamel,  but  has  hardly,  like  the  latter,  arisen  from  elongated 
cells.  If  we  consider  the  nature  of  the  parts  from  which  the  various 
substances  are  developed,  the  dentine,  formed  from  the  vascular  part  of 
the  mucous  membrane  of  the  mouth,  is  a  true  product  of  the  homologue 
of  the  derma  (schleimhaut-productiori),  the  enamel  an  epithelial  structure, 
and  the  cement  an  investing  substance,  afforded  by  the  mucous  membrane. 

§  143.  The  substance  of  the  perfect  tooth,  though  hard,  is  by  no 
means  incapable  of  molecular  change,  as  its  various  diseases  best  show. 
The  functions  of  the  lacunce  and  their  canaliculi  in  the  bones  are  here 
performed  by  the  dentinal  canals  with  their  ramifications,  the  lacunce  and 
canaliculi  in  the  cement,  and  the  fissures  between  the  prisms  of  the 
enamel.  All  these  cavities,  during  life,  contain  a  fluid,  derived  on  the 
one  side,  from  the  vessel  of  the  pulp,  on  the  other,  from  those  of  the 
alveolar  periosteum,  and  permit  of  changes  in  the  substance,  though 
they  may  be  slow.  Nothing  definite,  however,  is  known  about  the  latter, 
but  from  the  circumstance  that  perfect  dentine  is  not  colored  wh'en  an 
animal  is  fed  with  madder  (Hunter,  Flourens,  and  others  :  compare  Henle, 
p.  878),  it  may  be  concluded,  that  they  are  far  less  active  than  in  the 
bones,  and  perhaps  take  place  in  such  a  manner  that  the  calcareous 
matters  are  not  at  all  or  only  very  slowly  renewed.  The  dentine  is  un- 
doubtedly best  provided  with  fluid  supplies,  from  its  being  penetrated  by 
very  numerous  and  frequently  anastomosing  canals.  We  can  as  little 
.suppose  any  regular  circulation  in  it  as  in  the  bones ;  but  it  may  be 
.assumed  that  a  certain  movement  takes  place,  proportionate  to  the 
:amount  of  the  exudative  and  absorptive  processes  in  the  pulp,  of  the 
waste  in  the  tooth  itself,  and  of  the  supply  afforded  to  the  enamel  and 
>cement  and  probably  given  off  from  the  latter  tissues  externally.  Though 
the  enamel  is  not  impermeable,  it  permits  of  the  passage  of  fluids  with 
•difficulty,  as  is  best  shown  by  the  circumstance  that  the  nerves  of  the 
•dental  pulp  are  not  affected  by  acids,  so  long  as  the  coating  of  enamel 
is  entire,  but  readily  enough,  when,  as  in  the  incisors,  the  dentine  is  ex- 
tposed.  The  enamel,  again,  is  the  hardest  dental  tissue,  possesses  scarcely 
-any  organic  matrix  and  no  constant  systems  of  canals.  Nasmyth's 


THE    TEETH.  495 

membrane,  which  is  attacked  with  so  much  difficulty  by  chemical 
reagents,  is,  very  probably,  still  more  impenetrable  than  the  enamel 
itself,  and  hence  these  two  substances  serve  admirably  to  protect  the 
teeth.  The  sensibility  of  the  teeth  arises  from  the  nerves  of  their  pulp  ; 
they  are  affected  by  contact,  heat,  cold,  and  chemical  agents.  Slight 
mechanical  influence  can  only  act  by  the  vibrations  which  they  may 
communicate  to  the  substance  of  the  tooth  and  thence  to  the  pulp  ;  it 
is  therefore  the  more  remarkable  that  the  teeth  have  a  certain  sense  of 
locality,  so  that  it  is  possible  to  distinguish  whether  they  are  touched 
internally  or  externally,  above  or  below,  on  the  right  or  on  the  left  side. 
The  sensibility  of  the  teeth  is  indeed  tolerably  delicate,  especially  on 
the  masticating  surface,  where  the  smallest  foreign  bodies,  as  hairs, 
grains  of  sand,  &c.,  are  perceived  when  these  surfaces  are  rubbed 
against  one  another ;  and  as  regards  its  acuteness,  it  is,  in  disease  at 
least,  excessive,  which  is  sufficiently  explained  by  the  considerable  num- 
ber of  nerves  in  the  pulp  and  the  readiness  with  which  they  may  be 
compressed  within  their  hard  receptacle. 

With  age  the  teeth  become  denser ;  the  pulp  cavity  is  filled  with  a 
kind  of  irregular  dentine  and  may  be  totally  obliterated,  which  is,  per- 
haps, the  normal  cause  of  their  falling  out.  In  certain  cases  observed 
by  Tomes,  the  fangs  in  old  age  were  quite  transparent,  like  horn. 

The  following  remarks  may  be  made  upon  the  pathology  of  the  teeth. 
Permanent  teeth  which  have  fallen  out  are  sometimes  replaced  by  a  third 
dentition ;  but  it  must  not  be  forgotten  that  the  milk  teeth  occasionally 
remain  beyond  their  time,  and  care  must  be  taken  not  to  confound  a 
second  tooth,  late  in  its  eruption,  with  a  third.  Teeth  which  have  been 
extracted  may  be  replaced  (in  fifteen  months  a  canine  tooth  which  had 
been  extracted  from  the  upper  jaw  was  perfectly  firm  again).  An  abnor- 
mal development  of  the  teeth  takes  place  particularly  in  the  ovarium, 
but  also  elsewhere.  Fractures  of  the  teeth  may  be  reunited  when  they 
occur  within  the  alveoli,  by  imperfect  dentine  or  cement.  Regeneration 
of  the  worn  down  parts  takes  place  only  in  animals  (Rodents,  e.g.]  in 
which  the  teeth  constantly  grow.  Hypertrophy  of  the  cement  (the 
so-called  exostosis\  deposits  of  dentine  in  the  walls  of  the  pulp  cavity 
and  ossification  of  the  pulp  itself,  are  exceedingly  common,  and  result 
from  chronic  inflammation  of  the  periosteum  and  pulp.*  A  partial  dis- 

*  [Wedl  in  his  recent  work  (Grundziige  der  path.  Histol.)  has  added  some  very  inte- 
resting observations  to  our  knowledge  of  the  structural  changes  occurring  in  the  different 
parts  of  teeth.  In  hypertrophy  of  the  cement  he  observed  the  canaliculi  dilated,  so  as  to 
form  Haversian  canals,  and  agrees  with  Kolliker  (vid.  §  140  supra)  as  to  the  frequency  of  the 
hypertrophy  of  the  entire  cement  in  old  teeth.  In  partial  hypertrophies  of  the  cement  he 
detected  numerous  dentinal  globules,  bounded  by  irregular  fissures,  and  on  their  external 
border  many  bone-corpuscles.  These  latter  were  separated  from  each  other  by  a  yellowish 
intercorpuscular  substance,  and  in  many  instances  by  peculiar  simlous  cavities,  which  traversed 
the  lamella?  of  the  osseous  substance. 


496  SPECIAL    HISTOLOGY. 

appearance  of  the  fang  is  not  uncommon.  Necrosis  of  the  teeth  takes 
place  when  the  periosteum  has  been  stripped  off,  or  the  pulp  has  died. 
The  teeth  become  rough  and  dark,  even  black,  and  finally  fall  out.  The 
nature  and  causes  of  dental  caries  are  doubtful.  It  attacks  living  and 
false  teeth  (Tomes),  and  always  begins  on  the  exterior,  from  Nasmyth's 
membrane  (Ficinus),  whence  the  fluids  of  the  mouth  have  been  supposed 
to  have  considerable  influence  upon  it ;  it  does  not  follow,  however,  that 
one  living  tooth  may  not  be  more  disposed  to  it  than  another,  being  ren- 
dered less  capable  of  resistance  either  by  its  chemical  composition,  or  by 
the  mode  of  its  nutrition.  Caries,  however,  is  assuredly  not  a  simple 
solution  of  the  salts  by  the  oral  fluids,  but  a  solution  accompanied  by  a 
putrefactive  decomposition  of  the  organic  elements  of  the  tooth,  which 
becomes  covered  with  infusoria  and  fungi ;  in  fact,  according  to  Ficinus's 
observations,  the  latter  growths  would  appear  to  play  the  more  impor- 
tant part,  inasmuch  as  the  decay  of  the  teeth  usually  commences  in  those 
localities  in  which  undisturbed  opportunity  is  given  to  these  organisms 
to  develop,  as  in  the  cracks  and  pits  of  the  enamel,  in  the  depressions 
of  the  molar  teeth,  in  the  clefts  between  the  teeth,  but  not  where  the 
dentine  is  otherwise  exposed,  as  on  the  masticating  surface,  in  filed 
places,  &c.  The  usual  course  of  caries  is,  that  the  discolored  spots  of  the 
cuticle  of  the  enamel,  covered  with  living  and  growing  organisms  (infu- 
sorial animalcules,  similar  to  a  Vibrio,  which  Ficinus  calls  Denticola, 
mucedinous  fungi  (Erdl,  Klenke,  Tomes),  similar  to  those  which  are 
found  upon  the  tongue,  and  which  Ficinus  wrongly  refers  to  the  Denti- 
colce)  first  lose  their  calcareous  salts,  and  then  break  up  into  angular, 
cellular  pieces,  as  if  they  had  been  treated  with  hydrochloric  acid.  The 
decay  then  penetrates  through  the  enamel  to  the  dentine,  always  first 
softening  it,  so  that  it  yields  not  more  than  10  per  cent,  of  ash  (Ficinus), 
and  then  decomposing  it.  The  dentine  is  more  affected  by  this  process 
than  the  enamel,  its  canal  first  becoming  filled  with  the  fluids  proceeding 
from  its  decomposition,  which  may  reach  the  pulp  and  give  rise  to  pain, 
unless,  as  Tomes  found,  the  dentinal  canals  in  the  neighboring  healthy 

The  deposits  of  dentine  in  the  walls  of  the  pulp-cavity,  the  "  osteo-dentine"  of  Owen,  he 
regards  as  mainly  originating  from  the  dentinal  globules,  which  to  him  are  protein-bodies. 
This  osteo-dentine  partakes  in  some  instances  more  of  the  nature  of  bone,  than  of  dentine, 
but  consists  generally  of  a  central  substance  and  of  tubules  radiating  from  it;  it  frequently 
appears  to  be  formed  of  concentric  layers.  The  centraF  substance  Wedl  describes  as  con- 
sisting either  of  hyaline  dentinal  globules,  of  a  grayish,  amorphous  mass,  or  of  distinct 
bone-corpuscles  of  varying  shapes,  separated  by  spaces  resembling  Haversian  canals.  The 
newly-formed  tubules  run  from  this  central  mass  towards  the  dentine  of  the  tooth,  with  the 
canals  of  which  they  communicate.  Sometimes  they  are  intersected  in  their  course  by 
the  presence  of  many  dentinal  globules,  or  by  irregular  lacuna?.  In  all  instances  of  these 
formations,  that  he  has  examined,  the  dentinal  globules  existed  in  great  abundance.  The 
dark  color  of  the  globules,  wherever  met  with,  Wedl  is  disposed  to  attribute  to  their  retro- 
gressive metamorphosis,  whilst  he  regards  the  dark  color  of  the  interglobular  spaces  as 
dependent  on  a  deposit  of  brown  pigment  in  their  interior. — DaC.] 


THE    TEETH.  497 

portions  become  obliterated  by  deposits,  or  the  pulp  is  protected  by  new 
masses  of  dentine  developed  in  the  cavity*  (Ficinus,  Tomes).  Eventually 
a  brownish  deposit  takes  place  in  the  tubules  and  then  the  intermediate 
substance  becomes  completely  broken  up.  In  this  manner  the  process 
of  decomposition  extends  further  and  further,  until  at  last  the  crown 
collapses,  the  root  also  becoming  dissolved  and  finally  falling  out. 

In  jaundice,  the  teeth  not  uncommonly  assume  a  yellow  color,  which 
is  occasionally  almost  as  intense  as  in  the  skin,  and  in  asphyxiated  per- 
sons they  are  said  frequently  to  be  red ;  both  facts  being  explicable  only 
by  the  supposition  that  the  coloring  matter  of  the  bile  and  of  the  blood 
transudes  into  the  dentinal  tubuli.  In  rachitis  the  teeth  remain  unaf- 
fected. In  the  mucus  upon  the  teeth,  an  abundant  growth  of  the  muce- 
dinous  fungi  which  have  been  mentioned,  is  always  to  be  met  with  in  a 
finely  granular  matrix,  surrounding  mucus-  or  epithelium-corpuscles ; 
besides  which  we  find  the  infusoria  of  carious  teeth  and  the  earthy 
deposits  of  the  oral  fluids.  If  this  mucus  accumulates,  it  hardens  and 
forms  the  tartar  of  the  teeth,  which  consists,  according  to  Berzelius,  of 
earthy  phosphates  79-0,  mucus  12-5,  ptyalin  1*0,  organic  matter,  soluble 
in  hydrochloric  acid,  7 '5. 

The  best  mode  of  examination  of  the  teeth  is  by  making  fine  sections 
and  preparations  softened  in  hydrochloric  acid.  To  obtain  good  speci- 
mens of  the  former  it  is  necessary  to  employ  only  young  and  fresh  teeth, 
as  the  enamel  otherwise  readily  breaks  off.  A  longitudinal  or  trans- 
verse slice  should  be  first  taken  off  with  a  fine  saw,  and  may  then  be 
rubbed  down,  first  upon  a  coarser  and  then  upon  a  finer  stone,  as  thin 
as  possible ;  the  section  should  then  be  cleaned  and  polished  between 
two  glass  plates,  until  its  surface  is  as  smooth  and  shining  as  it  can  be 
made,  and  finally  washed  with  ether  in  order  to  remove  any  impurities 
it  may  have  contracted.  When  well  polished  and  dried,  all  the  dentinal 
canals  and  lacuna?  will  be  filled  with  air,  and  the  section  may  be  pre- 
served without  further  addition  under  a  glass  plate,  cemented  by  some 
thick  and  quickly  solidifying  varnish.  Such  polished  sections  are  pre- 
ferable to  any  others,  which,  on  account  of  their  irregular  surface,  re- 
quire to  be  covered  with  different  fluids,  as  Canada  balsam,  oil  of  tur- 
pentine, &c.,  in  order  to  be  examined  by  high  magnifying  powers.  It 
almost  always  happens,  in  fact,  that  some  portion  of  these  fluids  enters 
the  dentinal  tubules,  which  then  become  quite  clear  and  indistinct  and 
invisible  in  their  finer  ramifications.  A  very  viscid  varnish  alone  is  of 
any  service.  In  preparing  these  sections  of  the  teeth,  the  slices  may 

*  ["  It  is  worthy  of  mention,  also,  that  in  the  teeth  of  the  hare,  the  sow,  and  the  stag, 
especially  in  the  molars,  stony  masses  are  constantly  found.  They  are  semi-transparent,  for 
the  most  part  oval  and  rounded  bodies,  situated  in  the  axis  of  the  dental  pulp,  towards  its 
apex,  in  irregular  rows,  never  extending  the  whole  length  of  the  dental  pulp,  but  only  to  a 
greater  or  less  distance  from  the  coronal  extremity."  Raschkow,  Meletemata,  &c.,  cited  and 
translated  in  Nasmyth's  "Researches"  (1839),  p.  139. — TRS.] 

32 


498  SPECIAL    HISTOLOGY. 

also  first  be  affixed  to  pieces  of  glass  with  Canada  balsam,  and  then  be 
rubbed  down  with  a  file  and  polished,  on  one  side  first,  and  then  by 
warming  the  balsam  and  turning  the  section  round,  upon  the  other. 
When  such  a  section  has  been  washed  with  ether  and  dried,  it  is  as 
good  as  one  prepared  with  water  only.  Two  sections  made  perpendicu- 
larly to  one  another  through  the  middle  of  the  crown  and  fang  of  a 
tooth,  from  before  backwards,  and  from  right  to  left,  are  sufficient  to 
exhibit  the  most  important  features  of  the  teeth ;  but  sections  ought 
also  to  be  prepared,  showing  the  surface  of  the  pulp  cavity  and  that  of 
the  enamel ;  and  also  different  oblique  and  transverse  sections  through 
the  commencement  of  the  dentinal  canals  of  the  fangs,  to  exhibit  the 
anastomoses  of  their  branches.  The  dental  cartilage  is  easily  demon- 
strable by  maceration  in  hydrochloric  acid,  a  process  which  requires  a 
longer  or  shorter  time  according  to  the  concentration  of  the  acid  and 
its  more  or  less  frequent  renewal,  taking  3-4  days  in  strong  acid  and  in 
dilute,  from  5-8.  If  it  be  desired  to  soften  the  tooth  so  much  that  the 
tubules  may  be  isolated,  it  must  be  left  for  about  eight  days  in  con- 
centrated hydrochloric  acid ;  in  thin  sections  of  dental  cartilage  12-24 
hours'  treatment  with  sulphuric  and  hydrochloric  acid,  and  a  few  hours 
with  dilute  solutions  of  caustic  potassa  and  soda,  are  sufficient  for  this 
purpose.  It  is  very  instructive  also  to  macerate  thin  sections  of  teeth 
in  acid  and  to  examine  them  upon  glass  plates  at  intervals,  until  they 
entirely  break  up.  The  enamel  prisms  are  readily  isolated  in  develop- 
ing enamel ;  the  transverse  lines  are  seen  best  when  the  object  is  mois- 
tened with  hydrochloric  acid,  and  the  transverse  sections  of  the  prisms 
are  seen  exceedingly  well  in  longitudinal  sections,  in  some  layers.  The 
early  development  may  be  studied  in  embryos  of  two,  three  or  four 
months  with  the  simple  microscope  and  in  transverse  sections  of  parts 
hardened  in  spirit ;  the  structure  of  the  dental  sac,  and  the  development 
of  the  dental  tissues  in  foetuses  of  four,  five,  and  six  months,  and  in 
new-born  infants,  both  in  fresh  subjects  and,  if  it  be  desired  to  recognise 
the  relations  of  the  enamel  organ,  in  spirit-preparations  also,  in  which 
its  structure  is  very  well  retained.  The  pulp  of  mature  teeth  is  obtained 
by  breaking  them  in  a  vice,  and  their  nerves  are  best  seen  on  the  addi- 
tion of  dilute  solution  of  caustic  soda. 

Literature  of  the  Teeth. — L.  Frankel,  "  De  penitiori  dentium  human- 
orum  structur^  observationes,"  Vratislav,  1835  ;  and  Retzius,  "  Be- 
merkungen  tiber  den  innern  Bau  der  Zahnen,"  in  Mull.  "  Arch.,"  1837 ; 
J.  Tomes,  "  A  Course  of  Lectures  on  Dental  Physiology  and  Surgery," 
London,  1848;  R.  Owen,  "  Odontography,"  London,  1840-45,  1  vol., 
with  atlas  of  150  plates;  and  article  "Teeth,"  in  "Cyclopaedia  of 
Anatomy,"  IV.  p.  864 ;  Krukenberg,  "  Zur  Lehre  vom  Rohrensysteme 
der  Zahne  und  Knochen,"  in  Mull.  "  Archiv,"  1849,  p.  403  ;  J.  Czer- 
mak,  "  Beitrage  zur  mikroskopischen  Anatomie  der  menschlichen  Zahne, 


THE    PHARYNX.  499 

in  Zeitschr.  fur.  wiss.  Zool."  1850,  bd.  II.  p.  295;  Arnold,  in  "  der 
Salzblirger  med.  Zeitung,"  1831,  p.  236  ;  Raschkow,  "  Meletematacirca 
dentium  mammalium  evolutionem,"  Yratisl.  1835  ;  Goodsir,  in  "  Edinb. 
Med.  and  Surg.  Journal,"  1838,  No.  XXXI.  1;  and  Froriep's  "  Neue 
Notizen,"  Nos.  199,  200,  202,  203;  Marcusen,  "  Ueber  die  Entwick- 
lung  der  Zahne  der  Saugethiere,"  aus  dem  "  Bulletin  Phys.  Math."  VIIL, 
No  20,  Petersburgh,  1850.  On  Dental  Caries  consult  Erdl.  in  "  Allg. 
Zeitung  fiir  Chirurgie  von  Rohatzsch,"  1843,  No.  19  ;  Ficinus,  in 
"Journal  fiir  Chirurgie  von  Walther  and  Ammon,"  1846,  p.  1 ;  Klenke, 
"Die  Verderbniss  der  Zahne,"  Leipsig,  1850.  The  Comparative 
Anatomy  of  the  teeth  is  treated  of  microscopically  in  the  works  of  Owen 
and  Retzius  above  cited;  also  by  Erdl,  in  the  " Abhandlungen  der 
Math.  Phys.  Klasse,  der  Konigl.  Bayer.  Akad."  bd.  III.  Abth.  2 ; 
Tomes,  in  the  "Phil.  Trans."  1849-50 •  (Marsupialia  and  Rodentia)  ; 
Agassiz,  in  the  "Poissons  fossiles ;"  Henle  and  J.  Muller,  "  Syst. 
Beschreibung  der  Plagiostomen,"  1838. 

[To  these  should  be  added:  Blake,  "Essay,"  &c.,  1801;  Hunter, 
"Treatise  on  the  Natural  History  and  Diseases  of  the  Human  Teeth," 
edited  by  Thomas  Bell  (Works  by  Palmer,  1835,  vol.  ii.) ;  Tomes,  "On 
the  Structure  of  the  Teeth,  the  Vascularity  of  those  Organs,  and  their 
relation  to  Bone,"  Proceedings  of  the  Royal  Society,  June,  1838  ;  Owen, 
"  On  the  Structure  of  the  Teeth,  and  the  resemblance  of  Ivory  to  Bone," 
British  Association  Reports,  1838 ;  Nasmyth,  "  Medico-Chirurgical 
Transactions,"  1839  ;  "Proceedings  of  the  British  Association,"  1839; 
"  Researches  on  the  Development,  Structure,  and  Diseases  of  the  Teeth," 
1849 ;  Huxley,  "  On  the  Development  of  the  Teeth,"  "  Quarterly 
Journal  of  Micr.  Science,"  1853;  Salter,  "On  certain  appearances 
occurring  in  Dentine,"  ibid.  1853. — TRS.] 

OF  THE  ORGANS  OF  DEGLUTITION. 
I.    THE   PHARYNX. 

§  144.  The  alimentary  canal  assumes  a  greater  independence  in  the 
pharynx,  acquiring  a  special  investment  of  transversely  striated  muscles, 
the  constrictores  and  levatores,  which,  however,  do  not  entirely  surround 
it  and  arise  for  the  most  part  from  bones.  The  thickness  of  the  walls 
of  the  pharynx  is  about  2  lines  on  an  average,  depending  principally 
upon  this  muscular  layer,  external  to  which  there  is  a  tense  fibrous  mem- 
brane, composed  of  connective  tissue  and  elastic  fibres,  while  internally 
it  is  separated  by  a  layer  of  submucous  connective  tissue  from  the 
mucous  membrane.  The  latter  is  paler  than  that  of  the  oral  cavity  and 
its  structure  in  the  upper  half  of  the  pharynx  differs  considerably  from 
that  in  the  lower  half.  In  the  latter  locality,  that  is,  below  the  pha- 
ryngo-palatine  arches,  or  in  the  region  through  which  the  food  passes, 
it  possesses  a  tessellated  epithelium  similar  in  structure  and  thickness  to 


500  SPECIAL    HISTOLOGY. 

that  of  the  oral  cavity ;  above  them,  on  the  other  hand,  that  is,  on  the 
posterior  surface  of  the  soft  palate  from  its  free  edge,  upon  the  upper 
surface  of  the  uvula,  in  the  region  of  the  choance  and  Eustachian  tubes, 
and  upon  the  vault  of  the  pharynx,  there  is  a  ciliated  epithelium  like 
that  in  the  nasal  cavity  and  larynx,  to  the  description  of  which,  below, 
the  reader  may  be  referred.  In  this  upper  or  respiratory  section,  the 
mucous  membrane  is  also  redder,  thicker,  and  more  glandular  than  in 
the  lower  division,  otherwise,  however,  its  structure  is  pretty  much  the 
same,  with  the  exception  that  it  presents  no  papillae,  which,  however,  in 
some  parts  of  the  lower  division  are  very  little  developed  and  rare,  and 
would  even  appear  to  be  entirely  wanting.  Compared  with  that  of  the 
oral  cavity  I  find  the  mucous  membrane  of  the  pharynx  to  possess  much 
more  and  much  stronger  elastic  tissue,  which,  in  the  deeper  layers,  forms 
connected,  very  dense,  elastic  membranes. 

The  pharynx  contains  two  sorts  of  glands  ;  1,  racemose  mucous  glands 
(vide  supra,  §  134),  and,  2,  follicular  glands.     The  former  J-l  line  in 
diameter,  have  distinct  apertures  and  abound  more  particularly  in  the 
upper  portions  of  the  pharynx,  where  they  form  a  perfectly  continuous 
layer  on  the  posterior  wall,  in  the  neighborhood  of  the  pharyngeal  open- 
ing of  the  Eustachian  tubes,  and  upon  the  posterior  surface  of  the  velum, 
diminishing  in  number  lower  down.    Follicular  glands,  simple  as  well  as 
compound,  analogous  to  the  tonsils,  are  met  with  in  the  vault  of  the 
pharynx,  where  the  mucous  membrane  is  closely  attached  to  the  base  of 
the  skull.    Here  a  glandular  mass,  stretching  from  one  Eustachian  open- 
ing to  the  other,  and  from  one  to  four  lines  thick,  may  constantly  be  met 
with ;  it  is,  upon  the  whole,  smaller,  but  otherwise  its  structure  resem- 
bles, in  all  essential  respects,  that  of  the  tonsils  (§  135).     Besides  this 
mass,  whose  largest  sacculations  are  situated  in  the  middle  of  the  roof 
of  the  pharynx,  and  in  the  recesses  behind  the  Eustachian  apertures, 
and  which,  in  aged  persons,  frequently  present  enlarged  cavities,  filled 
with  puriform  masses,  there  occur  round  the  apertures  of  the  tubes, 
and  upon  them,  towards  the  choana?,  on  the  posterior  surface  of  the 
velum  palati,  and  on  the  lateral  walls  of  the  pharynx,  as  far  as  the 
level  of  the  epiglottis,  more  or  less  numerous,  smaller  and  larger  fol- 
licles, whose  size  is  too  great  for  apertures  of  the  mucous  glands,  and 
which  have  in  all  probability  the  same  structure  as  the  simple  follicles 
of  the  root  of  the  tongue,  and  receive  the  excretory  ducts  of  the  mucous 
glands. 

The  mucous  membrane  of  the  pharynx  is  rich  in  bloodvessels  and 
lymphatics.  The  former  constitute  superficially  a  network  with  elon- 
gated meshes,  sending  short  loops  into  the  rudimentary  papillae.  The 
nerves  are  very  numerous,  form  superficial  and  deep  plexuses,  the  former 
with  fine  fibres  of  0*001-'0015  of  a  line,  which  occasionally  divide,  and 
whose  ultimate  terminations  escape  the  eye. 


THE    (ESOPHAGUS. 


501 


II.    THE  OESOPHAGUS. 

§  145.  The  wall  of  the  oesophagus,  1  J-lf  lines  thick,  consists,  exter- 
nally, of  a  fibrous  membrane  composed  of  connective  tissue,  with  exceed- 
ingly beautiful  elastic  fibres.  To  this  succeeds  a  muscular  membrane 
f-1  line  thick,  composed  of  an  external,  longitudinally  fibrous  layer, 
having  a  thickness  of  0*5  of  a  line,  and  of  an  internal,  circularly  fibrous 
layer  of  0*24— 0-3  of  a  line,  which  are  in  close  apposition.  From  the 
pharynx,  where  the  longitudinal  fibres  arise  in  two  bundles  from  the 
constrictor  infimus,  united  with  a  third  from  the  cricoid  cartilage,  they 
extend  as  far  as  the  stomach,  with  whose  muscles  they  are  partly  con- 
tinuous. In  the  upper  third  of  the  oesophagus,  as  far  as  its  entrance  into 
the  thorax,  transversely  striated  muscles  alone  are  found,  arranged  in 
bundles  of  0-04-0-24  of  a  line,  which  sometimes  distinctly  anastomose. 
Further  downwards  smooth  muscles  of  the  same  structure  as  those  in 
the  intestine  (infra)  make  their  appearance,  in  the  first  place  in  the  cir- 
cular layer,  and  subsequently,  among  the  longitudinal  fibres ;  the  pro- 
rig.  198.  Fig.  199. 

4 

-y 

.f 


portion  of  these  gradually  increases, 
until  at  last,  in  the  lower  fourth, 
smooth  muscle  altogether  predomi- 
nates. Isolated,  transversely-stri- 
ated muscles,  however,  are,  accord- 
ing to  Ficinus,  to  be  met  with  as  far 
as  the  cardia.  Most  internally  we 
find,  separated  from  the  muscular 
coat  by  a  white,  soft  layer  of  sub- 
mucous  connective  tissue  (tunica  nervea  of  the  ancients),  the  pale-red 
mucous  membrane,  which  below  takes  on  a  whitish  tint.  Its  total  thick- 

Fia.  198. — Transverse  section  from  the  middle  of  the  resophagus  (Man),  magnified  1-2 
diameters:  a,  fibrous  investment;  6,  longitudinal  muscles  ;  c,  transverse  muscles ;  d,  tunica 
nervea  •  e,  longitudinal  muscles  of  the  mucous  membrane ;  /,  papillae  ;  g,  epithelium  ;  h,  aper- 
ture of  a  mucous  gland ;  i,  mass  of  fat. 

Fia.  199. — Muscular-fibre  cells  from  the  tssophageal  mucous  membrane  of  the  Pig,  after 
being  treated  with  nitric  acid  of  20  per  cent.;  magnified  15  diameters. 


502  SPECIAL    HISTOLOGY. 

ness  of  0-36-0-45  of  a  line  is  due,  to  the  extent  of  about  0-1-0-12  of  a  line, 
to  its  laminated,  tessellated  epithelium,  which  presents  the  same  structure 
as  in  the  oral  cavity,  with  the  exception,  however,  that  the  actual  epithe- 
lial plates  constitute  about  a  moiety  of  the  whole,  and,  after  a  short  mace- 
ration, or,  as  frequently  happens  in  the  dead  subject,  spontaneously, 
may  be  readily  stripped  off  in  large  white  sheets,  either  alone,  or  accom- 
panied by  adherent  portions  of  the  deeper  layers.  The  proper  mucous 
membrane,  measuring  on  the  average  O3  of  a  line,  possesses  numerous 
conical  papillae  of  0-04-0-05  of  a  line  in  length,  and  consists  of  ordinary 
connective  tissue,  with  fine  elastic  fibres,  among  which,  however,  as 
Brucke  and  I  have  ascertained,  a  great  quantity  of  longitudinal  bundles 
of  smooth  muscles,  and  in  addition,  more  isolated  groups  of  ordinary  fat 
cells  and  small  racemose  mucous  glands,  may  be  observed. 

The  oesophagus  is  moderately  provided  with  lymphatics  and  blood- 
vessels ;  the  latter  send  loops  into  the  papillae  and  form  at  their  bases, 
a  not  very  wide  network,  like  that  in  the  pharynx.  Nerves  may  also 
be  met  with  in  considerable  numbers  in  the  mucous  membrane,  contain- 
ing fine  fibres  of  0*0012-0-0015  of  a  line,  but  I  have  not  yet  succeeded 
in  tracing  them  into  the  papillae,  nor  in  observing  divisions,  nor  the 
modes  in  which  they  terminate. 

Literature. — C.  Th.  Tourtual,  "Neue  Untersuchungen  iiber  den  Bau 
des  Menschlichen  Schlund-und  Kehlkopfes,"  Leipzig,  1846. 


OF  THE  ALIMENTARY  CANAL. 
§  146.  Those  parts  which  constitute  what  may,  more  strictly  speaking, 
be  called  the  alimentary  canal,  are  the  least  fixed  of  all  which  compose 
the  alimentary  tract  and  are  almost  invariably  attached  by  special  mem- 
branous bands — the  mesenteria — in  the  great  cavity  of  the  abdomen, 
lined  by  the  peritonaeum.  With  the  exception  of  a  small  portion  of  the 
rectum,  the  walls  of  the  alimentary  canal  consist  everywhere  of  three 
tunics:  a  serous — the  peritonaeum;  a  muscular — consisting  of  two  or 
even  three  layers ;  and  a  mucous  membrane,  the  latter  containing  a 
great  number  of  glandular  structures,  which  may  be  divided  into  three 
groups,  racemose  mucous  glands,  tubular  glands,  and  closed  follicles. 

§  147.  The  peritonaeum  is  much  thicker  in  its  external  or  parietal, 
than  in  its  internal  or  visceral  layer  (in  the  former  case  0-04-0-06,  in 
the  latter  0-02-0-03  of  a  line),  though  its  structure  is  essentially  the 
same  in  each  locality.  It  consists  principally  of  connective  tissue  with 
distinct,  variously  interwoven  bundles,  and  abundant  reticulated  elastic 
fibres,  which  are  coarser  in  the  parietal  lamina.  A  loose  subserous  con- 
nective tissue,  containing  more  or  less  fat,  unites  the  peritonaeum  with 
the  other  organs,  or,  as  in  the  mesenteric  folds,  connects  its  layers 
together ;  under  the  visceral  lamina,  however,  it  is  very  little  developed 
except  in  certain  localities  (colon,  appendices  epiploicce],  and  in  certain 


THE    ALIMENTARY    CANAL.  503 

folds  of  the  peritonceum,  it  does  not  exist  at  all.  The  free  surface  of 
both  lamellae  of  the  peritonceum  is  lined  by  a  simple  tessellated  epithe- 
lium, whose  slightly  flattened,  polygonal,  nucleated  cells  measure,  on  the 
average,  0-01  of  a  line,  they  are  so  closely  united  and  so  constantly  kept 
moist,  that  the  free  serous  surface  appears  perfectly  smooth  and  shining. 
The  peritonceum  is,  in  general,  but  scantily  supplied  with  vessels  ;  they 
are  most  abundant  in  the  omenta,  in  the  visceral  layer  and  in  the  sub- 
serous  tissue,  in  which  last  alone,  lymphatics  have  as  yet  been  found. 
The  nerves  are  also  but  few,  and  are  especially  to  be  met  with  in  the 
omentum,  the  mesenteria,  and  hepatic  ligaments,  where  they  accompany 
the  arteries. 

§  148.  Muscular  tunic  of  tlie  alimentary  canal. — The  whole  alimen- 
tary tract,  from  the  stomach  to  the  rectum,  possesses  a  special  muscular 
coat,  which,  however,  does  not  everywhere  present  the  same  conditions. 

In  the  stomach  the  muscular  tunic  varies  in  thickness;  at  the  fundus 
it  is  thin  (J-J  of  a  line) ;  in  the  middle,  it  has  a  thickness  of  about  \  a 
line :  in  the  pyloric  region,  finally,  about  f  or  even  1  line.  It  consists 
of  three  incomplete  layers  :  1, 
most  externally,  longitudinal 
fibres,  especially  at  the  cardia, 
where  they  arise  from  the  ex- 
pansion of  a  part  of  the  lon- 
gitudinal fibres  of  the  oesopha- 
gus ;  and  also  at  the  pylorus 
and  in  the  pars  pylorica, 
whence,  tensely  stretched,  they 
are  continued  upon  the  duo- 
denum ;  2,  circular  muscles, 
in  the  middle  region,  from  the 
fundus  to  the  pylorus  ;  where 
they  are  accumulated,  consti- 
tuting the  so-called  sphincter 
of  the  pylorus  ;  3,  most  internally,  oblique  fibres,  which,  in  connection 
with  the  circular  fibres,  embrace  the  fundus  as  in  a  sling,  and  run  ob- 
liquely upon  the  anterior  and  posterior  walls  of  the  stomach,  towards  its 
greater  curvature,  where  they  terminate  upon  the  outer  surface  of  the 
mucous  membrane  or  unite  together. 

In  the  small  intestine,  the  muscular  coat  is  somewhat  thicker  in  the 
duodenum  and  the  upper  portions,  than  in  the  lower ;  it  has,  in  general, 
a  thickness  of  J-J  of  a  line,  and  is  composed  only  of  longitudinal  and 
transverse  fibres.  The  former  are  always  less  developed  and  do  not 

*  FIG.  200. — Stomach  of  Man,  reduced:  a,  (Esophagus,  with  the  longitudinal  fibres  ;  tr, 
transverse  fibres  (second  layer),  for  the  most  part  dissected  off;  tjj,  transverse  fibres  of  the 
fundus;  o,fibr&  obliqua  •  p,  pylorus  •  d,  duodenum. 


504  SPECIAL    HISTOLOGY. 

form  a  continuous  layer,  since  they  are  very  few  or  entirely  absent  along 
the  attachment  of  the  mesentery ;  they  are  usually  most  distinct  upon 
the  free  border,  though  even  here  they  may  be  readily  torn  away  with 
the  serous  membrane,  so  as,  at  once,  to  leave  the  second  layer  exposed. 
The  latter  is  complete  and  continuous,  consisting  of  circular  bundles, 
which  not  uncommonly  anastomose  at  very  acute  angles. 

In  the  large  intestine,  the  longitudinal  fibres  are  reduced  to  the  three 
ligamenta  coli,  muscular  bands  of  4-6,  or  even  8  lines  broad,  and  -J-J 
line  thick,  which  commencing  upon  the  caecum  are  united  upon  the 
sigmoid  flexure,  into  a  single  longitudinally  fibrous  layer,  which  is  con- 
tinued upon  the  rectum.  Beneath  these  bands  there  lies  a  continuous, 
circularly  fibrous  layer,  thinner  than  in  the  small  intestines  and  more 
especially  developed  in  the  duplicatures,  which  are  known  under  the 
name  of  the  plicae  sigmoidece. 

Fig.  201.  The  rectum  possesses  a  muscular  layer  of  1  line  and  more 
thick,  in  which  the  more  abundant  longitudinal  fibres  lie  ex- 
ternal to  the  circular.  The  ultimate,  somewhat  thickened  ex- 
tremity of  the  circular  fibres  is  the  sphincter  ani  internus,  with 
which  the  transversely  striated  sphincter  externus  and  levator 
ani  are  conjoined. 

In  their  elementary  structure,  all  the  muscles  of  the  proper 
alimentary  canal  belong  to  the  so-called  smooth  or  non-striated 
(vegetative,  organic)  muscles  (see  §  26).  Their  elements,  the 
fibre-cells,  are  fusiform,  on  the  average  0-002-0*003  of  a  line 
broad,  and  O'06-O'l  of  a  line  long,  pale,  flattened,  and  homo- 
geneous, and  provided  with  a  nucleus  0-006-0-012  of  a  line 
long,  and  0-001-0-0028  of  a  line  broad. 

Many  of  the  fibres  present  knot-like  enlargements  and  fre- 
quently zigzag  flexures,  which  produce  the  transversely  striated 
appearance  of  the  entire  bundles  of  such  muscles  so  frequently 
met  with  in  spirit  preparations.  The  arrangement  of  the 
fibre-cells  in  the  different  strata  is  simply  this  ;  mutually  applied 
in  their  length  and  breadth  and  coherent,  they  are  united  into 
thin  muscular  bands,  which  then,  invested  with  a  coating  of 
connective  tissue  and,  frequently,  also  united  into  secondary 
bundles,  constitute  the  thinner  or  thicker  muscular  tunics  of  the 
different  regions ;  which,  again,  are  surrounded  and  separated 
from  the  contiguous  parts,  by  considerable  layers  of  connective 
tissue. 

Bloodvessels  are  very  abundant  in  the  smooth  muscles ;  and 
their  capillaries,  of  0-003-0-004  of  a  line,  constitute  a  charac- 
teristic* network  with  rectangular  meshes. 

FIG.  201. — Muscular  fibre  cell  from  the  small  intestine  (human). 

*  [Hardly  characteristic ;  the  vessels  are  arranged  in  precisely  the  same  way  in  the  fascial 
aponeuroses;  e.  g.,  the/ascia  lata  of  the  thigh. — TRS.] 


THE    STOMACH. 


505 


Nothing  is  known  about  the  lymphatics  ;  nor  are  the  relations  of  the 
nerves  yet  ascertained,  except  that  Ecker  has  observed  the  division  of 

Fig.    202. 


fine  nervous  tubules  in  the  muscular  tunics  of  the  stomach  of  the  Frog 
and  Rabbit. 

MUCOUS  MEMBRANE  OF  THE  STOMACH. 

§  149.  The  gastric  mucous  membrane  is  soft  and  loose  in  texture ; 
and  its  color,  during  digestion,  is  reddish-gray  or  bright  red,  at  other 
times  grayish.  When  the  stomach  is  empty,  the  inner  surface  is  thrown 
into  longitudinal  folds,  which  disappear  in  its  distended  state.  Further- 
more, it  presents,  especially  in  the  pyloric  region,  around  the  apertures 
of  the  tubular  or  gastric  glands,  little  reticulated  folds  or  even  isolated 
villi*  (plicae  villosce,  Krause)  of  0-024-0-048  or  even  0-1  of  a  line, 
(A-s'u  Krause).  Not  unfrequently,  also,  the  mucous  membrane  is 
marked  out  especially  upon  the  right  side,  by  little  shallow  depressions, 
into  slightly  raised  polygonal  areas  of  J-2  lines,  the  so-called  "  etat 
mamelonne"'  of  pathologists,  which,  however,  is  also  exhibited  by  per- 
fectly healthy  stomachs.  The  mucous  membrane  is  thinnest  (J— J  of  a  line), 
at  the  cardia,  in  the  middle  it  becomes  thickened  to  J  a  line,  and  in  the 

FIG.  202. — Bloodvessels  of  the  smooth  muscles  of  the  intestine,  magnified  45  diameters. 

*  [These  gastric  villi  have  been  recently  accurately  described  and  depicted  by  Dr.  Neill, 
(vid.  Amer.  Journ.  of  Med.  Sc.,  Jan.  1851.)  By  the  aid  of  minute  injections,  Dr.  Neill 
found  that  the  ridges  between  the  orifices  of  the  tubuli,  formed  of  convoluted  capillaries, 
become  larger  and  more  elevated  in  the  antrum  pylori,  and  that  as  the  pyloric  orifice  is 
approached,  distinct,  conical  villi  make  their  appearance,  which  he  thinks,  have  not  been 
previously  described  as  constant  by  any  of  the  writers  on  the  subject.  These  villi  are  not 
as  large  as  those  of  the  small  intestines,  but,  otherwise,  similar  in  appearance.  They  are 
mainly  composed  of  capillaries  closely  united  by  a  basement  membrane,  and  are  covered 
with  a  cylinder-epithelium.  In  the  antrum  pylori,  alveoli  of  different  shapes  exist  in  the 
interstices  and  at  their  bases.  Whether  they  contain  lacteals  or  not  is  doubtful. 

The  uses  of  these  gastric  villi  have  not  as  yet  been  ascertained.  Dr.  Neill  (1.  c.)  suggests,  that 
they  may  be  connected  with  the  absorption  of  solutions  of  albuminous  compounds. — DaC.J 


506 


SPECIAL    HISTOLOGY. 


Fig.  203. 


pyloric  region  to  f  or  1  line,  which  depends  entirely  upon  the  glandular 
layer,  since  the  epithelium  and  muscular  layer  everywhere  possess  the 
same  thickness.  The  submucous  tissue  is  abundant  and,  as  throughout 
the  whole  intestine,  contains  occasional  fat-cells. 

§  150.   The  gastric  glands. — The  gastric  glands — the  most  important 
part  of  the  mucous  membrane — are  tubular  glands  which,  set  close 

together,  pass  straight  through  the  entire 
thickness  of  the  mucous  membrane  to  its 
muscular  layer,  and  therefore  vary,  in  the 
different  regions  of  the  stomach,  from  -J-  to  f , 
or  even  1  line,  but  are  on  the  average  J  a 
line  in  length.  Each  of  them  commences 
as  a  cylindrical  tube,  of  0-03-0-04  of  aline 
in  diameter,  at  the  surface  of  the  mucous 
membrane,  diminishes  inferiorly  to  as  little 
as  0-014-0-02  of  a  line,  and  terminates  by 
a  clavate  or  flask-shaped  enlargement  of 
0-02-0-026-0-036  of  a  line.  The  lower 
third  of  the  glands  is  usually  undulated  or 
even  twisted  into  a  corkscrew  shape,  espe- 
cially at  the  pylorus  ;  occasionally  it  gives 
off  a  shorter  or  longer  csecal  branch  before 
its  termination.  Every  gastric  gland  is  sur- 
rounded by  a  delicate  membrana  propria  and 

possesses  in  its  upper  third,  a  cylindrical  epithelium  continuous  with  that 
of  the  surface  of  the  stomach  ;  for  the  inferior  three-fourths  of  its  extent, 
on  the  other  hand,  it  presents  pale,  finely  granular,  polygonal  nucleated 
cells  of  0-006-0-01  of  a  line,  which  probably  never  constitute  a  distinct 
epithelium,  but  appear  completely  to  fill  the  tubes.* 

FIG.  203. — Perpendicular  section  through  the  tunics  of  the  Pig's  stomach,  from  the  pylorus, 
magnified  30  diameters:  a,  glands;  6,  muscular  layer  of  the  mucous  membrane;  c,  submu- 
cous tissue  (tunica  nerved),  with  divided  vessels ;  d,  transverse  layer  of  muscles ;  e,  longitudi- 
nal layer  of  muscles;  /,  serous  membrane. 

*  [Professor  Kolliker  ("  Verhandlungen  der.  Phys.  Med.  Gesellsch.  zu  Wiirzb."  vol.  IV.  1, 
p.  52),  has  recently  had  the  opportunity,  in  a  case  of  suicide  by  drowning,  of  examining 
the  human  gastric  mucous  membrane  in  a  fresh  and  normal  state.  He  directed  par- 
ticular attention  to  the  glandular  apparatus,  and  found  that  the  gastric  glands  are  not 
as  uniform  in  structure  as  above-described,  but  present  three  distinct  types.  1.  Simple 
tubular  glands  with  peptic  cells,1  (Lab-zellen).  2.  Compound  tubular  glands  with  peptic 
cells.  3.  Compound  tubular  glands  with  cylinder  epithelium.  The  first  are  the  most 
common ;  they  occur  in  the  middle  zone  of  the  stomach,  and  are  generally  simple 
tubular  glands,  some  of  which  at  their  termination,  give  off  short  csecal  branches.  The 
compound  tubular  glands  with  peptic  cells  occur  in  the  narrow  cardiac  zone.  They  commence 
by  a  tube  of  0-04  to  OOSmm  long,  0  03  to  0  04mm  broad,  lined  with  cylinders.  This  divides 
first  into  two  or  three,  and  then  into  four  or  seven  equally  long  cylindrical  tubules,  which 


1  Vid.  p.  508. 


THE    STOMACH. 


507 


In  animals,  the  gastric  glands  are   more  complicated  than   in  man, 
frequently  presenting  dichotomous  divisions  and  subdivisions  of  their 


FIG.  204. — A,  mucous  gastric  gland  of  a  Dog,  from  the  pylorus,  with  cylinder  epithelium : 
a,  wide  cavity  of  the  gland ;  6,  its  caeca!  appendages.  12,  peptic  gastric  gland  from  the 
middle  of  the  stomach  :  a,  common  trunk  of  the  gland  ;  b,  its  chief  branches ;  c,  terminal 
caeca.  Magnified  60  diameters.  C,  a  portion  of  the  cceca,  magnified  350  diameters,  and 
viewed  longitudinally.  7),  the  same  viewed  in  transverse  section  :  a,  membrana  propria  •  b, 
large  cells  close  to  it;  c,  small  epithelium  round  the  cavity. 


are  lined  by  rounded  or  oval  cells  (peptic-cells),  and  which  run  side  by  side  to  the  base 
of  the  mucous  membrane.  In  these  cells  minute  oil-globules  are  frequently  observed.  The 
terminal  tubules  have  a  peculiar  twisted  appearance,  which  is  dependent  on  numerous 
lateral  dilatations.  In  this  part  of  the  stomach  no  racemose  glands  exist,  although  they  are 
found  in  the  lower  part  of  the  oesophagus. 

Between  both  these  forms  of  "  peptic  gastric  glands,"  (Magensaftdriisen)  Professor  Ko'lli- 
ker  observed,  fasciculi  of  contractile  fibre-cells,  but  he  denies  the  existence  of  the  spiral 
fibre-cells  investing  the  glands,  as  described  by  Ecker. 

The  compound  tubular  glands  with  cylinder-epithelium  occur  in  the  pyloric  zone,  and  resem- 
ble the  last-described  variety,  with  the  exception,  that  the  tubules  are  larger  and  devoid  of 
the  rounded  finely  granulated  peptic  cells.  Neither  simple  glands,  nor  racemose  glands,  as 
stated  by  Ecker,  are  here  observable. 

These  investigations  of  Professor  Kolliker  confirm  the  opinion  of  Bonders,  as  to  the  exis- 
tence of  two  varieties  of  glands  in  the  human  stomach,  viz.:  the  proper  gastric  glands 
(called  by  Kolliker  from  their  secretion  "peptic"  gastric  glands)  and  the  simple  mucous 
glands.  These  two  distinct  forms  have  been  previously  described  in  the  stomach  of  Mam- 
malia by  Kolliker  (Vid.  §  150,  infra  and  "  Mikroscopische  Anatomic"  II.  2,  p.  240),  but  in  Man 
their  existence  has  hitherto  not  been  satisfactorily  ascertained. — DaCJ 


508  SPECIAL    HISTOLOGY. 

free  ends;  in  many  genera,  they  are  of  two  very  distinct  kinds,  the 
mucou-s  gastric  glands,  with  a  cylinder  epithelium  and  the  peptic  gastric 
glands  (Magensaftdriisen)  with  cells  similar  to  those  which  exist  in  man. 
A  more  detailed  description  of  some  forms  will  be  found  in  my  "  Mikro- 
skop.  Anatomic"  (II.  2,  p.  140) ;  and  I  here  subjoin  figures  (p.  507)  of 
the  two  forms  of  the  glands  in  the  dog,  merely  to  render  my  meaning 
intelligible. 

The  secretion  of  the  gastric  glands  has  not  been  so  completely  exa- 
mined in  man,  that  we  can  say  with  certainty  whether  they  all  secrete 
gastric  juice  or  not.  A  few  experiments  which  I  instituted  with  regard 
to  this  point,  tend  to  show  that  here,  as  in  animals,  it  is  only  particular 
glands — those  in  fact  of  the  middle  of  the  stomach — which  yield  the 
proper,  active  secretion ;  however,  further  observations  must  be  made 
on  stomachs  in  the  freshest  and  most  normal  state,  to  confirm  this 
result.  In  any  case,  the  secretion  of  the  glands  is  for  the  most  part  a 
fluid,  though  in  the  mucus,  a  small  quantity  of  which  usually  covers  the 
mucous  membrane,  we  not  only  meet  with  half-destroyed  cylinder 
epithelium,  but  almost  invariably,  with  a  certain  quantity  of  proper 
glandular  cells  ;  and  it  is  impossible  to  say  whether  these  are  essential, 
or  only  accidental  constituents  of  the  glandular  secretion. 

In  many  animals  there  are  two  secretions  ivitli  different  properties 
corresponding  with  the  two  forms  of  gastric  glands,  a  fact  to  which 
Bischoff  and  Wasmann  first  drew  attention,  and  which  I  can  confirm. 
In  the  Dog,  glands  with  cylinder  epithelium  exist  in  the  pylorus;  those 
with  round  cells  in  the  remainder  of  the  stomach ;  there  is  the  same 
arrangement  in  Ruminants  and  in  the  Rabbit ;  whilst  in  the  Pig,  it  is 
only  the  middle  of  the  stomach  and  especially  the  great  curvature, 
which  presents  the  latter  glands.  A  series  of  experiments  on  artificial 
digestion,  which  were  carried  out  by  Dr.  Goll,  of  Zurich,  and  myself, 
principally  with  the  pig's  stomach,  afforded  the  distinct  result,  that,  so 
far  as  their  solvent  powers  are  concerned,  the  glands  present  very 
different  relations  ;  those  with  round  cells  act  upon  protein  compounds 
which  have  been  coagulated  by  acids  in  a  very  short  time,  while  those 
with  cylinder  epithelium,  either  have  no  action  at  all  or  take  a  long  time 
to  produce  a  slight  effect.  Furthermore  a  well-marked  acid  reaction  is 
presented  by  that  region  of  the  stomach  only  in  which  the  former  glands 
are  situated.  The  active  organic  substance,  pepsin,  is  not  contained  in 
the  gastric  mucus,  which  consisting  of  detached  epithelium  cylinders, 
often  form  a  thick  covering  over  the  mucous  membrane,  but  in  the  finely 
granulated,  rounded  cells  of  the  peptic  gastric  glands,  to  which  there- 
fore the  term  peptic  cells  (Labzellen,  Frerichs)*  may  well  be  applied. 
According  to  my  observations,  however,  these  peptic  cells  do  not  neces- 
sarily become  thrown  off,  nor  take  any  direct  share  in  digestion,  but 

*  [Literally,  "rennet-cells."— TRS.] 


THE    STOMACH.  509 

frequently  exert  their  action  simply  by  pouring  the  juice  which  they 
prepare  into  the  glands. 

§  151.  We  have  seen,  that  beside  the  glands,  only  a  very  scanty  tis- 
sue enters  into  the  mucous  membrane.  Around  their  extremities  alone, 
do  we  find  a  dense,  continuous,  reddish  layer  0-022-0-044  of  a  line  in 
thickness  (Briicke),  the  muscular  layer  of  the  mucous  membrane,  con- 
sisting of  bundles  of  common  connective  tissue  and  of  smooth  muscles, 
interwoven,  the  latter  of  which  cross  one  another  principally  in  two 
directions,  and,  in  the  Pig,  even  pass  between  the  glands  and  into  the 
plicce  villosce.  In  man,  we  meet  only  with  vessels,  and  an  amorphous 
connective  tissue,  without  elastic  fibrils,  interposed  between  the  glands, 
forming  at  the  surface  of  the  mucous  membrane,  a  clear,  perfectly 
homogeneous  stratum,  the  structureless  membrane  of  authors,  which  is 
continuous  with  the  membrane  proprice  of  the  separate  glandular 
tubes,  but  cannot,  like  them,  be  isolated. 

The  whole  internal  surface  of  the  stomach  from  the  cardia  (where 
the  tessellated  epithelium  of  the  oesophagus  terminates  by  a  sharp 
notched  edge),  possesses  a  simple  covering  of  cylindrical  cells,  about 
0-01  of  a  line  long  on  the  average,  which  lie  immediately  upon  the 
outermost  homogeneous  portion  of  the  mucous  membrane,  without  any 
interposed  substance.  During  life,  this  cylinder  epithelium — whose 
other  relations  will  be  treated  of  below,  in  describing  the  small  intes- 
tine, where  a  layer  of  exactly  similar  nature  is  to  be  met  with — is 
closely  united  with  the  mucous  membrane,  though  not  so  intimately,  but 
that  its  elements  are,  at  times,  detached  to  a  larger  or  smaller  amount 
by  the  mechanical  violence  to  which  it  is  necessarily  occasionally  sub- 
jected in  the  stomach.  After  death  this  takes  place  so  readily,  that  the 
cells  can  be  seen  in  situ,  in  man,  only  under  very  favorable  circum- 
stances. Perhaps,  also,  detachment  of  the  epithelium  to  a  certain  ex- 
tent may  take  place  normally,  in  one  way  or  another,  during  digestion; 
at  least,  in  animals  the  quantity  of  loose  epithelial  cells  is  often  very 
great  and  they  frequently  almost  entirely  constitute  the  mucous  coating 
which  covers  the  surface  of  the  stomach. 

Besides  the  tubular  glands,  the  stomach  also  contains,  though  they 
are  inconstant  and  vary  very  much  in  number,  closed  follicles — the  so- 
called  lenticular  glands,  which  are  identical  in  structure  with  the  soli- 
tary follicles  of  the  small  intestine,  and  therefore  need  not  be  further 
described  in  this  place.* 

*  ["  Although  it  may  be  that  the  lenticular  glands  of  the  stomach  are  always  present  in 
children,  they  are  certainly  inconstant  in  adults,  since  in  many  cases  no  trace  whatever  can 
be  discovered  of  them.  In  other  instances  they  are  exceedingly  numerous,  covering  the 
whole  surface  of  the  stomach,  but  in  this  case,  the  invariably  diseased  state  of  the  alimen- 
tary tract,  suggests  the  idea,  that  they  stand  in  some  connection  with  it.  In  many  mammalia 
no  trace  of  such  structure  is  to  be  found,  while,  according  to  Bischoff  (Mull.  Arch.  1838), 


510 


SPECIAL    HISTOLOGY. 


The  bloodvessels  of  the  gastric  mucous  membrane  are  very  numerous, 
and  their  distribution  is  quite  characteristic  (compare  Fig.  205,  repre- 
Fi<r  205.  senting  the  vessels  of  the  large  intestine,  whose 

arrangement  is  almost  the  same).  The  arteries 
begin  to  divide  in  the  submucous  connective  tis- 
sue, in  such  manner,  that  only  their  finer  branches 
reach  the  mucous  membrane,  in  which,  gradually 
breaking  up  into  capillaries,  they  ascend  in  great 
numbers,  perpendicularly,  between  the  glands  and 
form  a  network  of  fine  capillaries  of  0-002-0-003 
of  a  line,  around  the  tubes,  which  extends  as  far 
as  to  the  apertures  of  the  glands.  Here  this 
network,  which  we  may  regard  as  continuous 
through  the  whole  stomach,  passes  into  a  super- 
ficial reticulation  of  somewhat  larger  capillaries, 
of  0-004-0-008  of  a  line,  whose  meshes,  in  man, 
are  polygonal,  0-02-0-04  of  a  line  in  diameter, 
and  encircle  the  apertures  of  the  glands ;  it  is 
more  complicated  or  more  simple,  according  to  the  breadth  of  the  in- 
terspaces of  the  glands  and  the  occurrence  of  elevations  upon  them,  but 
seems  never  to  consist  of  simple  vascular  rings.  From  this  network  the 
veins,  which  are  relatively  wide,  arise  by  many  radicles  ;  they  then,  fur- 
ther apart  from  one  another  than  the  arteries,  and  receiving  no  more 
blood,  penetrate  the  glandular  layer,  and  upon  the  outer  surface  of  the 
mucous  membrane,  enter,  often  at  right  angles,  a  wide  venous  network 
with  partly  horizontal  vessels,  in  the  submucous  tissue. 

The  lymphatics  of  the  stomach  form  a  superficial  fine  network  and 
a  deep,  coarse,  one  ;  and  can  only  be  demonstrated  by  injection.  The 
numerous  small  branches  which  pass  from  the  mucous  membrane,  their 
aggregation  into  larger  trunks,  and  final  penetration  of  the  muscular 
tunic,  are  readily  seen  in  large  Mammalia,  killed  during  digestion.  The 

FIG.  205. — Vftssels  of  the  large  intestine  of  a  Dog,  the  raucous  membrane  being  cut 
through  perpendicularly ;  a,  artery ;  6,  capillary  network  of  the  surface,  with  glandular 
apertures ;  c,  vein ;  d,  capillary  network  round  the  glandular  tubules  in  the  thickness  of  the 
mucous  membrane. 

they  occasionally  exist  in  the  dog,  invariably  in  the  pig,  and  so  far  as  the  latter  animal  is 
concerned,  I  can,  w;ih  Wasmann,  confirm  this  statement.  They  are  here,  as  Bischoff  sup- 
poses and  as  is  evident  from  Wasmann's  description,  not  isolated,  but  aggregated  glands,  true 
minute  Peyer's  glands.  The  aggregations  measure  1-2^  lines,  are  distributed  especially  upon 
the  cardia  and  small  curvature,  and  are  readily  seen  upon  stripping  off  the  muscular  and  sub- 
mucous  tissue.  At  first  sight,  they  appear  to  lie  entirely  in  the  last-named  layer,  but  if  the 
attempt  be  made  to  detach  them,  it  is  found,  that  this  cannot  be  done  without  tearing  the 
mucous  membrane,  to  which  they  closely  adhere.  On  the  internal  surface,  small  depres- 
sions are  seen  where  these  patches  occur,  and  the  gastric  glands  are  here  either  absent  or 
undeveloped."  Kolliker.  Mikr.  Anat.  II.  2,  p.  151.— TRS.] 


THE    INTESTINES.  511 

nerves  of  the  stomach,  derived  from  the  vagus  and  sympathetic,  are 
readily  traced  into  the  submucous  tissue  and  they  may  also  be  observed 
entering  the  muscular  layer  of  the  mucous  membrane ;  but  it  becomes 
impossible  to  follow  them  further,  principally  because,  in  the  interior  of 
the  mucous  membrane  itself,  they  present  no  more  dark-edged  tubules, 
but  probably  only  the  pale  embryonic  fibres.* 

MUCOUS  MEMBRANE  OF  THE  SMALL  INTESTINE. 

§  152.  The  mucous  membrane  of  the  small  intestine  is  thinner  than 
that  of  the  stomach,  but  more  complex  in  its  structure,  inasmuch  as, 
besides  the  tubular  or  Lieberkuhnian  glands,  it  presents  a  great  number 
of  permanent  folds  and  villi  ;  also,  imbedded  in  its  substance,  peculiar 
closed  follicles,  the  so-called  solitary  and  Peyer's  glands  and,  in  the  sub- 
mucous  tissue  of  the  duodenum,  Brunners  glands. 

The  mucous  membrane  consists  of  connective  tissue,  which  is  inter- 
nally homogeneous  or  indistinctly  fibrillated;  except  where  certain 
glands  exist,  there  is  but  little  submucous  tissue,  so  that  it  is  pretty 
closely  connected  with  the  muscular  tunic.  Upon  the  inner  surface  of 
the  mucous  membrane,  there  rests  a  cylinder  epithelium,  to  which  further 
reference  will  be  made  under  the  head  of  the  villi;  whilst  externally, 
towards  the  submucous  tissue,  it  is  bounded  by  a  layer  of  smooth  muscles, 
discovered  by  Brlicke,  which  measures,  at  most,  0-0177  of  a  line ;  they 
are  disposed  longitudinally  and  transversely,  but  in  man  their  slight 
development  renders  it  often  very  difficult  to  discover  them. 

§  153.  The  villi  of  the  small  intestine  are  small,  whitish  elevations  of 
the  innermost  portion  of  the  mucous  membrane,  readily  distinguishable 
with  the  naked  eye  and  which,  distributed  upon  and  between  the  valvulce 
conniventes  (Kerkringian  valves)  through  the  whole  extent  of  the  small 
intestine,  from  the  pylorus  to  the  sharp  edge  of  the  ileo-c0ecal  valve 
(valvula  Bauhini),  are  set  so  close  together  as  to  give  the  mucous  mem- 
brane its  well-known  velvety  appearance.  They  are  most  numerous 
(50-90  upon  a  square  line)  in  the  duodenum  and  jejunum,  less  so  in  the 
ileum  (40-70  upon  a  square  line).  In  the  duodenum  they  are  broader 
and  less  elevated,  resembling  folds  and  laminae  1-10-1-4  of  a  line  in 
height,  1-6-1-2  or  even  3-4  of  a  line  in  breadth.  In  the  jejunum,  they 

*  [  In  his  "  Mikroskopische  Anatomic,"  B.  II.  2,  pp.  149, 153, 164,  Professor  Koiliker  shows 
that  the  nvuscular  layer  of  the  raucous  membrane  of  the  stomach  and  intestine  was  discovered 
by  Middeldorpf  (De  Glandulis  Brunnianis,  Vratisl.  1846,  c.  tab.)  but  remained  unnoticed 
until  it  was  rediscovered  by  Brilcke  and  himself.  In  the  small  intestine  there  are,  when 
this  muscular  stratum  is  well  developed,  two  layers,  though  they  are  not  always  complete  ; 
the  external  layer  is  composed  of  longitudinal,  the  internal  of  transverse  fibres. 

In  the  villi,  the  smooth  muscular  fibres  have  been  found  not  only  in  many  mammalia,  but 
also  in  birds.  The  contraction  of  the  villi  which  they  effect  appears  to  have  been  noticed 
by  Lacauchie,  Gruby  and  Delafond,  so  long  ago  as  1842. — TRS.] 


512 


SPECIAL    HISTOLOGY. 


appear  for  the  most  part  to  be  conical  and  flattened ;  frequently,  they 
are  even  foliated  or  cylindrical,  clavate  or  filiform,  the  three  latter  forms 

Fig.  206.  Fig.  207. 


predominating  in  the  jejunum.  The  length  of  the  villi  is  from  1-5-1-2 
of  a  line;  the  breadth  from  1-6-1-10,  even  1-25  of  a  line;  the  thickness 
in  the  flattened  forms  1-20  of  a  line. 

The  villi  are  composed  of  two  portions,  a  deeper,  belonging  to  the 
mucous  membrane  and  an  epithelial,  superficial  coat.  The  contour  of 
the  former  or  villus  proper,  is  similar  to  that  of  the  entire  villus;  it  is 
simply  a  solid  process  of  the  mucous  membrane,  containing  bloodvessels, 
lymphatics  and  smooth  muscles,  whose  matrix,  through  which  a  variable 
number  of  roundish  nuclei  are  scattered,  in  general  exhibits  no  morpho- 
logical character  more  decided  than  that  of  the  mucous  membrane  itself, 
yet  must  most  undoubtedly  be  regarded  as  a  metamorposed  connective 
tissue,  without  any  intermixture  of  elastic  tissue.  The  bloodvessels  of  the 

FIG.  200. — Section  through  the  walls  of  the  lowest  portion  of  a  Calf's  ileum,  magnified  60 
diameters:  a,  villi ;  6,  Lieberkilhn's  glands;  f,  muscular  layer  of  the  mucous  membrane;  d, 
follicles  of  a  Peycrs  patch;  e,  remainder  of  the  submucous  tissue  under  them;  f,  circular 
muscles;  g,  longitudinal  muscles. 

FiG.  207. — Intestinal  villus  of  a  young  Kitten  without  its  epithelium,  to  which  acetic  acid 
has  been  added ;  o,  boundary  of  the  villus;  6,  subjacent  nuclei ;  c,  nuclei  of  the  smooth  mus- 
cles ;  rf,  round  nuclei  in  the  centre  of  the  villus. 


THE    INTESTINES. 


513 


Fig.  209. 


villi  (Fig.  208)  are  so  numerous,  that  when  well  injected,  those  whose  epi- 
thelium has  be"en  detached  become  colored  throughout ;  and,  in  living 
animals,  or  those  which  have 
just  been  killed,  each  villus,  if 
viewed  from  above,  appears  as 
a  red  dot  surrounded  by  a 
clear  ring.  In  man,  every 
villus  contains  a  close  network 
of  capillaries  of  0-003-0-005 
of  a  line,  with  rounded  or  elon- 
gated nuclei,  which  lies  imme- 
diately beneath  the  homoge- 
neous external  layer  of  the 
matrix*  and  is  supplied  by  one, 
two,  or  three  small  arteries  of 

0-01-0-016  of  a  line.  The  blood  is  usually  carried  back  directly  into  the 
larger  trunks  of  the  submucous  tissue,  by  a  vein  of  0-022  of  a  line, 
which  does  not  arise,  as  in  animals,  by  the 
arching  round  of  the  artery,  but  proceeds 
from  the  gradual  confluence  of  the  finest  capil- 
laries. 

The  relations  of  the  lacteals  in  the  villi 
of  man,  have  not  hitherto  been  perfectly 
made  out;  for  although  the  majority  of 
investigators  are  inclined,  like  the  older  ob- 
servers, to  suppose  that  they  commence  by 
one  or  two  csecal  branches,  yet  recently,  more 
and  more  voices  Appear  to  be  raised  for  the 
view  that  they  originate  in  a  plexiform  man- 
ner. As  to  my  own  opinion,  I  can  affirm  no- 
thing with  respect  to  the  human  subject,  since  I 
have  never  succeeded  in  meeting  with  villi  dis- 
tended with  chyle,  and  in  empty  ones,  I  have 
been  unable  to  obtain  any  decisive  evidence ; 
on  the  other  hand,  in  animals,  I  feel  certain 
that  in  many  cases  only  a  single  lacteal,  which 
has  a  csecal  and  frequently  enlarged  end,  and 
whose  diameter  is  much  greater  than  that  of 
the  capillaries,  traverses  the  axis  of  the  villus 
(Fig.  209.) 

FIG.  208. — Vessels  of  a  few  villi  of  the  Mouse,  after  one  of  Gerlach's  injections;  magni- 
45  diameters. 

FIQ.  209. — Two  villi  without  epithelium  and  with  the  lacteal  in  their  interior  (from  the 
Calf),  magnified  350  diameters,  and  treated  with  a  dilute  solution  of  caustic  soda. 

*  [The  "  basement  membrane"  of  Tocld  and  Bowman. — ED.] 

33 


m 


514 


SPECIAL    HISTOLOGY. 


Fig.  210. 


For  my  own  part  in  fact,  I  believe  that  all  the  narrow  cylindrical  and 
filiform  villi  will  be  found  to  present  this  condition,  but  that,  on  the 
other  hand,  the  number  and  mode  of  origin  of  the  lacteals  may  possibly  be 
different  in  the  broad  and  foliaceous  forms  (see  Mikr.  Anat.,  ii.  2,  p.  160). 
In  addition  to  these  organs,  the  villi  also  contain,  as  Brucke  dis- 
covered a  short  time  ago,  a  thin  layer 
of  longitudinal  smooth  muscles  situ- 
ated more  centrally  round  the  lacteals  ; 
these,  however,  are  not  always  distinct 
in  man.  They  produce  contractions  of 
the  villi  (Fig.  210),  which  are  very 
evident  immediately  after  death,  and 
which,  according  to  Briicke,  are  also 
perceptible  in  the  living  animal.  They 
have,  in  all  probability,  an  important 
influence  over  the  propulsion  of  the 
chyle  and  of  the  venous  blood  in  the 
villi — always  supposing  that  there  is  no 
objection  to  the  assumption  that  they 
perform  repeated  contractions  during  life.  Nothing  is  known  of  the 
nerves  in  the  villi. 

The  epithelium  of  the  villi  and  of  the  rest  of  the  surface  of  the 
mucous  membrane,  although  it  is  very  intimately  united  with  the  deeper- 
seated  parts  during  life,  only  becoming  detached  accidentally  or  by  dis- 
ease, separates  very  readily  in  the  dead  subject,  and  can  only  be  ob- 
served in  perfectly  fresh  portions  of  intestine.  It  consists  everywhere 
of  a  simple  layer  of  cylindrical  cells  slightly  narrowed  below,  of  0-01- 
0-012  of  a  line  in  length,  and  0-003-0-004  of  a  line  in  breadth,  whose 
contents  are  usually  nothing  but  fine  granules  and  an  oval,  clear,  vesi- 
cular nucleus,  provided  with  one  or  two  nucleoli.  During  life,  these 
cells,  which  agree  in  all  their  chemical  characters  with  the  deeper  cells 
of  the  oral  epithelium,  are  so  intimately  united,  that  even  after  death 
their  contours,  in  a  longitudinal  view,  are  at  first  either  not  at  all,  or 
only  indistinctly  distinguishable,  though  on  the  surface  they  have  the 
appearance  of  a  beautiful  mosaic.  The  cylinders  only  become  quite 
distinct  when  they  are  either  spontaneously  or  artificially  detached,  a 
process  which  usually  takes  place  in  such  a  manner  that  they  hang 
together  in  continuous  portions,  all  the  cells  covering  a  villus  sometimes 
coming  off  together  like  the  calyptra  of  a  moss.  The  addition  of  water 
to  these  cells  produces  a  separation  of  the  cell  contents  from  the  broad 
end,  giving  rise,  in  separate  cells,  to  the  appearance  of  a  membrane 
thickened  upon  one  side  and  in  series  of  cells  or  entire  villi,  to  that  of 


FIG.  210. — Two  intestinal  villi  of  the  Cat,  contracted,  and  magnified  60  diameters. 


THE    INTESTINES. 


515 


a  peculiar  structureless  coat,  like  the  cuticle  of  plants ;  by  its  longer 
action,  however,  or  by  -that  of  the  intestinal  fluids,  the  bursting  of  the 


Fig.  211. 


cells  produces  apertures  in  them,  or  they  become  distended  into  large 
pyriform  clear  vesicles. 

We  may  here  refer  to  the  changes  which  the  epithelial  cells  and  the 
mlli  in  general  undergo  during  digestion.  The  most  striking  circum- 
stance is  the  occurrence  of  fat  in  different  parts  of  the  villi,  which  may 
always  be  observed  during  the  formation  of  a  fatty,  milk* white  chyle. 
The  succession  of  the  morphological  steps,  at  least  as  I  have  observed 
them  in  animals,  is  as  follows:  The  fat  contained  in  the  chyme  at  first 
enters  only  isolated  epithelial  cells  in  different  regions  of  the  villi,  so 
that  in  each  we  soon  observe  a  large  ovate  shining  drop.  The  number 
of  these  fat-cells  rapidly  increases,  and  then  the  mlli  acquire  a  very 
peculiar  appearance,  often  as  if  beset  with  pearls,  from  the  irregular 
alternation  of  cells  filled  with  fat  and  consequently  bright  and  shining, 
with  those  which  are  empty  and  pale.  In  the  end,  all  the  cells  become 
filled  with  these  drops  and  the  epithelium  appears  quite  dark  by  trans- 
mitted, but  whitish  by  reflected  light,  giving  its  aspect  to  the  whole 
villus^  With  the  repletion  of  the  entire  epithelial  covering  of  the  villus 

FIG.  211. — jl,  two  villi,  with  their  epithelium,  from  the  Rabbit;  magnified  73  diameters: 
o,  epithelium  •  b,  parenchyma  of  the  villus.  B,  a  detached  sheet  of  epithelium,  magnified  300 
diameters :  a,  membrane  raised  up  by  the  action  of  water.  C,  single  epithelial  cells,  mag- 
nified 350  diameters :  a,  with,  b,  without,  a  raised-up  membrane ;  c,  a  few  cells  from  the 
surface. 


516  SPECIAL    HISTOLOGY. 

absorption  commences,  but  up  to  tbis  time  nothing  bas  entered  tbe  lac- 
teals.  This,  however,  soon  takes  place,  and  the  first  indication  we  ob- 
serve, is  the  breaking  up  of  the  large  drops  of  fat  in  the  cells  into  many 
tolerably  minute  fatty  molecules.  When  this  has  occurred,  these  drops 
penetrate  by  degrees,  from  all  sides,  into  the  parenchyma  of  the  villus 
itself,  fill  it  more  and  more  and,  at  last,  enter  the  central  lacteal,  whose 
whole  length  they  eventually  occupy.  In  the  meanwhile,  fresh  fat  has 
been  continually  passing  in  from  the  intestinal  canal,  not  in  the  form  of 
large  drops,  however,  but  henceforward,  in  small  molecules  or  drops  of 
the  same  kind  as  those  which  were  at  first  developed  secondarily  in  the 
cells.  On  the  other  hand,  at  a  subsequent  period,  we  not  uncommonly 
meet,  in  the  interior  of  the  villi,  with  large  round  drops,  which  appear 
especially  inclined  to  form  considerable  accumulations  at  their  apex. 
In  man,  I  have  not  yet  had  the  opportunity  of  tracing  the  process  of 
the  absorption  of  fat,  step  by  step,  but  we  may  here  so  frequently  ob- 
serve, on  the  one  hand,  cylindrical  epithelial  cells  filled  with  fatty  mole- 
cules, and  on  the  other,  collections  of  larger  and  smaller  drops  of  fat 
in  the  parenchyma  of  the  villi,  especially  at  their  points  and  in  their 
axes,  that  I  do  not  at  all  hesitate  to  suppose  the  process  to  be  the  same 
as  in  animals,  without,  however,  wishing  to  imply  that  all  the  steps  are 
identical.  These  observations  demonstrate  that  fatty  matters  are  ab- 
sorbed as  such  and  are  not  saponified ;  on  the  other  hand,  it  cannot  at 
present  be  certainly  stated  how  it  is  possible  that  they  penetrate  the 
membrane  of  the  epithelial  cells,  the  parenchyma  of  the  villi,  and  the 
walls  of  the  lacteals.  I  should  be  most  inclined  to  compare  the  whole 
process  to  the  imbibition  of  an  emulsive  fluid,  such  as  milk,  by  a  porous 
body ;  and  I  believe  that  the  fatty  molecules  of  the  chyme  are  absorbed 
simply  in  consequence  of  their  being  carried  along  with  its  fluid  part.* 

*  [Professor  Brucke,  in  a  series  of  important  papers  on  the  "  Lacteals  and  on  the  Absorp- 
tion of  Chyle"  (Ueber  die  Chylusgefftsse  und  die  Resorption  des  Chylus),  published  in  the 
Transactions  of  the  Vienna  Academy  for  1854,  has  thrown  much  light  on  the  difficult 
question  of  the  anatomy  and  physiology  of  the-parts  concerned  in  digestive  absorption. 

As  the  result  of  his  observations  on  Man  and  on  the  Mammalia,  Brucke  states,  that  the 
cylindrical  epithelial  cells  covering  the  villi,  are  open  at  one  extremity,  and  are  not,  as  is 
generally  supposed,  closed  by  a  membrane,  but  merely  by  a  thin  layer  of  a  mucilaginous 
substance.  This,  he  asserts,  can  be  proved  by  observations  on  animals  recently  killed;  for 
if  a  portion  of  their  intestinal  mucous  membrane  be  brought  under  the  field  of  the  micro- 
scope, the  formation  of  transparent  vesicles,  corresponding  to  each  epithelial  cell  may  be 
easily  seen.  These  vesicles  form  along  the  margin  of  the  villus,  and  are  the  cell-contents 
•which  have  escaped  from  the  open  extremity  of  the  cylindrical  cell,  enclosed  by  the  muci- 
laginous substance.  They  have  hitherto  been  regarded  as  the  cell- wall  rendered  prominent 
by  an  expansion  of  the  cell-contents  (vid.  supra,  Fig  211,  C  a)  ;  but  that  this  view  is  in- 
correct, is  evident  from  the  circumstance,  that  they  lie  perfectly  isolated  by  the  sidje  of  the 
cells,  without  any  change  in  the  membrane  of  the  latter  being  observable. 

As  another  evidence  of  these  epithelial  cells  not  being  closed  cavities,  Professor  Brucke 
adduces  the  fact,  that  even  by  the  aid  of  the  highest  magnifying  powers,  no  cell  membrane 
with  pores  can  be  distinguished.  Yet  the  oil  globules,  which  are  always  of  a  distinctly  re- 
cognizable size,  are  known  to  enter  the  cells,  and  it  is  difficult  to  understand  how  they  can 
traverse  a  homogeneous  membrane. 


THE    INTESTINES.  517 

While  digestion  is  going  on,  we  frequently  find  the  whole  parenchyma 

of  the  mlli  densely  filled  with  small  nuclei,  here  and  there  surrounded 

,  • 

This  difficulty  is  increased  when  we  consider,  that  a  trustworthy  observer  (Osterlein)  has 
detected  solid  particles  in  the  interior  of  the  epithelial  cells.  By  assuming,  however,  that 
these  latter  are  open  at  one  extremity,  and  are  isolated  from  the  intestinal  tube  merely  by  a 
thin  layer  of  mucilaginous  substance,  which  is  easily  traversed,  Professor  Brucke  thinks  the 
difficulty  may  be  solved.  The  chyle,  he  states,  passes  from  within  the  cell  through  an 
opening  in  the  opposite  extremity  into  the  villus.  Within  the  villus,  the  molecules  of  chyle 
lie  in  the  lacteal  and  in  the  interstices  of  the  delicate  stroma,  which  connects  the  walls  of 
the  villus  with  its  muscular  fibres  and  bloodvessels.  The  lacteal,  Professor  Briicke  regards 
not  as  a  vessel,  but  as  a  mere  cavity  in  the  centre  of  the  villus,  without  distinct  walls.  In 
Cylindrical  villi  he  generally  found  one  cavity,  in  broad  villi,  two,  three,  or  even  four  dis- 
tinct canals.  Of  the  structureless,  thin  membrane,  described  by  Kolliker  as  surrounding  the 
lacteals,  he  was  not  able  to  observe  any  traces.  He  also  denies  the  commencement  of  the 
lacteal  by  a  distinct  network,  as  stated  by  Hewson,  Krause,  and  Hyrtl,  and  thinks  that  these 
observers  have  mistaken  capillaries  for  lacteals.  The  lacteal  he  regards,  on  the  contrary, 
as  originating  by  irregular  channels  formed  by  the  interstices  in  the  tissues  of  the  villus. 

The  commencement  of  the  complete  chyliferous  vessels  occurs  in  the  deeper  part  of  the 
mucous  membrane.  In  the  submucous  areolar  tissue  large  vessels  with  distinct  walls,  and 
furnished  with  valves  and  an  epithelium,  are  observable.  In  the  smaller  ramifications 
these  cannot  be  detected;  nor  can  a  separate  tunica  propria  of  the  walls  be  distinguished 
from  the  areolar  tissue  which  forms  the  adventitia.  In  the  muscular  layer  the  chyliferous 
vessels  have  valves ;  they  are  accompanied  on  each  side  by  an  artery  and  vein.  In  the 
mucous  and  submucous  tissue  no  such  arrangement  of  the  bloodvessels  exists. 

The  chyle,  Professor  Brucke  asserts,  does  not  enter  the  vessels  merely  from  the  villi,  but 
also  from  between  them,  and  principally  from  between  the  glands  of  Lieberkiihn,  where  it 
may  be  observed  lying  free  in  the  interstices  of  the  tissue.  This  commencement  of  the 
chyliferous  vessels  by  open  extremities  in  the  interstices  of  the  stroma  of  tissues,  he  regards 
as  sufficient  to  account  for  the  circumstance,  that  absorption  may  take  place  in  parts  of  the 
intestinal  canal  not  possessed  of  villi,  as  in  the  large  intestine.  The  lymphatics,  as  well  as 
the  chyliferous  vessels,  he  considers  to  commence  by  channels  in  the  tissues,  and  thus 
the  curious  fact  noticed  by  him  (vid.  "  Denkschriften  der  Wien  Acad.,"  vol.  ii.  p.  21), 
that  a  colored  solution  may  penetrate  through  the  capsules  of  the  Peyerian  glands  and  reach 
the  thoracic  duct,  is  readily  explained. 

With  regard  to  the  anatomy  of  the  chyliferous  vessels  after  they  leave  the  intestinal  walls, 
Brucke  confirms  the  recent  observations  of  Ludwig  and  Noll  (yid.  §  219,  infra).  The  best 
method  to  examine  the  commencements  of  the  chyliferous  vessels,  is  to  allow  the  chyle 
time  to  coagulate  in  the  vessels,  and  then  to  render  the  walls  of  the  intestine  transparent. 
This  is  most  readily  effected  by  a  solution  of  albumen  in  caustic  potassa,  to  which  enough 
hydrochloric  acid  has  been  added  to  neutralize  the  alkali. 

In  the  animals  he  examined,  Professor  Brucke  found  the  arrangement  of  the  chyliferous 
vessels  to  be  in  the  main  similar  to  that  in  Man.  In  the  Weasel  there  is  no  difference.  Tri 
the  Rabbit  the  chyle  is  not  contained  in  separate  channels,  but  is  situated,  throughout  the 
whole  thickness  of  tlie  intestinal  wall,  in  the  interstices  between  the  sheaths  of  the  blood- 
vessels. In  this  animal,  therefore,  the  chyle  is  separated  from  the  blood  merely  by  the 
thickness  of  the  membranes  of  the  bloodvessels,  whilst  in  Man  this  is  the  case  only  in  the 
mucous  layer  of  the  intestine.  In  the  Pig,  the  walls  of  the  chyliferous  vessels  exhibit  a 
distinct  layer  of  muscular  fibres.  In  the  Mouse,  the  deposits  of  chyle  in  the  interstices  be- 
tween the  glands  of  Lieberkuhn  are  readily  seen. 

The  contractions  of  the  intestinal  canal  Brucke  considers  to  be  the  principal  means  by 
which  the  chyle  is  forced  into  the  villi,  these  latter  being  kept  erect  and  distended  by  the 
pressure  of  the  blbod  in  their  bloodvessels.  As  the  chyle  in  the  villi  surrounds  the  blood- 
vessels, a  mutual  interchange  of  some  of  the  elements  takes  place  ;  the  blood  yields  up  fibrine 
to  the  chyle,  and  the  chyle  a  portion  of  its  soluble  parts  to  the  blood. 

When  the  villi  are  filled,  the  contraction  of  their  muscular  fibres  presses  the  chyle  into 


518  SPECIAL    HISTOLOGY. 

by  cell  membranes,  elements  which  are  perhaps  never  entirely  absent 
in  a  villus,  but  are  at  other  times  far  fewer,  and  particularly  are  not  to 
be  distinguished  in  its  interior.* 

§  154.  G-lands  of  the  small  intestine. — The  small  intestine  contains 
only  two  kinds  of  true  glands ;  viz.,  1,  tubular  glands,  which  are  dis- 

the  channels  between  the  mucous  and  submucous  membrane.  If  the  villi  be  much  dis- 
tended, a  portion  of  the  chyle  passes  back  again  through  the  epithelial  cells  into  the  cavity 
of  the  intestinal  tube,  and  this  is  especially  apt  to  occur  when  the  chyle  contains  any  par- 
ticles too  coarse  to  circulate.  The  chyle  is  propelled  further  by  the  muscular  con- 
tractions of  the  intestines  into  the  vessels  of  the  mesentery,  whence  it  is  pumped,  as  it 
were,  into  the  thoracic  duct,  by  the  alternating  pressure  on  the  intestinal  walls  during  the* 
movements  of  respiration.  This  action  is  also  aided  to  a  slight  extent  by  the  contractions 
of  the  muscular  tissue  of  the  chyliferous  vessels. 

The  results  arrived  at  by  Professor  Briicke,  will,  if  corroborated  by  future  research,  tend 
greatly  to  elucidate  much  that  has  hitherto  been  obscure  in  the  physiology  of  the  digestive 
as  well  as  of  interstitial  absorption. — DaC.] 

*  [One  of  the  most  important  contributions  to  our  knowledge  of  the  anatomy  of  the  villi 
and  the  general  physiology  of  digestive  absorption,  which  has  appeared  for  a  long  time,  is 
Professor  Briich's  "Beitrage  zur  Anatomic  und  Physiologic  der  Dtlnndarm-Schleimhaut," 
in  Siebold  and  Kolliker's  "  Zeitschrift,"  for  April,  1853.  We  subjoin  the  principal  results 
at  which  the  Professor  has  arrived. 

The  epithelium  is  not  cast  off  during  normal  digestion  and  in  freshly  killed  animals  it  is 
somewhat  difficult  to  detach  it  from  the  mucous  membrane.  The  cells  of  the  epithelium 
do  not,  as  Weber  stated,  undergo  any  change  of  form  during  digestion  and  chylification,  but 
they  become  filled  with  fat,  which  gradually  passes  on  into  the  villi,  &c.,  so  that  in  the 
fasting  state  they  are  again  free  from  any  foreign  contents. 

The  villi  ordinarily  contain  two,  but  sometimes  many,  capillary  trunks,  which  ramify 
principally  at  their  apices,  and  superficially.  Ramifications  and  anastomoses  in  the  body  of 
the  villi  are  less  common.  In  dogs,  many  parallel  vessels  often  run  undivided  for  a  con- 
siderable distance,  and  have  doubtless  been  confounded  with  a  central  lacteal. 

In  all  the  animals  Briich  examined,  and  in  man,  he  found  that  the  villi  had  a  striking 
uniformity  of  structure.  A  single  lacteal  ran,  without  dividing,  through  the  villus,  and  terminated 
shortly  before  reaching  its  apex,  in  a  ccecal  commonly  enlarged  end  (Liberkiihn's  ampulla).  The 
lacteal  had  no  wall,  appearing  to  be  a  mere  excavation  in  the  villus.  In  cleft  villi,  the 
lacteal  was  cleft,  each  end  terminating  in  a  caecum.  In  very  rare  cases,  there  were  in 
broad  villi  two  lacteals,  a  shorter  and  a  longer,  terminating  in  distinct  ampulla,  side  by  side. 
In  the  mucous  membrane  itself,  the  lacteals  form  a  wide  superficial  network. 

Bruch  accounts  for  the  supposed  lacteal  network  of  the  villi,  by  showing  that  the  blood- 
vessels are  as  capable  of  absorbing  fat  as  the  lacteals,  and  when  filled,  of  course  acquire  the  ap- 
pearance of  a  lacteal  network.  In  some  cases  he  found  the  superficial  capillary  network  of 
a  villus  half  red  and  half  white,  and  it  was  frequently  possible,  when  the  fatty  contents  of 
the  capillary  network  were  hidden  by  the  preponderating  blood,  to  render  them  obvious  by 
the  action  of  water,  which  dissolved  out  the  coloring  matter  and  thus  apparently  converted 
a  capillary,  into  a  lacteal  network. 

Professor  Bruch  considers  that  the  absorption  of  fat  is  a  purely  mechanical  process,  "just 
as  quicksilver  is  pressed  through  leather,"  and  he  doubts  altogether  that  the  lacteals  have 
any  special  absorbent  function,  or  differ  from  ordinary  lymphatics.  However,  we  think 
that  the  mechanical  nature  of  the  process  is  open  to  very  great  question,  and  we  should 
rather  compare  the  manner  in  which  fat  enters  a  villus,  to  that  in  which  the  ingesta  enter 
an  JLctinophrys  ;  one  can  as  readily  comprehend  the  existence  of  a  selective  power  in  the 
former  as  in  the  latter  case.  That  some  such  faculty  exists  would  seem  to  be  indicated  by 
the  fact  stated  by  Bruch,  that  the  Lieberkuhnian  and  Peyerian  glands  take  no  share  in  fatty 
absorption ;  though,  on  the  other  hand,  it  must  be  remembered  that  Kolliker  found  the  eggs 
of  Entozoa  in  the  villi  of  rabbits  ("Mikr.  Anat.,"  B.  II.  2,  173). — TRS.] 


THE    INTESTINES. 


519 


posed  over  the  whole  mucous  membrane ;  and  2,  racemose  glands,  in 
the  submucous  tissue  of  the  duodenum. 

The  racemose  glands,  or  as  they  are  more  commonly  named,  after 
their  discoverer,  Brunner's  glands,  form,  at  the  commencement  of  the 
duodenum,  upon  the  outer  side  of  the  mucous  membrane,  a  continuous 
layer,  which  is  best  developed  and  thickest,  close  to  the  pylorus,  where 
it  constitutes  a  considerable  glandular  ring  and  extends -about  as  far  as 
the  aperture  of  the  biliary  ducts.  If  the  two  layers  of  the  muscular 
tissue  be  dissected  off  a  stretched  or  distended  duodenum,  the  glands 
may  readily  be  recognized  as  yellowish,  flattened  bodies  of  To-lJ  ^nes 
(on  the  average  £-J  a  line,)  with  their  angles  rounded  off,  which,  en- 
closed within  a  little  connective  tissue,  lie  close  to  the  mucous  membrane 
and  send  short  excretory  ducts  into  it.  In  their  minute  structure, 
Brunner's  glands,  the  terminal  vesicles  of  which  measure  0-03-0-06, 
even  0-08  of  a  line,  agree  perfectly  with  the  racemose  glands  of  the  oral 
cavity  and  oesophagus.  Their  secretion  is  an  alkaline  mucus,  in  which 
no  formed  elements  are  contained,  having  no  digestive  action  upon 
coagulated  protein  compounds  and  probably  merely  subservient  to 
mechanical  ends. 

The  tubular,  or  Lieberkiihnian  glands  (cryptce  mucosoe),  are  distri- 
buted over  the  whole  small  intestine,  including  the  duodenum,  as  innu- 
merable, straight,  narrow  caeca,  which  occupy  the  entire  thickness  of 
the  mucous  membrane  and  are  frequently  slightly  enlarged  at  their  ex- 
tremities, though  hardly  ever  dichotomously  divided.  The  best  idea  of 
their  number  is  obtained  by  viewing  the  mucous  membrane,  either  from 
above  or  in  vertical  section,  under  a  low  power.  In  the  latter  case,  we 
see  the  cseca  standing  close  together,  almost  like  palisades  (Fig.  206) ; 
in  the  former,  we  observe  that  the  glands  do  not  occupy  the  whole  sur- 
face, but  only  the  interspaces  between 
the  villi :  here,  however,  they  exist  in 
such  numbers,  as  to  leave  no  intervals 
of  any  width,  the  mucous  surface 
between  the  villi  appearing  pierced 
like  a  sieve.  Even  on  Peyer's  patches 
and  over  the  solitary  follicles,  these 
glands  are  to  be  met  with  ;  but  in  man, 
they  leave  those  portions  of  the  mu- 
cous membrane  which  lie  immediately 
over  the  centre  of  the  follicles  free, 
and  therefore  are  arranged  like  rings 
around  the  follicles.  The  length  of 
the  Lieberkiihnian  glands  equals  the 
thickness  of  the  mucous  membrane  and 

FIG.  212. — Lieberkiihnian  glands  of  the  Pig,  magnified  GO  diameters:  a:  membrana  propria 
and  epithelium  ;  6,  cavity. 


Fig.  212. 


520  SPECIAL    HISTOLOGY. 

varies  from  M  of  a  line;  their  breadth  is  0-028-0-036  of  a  line  ;  that 
of  their  aperture,  0-02-0-03  of  a  line.  They  are  composed  of  a  delicate 
homogeneous  membrana  propria  and  of  a  cylindrical  epithelium,  which, 
even  during  chylification,  never,  like  that  of  the  intestine,  contains  fat ; 
their  cavity  is  filled,  during  life,  by  a  clear,  fluid  secretion,  the  so-called 
intestinal  juice ,  which,  however,  becomes  rapidly  changed  after  death,  or 
on  the  addition  of  water,  so  that  the  glands  appear  to  be  filled  with  cells, 
or  with  a  granular  mass. 

The  vessels  of  Brunner's  glands  have  the  same  arrangement  as  those 
of  the  salivary,  whilst  around  Lieberklihn's  caeca  they  follow  exactly 
the  type  of  those  of  the  stomach.  A  fine  network  of  capillaries  of 
0-003  of  a  line,  passes  up  round  the  cceca  and,  upon  the  surface  of  the 
mucous  membrane,  enters  an  elegant  polygonal  reticulation  of  some- 
what wider  (0*01  of  a  line)  vessels,  which  communicates  on  one  side  with 
the  vessels  of  the  villi,  on  the  other  is  directly  continuous  with  veins, 
which,  after  communicating  with  those  of  the  villi,  run  directly  out  of 
the  mucous  membrane.  Hence,  in  this  case  also,  the  veins  are  con- 
nected only  with  the  superficial  network  round  the  glandular  apertures 
and  with  that  in  the  villi,  but  not  with  that  which  surrounds  the  glands, 
so  that,  as  in  the  stomach,  the  vessels  which  supply  the  secretion  im- 
mediately succeed  the  arteries,  and  precede  those  to  which  the  absor- 
bent function  is  more  especially  assigned  (comp.  Frei,  cited  below). 

"Whence  the  small  round  cells,  with  a  single  nucleus,  which  are  to  be 
met  with  in  the  intestinal  mucus,  proceed,  is  doubtful.  I  ha*e  not  found 
them  in  the  glands  and  I  can  only  refer  them  to  the  epithelium,  whence 
I  am  inclined  to  suppose  that  these  cells,  which  are  usually  few,  arise 
upon  the  surface  of  the  mucous  membrane,  like  the  mucous  corpuscles  of 
the  oral  cavity. 

In  various,  particularly  intestinal,  disorders,  in  inflammations,  typhus, 
peritonitis,  Bohrn  found  a  white  viscid  secretion  in  many  Lieberkiihnian 
glands  (Gland,  int.,  p.  34),  which,  as  subsequent  observations  of  the 
same  author  (Darmschleimhaut  in  der  Cholera,  p.  63)  would  indicate, 
was  merely  an  epithelium  detached  from  the  walls  of  the  cavity,  and 
which  had  become  aggregated  into  a  compact  plug.  In  cholera,  accord- 
ing to  Bbhm,  this  epithelium,  as  well  as  that  of  the  whole  intestine,  is 
thrown  off". 

§  155.  Closed  follicles  of  the  small  intestines.—  Vesicles  of  a  peculiar 
kind  are  found  scattered,  singly  or  in  groups,  over  the  walls  of  the  small 
intestine,  of  whose  anatomical  and  physiological  import  we  have,  as  yet, 
attained  no  very  clear  idea  and  which  may  therefore,  for  the  present,  be 
most  fittingly  described  under  a  general  denomination. 

The  most  important  of  these  are  Peyer's  patches  (glandulce  agminatcz). 
They  are  rounded,  flattened  organs,  invariably  situated  along  that  sur- 


THE    INTESTINES. 


521 


face  of  the  intestine  which  isropposite  to  the  mesentery;  they  are  most 
distinct  upon  the  inner  surface,  where  they  appear  as  rather  depressed, 
smooth  spots,  without  any  very  sharp  definition,  but  they  are  also  recog- 
nizable from  the  exterior,  by  the  slight  elevation  to  which  they  give  rise; 
by  transmitted  light  they  look  like  more  opaque  portions  of  the  mem- 
brane. These  patches  are  usually  most  abundant  in  the  ileum,  but  they 
are  not  uncommonly  to  be  met  with  in  the  lower  part  of  the  jejunum : — 
occasionally  they  exist  in  its  upper  portion  close  to  the  duodenum  and 
even  in  the  inferior  horizontal  portion  of  the  duodenum  itself.  Ordi- 
narily there  are  20-30  of  them;  when  they  are  found  higher  up  there 
may  be  as  many  as  50-60  ;  but  they  are 
always  most  closely  set  in  the  lowest 
portion  of  the  ileum.  The  dimensions 
of  the  separate  patches  are  in  general 
the  larger,  the  closer  they  are  to  the  cce- 
cum;  their  length  is  usually  5-1 J  lines, 
but  may  diminish  to  3  and  increase  to 
3-5  lir>es,  or  even  1  inch ;  their  breadth 
varies  from  3  to  5  or  9  lines.  Where 
the  patches  lie,  the  valvulce  conniventes 
are  usually  interrupted;  in  the  jejunum, 
however,  these  folds  are  also  to  be  met 
with ;  upon  the  Peyer's  patches  and  in  the 
ileum,  rows  of  closely  set  villi  often  take 
their  place. 

More  minutely  examined,  every  Pey- 
er's patch  is  seen  to  be  an  aggregation 
of  closed  follicles,  of  1-6-1-2-1   line  in 
diameter,  either  rounded  or  slightly  co- 
nical towards  the  intestinal  cavity,  which  lie  partly  in  the  mucous  mem- 
brane itself,  partly  in  the  submucous  tissue,  and  are,  on  the  one  side  not 
more  than  0-02-0-03  of  a  line  distant  from  the 
mucous  surface,  while  on  the  other,  they  are  in 
immediate  contact  with  the  muscular  tunic,  which 
is  here  somewhat  more  closely  united  with  the 
mucous  membrane.     Viewed  from  the  interior  of 
the  intestine,  their  most  striking  feature  in  Man 
is  the  presence  of  many  small  rounded  depres- 
sions j— J-l  line  apart,  which  correspond  with 
the  separate  follicles,  and  whose  floor  is,  indeed, 

FIG.  213. — A  Peyer's  patch  (Man),  magnified  4  diameters:  a,  ordinary  mucous  surface, 
with  villi;  6,  depressions  upon  the  patches  corresponding  with  the  follicles;  c,  intermediate 
substance,  with  small  villi. 

FIG.  214.— Portion  of  a  Peyer's  patch  of  an  old  Man,  after  Flouch  :  a,  follicle,  surrounded 
by  the  apertures  of  the  Lieberkuhnian  glands;  6,  villi;  c,  more  isolated  Lieberkuhnian 
follicles. 


Fiar.  214. 


522  SPECIAL    HISTOLOGY. 

rendered  slightly  convex  by  the  latter,  but  which  present  no  villi  what- 
soever. The  remainder  of  the  patch  is  occupied  by  common  villi,  or  by 
reticulated  folds  and  by  the  apertures  of  the  Lieberkuhnian  glands  ;  the 
latter  are  disposed  around  the  slight  elevations  produced  by  the  follicles, 
in  circlets  of  6-10  and  more  apertures,  the  coronce  tubulorum  of  authors. 
~E>&ch  follicle  of  a  patch  possesses  a  perfectly  closed,  thick  and  tolera- 
bly strong  coat  of  indistinctly  fibrillated  connective  tissue,  with  inter- 
spersed nuclei ;  within  this  are  the  contents,  which  are  soft  and  grayish 
(never  milk-white).  They  become  slowly  diffused  through  water  and 
consist  of  a  little  fluid,  with  innumerable  nuclei  and  round  cells  of 
0-004-0-008  of  a  line,  which,  when  recent,  appear  quite  homogeneous 
and  of  a  dull  gray  color,  but  are  first  cleared  up  and  ultimately  de- 
stroyed by  the  action  of  water  and  of  acetic  acid,  the  nuclei  at  the  same 
time  becoming  granular  and  very  distinct.  Among  these  elements, 
which  here  and  there  also  contain  fatty  granules,  and  which,  as  the 


Fig.  215. 


comparison  of  their  various  forms  shows,  are  constantly  undergoing 
progressive  and  retrogressive  development,  Frei  and  Ernst  have  demon- 
strated the  existence  of  numerous,  but  very  fine  bloodvessels  of  0*0015 
-0-004  of  a  line,  which  are  connected  with  a  rich  vascular  network 
surrounding  the  follicle,  and  may  be  readily  recognized  in  the  contents 
of  the  follicles  of  animals  (Pig,  e.  g.\  if  they  be  quite  fresh,  and  have 
been  extracted  with  care. 

Little  is  known  of  the  lymphatics  of  Peyer's  patches.     This  much  is 
certain,  however,  that  the  number  of  lacteals  which  may  be  traced  du- 

FiG.  215. — Horizontal  section  from  the  middle  of  three  Peyer's  follicles  of  the  Rabbit, 
an  order  to  show  their  internal  vessels.     After  an  injection  by  Frei. 


THE    INTESTINES.  523 

ring  digestion  from  the  Peyerian  patches,  is  greater  than  that  in  other 
parts  of  the  intestine,  although  their  villi  are  fewer  and  less  developed  ; 
on  the  other  hand,  we  know  nothing  of  the  internal  relations  of  these 
vessels.  They  would  seem  to  form  networks  around  the  separate  folli- 
cles, at  least  we  see  that  they  compass  them  externally ;  but  they  do 
not  become  inserted  into,  nor  enter  them,  at  any  rate  upon  this  surface, 
as  their  milk-white  color  would  render  their  detection  easy.  Although, 
then,  Brucke  has  recently  affirmed  the  direct  communication  of  the 
follicles  with  lymphatics,  I  must,  for  these  and  other  reasons  (see  Mikr. 
Anat.  II.  2,  p.  188),  at  present  doubt  the  fact. 

The  solitary!  follicles  (glandulce  solitaries)  resemble  the  separate  ele- 
ments of  Peyer's  patches  so  closely  in  size,  contents  (I  have  also  seen 
the  internal  vessels  in  them),  and  general  structure, 
that  there  is  no  reason  for  considering  them  as  dis- 
tinct, particularly  since  the  number  of  the  follicles 
is  subject  to  all  possible  varieties ;  and  since,  in 
animals  at  least,  we  find  Peyer's  patches  with  2—3— 
5  follicles.  In  man,  as  all  writers  justly  agree, 
their  number  is  exceedingly  inconstant;  sometimes 
not  one  can  be  found,  whilst  in  other  cases,  the  whole 
intestine,  as  far  as  the  margins  of  the  ileo-csecal  valve,  is  thickly  beset 
with  them,  or  lastly,  they  may  occur  in  the  ileum  and  jejunum,  but  in 
no  very  great  number.  Their  entire  absence  must  probably  be  con- 
sidered abnormal,  since  they  are  constant  in  newly-born  children,  being 
more  abundant  in  the  jejunum  than  in  the  ileum. ;  The  miliary  vesicles, 
however,  which  are  often  met  with  in  immense  quantities  in  the  small 
intestine  and  stomach,  in  catarrhal  affections  of  the  alimentary  tract, 
may  very  probably  be  entirely  or  partially  pathological,  since  the  occur- 
rence of  such  follicles  has  been  demonstrated  in  other  organs  also  (in 
the  liver,  according  to  Virchow).  The  solitary  follicles  have  the  same 
position  as  the  elements  of  the  patches,  only  they  occur  also  in  the 
mesenteric  border  and  support  villi  upon  their  intestinal  surface,  which 
is  usually  somewhat  convex. 

I  consider  it  as  quite  certain,  that  the  follicles  of  Peyer's  patches 
have  no  apertures,  but  I  may  here  adduce  the  following  facts.  1.  In 
animals  examined  while  fresh,  the  capsules  are  invariably  closed,  as  may 
be  very  readily  seen  in  the  well-developed  patches  of  the  Pig,  Sheep, 
Cat,  Dog,  &c.,  which  I  particularly  recommend  for  the  examination  of 
these  organs,  because  the  patches  in  the  human  subject  have  so  fre- 
quently undergone  alteration.  2.  The  appearance  of  an  aperture  may 
proceed  from  the  depression  of  the  mucous  membrane  over  the  single 
follicles,  especially  when  the  projecting  portion  of  the  wall  of  the  folli- 

FIG.  21G. — A  solitary  follicle,  covered  with  villi,  from  the  small  intestine.     After  Bo'hm. 


524  SPECIAL    HISTOLOGY. 

cles  is  not  very  tense.  3.  In  man,  the  closed  follicles  of  the  intestine 
are  subject  to  very  many  morbid  changes  ;  they  are  frequently  ruptured 
and  so  altered,  that  in  place  of  the  patches  nothing  remains  but  a  reti- 
culated, indistinctly  pitted  surface.  As  Virchow  was  the  first  to  show 
(Med.  Reform.  1848,  No.  10,  p.  64),  they  may  also  burst  after  death, 
if  they  are  allowed  to  stand  in  water  or  in  a  warm  place ;  whence,  per- 
haps, many  of  those  apertures  which  are  met  with  in  the  dead  subject 
should  be  regarded  as  the  result  of  putrefactive  change. 

It  is  easy  to  understand,  that  little  can  be  said  concerning  the  phy- 
siology of  Peyer's  follicles  so  long  as  their  relations  to  the  lymphatics 
are  not  understood.  They,  and  the  follicles  of  the  intestine  in  general, 
appear  to  me  to  be  closed  glandular  organs,  analogous  to  the  splenic 
follicles,  the  tonsils,  and  the  lymphatic  glands,  which  contain  peculiar 
elements  and  a  vascular  network.  In  these  a  constant  development  of 
cells  takes  place  and  at  the  same  time,  substances  are  elaborated  from 
the  plasma,  supplied  by  the  bloodvessels  and  perhaps  also  from  matters 
not  of  a  fatty  nature,  absorbed  from  the  intestine,  a  part  of  which,  in 
all  probability,  is  at  once  taken  up  by  the  internal  bloodvessels,  while 
the  larger  proportion  is  excreted  and  absorbed  by  the  lymphatics.  The 
period  of  their  greatest  activity  (when  they  become  distended)  coincides 
with  that  of  the  intestinal  absorption,  either  because  they  absorb  from 
the  intestine  or  because  they  simply  participate  in  the  greater  activity 
of  the  intestine  at  this  time ;  and  perhaps  the  more  albuminous  matters 
which  they  yield  may  be  connected  with  the  development  of  cells  in  the 
chyle.  This  hypothesis  will  hold  good  in  its  principal  outlines,  even  if 
in  future  the  direct  connection  of  the  lymphatics  with  the  follicles,  or  the 
occurrence  of  lacteals  within  them,  should  be  demonstrated ;  at  any  rate, 
it  will  not  be  blamed  for  being  too  wide  of  the  facts. 

§  156.  Mucous  membrane  of  the  large  intestine. — The  structure  of 
the  mucous  membrane  in  the  large  intestine  agrees  so  closely  in  essen- 
tials with  that  of  the  small  intestine,  that  it  may  suffice  here  to  draw 
attention  to  a  few  points  only. 

The  mucous  membrane  of  the  large  intestine,  if  we  except  the  rectum, 
has  no  proper  folds,  for  the  transversely  fibrous  muscular  layer  also 
enters  into  the  pliccs  sigmoidece.  The  villi  also  are  absent,  from  the 
edge  of  the  ileo-caecal  valve,  into  which  the  muscular  tunic  likewise 
enters,  onwards ;  and  the  mucous  surface,  apart  from  some  occasional, 
hardly  perceptible,  small,  wart-like  elevations,  is  even  and  smooth.  It 
is  difficult  to  detect  the  muscular  layer  of  the  mucous  membrane  in  tne 
human  colon,  though  it  is  unquestionably  present ;  it  is  more  distinct  in 
the  rectum.  In  animals  I  find  it  well  developed.  According  to  Briicke, 
in  the  colon  (of  animals?)  its  longitudinally  and  transversely  fibrous 
Jaycrs,  which  also  exist  here,  are  only  0'013  of  a  line  thick,  the  diminu- 
tion having  taken  place  at  the  expense  of  the  external  longitudinal 


THE    INTESTINES. 


525 


fibres,  which  are  reduced  to  a  threefold  or  even  only  a  twofold  stratum  ; 
in  the  rectum,  the  layers  are  again  of  equal  thickness,  and,  taken  to- 
gether, measure  about  0-022,  at  the  anus  even  0-088  of  a  line  and 
more. 

The  glandular  organs  of  the  large  intestine  are  LieberTcuhn'  s  glands 
and  solitary  follicles  ;  the  former,  also  termed  glands  of  the  large  intes- 
tine, are  distributed  over  its  whole  surface  from  the  ileo-csecal  valve  to 
the  anus  and  in  the  processus  vermicular  is.  They  are  closely  set,  and 
have  exactly  the  same  structure  as  those  of  the  small  intestine,  only,  in 
accordance  with  the  greater  thickness  of  the  mucous  membrane,  they 


Fig.  217. 


are  longer  and  broader  (J--J  of  a  line  long,  yVVo  of  a  line  broad). 
Here  also  I  have  found,  in  man  and  in  animals,  in  the  fresh  state,  no 
formed  contents  besides  a  beautiful  cylinder  epithelium  ;  so  that  we  have 
no  reason  to  suppose  that  the  secretion  is  at  all  different  from  that  in 
the  glands  of  the  small  intestine,  especially  as  the  mucous  membrane 
has,  like  that  of  the  latter,  an  alkaline  reaction,  and,  so  far  as  my  own 
experiments  go,  is  equally  devoid  of  digestive  action. 

The  solitary  follicles  are  arranged  close  together  in  the  processus  ver- 
micularis,  are  very  frequent  in  the  ccecum  and  rectum,  and  are  also 
usually  more  abundant  in  the  colon 
than  in  the  small  intestine.  They 
are  distinguished  from  those  of  the 
latter  locality  by  their  larger  size 
(f-l-lj  lines)  and  by  the  circum- 
stance that  upon  each  of  the  little 
prominences  of  the  mucous  mem- 
brane to  which  the  follicles  give  rise, 
there  is  a  small  pit-like,  elongated 
or  rounded  aperture,  of  1-9-1-12  of 
a  line,  which  leads  to  a  little  depres- 
sion of  the  mucous  membrane  above 
the  follicles.  These  pits,  which  are 
totally  absent  in  the  normal  follicles 

of  the  small  intestine,  led  Bohm  formerly  to  regard  the  follicles  as  csecal 
glands  provided  with  apertures  :  this,  however,  is  incorrect,  for  at  the 
bottom  of  this  depression  lies,  as  Brucke  has  also  remarked,  a  closed, 
somewhat  flattened  follicle  of  exactly  the  same  structure,  even  to  the 
internal  vessels,  as  those  of  the  small  intestine. 

The  bloodvessels  of  the  glands  and  follicles  of  the  large  intestine  pre- 
sent the  same  relations  as  in  the  small.  Every  Lieberklihnian  aperture 
is  encircled  by  a  ring  of  vessels  of  0-006-0-01  of  a  line,  which  is  some- 

FIG.  217.  —  Solitary  follicle  from  the  colon  of  a  Child,  magnified  45  diameters:  a,  Lieber- 
ktihn's  glands  ;  b,  muscular  layer  of  the  mucous  membrane  ;  c,  submucous  tissue  ;  rf,  trans- 
verse muscles  ;  e,  serous  membrane  ;  /,  depression  of  the  mucous  membrane  above  the 
follicle,  a. 


526  SPECIAL    HISTOLOGY. 

times  single,  sometimes,  especially  in  the  neighborhood  of  the  solitary 
follicles,  multiple. 

From  these  vessels  wider  venous  trunks  arise  and  penetrate  deeply 
between  the  glands,  which  are  themselves  surrounded  by  a  dense  network 
of  fine  capillaries  derived  immediately  from  the  arteries  (Fig.  205). 
Nothing  is  known  of  either  the  lymphatics  or  the  nerves  in  the  mucous 
membrane.  The  epithelium  is  precisely  similar  to  that  of  the  small 
intestine,  and,  at  the  anus,  is  separated  by  a  pretty  sharp  line  of  demar- 
cation, from  the  external  epidermis. 

§  157.  Development  of  the  intestinal  canal.  The  entire  wall  of  the 
intestine,  various  as  its  different  structures  may  afterwards  become,  pro- 
ceeds from  two  points  of  development:  viz.  in  the  first  place  from  the 
inferior  lamina  of  the  germinal  membrane  (mucous  layer  of  Pander  and 
Baer;  mucous  tunic,  Reichert;  glandular  layer  or  intestinal  glandular 
layer,  of  Remak),  which  is  not  the  foundation  of  the  whole  mucous  mem- 
brane, but  only  of  the  intestinal  epithelium  and  of  the  intestinal  glands  ; 
and  2,  from  the  middle  layer  of  the  germinal  membrane  (vascular  lamina, 
Pander,  memlrana  intermedia,  Reichert),  which  gives  rise,  in  addition 
to  many  other  parts  (muscles,  bones,  nerves,  heart),  to  the  vascular  and 
nervous  fibrous  coats  of  the  intestine,  as  well  as  to  the  vessels,  nerves, 
and  coats  of  the  intestinal  glands. 

The  inner  layer  or  the  epithelial  tube  consists  from  first  to  last  of  no- 
thing but  cells  and  becomes  metamorphosed  by  their  continual  multipli- 
cation, superficially  and  perpendicularly,  which,  according -to  Remak, 
takes  place  by  division,  in  the  first  place,  into  the  future  epithelia  ;  and  in 
the  second,  into  the  glands  of  the  intestine.  Of  the  latter,  the  Lieber- 
kiihnian  follicles  are  from  the  first,  hollow  diverticula  of  the  epithelium, 
whilst  the  salivary  and  Brunner's  glands  arise,  like  the  sudoriparous 
glands,  as  solid  processes,  which  only  subsequently  acquire  cavities  and 
become  branched.  The  gastric  glands  and  those  of  the  large  intestine 
also  certainly  arise  from  the  primitive  epithelial  tube — whether  as  diver- 
ticula or  as  solid  processes  is  not  yet  made  out — and  form  at  the  com- 
mencement a  layer  completely  separated  from  the  fibrous  lamina  of  the 
intestine ;  whence,  also,  the  epithelium  in  their  neighborhood  appears 
much  thicker  than  it  subsequently  is.  At  a  later  period,  delicate  vas- 
cular processes  grow  from  the  fibrous  layer  between  the  glands,  until  at 
length  both  layers,  intimately  united,  constitute  the  proper  mucous  mem- 
brane. Similar  and  more  considerable  processes  of  the  fibrous  layer 
form  the  villi,  whilst  the  muscular  and  serous  tissues  are  developed  from 
its  external  portion. 

The  examination  of  the  intestinal  mucous  membrane  presents  greater 
difficulties  than  that  of  other  parts.  The  epithelium  is  usually  in  a  good 


I 

THE    INTESTINES.  527 

state  of  preservation  only  in  quite  fresh  subjects,  and  generally  breaks 
up  into  its  elements  with  extreme  ease.  The  villi  are  best  seen  in  thin 
perpendicular  sections,  made  with  fine  scissors,  viewed  with  a  low  power, 
and  illuminated  from  above.  During  absorption,  they  are  usually  found 
full  of  fat  and  nuclei,  so  that  their  separate  portions  are  not  perceived, 
with  the  exception  of  the  lacteals,  which  become  distinct  by  the  use  of 
acetic  acid  and  still  better  by  that  of  dilute  caustic  soda.  At  other 
times,  the  muscles  of  the  villi  are  easily  recognized  by  their  nuclei,  on 
the  addition  of  acetic  acid.  Injections  are  required  for  the  bloodvessels : 
the  best  are  made  by  injecting  from  both  arteries  and  veins  at  the 
same  time,  and  should  be  preserved  in  fluid.  The  same  holds  good  of 
the  other  parts  of  the  intestine,  for  which  perpendicular  sections  are 
especially  instructive.  For  the  glands,  recent  pieces  of  intestine  are 
particularly  required,  although  it  is  often,  as  in  the  stomach,  exceed- 
ingly difficult  to  prepare  them.  Mucous  membrane,  hardened  in  alcohol, 
pyroligneous  acid,  or  chromic  acid,  or  boiled  in  acetic  acid  of  80  per 
cent,  and  dried,  according  to  the  method  of  Purkinje  and  Middeldorpf, 
or  saturated  with  gum  and  dried,  thin  transverse  and  longitudinal  sec- 
tions being  made  with  a  sharp  knife,  according  to  Wasmann's  method, 
may  be  used,  being  first  rendered  clear  by  a  little  soda.  The  analysis 
of  the  gastric  mucous  membrane  into  its  elements,  presents  the  greatest 
difficulties,  especially  when  it  is  as  thick  as  in  the  Horse  and  Pig.  In 
the  Dog,  Cat,  Rabbit,  and  in  the  Ruminants,  the  process  is  easier,  since, 
frequently,  by  merely  scraping  the  mucous  membrane  with  the  back  of 
a  knife,  the  epithelium  of  the  glands  may  be  drawn  out  in  a  connected 
state  and  affords  all  the  information  required  as  to  their  form  and  lining. 
Simple  teasing  out  is  also  frequently  sufficient  to  reduce  the  mucous 
membrane  of  the  animals  in  question  into  its  elements. 

Brunners  glands  offer  no  difficulties  except  in  their  excretory  ducts, 
which  may,  however,  be  clearly  seen  in  perpendicular  sections  and  in 
animals,  by  teasing  out  the  mucous  membrane.  The  Lieberkuhnian 
glands,  also,  may  generally  be  very  readily  isolated  in  their  entire 
length ;  while  the  closed  follicles  should  be  carefully  exposed  from 
without,  isolated  and  opened ;  'or  they  may  be  studied  in  perpendicular 
sections.  The  muscular  tissue  of  the  mucous  membrane  must  be  exposed 
by  removing  the  tunica  nervea  on  its  exterior  and  then  separating  it  in 
small  segments  from  the  glandular  layer ;  its  elements  maybe  very  well 
seen  by  macerating  it  in  nitric  acid  of  20  per  cent. 

Literature  of  the  intestinal  canal. — Th.  L.  W.  Bischoff,  "Ueber  den 
Bau  der  Magenschleimhaut,"  Mull.  Arch.  1838,  p.  503,  with  figures; 
Wasmann,  "  De  digestione  nonnulla,"  Berol.,  1839,  cum  tab.;  L. 
Bohm,  "  De  glandularum  intestinalium  structura,  penitiori,"  Berol., 
1835,  8  c.  tab. ;  and  "  Die  kranke  Darmschleimhaut  in  der  Asiatischen 
Cholera,"  Berl.,  1838 ;  J.  Henle,  "  Symbols  ad  anatomiam  villorum 


528  SPECIAL    HISTOLOGY. 

intestinalium  impr.  eorum  epithelii  etvasorum  lacteorum,"  c.  tab.  Berol., 
1837,  4to. ;  J.  Flouch,  "  Recherches  stir  la  membrane  muqueuse  intes- 
tinale,  in  Mem.  de  la  societe  d'histoire  natur.  de  Strasbourg,"  III.  3, 
Strasb.,  1845;  A.  Th.  Middeldorpf,  "De  glandulis  Brunnianis," 
Vratisl.  1846,  c.  tab.  ;  E.  H.  Weber,  in  "  Muller's  Archiv,"  1847,  p. 
400  ;  and  in  "  Berichte  der  Koniglichen  Sachsischen  Gesellschaft  der 
Wissenschaften,"  Heft  VII.  18  May,  1847,  p.  245;  Frerichs  (and 
Frei),  Article,  "  Verdauung,  in  Wagner's  Handw.  d.  Physiologic,"  Bd. 
III.  p.  738-755;  R.  0.  Ziegler,  "  Ueber  die  solitaren  und  Peyer'- 
schen  Follikel,"  Wurzburg,  1850,  Diss. ;  E.  Brucke,  1.  "  Ueber  den 
Bau  und  die  physiologische  Bedeutung  der  Peyer'schen  Drusen,  in 
Denkschriften  der  Wiener  Akademie,"  bd.  II.  1850,  p.  21,  with  1  plate; 
2.  "  Das  Muskelsystem  der  Schleimhaut  des  Magens  ;"  and  3.  "  Ueber 
ein  in  der  Darmschleimhaut  aufgefundenes  Muskelsystem,"  in  the  "  Be- 
richten  der  Akademie,"  1851 ;  Kblliker,  "  Ueber  das  Vorkommen  von 
glatten  Muskelfasern  in  Schleimhauten,"  in  "  Zeitschrift  fur  wiss. 
Zoologie,"  III.  1851,  p.  106,  und  Nachtrag  dazu.  Heft  II. ;  F.  Ernst, 
"  Ueber  die  Anordnung  der  Blutgef  asse  in  den  Darmhauten,"  Zurich, 
1851,  Diss.  c.  tab. 

[Briich,  "Beitrage  zur  Anatomic  und  Physiologic  des  Dunndarm- 
Schleimhaut,"  Siebold  and  Kolliker's  "Zeitschrift,"  1853;  also  three 
most  important  papers  by  Brucke,  "  Ueber  die  Aufsaugung  des  Chy- 
lus,"  Sitzungsberichte  d.  Wiener  Akad.  Dec.  1852  ;  "  Ueber  den  Urs- 
•prung  und  den  Verlauf  der  Chylusgefasse,"  ibid.  January,  1853,  and 
'"  Ueber  die  Chylusgefasse  und  die  Fortbewegung  des  Chylus,"  ibid., 
.March,  1853,  which  have  come  into  our  hands  too  late  for  further  re- 
ference.*— Tus.] 

OF  THE  LIVER. 

§  158.  The  liver,  a  large  gland,  is  at  once  distinguished  from  those 
ccompound  glands,  such  as  the  salivary,  which  have  hitherto  been  de- 
scribed, by  the  intimate  connection  of  its  larger  subdivisions  and  by  the 
very  peculiar  structure  of  its  secreting  parenchyma,  which  elaborates 
rthe  bile.  The  component  parts  are,  the  secreting  parenchyma,  consist- 
ing of  the  lobules  or  islets  of  the  liver  and  of  the  networks  of  hepatic 
'Cells ;  the  biliary  passages  which  are  formed  in  this,  and  the  efferent 
biliary  ducts ;  very  numerous  bloodvessels ;  a  considerable  number  of 
.lymphatics  and  nerves  ;  and  finally,  a  peritoneal  investment. 

§  159.  Secreting  parenchyma,  hepatic  lobes  and  hepatic  substance. — 
If  the  surface  or  a  section  of  the  liver  be  regarded,  it  generally  exhi- 
bits a  mottled  appearance,  which  is  usually  of  such  a  kind,  that  small, 

*  [See  note,  p.  516.— DaC.j 


THE    LIVER.  529 

stellate,  reddish  or  brown  spots  are  enclosed  within  a  more  yellowish-red 
substance — medullary  and  cortical  substance  (Ferrein).  This  variega- 
tion proceeds  from  the  usually  unequal  distribution  of  the  blood  in  the 
smallest  trunks  and  in  the  capillaries,  and  in  healthy  persons  it  is  re- 
placed by  a  uniform  reddish-brown  color.  The  mottling  of  the  surface 
of  the  liver  is  frequently  so  regular  as  to  have  given  rise  to  the  suppo- 
sition that  it  consists  of  lobes,  especially  as  in  an  animal  which  is  a  fre- 
quent subject  of  investigation, — the  Pig, — they  are  very  obvious  ;  but, 
as  E.  H.  Weber  was  the  first  to  demonstrate,  in  1842,  in  the  human 
liver  nothing  of  the  kind  exists  ;  here,  in  fact,  not  only  the  secreting 
elements,  but  the  most  important  parts  of  the  vascular  system,  i.  e.  the 
capillary  network  between  the  portal  and  hepatic  veins  are  intimately 
connected  together  throughout  the  whole  organ.  Nevertheless,  it  would 
be  very  erroneous  to  suppose  that  the  secreting  parenchyma  of  the 
liver  is  everywhere  homogeneous.  Ultimate  segments  may  be  observed 
in  it,  which  have  a  certain  independence,  although  they  are  in  nowise 
isolated.  These  hepatic  lobules,  as  they  may  be  called,  if  the  term  be 
used  in  its  most  general  signification,  or  hepatic  islets,  are  thus  pro- 
duced :  1.  The  smallest  branches  of  the  afferent  and  efferent  blood- 
vessels, the  vence  inter-  and  intra-lobulares  (Kiernan)  are  distributed  at 
pretty  equal  intervals  through  the  whole  liver,  so  that  a  portion  of  he- 
patic substance  of  J-J-1  line  in  diameter,  is  always  found  to  give  origin 
in  its  interior,  to  a  small  twig  of  the  hepatic  vein  receiving  externally  a 
certain  number  of  the  minutest  branches  of  the  portal  vein  and  of  the 
hepatic  artery  ;  and,  2,  The  hepatic  ducts  do  not  commence  irregularly 
in  the  parenchyma,  but  are  so  disposed  that  they  invariably  arise  at  a 
distance  of  i-J  a  line  from  the  origins  of  the  hepatic  veins  and  take 
the  same  course  as  the  finest  ramifications  of  the  portal  vein.  In  this 
manner  little  masses,  containing  only  secreting  parenchyma,  capillaries 
and  the  origins  of  hepatic  veins,  are  marked  out  in  the  liver ;  whilst  in 
their  interspaces,  together  with  parenchyma  and  capillaries,  lie  the  ulti- 
mate branches  of  the  portal  vein  and  hepatic  artery  and  the  origins  of 
the  hepatic  ducts,  which,  as  they  do  not  approach  the  masses  from  one, 
but  always  from  many  sides,  and  are  also  supported  and  partially  united 
by  connective  tissue,  form,  if  not  complete,  at  all  events  partial  zones 
around  them. 

The  livers  of  those  animals  which  present  lobes  (Polar  Bear,  J.  Mutter, 
Pig),  are  of  the  greatest  value  in  comprehending  the  structure  of  the 
organ,  arid  I  therefore  here  subjoin  an  account  of  the  structure  of  the 
Pig's  liver.  If  we  examine  this  organ  in  sections  or  otherwise,  it  is  al- 
ways seen  to  be  divided  into  numerous  small,  rounded,  polygonal,  not 
very  regular  arece  of  tolerably  uniform  size  (J— 1 J  lines),  which  consist  of 
the  proper  parenchyma  of  the  liver  and  are  bordered  by  whitish  parti- 

34 


530 


SPECIAL    HISTOLOGY. 


tions,  readily  visible  to  the  naked  eye.  If  a  cut  surface  be  scraped 
with  the  handle  of  a  scalpel,  angular  masses  of  liver,  equal  in  size  to 
these  arece,  are  detached,  the  capsules  which  surrounded  them  remain- 
ing behind  as  empty  compartments,  like  a  honeycomb.  These  become 
still  more  distinct  if  a  thin  section  of  the  liver  is  gently  kneaded  with 
the  fingers  in  water,  and  then  washed  and  examined  on  a  black  ground, 
in  which  case  many  compartments  remain  almost  completely  closed,  and 
still  more  resemble  closed  capsules.  It  must  not  be  supposed,  however, 
that  there  are  any  complete  special  investments  around  each  hepatic 
lobule.  On  the  other  hand,  the  membranes  by  which  they  are  formed, 
always  appertain  to  many  lobules  in  common,  so  that  the  whole  con- 
stitutes a  cellulated  substance  continuous  throughout,  whose  partitions 


Fig.  218. 


.  219. 


are  all  simple  and  cannot  be  divided  into  a  number  of  lamellae.  If  we 
trace  out  the  capsules,  or  as  they  might  better  be  termed,  the  partitions 
of  the  lobes,  we  find  that  they  are,  for  the  most  part,  expansions  of  the 
connective  tissue,  which  accompanies  the  vena  portce,  <fv?.,  or  of  the  so- 
called  capsule  of  Glisson,  but  are  also  connected  with  the  serous  in- 
vestment of  the  liver  and  accompany  the  larger  hepatic  veins.  Kiernan 
was  the  first  to  take  a  just  view  of  the  relation  of  the  lobules  to  the 
hepatic  vessels,  when  he  said,  that  they  are  seated  upon  the  branches 
of  the  hepatic  vein,  like  leaves  upon  their  stalk.  In  fact  we  find,  if  a 
small  branch  of  the  hepatic  vein  be  slit  up  (Fig.  218,  b  b  b)  that  it  is 

,  FIG.  218. — Segment  of  a  Pig's  liver,  with  an  hepatic  vein  laid  open,  somewhat  magni- 
fied: a,  large  vein,  into  which  as  yet  no  intralobular  veins  open;  6,  its  branches,  with  in- 
tralobular  veins,  and  the  bases  of  the  lobes  shining  through.  After  Kiernan. 

FIG.  219.— Portal  vessel  of  the  Pig,  cut  open,  with  its  accompanying  branches  of  the  he- 
patic artery  and  duct.     After  Kiernan. 


THE    LIVER.  531 

surrounded  on  all  sides  by  the  hepatic  lobules  and  receives  a  single  vein 
from  each,  so  that  they  actually  appear  to  be  attached  to  it  by  short 
pedicles.  Now  since  this  takes  place  in  exactly  the  same  manner  from 
the  veins  of  moderate  size  up  to  the  intralobular  veins,  the  hepatic 
veins  and  lobules  may,  not  without  reason,  be  compared  to  a  tree  whose 
branches  are  so  numerous  and  so  closely  beset  with  polygonal  leaves 
that  the  foliation,  so  to  speak,  constitutes  one  mass.  Imagine  now, 
that  another  ramified  system,  composed  of  vessels,  is  introduced  into 
the  expanded  head  of  this  tree,  in  such  a  manner  that  the  larger  vessels 
lie  in  the  clefts  between  its  principal  masses,  the  smaller  and  smallest 
in  those  between  the  subordinate  masses,  ultimately  penetrating  into 
the  lobules  themselves,  so  that  every  lobule  is  connected  with  many  of 
the  finest  twigs,  receiving  a  coat  from  the  connective  tissue  which  ac- 
companies them,  and  we  shall  have  as  distinct  an  idea  as  possible  of  the 
relations  of  the  vena  portoe.  The  hepatic  duct  and  artery  merely 
accompany  the  vena  portce,  and,  therefore,  require  no  special  notice. 

In  form,  the  lobes  of  the  Pig's  liver  are  angular,  usually  presenting 
irregular  four,  five  and  six-sided  figures  in  longitudinal  and  transverse 
sections. 

In  the  human  liver,  but  very  little  connective  tissue  accompanies  the 
vena  portoe.  between  the  hepatic  islets,  and  the  latter  can  neither  be  said 
to  possess  coats  nor  to  be  in  any  complete  manner  enclosed  by  the  vessels. 
In  cirrhosis  of  the  liver,  on  the  other  hand,  an  enormous  increase  takes 
place  in  the  amount  of  connective  tissue  contained  in  the  parenchyma  of 
the  liver,  and  the  individual  secreting  segments  may  become  prominent 
or  even  form  isolated  lobules.  The  reddish-brown  hepatic  substance  is 
softer,  because  more  macerated,  and  sinks  in  more  than  the  rest,  upon 
the  surface  and  in  sections  ;  it  may  also  be  more  easily  scraped  away  and 
sometimes  readily  falls  out  in  fine  segments.  The  cortical  layer,  which 
forms  a  reticulation  around  the  reddish-brown  spots,  presents  narrower 
places,  fasurce  interlobulares,  Kiernan,  and  wider,  spatia  interlobularia, 
in  which  not  uncommonly  a  bloody  point  may  be  seen,  arising  from  a 
portal  vessel,  but  not  so  regularly  as  in  the  brown  spots,  where  it  arises 
from  the  vena  intralobular  is  and  often  appears  stellate. 

By  the  more  complete  filling  up  of  the  capillary  network,  it  may  hap- 
pen, and,  according  to  Theile,  this  is  in  fact  the  usual  case  in  the  majority 
of  human  livers,  that  the  fasurce  interlobulares  disappear,  the  brown 
substance  representing  a  network,  and  the  yellow,  occurring  in  isolated 
spots.  I  find,  as  I  have  stated  above,  that  perfectly  fresh  livers  are,  for 
the  most  part,  uniformly  colored  throughout.  Kiernan  describes,  in 
children,  even  a  reversal  of  the  coloring,  which  he  considers  to  be 
dependent  upon  congestion,  more  particularly  of  the  vena  portce,  the 
external  portions  of  the  hepatic  lobes  being  thus  more  injected.  Neither 
Theile  nor  I  have  hitherto  noticed  this  form. 


532 


SPECIAL    HISTOLOGY. 


Fig.  220. 


§  160.  Hepatic  cells  and  cell-networks. — Every  hepatic  islet  contains 
two  elements ;  1,  a  network  of  capillaries,  which,  on  the  one  hand,  is 
continuous  with  the  finest  portal  branches,  and  on  the  other,  unites  into 
the  intralobular  vein,  one  of  the  roots  of  the  hepatic  vein ;  and  2,  an 
interlaced  tissue  of  delicate  columns,  composed  of  nothing  but  cells,  the 
so-called  hepatic  cells,  in  close  and  immediate  apposition.  These  two 
networks  are  so  interwoven  that  the  interstices  of  the  one  are  completely 
filled  by  the  solid  portions  of  the  other  and  leave  no  interspaces,  at  least 
when  the  vessels  contain  blood  or  are  injected.  Not  a  trace  of  biliary 
ducts  is  to  be  observed  in  this  network :  they  are  first  met  with  at  the 
periphery  of  the  hepatic  islets,  where  also  the  finest  portal  branches 
occur,  without  its  having  been  possible,  hitherto,  to  make  out,  directly, 
their  connection  with  the  hepatic-cell-network,  which  is  indubitably  the 
secreting  portion  of  the  liver. 

The  hepatic  cells,  which  may  be  isolated  with  the  greatest  ease,*  have 
a  diameter  of  0-008-0-012  of  a  line  on  the  average,  0-006-0-016  of  a 
line  in  extreme  cases,  and  resemble  tessellated  epithelium-cells  in  form, 
except  that  they  are  more  irregular.  Their  membrane  is  delicate,  and 

perfectly  closed,  and  their  con- 
tents, in  perfectly  normal  livers, 
such  as  are  rarely  met  with  in 
man,  but  readily  enough  in  ani- 
mals, are  a  granular,  yellowish, 
semifluid  substance,  which,  as 
microscopic  investigation  shows, 
probably  contains  the  essential 
element  of  the  bile.  In  this  lies  a 
round  vesicular  nucleolated  nu- 
cleus, of  0-003-0-00-4  of  a  line  ; 
and  in  many  cells  there  are  two. 

Besides  these,  fat-drops  and  pigment  granules  are  frequently  to  be  met 
with.  The  former  (Fig.  220  e)  occur  in  all  the  cells,  when  the  liver  has 
undergone  fatty  degeneration,  in  such  quantities  that  they  become  very 
similar  to  certain  forms  of  fat-cells ;  and  generally,  as  a  few  large  or 
many  small  drops,  entirely  fill  the  cell,  so  that  the  nucleus  becomes  invi- 

FIG.  220. — Hepatic  cells  of  Man,  magnified  400  diameters :  a,  more  normal  cells ;  b,  with 
pigment ;  c,  with  fat. 

*  [This  is  true  of  the  hepatic  "  cells''  of  Man  and  many  Mammalia,  but  not  of  all.  In  the 
Rat,  we  could  find  no  demarcation  of  the  hepatic  tissue  into  cells,  the  tissue  resembling  very 
nearly  that  of  the  spleen.  In  Fishes,  Dr.  Handfield  Jones  has  pointed  out  the  existence  of 
all  varietes  in  this  respect,  from  free  "  nuclei,"  with  oily  and  granular  matter  scattered  through 
a  matrix,  up  to  perfectly  formed  "cells."  In  the  Pigeon,  the  same  author  finds  no  fully 
formed  cells,  nor  in  the  Duck;  and  he  therefore  draws  the  general  conclusion,  "that  the 
secreting  process  by  no  means  requires  the  formation  of  perfect  cells  in  order  to  effect  its 
peculiar  changes;  these  may  certainly  occur  in  blastematous  matter,  if  the  nucleus  only  be 
present."  "Philosoph.  Transactions,"  1849,  p.  132. — TRS.] 


THE    LIVER. 


533 


sible.  Every  transition  may  be  traced  from  these  well-marked  forms  to 
ordinary  cells  with  a  few  minute  drops  or  a  single  somewhat  larger  one; 
and,  in  fact,  these  less  fatty  cells  occur  to  a  certain  extent  in  almost 
every  body  ordinarily  subjected  to  examination,  so  that  if  their  absence 
in  animals  were  not  kept  in'  mind,  their  occurrence,  at  least  to  a  small 
amount,  might  be  regarded  as  normal.  The  same  may  be  said  with 
respect  to  the  pigment  molecules  (Fig.  220  6).  When  these  are  very 
abundant  they  are  certainly  pathological;  but  when  few,  they  can  only 
be  regarded  as  a  slight  deviation  from  the  normal  state.  They  are  small, 
hardly  exceeding  0*001  of  a  line,  of  a  yellow,  or  brownish  yellow  color; 
their  chemical  reactions  are  identical  with  those  of  the  coloring  matter  of 
the  bile  as  it  occurs  in  the  intestinal  canal,  inasmuch  as  they  are  not 
altered  in  color  by  nitric  acid,  nor  dissolved  by  caustic  alkalies. 

The  hepatic  cells  are  so  arranged  in  the  islets  as  to  form  a  network 
by  the  simple  apposition  of  their  flat  surfaces,  without  the  assistance  of 
any  foreign  connecting  intermediate  substance  or  investing  coat.  The 
simple  or  branched  columns  of  hepatic  cells,  which  are  almost  always 
to  be  found  among  scraped  off  particles  of  the  liver,  and  to  which  Henle 
drew  attention  (Allg.  Anat.,  p.  903),  are  nothing  but  fragments  of  the 
hepatic  cell-network,  whose  elements  do  not  cohere  very  firmly.  Taken 
altogether,  the  network  of  every  hepatic  islet  presents  more  rounded 
meshes  at  the  periphery,  while  in  the  centre  they  are  constantly  dis- 
posed radially,  whence,  in  a  transverse  section  through  the  interlobular 
vein,  long  ramified  columns  of  hepatic  cells  are  seen  stretching  from  the 
latter  on  all  sides  and 
uniting  by  short  lateral 
anastomoses,  so  that  the 
intermediate  meshes  ap- 
pear like  narrow  elonga-  Jg-^A' 
ted  clefts.  The  hepatic 
columns  consist  of  1-3, 
more  rarely  of  4-5  rows 
of  cells,  have  a  diameter 
of  0-01-0-015  of  a  line 
on  the  average,  0-006— 
0-02  of  a  line  in  extreme 
cases,  and  are  generally 
cylindrical  or  prismatic, 
but  not  at  all  regularly 


so 


their  surfaces  are  arched,  plane,  or,  in  some  localities,  depressed, 
and  have  rounded  or  sharp  angles.  The  meshes  of  the  hepatic  cell- 
network  correspond  with  the  diameters  of  the  capillaries  and  of  the  larger 


FIG.  221. — Hepatic  cell-network,  6,  and  finest  ductus  intcrlobulares,  or,  of  Man,  after  nature, 
the  union  of  the  two,  diagrammatic;  magnified  350  diameters:  c,  vascular  spaces. 


534  SPECIAL    HISTOLOGY. 

vessels  which  border  upon  the  hepatic  islet,  by  which  they  are  perfectly 
filled  during  life,  and  will  be  more  thoroughly  considered  below. 

If,  as  results  from  the  above  analysis,  the  secreting  parenchyma  of 
the  liver  consists  of  a  solid  network  of  hepatic  cells,  one  cannot  but  be 
struck  with  its  great  difference  from  all  the  other  glands  of  the  body  ; 
and  the  important  question  arises,  how,  with  this  arrangement,  the  secre- 
tion is  conveyed  from  the  interior  of  the  cells,  in  which  we  suppose  it  to 
be  formed,  and  finally  carried  away.  Anatomy  here  gives  no  sufficient 
reply ;  for  although  the  ramifications  of  the  hepatic  ducts  have  been 
traced  accompanying  the  vena  portce  as  far  as  the  hepatic  islets,  yet,  as 
respects  the  connection  of  their  finest  twigs  with  the  hepatic  network  of 
cells,  no  definite  answer  has  been  afforded ;  and  indeed,  up  to  the  pre- 
sent time,  no  satisfactory  account  even  of  the  structure  of  the  former 
has  been  given.  Without  entering  further,  in  this  place,  into  the  dis- 
tribution of  the  hepatic  ducts,  I  will  only  observe,  that  in  carefully 
made  microscopic  preparations,  we  not  unusually  find  fragments  of  the 
finer  and  finest  ducts,  the  ductus  interlobulares  of  Kiernan,  between  the 
hepatic  islets,  and  readily  obtain  evidence  that  they  are  constructed 
according  to  the  ordinary  type  of  excretory  ducts.  The  minutest  of 
these  canals,  which  I  have  met  with,  measured  yj^  of  a  line  in  diameter, 
possessed  a  cavity  of  0*0033  of  a  line,  and  were  composed  of  a  simple 
layer  of  common  tessellated  epithelium-cells,  which  were  distinguished 
from  the  hepatic  cells  by  their  small  size  (0-004-0-005  of  a  line),  their 
pale  contents  and  the  minuteness  of  their  nuclei.  I  have  frequently  met 
with  such  ducts  as  these ;  they  had  no  fibrous  coat,  perhaps  because  it 
had  been  stripped  off  in  preparing  them  ;  but  occasionally  they  seem  to 
possess  a  membrana  propria,  at  least  their  external  contours  were 
sharply  defined.  Larger  canals,  of  0-04-0*05  of  a  line,  always  pos- 
sessed a  coat,  and  the  epithelium  was  more  cylindrical,  though  not  com- 
pletely so,  inasmuch  as  the  cells,  with  a  breadth  of  0-0048-0-0056  of  a 
line,  measured  only  0-006-0-0068  of  a  line  in  length.  Often  as  I  have 
sought  for  a  direct  communication  of  the  finest  canals  with  the  hepatic 
networks,  I  have  not  yet  directly  observed  it ;  which  is,  indeed,  by  no 
means  surprising,  if  we  consider  the  softness  of  the  parts  with  which  we 
have  to  do ;  but  unfortunately  the  result  is  a  hiatus  in  the  minute 
anatomy  of  the  parts,  which  can  hardly  be  made  good  by  hypotheses. 
As  such,  however,  I  would  offer  the  supposition,  that  the  finest  ducts 
impinge  directly  upon  the  columns  of  the  network  of  hepatic  cells,  as 
the  diagram  in  Fig.  221  shows,  so  that  their  cavity  is  terminated  by 
hepatic  cells  :  and,  judging  from  the  scantiness  of  the  finest  branches  of 
the  hepatic  duct,  I  believe  that  such  communications  exist,  in  no  very 
great  numbers,  at  the  circumference  of  the  hepatic  islets. 

Whatever  view  we  may  take  of  the  connection  of  the  hepatic  cell-net- 
works with  the  efferent  biliary  canals,  it  is  undeniable  that  any  such 


THE    LIVER.  535 

connection  only  takes  place  upon  the  surface  of  the  hepatic  islets  and  not 
in  their  interior,  and  that,  therefore,  the  bile  which  is  formed  here,  must 
be  transmitted  out ivards  from  cell  to  cell.  Such  a  process  of  transmis- 
sion through  closed  cells,  involves,  as  vegetable  physiology  teaches  us, 
no  impossibilities;  but  it  can  hardly  take  place  so  rapidly  as  in  those 
localities  where  actual  canals  subserve  this  purpose.  Since  the  bile,  as 
late  investigations  tend  to  show  with  increasing  clearness,  is  not  only 
excreted  from  the  blood,  but  absolutely  formed  in  the  liver,  and  is  at  the 
same  time  by  far  the  most  complicated  of  all  the  secretions,  it  may  be 
presumed  that  the  peculiar  arrangement  of  the  secreting  parenchyma 
in  the  liver  stands  in  relation  with  these  peculiarities.  In  fact,  the 
plasma  of  the  blood,  in  passing  through  many  cells  and  being  subjected 
to  the  metabolic  influence  of  each  before  it  reaches  the  efferent  duct, 
must  undergo  very  different  changes  from  those  which  it  suffers  when 
it  is  separated  from  the  glandular  canals  only  by  a  single  layer  of  cells 
and  one  or  two  structureless  membranes.  The  resulting  necessary 
slowness  of  the  secretion  is  compensated  by  the  size  of  the  organ  and 
the  elaboration  of  the  product. 

If  nitric  acid  be  added  to  the  hepatic  cells,  they  assume  a  greenish- 
yellow  color,  as  was  originally  stated  by  Backer.  Sugar  and  sulphuric 
acid  turn  them  red ;  water  produces  an  abundant  precipitate  of  dark 
granules  in  the  cells,  which  are  usually,  readily  and  completely  soluble 
in  acetic  acid,  so  that  they  become  more  of  less  pale,  often  to  a  consi- 
derable extent ;  the  same  thing  occurs  if  the  acid  be  added  directly. 
If  the  liver  be  boiled,  its  parenchyma  becomes  hard  and  the  cells  ac- 
quire a  concentrated  and  wrinkled  appearance.  Dilute  caustic  alkalies 
rapidly  attack  the  hepatic  cells  in  animals,  and  dissolve  them ;  in  man 
they  resist  somewhat  longer,  but  from  the  very  first  swell  up  to  about 
twice  their  size,  become  very  pale,  and  eventually  also  disappear. 
Ether  and  alcohol  render  the  cells  smaller  and  granular,  as  do  sulphuric 
and  nitric  acids.  The  result  of  these  and  the  above-mentioned  facts  is, 
that  the  hepatic  cells  contain  a  considerable  quantity  of  nitrogenous 
substances,  fat,  coloring  matter  of  the  bile,  and  perhaps  also  its  acids. 
The  nitrogenous  compounds  are  of  several  kinds  :  albumen,  which  is  met 
with  in  the  watery  extract  of  the  liver,  and  a  substance  which  is  preci- 
pitated by  water,  is  readily  soluble  in  acetic  acid  and  resembles  the 
casein-like  matter  found  in  the  serum  of  the  blood  (Pannum  in  Virchow 
and  Reinhard's  Archiv,  b.  IV.  1).  The  existence  of  the  coloring  matter 
of  the  bile  in  the  hepatic  cells  is  not  so  much  manifested  by  their  re- 
action with  nitric  acid,  which  is  also  exhibited  by  many  other  cells,  as 
by  their  general  tint,  and  the  frequent  occurrence  in  them  of  precipated 
coloring  matter  of  the  bile.  The  existence  of  the  fatty  acids  of  the  bile 
in  the  hepatic  cells  is  not  directly  demonstrable,  since  both  albumen  and 
fat  become  red  by  the  action  of  sulphuric  acid  and  sugar  (Schultze),  but 


536  SPECIAL    HISTOLOGY. 

is  probable.  Fat,  however,  certainly  exists  in  them,  even  when  it  is  not 
microscopically  demonstrable,  as  the  collective  analyses  of  the  liver  show-. 
Probably,  also,  the  sugar  which  recent  researches  have  demonstrated  in 
the  liver  will  be  found  to  exist  in  the  parenchyma ;  in  the  cells,  there- 
fore, and  not  in  the  blood  only. 

As  the  principal  mass  of  the  liver  is  formed  by  the  hepatic  cells,  I 
here  add  the  results  of  one  of  the  many  analyses  of  the  liver  by  Von 
Bibra  ("  Chem.  Fragmente  iiber  die  Leber  und  Galle,"  Braunschweig, 
1849).  He  found,  in  100  parts  of  the  substance  of  the  liver  of  a  young 
man  who  died  suddenly — 

Protein  substance,  insoluble  in  water, 9'44 

Albumen, 2-40 

Collagenous  substance,    . 3'37 

Extractive  matter, 6'07 

Fat, 2-50 

Water,    .         .         . .  76' 17 


100-00 


One  hundred  parts  of  the  water  yielded  3-99  of  ash,  containing  espe- 
cially phosphate  of  potassa,  then  phosphate  of  lime,  some  silica  and  iron, 
and  chloride  of  sodium.  The  protein  substance,  insoluble  in  water,  pro- 
ceeds from  the  nuclei  and  membranes  of  the  hepatic  cells  and  from  the 
contents  to  which  we  have  referred.  The  albumen  partly  proceeds  from 
the  blood,  but  certainly  from  the  cells  also.  Von  Bibra  found  neither 
kreatin  nor  kreatinin  in  the  extractive  matters  ;  the  coloring  matter 
which  they  contained  did  not  present  the  same  reaction  as  that  of  the 
bile,  whence  Von  Bibra  draws  the  conclusion  that  this  ingredient  does 
not  exist  as  such  in  the  cells.  Finally,  I  may  advert  to  the  acid  reac- 
tion of  the  parenchyma  of  fresh  liver,  which  1  discovered  (Art.  "Spleen," 
in  Todd's  Cyclopaedia),  and  which,  in  this  case,  is  even  more  remarkable 
than  in  the  spleen.  Von  Bibra  also  found  the  watery  extract  of  the 
Ox's  liver  to  have  an  acid  reaction  (1.  <?.,  p.  33),  and  has  demonstrated 
the  existence  of  lactic  acid  in  it. 

There  is  no  subject  of  minute  anatomy  upon  which  opinions  are  so 
various,  at  the  present  time,  as  upon  the  structure  of  the  secreting 
parenchyma  of  the  liver ;  and  yet,  with  the  views  which  have  been  ex- 
pressed in  the  preceding  section,  the  only  question  that  can  arise  is, 
whether  the  finest  biliary  ducts  are  intercellular  spaces,  canalicular 
spaces  between  the  hepatic  cells,  as  Henle  and  Gerlach  consider,  or 
whether  they  consist  of  the  columns  of  hepatic  cells  surrounded  by 
membrance  proprice.  I  have  endeavored  to  show,  in  my  "  Mikr.  Anat." 
II.  p.  221,  that  these  notions  are  untenable,  and  that  nothing  remains 
but  to  accept  the  view  which  has  been  offered,  however  paradoxical,  as 
the  only  one  which  at  all  corresponds  with  nature.* 

*  [In  animals  the  structure  of  the  secreting  parenchyma  of  the  liver  differs  in  many  respects 


THE    LIVER.  537 

§  161.  Excretory  ducts  of  the  liver. — The  biliary  duct  and  its  branches 
accompany  the  vena  portce  and  hepatic  artery,  so  that  on  one  side  of  a 
portal  branch  there  is  always  a  much  smaller  biliary  duct  and  artery, 
which  are  included  with  it  in  a  sheath  of  connective  tissue,  the  so-called 
capsule  of  Glisson.  The  hepatic  ducts  ramify,  in  Man,  with  the  vena 
portce  and  may  be  dissected  out  for  a  long  distance  ;  and  with  the  mi- 
croscope they  may,  in  fresh  and  injected  livers,  be  traced  as  far  as  the 
lobules.  Before  reaching  the  latter,  they  either  do  not  anastomose  at 
all  or  very  sparingly ;  the  ductus  interlobulares,  however,  as  they  have 
been  termed,  appear  to  be  continuous  with  each  other  and  thus  to  invest 
the  hepatic  islets.  From  these  ducts  of  1-90-1-120  of  a  line  branches 
of  1-100-1-120  of  a  line  proceed,  in  no  very  great  numbers,  to  the 
hepatic  islets  and  become  continuous  with  the  hepatic  network  in  the 
mode  above  described.  Perhaps  the  very  fine  biliary  ducts,  which  I 
have,  as  stated  above,  observed  microscopically,  with  a  diameter  of  0-01 
and  a  cavity  of  0'0033  of  a  line,  are  identical  with  a  part,  at  all  events, 

from  that  of  Man.  In  the  lowest  forms  of  animal  life,  where  no  distinct  digestive  apparatus 
exists  no  trace,  according  to  Prof.  Leidy,  of  biliary  structure  is  observable.  When  we  rise 
a  little  in  the  scale,  as  in  the  Polypi,  certain  cells  forming  part  of  the  digestive  cavity,  pos- 
sess the  power  of  secreting  a  fluid  analogous  to  bile.  In  many  of  the  Annelida,  we  find 
appended  to  the  sides  of  the  alimentary  canals  caeca  lined  by  small  cells,  which  probably 
secrete  a  biliary  fluid.  A  similar  substance  is  formed  in  the  Myriapoda  by  the  cells  of  the 
long  and  delicate  tubes,  which  empty  into  the  intestine. 

In  insects  the  liver  is  formed  of  distinct,  filiform,  tortuous  tubes,  opening  near  the  pyloric 
extremity  of  the  stomach  by  separate  orifices  into  the  sides  of  the  alimentary  canal.  These 
tubes  consist  of  a  transparent,  amorphous,  basement  membrane,  the  inner  surface  of  which 
is  covered  by  secreting  cells.  These  cells  are  generally  round  or  oval,  and  contain  molecular 
matter,  numerous  fine  oil-globules,  a  central  granular  nucleus  and  a  transparent  nucleolus. 
The  tubes  are  filled  with  fine  granules  and  a  great  amount  of  oil  5  extremely  minute  respi- 
ratory tracheae  are  distributed  to  them. 

In  the  Crustacea,  as  in  the  Cray-fish,  the  liver  is  formed  of  two  large  lobes,  one  on  each 
side  of  the  intestine,  united  by  an  isthmus.  Each  lobe  consists  of  conical  caeca,  composed 
of  a  sac  of  basement  membrane  lined  with  numerous  secreting  cells,  of  a  more  or  less 
polygonal  form.  These  cells  have  an  average  diameter  of  O2  of  a  line  ;  they  increase  in 
size  from  the  bottom  of  the  caecum  upwards,  and  obtain  a  gradual  addition  of  oil-globules. 
The  central  cavity  of  the  caeca  is  filled  with  fat-globules  and  a  finely  granular  mass. 

In  the  Molluscs,  as  in  the  Snail  and  Slug,  the  liver  is  formed  of  several  lobes,  subdivided 
into  lobule?,  which  are  composed  of  numerous  bulbiform  caeca  of  a  polygonal  shape.  These 
caeca  do  not  differ  in  structure  from  the  caeca  in  the  liver  of  the  Crustacea.  They  are  lined 
with  cells  of  an  average  diameter  of  0'2  to  0'4  of  a  line,  filled  with  oil-globules,  and  contain- 
ing a  granular  nucleus  with  a  hard  transparent  nucleolus.  Around  the  caeca  there  is  a  net- 
work of  bloodvessels,  to  the  parietes  of  which,  Prof.  Leidy  states,  minute  oil-globules  and 
nucleated  fat-cells  are  frequently  attached. 

In  the  Vertebrata,  the  facts  observed  by  Prof.  Leidy  confirm  the  researches  of  Kiernan  and 
other  recent  observers.  He  considers,  however,  the  biliary  tubes  to  commence  within  the 
lobules,  arid  not  merely,  as  stated  by  Koiliker,  as  a  layer  of  cells,  but  as  a  network  of  distinct 
tubules  lined  with  a  basement  membrane  and  an  epithelium.  Their  diameter  in  different 
animals  is  generally  two  and  a  half  times  the  size  of  the  secreting  cells.  (Vid.  Leidy, 
"  Researches  into  the  Comparative  Structure  of  the  Liver,"  in  American  Journal  of  Medical 
Sciences,  January  1848.) — DaC.] 


538  SPECIAL    HISTOLOGY. 

of  those  which  have  been  injected  as  the  origins  of  the  hypothetical 
lobular  biliary  ducts. 

All  the  biliary  ducts,  down  to  those  which  have  a  diameter  of  0-1  of 
a  line,  possess  a  thick  fibrous  membrane,  composed  of  dense  connective 
tissue  with  many  nuclei  and  elastic  fibres,  and  a  cylinder  epithelium 
0-01  of  a  line  thick,  which,  in  ducts  under  0-04-0-05  of  a  line,  becomes 
gradually  changed  into  a  tessellated  epithelium.  The  ductus  communis 
choledochus  and  the  cystic  duct  are  similarly  constituted,  only  their  walls 
are  thinner,  and  they  may  be  readily  separated  into  a  fibrous  and  a  mu- 
cous layer,  the  latter  of  which  contains  also  a  few  muscular  fibre-cells, 
but  on  the  whole  so  sparingly,  that  these  ducts  cannot  be  said  to  possess 
any  special  muscular  coat. 

The  gall-bladder  has,  between  its  peritoneal  covering  and  the  abundant 
subsereus  connective  tissue,  a  delicate  layer  of  muscles,  whose  fibre-cells, 
0-03-0-04  of  a  line  long,  take  more  particularly  a  longitudinal  and  a 
transverse  direction  and  present  only  indistinct  nuclei.  The  mucous 
membrane  is  distinguished  by  many  reticulated,  more  or  less  prominent 
folds,  which  contain  a  capillary  network,  exactly  like  that  of  the  folia- 
ceous  intestinal  villi,  and  it  is  also  provided  with  a  cylinder  epithelium, 
whose  cells  are  often,  like  the  membranes  of  the  gall-bladder,  thoroughly 
stained  with  bile ;  their  nuclei  are  not  always  distinct. 

The  walls  of  the  biliary  ducts  contain  a  multitude  of  small,  racemose, 
yellowish  mucous  glands,  the  glands  of  the  biliary  ducts,  whose  vesicles 
of  0-016-0*024  of  a  line,  differ  in  no  essential  respect  from  those  of 
other  racemose  glands.  In  the  ductus  hepaticus,  choledochus,  and  in  the 
lower  portion  of  the  systicus,  the  glands  in  the  fibrous  tunic  and  parts 
external  to  it,  are  very  numerous,  |-1  line  in  diameter,  opening  singly 
or  many  together  by  foramina  of  0-1-0-14  of  a  line,  visible  to  the 
naked  eye,  which  give  the  mucous  membrane  of  those  canals  a  reticulated 
appearance.  At  the  commencement  of  the  cystic  duct  the  glands 
are  few,  and  in  the  gall-bladder  itself,  in  which  they  are  said  to  have 
been  met  with,  their  occurrence  is  certainly  not  constant.  On  the  other 
hand,  in  the  branches  of  the  hepatic  duct,  down  to  Jd  of  a  line  in  diame- 
ter, such  glands  are  again  met  with,  many  of  them  opening  by  a  double 
series  of  fine  apertures  which  exist  in  these  canals. 

We  may  refer  here  to  certain  peculiar  ramifications  of  the  biliary 
duct,  vasa  aberrantia  (E.  H.  Weber).  They  exist :  1,  in  the  ligamentum 
triangulare  sinistrum,  as  6—10  and  more  canals,  0'006-0%0027  of  a  line 
in  diameter,  consisting  of  a  fibrous  membrane  and  small  cells.  Ferrein 
and  Kiernan  traced  them  as  far  as  the  diaphragm,  though  for  the  most 
part  they  only  extend  to  the  middle  of  the  ligament,  or  not  so  far, 
branching  out,  forming  networks,  or  anastomosing  in  loops.  According 
to  Theile,  tolerably  large  biliary  ducts  frequently  proceed  as  far  as  the 


THE    LIVER.  539 

edge  of  the  left  lobe  of  the  liver  -without  entering  the  triangular  liga- 
ment.* 2.  Anastomosing  biliary  ducts  are  also  to  be  met  with  in  the 
membranous  bridge  which  unites  the  Spigelian  and  right  lobes  behind  the 
inferior  vena  cava,  also  in  the  membranous  band  which  frequently  covers 
the  umbilical  vein  and  at  the  edge  of  the  cystic  fossa.  3.  In  the  trans- 
verse fissure  of  the  liver,  according  to  E.  H.  Weber,  the  right  and  left 
branches  of  the  ductus  hepaticus  and  their  smaller  twigs  give  off  nume- 
rous fine  ramuscules,  which  are  distributed  through  the  connective  tissue 
of  the  capsule  of  Glisson  covering  the  fossa  and  form  a  network,  which 
unites  the  right  and  left  hepatic  ducts.  Many  small  branches  of 
these  ducts  terminate  by  enlarged  ends  of  1-25-1-18  of  a  line,  and 
upon  their  walls  a  multitude  of  rounded  elevations  are  met  with,  which, 
like  the  walls  of  the  smallest  bronchice,  appear  to  be  formed  by  flattened 
cells,  which  have  coalesced  with  the  canals  and  retain  wide  communi- 
cations with  their  cavities.  What  Weber  thus  describes  as  vasa  aber- 
rantia,  were  subsequently  described  by  Theile  as  glands  of  the  biliary 
ducts.  He  says,  that  the  elongated  glands  are  not  merely  curved  in 
various  directions,  but  divide,  the  resulting  branches  reuniting  with  one 
another,  and  with  the  surrounding  glands,  as  may  be  observed  in  the 
glands  of  the  coarser  and  middle-sized  biliary  ducts — especially,  also, 
in  the  connective  tissue  of  the  transverse  fissure,  where  the  glandular 
networks  are  connected  with  both  branches  of  the  biliary  ducts.  In 
opposition  to  these  views,  Weber,  in  his  latest  work,  adheres  to  his 
former  interpretation,  and  shows,  against  Theile,  that  mucous  glands 
and  their  ducts  form  networks  and  connect  the  ducts  of  other  glands 
nowhere  else ;  furthermore,  that  in  the  new-born  infant,  although 
the  network  of  the  biliary  ducts  exist  in  the  transverse  fissure,  those 
branches  which  terminate  in  enlarged  extremities  are  almost  entirely 
absent. 

The  relations  of  the  finest  ramifications  of  hepatic  ducts,  or  of  the 
ductus  interlobulares  of  Kiernan,  have  not  yet  been  perfectly  made  out, 
a  subject  which  gave  rise  to  many  remarks  in  the  previous  section.  I 
will  only  add  here,  that  some,  as  more  especially  Guillot,  suppose,  not 
only  that  the  ductus  interlobulares  anastomose,  but  also  that  their 
branches  are  inter-connected  in  many  ways,  whilst  others,  as  Theile, 
describe  their  communications  as  scanty.  For  myself,  though  I  have 
observed  anastomoses  of  the  interlobular  ducts,  I  have  as  yet  met  with 
no  communications  between  their  branches,  which,  though  they  do  not 
enter  the  hepatic  islets,  may  be  called  lobular  branches.  If  they  occur, 
they  are  certainly  few  in  number,  for  such  branches  may  be  isolated 
for  a  considerable  distance  without  any  other  trunks  being  seen  either 
to  be  given  off  from  or  to  join  them.  Upon  the  whole,  the  interlobular 
branches  are  anything  but  abundantly  distributed,  and,  therefore,  the 
slowness  of  the  biliary  secretion  is  determined,  not  only  by  the  pecu- 


540  SPECIAL    HISTOLOGY. 

liar  structure  of  the  hepatic  parenchyma,  but  also  by  the  small  number 
of  the  excreting  canals. 

The  bile  is  normally  quite  fluid,  being  only  accidentally  mixed  with 
cylindrical  epithelium-cells,  derived  from  the  coarser  biliary  ducts.  I 
have  never  met  with  hepatic  cells  in  them,  and  the  statements  of  those 
who  have  affirmed  their  existence  have  arisen,  either  from  a  mistake,  or 
from  confounding  with  them  the  polygonal  cells  of  the  epithelium  of 
the  ductus  interlobulares.  Constitutents  which,  though  abnormal,  are 
very  frequent,  are — fat-drops,  coloring  matter  of  the  bile  in  granules 
or  granular  masses,  which,  as  in  the  hepatic  cells,  so  also  in  the  bile 
itself,  are  occasionally  abundantly  excreted  ;  more  rarely  there  are 
crystals  of  cholesterine,  and  especially  the  reddish  needles  of  bilifulvin, 
lately  observed  by  Virchow  ("Mittheil  d.  Wiirzburg,  Phys.  Med.  Ges." 
I.  p.  311).* 

*  [The  view  which  Professor  Kolliker  takes  of  the  mode  of  termination  of  the  hepatic 
ducts,  can  hardly  be  said  to  present  any  essential  difference  from  that  which  Dr.  Handfield 
Jones  has  ably  advocated  in  several  successive  papers  in  the  "  Philosophical  Transactions" 
(for  1846,  1849,  and  1853),  and  which  we  here  subjoin  in  his  own  words  :  — 

"  The  liver,  in  all  vertebrate  animals,  may  be  regarded  as  consisting  of  a  secretory 
parenchyma  and  of  excretory  ducts. 

"  The  size  of  the  excretory  apparatus  bears  only  a  small  proportion  to  that  of  the 
secretory. 

"  These  two  portions  of  the  liver  are  not  continuous  with  one  another,  but  are  disposed 
simply  in  a  relation  of  juxtaposition. 

"  The  action  of  the  liver  seems  to  consist  in  the  transmission  of  bile,  as  it  is  formed,  from 
cell  to  cell,  till  it  arrives  in  the  neighborhood  of  the  excretory  ducts,  by  which  it  is  absorbed. 
This  action  is  probably  slow  and  very  liable  to  be  interfered  with,  contrasting  remarkably 
with  that  of  the  kidney,  where  a  particular  apparatus  is  added  to  insure  completeness  and 
rapidity  of  action. 

"  The  secretion  of  the  hepatic  cells  is  very  liable  to  be  retained  within  the  gland,  either  in 
the  cells  or  in  a  free  state. 

"  This  circumstance,  as  well  as  its  structural  relations,  seem  to  point  out  the  liver  as  ap- 
proximating to  the  class  of  ductless  glands. 

"  For  the  same  reason  it  is  highly  probable  that  a  part  of  the  secretion  of  the  cells  is 
directly  absorbed  into  the  blood  which  traverses  the  lobules"  ("  Phil.  Trans.,"  1849,  p.  132). 
From  an  extensive  series  of  researches  in  all  classes  of  the  Vertebrata,  Dr.  H.  Jones  comes 
to  the  conclusion  that  the  excretory  system  of  the  liver  always  terminates  in  closed  tubes. 
The  ducts  of  the  Sheep's  liver,  which  in  all  essential  particulars  agrees  with  that  of  Man 
and  of  the  Pig,  are  thus  described : — 

"  In  the  minutest  branches  (of  the  biliary  ducts)  which  seem  to  be  approaching  their 
termination,  and  which  can  sometimes  be  examined  and  isolated  in  the  most  satisfactory 
manner,  the  epithelial  particles  are  remarkably  modified ;  they  can  scarcely  be  said  to  exist 
as  separate  individuals,  but  rather  their  nuclei,  which  are  often  large  and  distinct,  are  set 
close  together  in  a  subgranular  or  homogeneous  basis  substance.  In  ducts  where  this  con- 
dition of  epithelium  exists,  there  is  seldom  any  distinct  trace  of  basement  membrane  ;  the 
margin,  though  sufficiently  even,  yet  exhibiting  the  bulging  outlines  of  the  component  nuclei; 
still  less  is  there  any  proper  fibrous  coat,  though  the  ducts  may  be  more  or  less  involved  in 
the  filamentary  expansions  of  the  capsule  of  Glisson.  Ducts  of  this  character  have  usually 
a  diameter  of  about  yg^th  of  an  inch;  they  can  sometimes  be  followed  for  a  considerable 
distance  without  being  seen  to  give  off  any  branches,  or  to  diminish  much  in  calibre.  Their 
mode  of  termination  is  various — several  have  been  distinctly  seen  to  terminate  by  rounded 


THE    LIVER.  541 

§  162.  Vessels  and  nerves  of  the  liver. — The  arrangement  of  the  blood- 
vessels in  the  liver  distinguishes  it  from  all  other  organs,  inasmuch  as, 
besides  an  artery  and  an  efferent  vein,  it  possesses  an  additional, 
afferent  vein,  the  vena  portce.  While  the  latter  is  appropriated  to  the 
supply  of  the  secreting  parenchyma,  being  directly  continuous  through 
the  capillary  network  with  the  hepatic  vein,  the  artery  is  more  espe- 
cially distributed  to  the  walls  of  the  biliary  ducts  and  of  the  portal  vein, 
to  Glisson's  capsule,  and  to  the  serous  investment  of  the  liver,  taking 
only  a  subordinate  share  in  supplying  the  capillary  network  of  the 
hepatic  islets.  The  ramifications  of  the  portal  vein,  and  of  a  few  small 
veins  of  the  stomach  and  gall  bladder  (see  Weber,  Ann.  Acad.  1845), 
which  enter  the  liver  independently,  take  place  for  the  most  part  dichoto- 
mously  ;  but  both  larger  and  smaller  branches,  besides  the  main  trunk, 
into  which  they  divide,  give  off  a  number  of  small  vessels  at  right  angles. 
The  latter,  often  after  a  very  short  course,  at  once  enter  the  hepatic 
islets  contiguous  to  the  largest  vascular  canals,  while  the  larger  portal 
branches,  ramifying  continually,  and  becoming  finer  and  finer,  have, 
according  to  their  diameter,  to  take  a  longer  or  a  shorter  course  through 
the  hepatic  parenchyma  in  the  canals  lined  by  the  capsule  of  Glisson, 
before  they  enter  the  hepatic  islets  or  lobules.  Each  of  these  receives, 

and  closed  extremities,  which  have  nearly  the  same  diameter,  as  the  duct  itself;  others  seem 
to  lose  their  tubular  character,  their  nuclei  becomes  less  closely  set  together,  and  the  uniting 
substance  more  faintly  granular  and  indefinite;  the  duct,  in  short,  gradually  ceases,  losing 
all  determinate  structure.  In  some,  of  rather  minute  size,  yg^ff-rAff1*1  °f  an  mch  in  dia- 
meter, the  exterior  form  remains  distinct,  but  the  canal  is  almost  obliterated  by  the  close  ap- 
proximation of  the  nuclei  of  the  opposite  walls.  These  structures  now  described,  I  believe 
to  be  truly  the  terminal  branches  of  the  hepatic  duct,  from  which  they  certainly  originate. 
They  seem  gradually  to  lay  aside  the  several  component  tissues  of  the  larger  ducts,  the 
fibrous  coat  blending  with  the  ramifications  of  Glisson's  capsule,  the  basement  membrane 
imperceptibly  ceasing,  and  the  epithelium  becoming  resolved  at  last  into  its  simple  funda- 
mental nuclei"  (1.  c.,  p.  125). 

It  is  important  to  remark,  that  in  a  Dog,  Dr.  H.  Jones  found  biliary  matter  in  the  interlo- 
bular  fissures. 

From  the  fact  that  in  the  contents  of  the  hepatic  ducts  of  Man  and  the  Sheep,  extracted  by 
means  of  a  forceps  and  without  injuring  the  organ,  hepatic  cells  may  be  detected,  Mr.  Whar- 
ton  Jones  ("  Phil.  Trans.,"  1848)  draws  the  conclusion  that  the  hepatic  cells  are  endogenous 
cells,  answering  to  the  epithelium  of  other  glands — which  was  Henle's  view.  It  is  impossi- 
ble to  doubt  a  fact  stated  by  so  careful  an  observer;  but,  however  these  cells  may  have  got 
into  the  large  biliary  ducts,  it  is  quite  clear,  from  a  comparison  of  diameters,  that  they  can- 
not enter  the  minutest  ones — the  total  diameter  of  the  latter  being  the  same  as  that  of  the 
cells,  viz.  y^^th  of  an  inch. 

We  are  strongly  inclined  to  believe   that  the  view  taken  by  Dr.  H.  Jones  is  in  the  main  \ 
correct — that  the  liver  is  essentially  of  the  same  order  as  the  "•  ductless"  glands,  and  should  \ 
be  placed  in  the  same  category  as  the  Peyerian  follicles,  spleen,  &c.     In  fact,  startling  as  this    ( 
view  may  at  first  appear,  a  very  clear  transition  between  the  Peyerian  follicles,  &c.,  and  the     \ 
liver,  is  afforded  by  the  tonsils  ;  which,  on  the  one  hand,  are  identical  with  Peyer's  follicles, 
in  so  far  as  they  are  solid  vascular  networks,  whose  meshes  are  filled  by  a  morphologically 
indifferent  tissue  ;  while,  on  the  other  hand,  without  differing  from  the  liver  in  this  respect 
they  resemble  it  in  having  these  elements  arranged  around  diverticula  of  the  intestinal 
mucous  membrane. — TBS.] 


542 


SPECIAL    HISTOLOGY. 


from  one  or  other  set  of  vessels,  at  least  3,  usually  4-5,  smaller  vessels  of 
1-120-1-60  of  a  line,  which  Kiernan  calls  vence  interlobulares.  Such  a 
vein,  however,  is  never  distributed  to  only  one  hepatic  islet,  but  always 
to  two,  or  even  three.  Their  ultimate  branches,  the  rami  lobulares  of 
Kiernan,  10-20  in  number,  enter  the  neighboring  hepatic  islets,  usually 
at  a  right  angle,  and  divide  immediately  into  the  capillary  network, 
without  becoming,  in  man,  directly  united  with  one  another.  In  fact, 
the  branches  of  the  portal  vein  nowhere  anastomose,  but  are  connected 
merely  by  the  finest  vascular  network  of  the  organ. 


Fig.  222. 


The  capillary  network  of  the  islets  (Fig.  222)  completely  fills  the 
interspaces  of  the  hepatic  cell-network,  so  that  the  secreting  parenchyma 
consists  actually  of  only  two  elements,  the  hepatic  cells  and  the  capilla- 
ries. Exactly  as  the  hepatic  cell-network  is  continuous  through  the 
entire  liver,  though  being  interrupted  by  the  biliary  ducts  which  pass  off 
and  the  vessels  which  enter,  at  regular  intervals,  it  is  divided  into  sepa- 
rate, very  minute  areace — so  the  capillary  network  of  the  bloodvessels 
passes  from  one  hepatic  islet  to  another,  but  is  nevertheless  discontinuous 
in  certain  spots.  The  diameter  of  the  capillaries  is,  in  general,  some- 
what less  than  that  of  the  hepatic  cell-network,  though  relatively  con- 
siderable; in  man  it  is,  on  the  average,  0-004-0-0055,  0-002-0-01  of  a 
line,  in  extreme  instances ;  the  wide  vessels  being  more  especially  found 
in  the  neighborhood  of  the  afferent  and  efferent  veins,  the  narrowest  in 

FiG.  222. — Hepatic  cell-network  and  its  capillaries,  magnified  350  diameters  ;  from  the 
Pig.  Spaces  are  purposely  left  here  and  there  between  the  cells  and  capillaries,  which  do 
not  exist  in  nature. 

FIG.  223. — Segment  of  a  very  successful  injection  of  the  hepatic  veins  of  the  Rabbit, 
magnified  35  diameters.  One  vena  intralobularis  is  visible  in  its  entire  course,  but  only  the 
radicles  of  the  other.  The  capillaries  of  the  lobules  partly  coalesce,  and,  in  one  place,  two 
venous  radicles  do  so. 


THE    LIVER.  543 

the  interval  between  them.  The  meshes  of  the  network  correspond,  of 
course,  in  form,  with  the  hepatic  cell-network,  and  are  thence  more  elon- 
gated in  the  interior  of  the  hepatic  islets,  more  rounded  externally, 
whilst  their  breadth  corresponds  with  that  of  the  columns  of  the  hepatic 
cells,  being  about  0-006-0-02  of  a  line. 

The  hepatic  veins  essentially  resemble  the  portal  vein,  in  so  far  as 
they  possess  no  valves,  branch  out  at  acute  angles  and  do  not  anasto- 
mose ;  their  larger  branches  also  receive  numerous  minute  vessels,  but 
these  lie  isolated  in  special  canals  in  the  hepatic  substance  to  which  they 
are  firmly  attached,  whence  they  do  not  collapse  when  cut  across,  and, 
at  least  in  their  finer  ramifications,  possess  no  external  investment  of 
connective  tissue,  which  is  indeed  but  very  rudimentary,  even  in  the 
largest  trunks.  The  relations  of  the  ultimate  branches  of  the  hepatic 
vein,  termed  by  Kiernan  intra-lobular  veins,  and  by  Krukenberg,  vence 
cent-rales  lobulorum,  are,  however,  totally 'different  from  those  of  the 
portal  ramuscules.  These  veins,  which  in  Man  are  0*012-0-03  of  a  line 
in  diameter,  are  best  studied  in  some  animal  whose  liver  breaks  up  into 
isolated  lobules,  as  the  Pig ;  after  which  Kiernan  has  given  his  some- 
what diagrammatic  figure.  If  we  here  open  a  small  branch  of  the 
hepatic  vein,  polygonal  arese  are  descried  through  the  walls  of  the  ves- 
sel— the  outlines  of  those  surfaces  of  the  lobules  which  are  turned  towards 
the  vein  (Fig.  218). 

A  minute  vein  which,  in  the  centre  of  each  of  these  surfaces,  termed 
by  Kiernan  "  bases  of  the  lobules,"  opens  directly  into  the  larger  vessel 
leads,  if  we  trace  it  in  the  opposite  direction,  into  the  interior  of  a  lobule, 
where  it  arises  from  the  capillary  network  ;  but  under  no  circumstances 
is  it  continued  into  a  second  or  third  lobule.  In  this  way  only  a  single 
vein,  which  may  thence  be  called  vena  intralobular  is ,  arises  in  each 
lobule.  The  vessels  into  which  these  veins  directly  open  are  called  by 
Kiernan  sublobulares,  because  they  run  along  the  basal  surfaces  of  the 
lobules.  They  are  sometimes  large,  attaining  as  much  as  1—2  lines  in 
the  Pig,  and  then  lie  in  canals  which  are  surrounded  by  the  basal  sur- 
faces of  a  certain  number  of  lobules ;  at  other  times  they  are  smaller, 
down  to  1-30  of  a  line,  in  which  case  they  only  pass  between  the  lobules. 
The  sublobular  veins  unite  into  larger  veins,  which  continue  to  receive, 
directly,  but  few  or  no  other  intralobular  veins,  and  thence,  are  only 
partly  or  not  at  all  bounded  by  the  basal  surfaces  of  the  lobules,  but 
only  by  their  lateral  or  apical  surfaces  ("  capsular  surfaces,"  Kiernan). 
Such  veins,  when  they  are  smaller,  still  receive  sublobular  veins  from 
the  groups  of  lobules  which  immediately  surround  them  ;  or,  lastly,  only 
larger  veins,  which  have  the  same  relations  as  themselves. 

The  intralobular  veins  are  very  simply  arranged.  Each  of  them 
penetrates  directly  into  the  axis  of  an  hepatic  islet,  or  lobule,  dividing 
in  the  middle  into  two  or  three  principal  branches,  which  frequently 


544  SPECIAL    HISTOLOGY. 

again  subdivide.  The  capillaries  open,  not  merely  into  the  terminations 
of  these  veins,  but  also  into  their  trunks  throughout  their  course;  in- 
_deed,  according  to  Theile,  the  origins  of  the  sublobular  veins  also  re- 
ceive capillaries.  In  all  those  hepatic  lobules  or  islets  whose  apices  are 
turned  either  towards  the  surface  of  the  liver,  or  to  a  large  vascular 
trunk,  the  interlobular  veins  extend  nearly  to  their  extremities ;  whilst 
in  others  they  stop  more  nearly  in  the  middle,  so  that  they  are  always 
about  half  the  diameter  of  the  lobules  distant  from  the  nearest  inter- 
lobular  veins  of  the  vena  j)  or  tee. 

The  hepatic  artery,  for  the  most  part,  accompanies  the  portal  vein  and 
the  biliary  canals,  is  enclosed  with  the  latter  in  Glisson's  capsule,  and, 
in  its  principal  ramifications,  presents  precisely  the  same  relations  as 
the  portal  vein.  It  is  finally  distributed  upon  the  vessels  and  biliary 
ducts,  in  Glisson's  capsule,  in  the  fibrous  and  serous  coats  of  the  liver, 
and  in  the  hepatic  islets,  whence  its  branches  are  denominated  rami 
vascular  es,  capsulares,  and  lobulares. 

1.  Kami  vasculares. — As  it  divides,  in  company  with  the  vena  portce, 
the  hepatic  artery  gives  off  numerous  small  branches,  almost  at  right 
angles,  which  form  a  plexus  in  Glisson's  capsule,  from  which  some  lobu- 
lar  branches  for  the  parietes  of  the  portal  canal  arise,  on  the  side  oppo- 
site to  the  arterial  trunks ;  while  many  twigs  proceed  to  the  walls  of  the 
portal  vein,  the  larger  branches  of  the  artery  itself,  the  hepatic  veins, 
Glisson's  capsule  and  the  biliary  ducts.     The  distribution  of  the  vessels 
is  particularly  remarkable  in  the  latter  canals,  so  that,  in  a  good  injec- 
tion, they  appear  almost  as  red  as  the  arteries  themselves. 

A  moderately  close  capillary  network  exists  around  all  these  parts, 
even  the  glands  of  the  biliary  ducts,  whence  the  vence  vasculares  arise 
and  open,  as  Ferrein  discovered  and  as  all  the  moderns  since  Kiernan 
have  agreed,  not  into  the  hepatic  vein,  but  into  small  portal  twigs,  as 
these  are  leaving  the  larger  branches  in  Glisson's  capsule,  and  are  there- 
fore to  be  regarded  as  internal,  or  hepatic  radicles  of  the  portal  vein. 
From  this  cause  the  portal  vein  may  be  partially  injected  from  the 
hepatic  artery  and  conversely.  Again,  in  injecting  the  hepatic  artery 
and  the  portal  vein,  the  vascular  network  in  question  maybe  filled  from 
both  sides ;  while  it  is  not  possible  directly  to  force  injection  from  the 
hepatic  vein  into  them. 

2.  Rami  capsulares. — Independently  of  a  few  branches  given  off  by 
the  artery,  before  its  entrance  into  the  liver,  to  the  fossa  ductus  venosi, 
to  the  ligamentum  teres  and  suspensorium,  all  the  arterial  twigs  of  the 
coats  of  the  liver  are  the  terminal  prolongations  of  certain  arteries  which 
penetrate  the  liver  and  appear  in  different  parts  of  its  surface  between 
the  hepatic  islets.  At  the  points  of  exit,  and  even  before  reaching  them, 
these  vessels,  which  have  a  diameter  in  the  adult  of  1-30-1-20  of  a  line, 
in  children  as  much  as  1-5  of  a  line,  break  up  into  3-5  radiated  subordi- 


THE    LIVER. 


545 


nate  branches,  take  for  the  most  part  a  remarkable,  corkscrew-like, 
coiled  course,  repeatedly  anastomosing,  and  thus  spread  over  the  whole 
surface  of  the  organ,  as  far  as  the  great  venous  trunks  (vence  hepaticce, 
vena  portce,  cava  inferior),  t\\Q  fossce  of  the  liver  and  its  edges,  as  an 
elegant  arterial  network.  In  the  end,  these  arteries  everywhere  form 
a  capillary  plexus  with  wide  meshes,  from  whence,  in  many  parts — 
whether  universally  or  not  I  do  not  know — veins  arise,  which  run  back 


parallel  with  the  arteries,  enter  the  liver  and  open  into  the  portal 
branches.  Portal  radicles,  or  vence  advehentes  capsulares,  must  be  de- 
rived, therefore,  from  this  region  also.  The  arteries  and  veins  of  the 
hepatic  coats  are  in  their  terminal  expansion  connected,  on  the  one 
hand,  with  prolongations  of  the  internal  mammary,  phrenic,  cystic  and 
even  the  right  suprarenal  and  renal  vessels  (Theile),  and  anastomose,  on 
the  other  side,  in  the  hepatic  fossce,  with  those  of  Glisson's  capsule,  with 
the  vena  cava  and  hepatic  vein. 

3.  Rami  lobulares. — With  every  interlobular  vein  there  runs  a  branch 
of  the  hepatic  artery,  of  at  most  lis  rof  a  line  in  diameter  (Theile), 
which,  in  the  Pig,  divides  between  the  hepatic  islets,  in  the  capsules  of 
the  lobules,  into  fine  anastomosing  twigs,  and  is  directly  connected  with 
the  peripheral  part  of  the  capillary  network  of  the  hepatic  islets  or 
lobules,  formed,  as  stated  above,  by  the  portal  vein.  Arterial  blood, 
therefore,  takes  a  part,  although,  perhaps,  a  minor  one,  in  the  prepara- 
tion of  the  bile,  and  the  hepatic  artery  is  thus  distinguished  from  the 
bronchial  arteries,  whose  blood  is  carried  away  by  special  veins. 

The  lymphatics  of  the  liver  are  very  numerous,  and  may  be  divided 
into  superficial  networks,  under  the  peritoneum;  and  deep  vessels, 

FIG.  224. — Arterial  network  upon  the  convex  surface  of  a  child's  liver.    Natural  size. 

35 


546  SPECIAL    HISTOLOGY. 

which  accompany  the  portal  vein,  and,  in  animals,  at  least,  the  hepatic 
veins  also.  Both  kinds  of  vessels  are  connected  and  proceed  partly 
through  the  diaphragm  into  the  thorax,  partly  to  small  lymphatic 
glands  in  the  porta  hepatis,  and  to  the  intestinal  plexus.  The  lympha- 
tics of  the  gall-bladder  are  also  exceedingly  numerous. 

The  nerves  of  the  liver  are  relatively  very  abundant.  They  arise 
from  the  sympathetic,  and,  in  a  smaller  proportion,  from  the  vagus,  and 
are  chiefly  distributed  with  the  hepatic  artery,  around  which  they  form 
closer  and  wider  networks  without  ganglia.  They  always  contain, 
together  with  many  fine  tubules,  and  "  RemaTcs  fibres,"  a  few  thick 
fibres,  and  may  be  traced  ;  1,  to  the  gall-bladder  and  large  biliary 
ducts  ;  2,  in  Grlisson's  capsule  as  far  as  the  interlobular  arteries,  where 
their  finest  twigs,  of  0-008-0*012  of  a  line,  contain  only  nucleated 
fibres ;  3,  to  the  hepatic  veins  ;  and  lastly,  4,  into  the  coats  and  liga- 
ments of  the  organ. 

§  163.  According  to  the  latest  observations,  particularly  of  Bischoff 
and  Eemak,  the  development  of  the  liver  may  thus  be  best  understood. 
The  primary  rudiment  of  the  liver,  which  appears  at  a  very  early  period 
(about  the  55-58  hour,  in  the  Chick ;  in  Mammals,  after  the  WolfBan 
bodies  and  the  allantois)  consists  of  two  masses  of  cells,  an  external, 
proceeding  from  the  fibrous  membrane  of  the  intestine,  and  an  internal, 
epithelial,  which  at  first  form  a  simple,  and  afterwards  a  dichotomously 
divided  sac.  Solid  processes,  the  hepatic  cylinders  of  Remak,  are  now 
developed  from  the  epithelial  lamina,  which,  as  in  the  intestine,  consists 
at  first  of  round  cells,  probably  in  many  layers,  by  the  multiplication  of 
its  cells,  and  extend  into  the  outer  lamina,  branching  out  and  anastomos- 
ing, whilst,  at  the  same  time,  the  cells  of  the  outer  lamina  included  in 
the  meshes  of  this  network,  multiply  and  become  successively  changed 
into  vessels,  nerves,  connective  tissue,  &c.  The  difficulty  is  to  say  how 
this  peculiar,  reticulated  parenchyma  of  cells  and  rudimentary  vessels 
becomes  ultimately  arranged  as  we  know  it  to  be.  In  the  first  place,  as 
regards  the  hepatic-cell-network  and  the  islets  or  lobules  of  the  complete 
liver.  They  evidently  proceed  from  the  further  growth  of  the  original 
hepatic-cell-network,  to  which  by  a  continual  new  development  of  cells, 
fresh  processes  are  added,  which  unite  into  new  networks,  so  that  the 
hepatic-cell-network  of  the  adult  liver  is  the  direct  progeny  of  the  ori- 
ginal reticulation.  More  detailed  information  concerning  the  separate 
steps  of  the  formation  of  the  hepatic-cell-network,  is  at  present  wanting ; 
yet  from  what  is  known  it  would  appear  to  take  place  in  somewhat  dif- 
ferent modes.  Sometimes,  in  the  subsequent  stages,  free  cylindrical 
processes  of  the  hepatic-cell-network  do  not  exist  to  any  extent,  but  it 
would  appear  to  increase  by  the  continual  addition  of  new  meshes  at  its 
edges,  perhaps  also  by  the  constant  elongation  of  the  existing  columns 
of  hepatic  cells  and  the  development  of  fresh  anastomoses  between  them ; 


THE    LIVER.  547 

this  is,  if  I  have  observed  rightly,  the  case  in  man,  where  even  in  the 
seventh  week  I  did  not  succeed  in  clearly  distinguishing  free  hepatic 
columns.  At  other  times,  free  terminations  of  the  hepatic  columns  are 
apparently  developed  for  a  considerable  period,  perhaps  until  the  whole 
organ  has  nearly  arrived  at  perfection,  their  formation  appearing  to 
precede  by  some  time  that  of  new  anastomoses,  as  is  the  case  in  the 
Chick  and  other  Birds,  and  according  to  J.  Muller,  in  a  few  Mammals  ; 
in  the  latter  of  which,  according  to  Muller's  figures,  the  hepatic  columns 
are  grouped  in  lobes.  These  free,  superficial  hepatic  columns  may  perhaps 
throw  some  light  upon  the  meaning  of  Weber's  and  Krause's  statements 
respecting  the  biliary,  ducts  with  coecal  ends  upon  the  surface  of  the 
liver.  With  regard  to  the  biliary  ducts,  they  are  assuredly  nothing  but 
secondary  excavations  of  a  part  of  the  primarily  solid  hepatic  columns 
and  of  the  larger  internal  tracts,  which  border  upon  the  original  epithe- 
lial diverticulum  and  which  all  consist  of  many  series  of  cells.  The  ex- 
cavation commences  in  the  common  biliary  duct,  proceeds  towards  its 
branches,  and  must  be  considered  to  take  place  exactly  as  in  other  glands, 
i.  e.  either  by  solution  of  the  inner  cells  of  the  rudimentary  structures, 
or  by  the  excretion  of  a  fluid  between  them  and  the  consequent  produc- 
tion of  a  cavity.  In  this  mode  of  regarding  the  matter,  there  is  only 
one  point  for  consideration  ;  viz.,  that  according  to  Remak,  all  the 
hepatic  columns,  even  the  largest,  form  anastomoses,  whilst,  as  is  well 
known,  the  biliary  ducts  ramify  without  anastomosing.  The  only  solu- 
tion of  this  difficulty,  consists  in  assuming  that  the  anastomoses  of  the 
primary,  largest  hepatic  columns  do  not  continue  in  the  course  of  the 
further  development,  but  that  they  are  re-absorbed,  a  process  which  has 
its  analogue  in  many  phenomena  of  foetal  growth.  In  Man  alone 
might  we  find  an  exception,  for  it  seems  to  me  that  the  anastomoses  of 
the  right  and  left  hepatic  duct,  in  the  fossa  hepatis,  described  by  E.  H. 
Weber,  are  perfectly  well  explained  by  Remak's  observations,  and  are 
simply  the  embryonic  anastomoses  of  the  rudiments  of  these  canals, 
which  have  attained  to  some,  though  no  very  great  development.  The 
mode  of  origin  of  %  the  fibrous  membranes  of  the  biliary  ducts  becomes 
readily  comprehensible,  if  we  reflect  how  the  networks  of  hepatic  columns 
and  the  fibrous  layers  of  the  liver  interdigitate ;  so  that  layers  of  con- 
nective tissue,  &c.,  might  be  readily  formed  around  the  hepatic  cylin- 
ders from  those  elements  of  the  fibrous  layer  which  are  nearest  to  them. 
The  further  development  of  the  vessels,  nerves,  &c.,  presents  no  difficul- 
ties, taking  place  in  the  same  way  as  in  other  organs.  The  gall-bladder 
in  the  Chick,  according  to  Remak,  is  a  process,  at  first  solid,  of  one 
hepatic  duct,  which  subsequently  becomes  hollow  and  rapidly  increases 
in  size.  I  saw  the  folds  of  its  mucous  membrane,  as  early  as  in  the 
fifth  month,  in  a  human  foetus.* 

*  [In  his  last  memoir  (Philosophical  Transactions,  1853),  Dr.  Handfield  Jones  maintains 
that,  in  Fishes,  Amphibia,  and  Birds,  the  liver  is  developed  independently  of  the  intestine, 


548  SPECIAL    HISTOLOGY. 

The  investigation  of  the  liver  is  best  undertaken  in  the  Pig,  in  which 
animal  the  distinct  demarcation  of  the  lobules  greatly  facilitates  the 
comprehension  of  the  relations  of  the  secreting  parenchyma,  to  the  ves- 
sels and  hepatic  ducts.  The  hepatic  cells  may  be  isolated  with  the 
greatest  ease  in  all  animals,  either  singly,  in  series,  or  in  reticulated 
fragments  ;  but  to  comprehend  rightly  their  collective  arrangement  no 
better  means  exist  than  the  making  of  fine  sections  in  a  fresh  liver  with 
the  double  knife,  for  which,  sections  made  off-hand  with  a  razor,  even 
in  a  liver  previously  hardened  in  alcohol,  pyroligneous  acid,  chromic 
acid,  &c.,  are  by  no  means  sufficient  substitutes.  We  do  not  mean  to 
say  that  the  hepatic-cell-network  cannot  be  seen,  at  all  in  this  manner, 
for  it  is  visible  even  in  opaque  sections  of  liver  by  reflected  light,  but 
merely  that  no  complete  view  can  thus  be  obtained.  The  finest  hepatic 
ducts  are  not  readily  found,  though  a  careful  search  in  nearly  all  sec- 
tions which  include  many  lobules,  will  almost  certainly  detect  scattered 
fragments  of  them,  readily  recognizable  by  their  small  polygonal  cells, 
at  the  edges  of  the  lobules,  and  long  examination  may  perhaps  eventu- 
ally discover  such  a  fragment  in  connection  with  the  hepatic-cell-net- 
work, which,  however,  I  have  not  yet  succeeded  in  doing.  The  coarser 
biliary  ducts  present  no  difficulties.  Their  glands  are  seen  readily, 
partly  with  the  naked  eye,  partly  by  the  use  of  dilute  caustic  soda. 
Weber's  anastomoses  of  the  two  hepatic  ducts  mihe  fossa  transversa,  are 
visible  in  good  injections.  The  vasa  aberrantia,  in  the  left  triangular 
ligament  and  in  other  localities,  are  readily  perceived  even  without  in- 
jection, on  the  addition  of  acetic  acid  or  of  caustic  soda.  The  nerves 
and  lymphatics  of  the  liver  are,  except  their  finest  portions,  easily  seen 
in  Man.  The  bloodvessels  require  good  injections,  for  which  purpose, 
in  the  human  subject,  I  especially  recommend  children's  livers,  in  which 
the  distribution  of  the  arteria  hepatica  in  the  serous  coat,  on 'the  ves- 
sels, &c.,  is  beautifully  distinct.  The  capillary  network  of  the  lobes 
may  readily  be  filled  with  fine  injection,  and  a  series  of  excellent  pre- 
parations of  this  kind,  by  various  masters  of  the  art,  are  everywhere 
to  be  met  with. 

Literature  of  the  Liver. — F.  Kiernan,  "  The  Anatomy  and  Physio- 
logy of  the  Liver,"  in  "  Phil.  Trans.,"  1833 ;  E.  H.  Weber,  "  Anriotat, 
Anat,  and  Physiol.,"  Prol.  VI.  VII.'  and  VIII.  Lips.  1841  and  1842, 
and  "  Prograrnmata  collecta  Fasc.,"  II.  Lips.,  1851;  "  Ueber  den 

and,  that  the  first  rudiment  of  the  excretory  apparatus  is  the  gall  bladder,  whence  ducts 
extend  on  the  one  hand  into  the  intestine,  and  on  the  other  into  the  liver.  He  has  not 
traced  the  development  of  the  liver  in  Mammalia. 

Vogt,  however  (Embryogenie  des  Saumons,  p.  175),  states  that  in  Corcgonus  palea,  the 
liver  is  at  first  a  rounded,  solid  mass  of  cells,  in  contact  with  a  diverticulum  of  the  intes- 
tine— the  future  ducius  choledochus  •  and  that,  in  the  course  of  development,  the  diverticulum 
grows  into  and  ramifies  in  the  mass — its  ultimate  branches  terminating  in  caeca.  The  gall- 
bladder is  not  formed  till  very  late. — TRS.] 


THE    PANCREAS.  549 

feineren  Ban  der  menschlichen  Leber,"  in  "  Muller's  Archiv,"  1843,  p. 
318  ;  "  Zusatze  zu  seinen  Untersuchungen  liber  den  Bau  der  Leber,"  in 
"Berichte  d.  K.  Sachs.  Ges.  d.  Wissenscb.  zu  Leipzig,"  1850,  p.  151 ; 
A.  Krukenberg,  "  Untersuchungen  uber  den  feineren  Bau  der  mensch- 
lichen Leber,"  in  "  Mull.  Arch.,"  1843  ;  Joh.  Miiller,  in  his  great 
Work  on  the  Glands,  in  his  "  Physiology,"  and  "  Muller's  Archiv," 
1843,  p.  338;  Theile,  article  "Leber,"  in  R.  Wagner's  "  Handw.  der 
Phys."  II..  p.  308,  1844;  C.  L.  J.  Backer,  "  De  Structura  subtiliori 
Hepatis  sani  et  morbosi.  Diss.  Inaug.  Trajecti  ad  Rhenum,"  1845; 
Natalia  Guillot,  "  Sur  la  Structure  duFoie  des  Animaux  vertebras,"  Ann. 
d.  Sc.  Nat.,  1848,  p.  129;  R.  Retzius,  "  Ueber  den  Bau  der  Leber," 
in  "Mull.  Arch.,"  1849,  II.  p.  141 ;  C.  Wedl,  "Ueber  die  traubenfor- 
migen  Gallengangdrusen,"  in  "  Sitzungsbericht  der  Wiener  Akad.," 
1850,  Dec.,  p.  480,  c.  Tab.  ;  N.  Weja,  "Beitrage  zur  feineren  Anato- 
mie  der  Leber,"  in  "  Mull.  Arch."  1851,  p.  79  ;  E.  Yon  Bibra,  "  Che- 
mische  Fragmente  Uber  die  Leber  und  die  Galle,"  Braunschweig,  1849. 
The  more  minute  comparative  anatomy  of  the  Liver  is  treated  of  by  II. 
Karsten,  "  Disq.  microsc.  et  chem.  hepatis  et  bilis  Crustaceorum  et 
Molluscorum,"  in  "Nova  Acta  Acad.  Cur.,"  vol.  XXI.  1,  p.  295; 
T.  F.  G.  Schlemm,  "Dehepate  et  bile  crustaceorum  et  molluscorum 
quorundam,"  Diss.  Berol.,  1844 ;  Williams,  in  "  Guy's  Hosp.  Rep."  1846  ; 
H.  Meckel,  "  Mikrographie  einiger  Driisenapparate  der  niederen 
Thiere,"  in  "Mull.  Arch.,"  1849,  p.  1  ;  Fr.  Will.  "  Ueber  die  Absori- 
derung  d.  Galle,"  Erlangen,  1849 ;  H.  Jones,  "Phil.  Trans.,"  1846, 
1849;  [J.  Leidy,  "  Researches  into  the  Comparative  Structure  of  the 
Liver,"  in  Amer.  Jour,  of  Med.  Sciences,  1848 ;  Wharton  Jones, 
" Phil.  Trans.,"  1848;  Handfield  Jones,  "PhiL  Trans.,"  1853.— DaC.] 

OF  THE  PANCREAS. 

§  164.  The  pancreas  is  a  compound  racemose  gland,  which  so  closely 
resembles  the  salivary  glands,  that  a  short  exposition  of  its  peculiarities 
will  suffice.  As  in  all  such  glands,  larger,  smaller,  and  smallest  lobes, 
may  be  very  distinctly  made  out,  the  last  being  composed  of  microscopic 
glandular  vesicles,  which  are  here  characterized  by  their  moderate  size 
0-02-0-04  of  a  line,  and  their  usually  rounded  form.  They  possess  a 
membrana  propria  and  a  tessellated  epithelium,  whose  cells  are  very  fre- 
quently remarkable  .from  the  great  number  of  fat-granules,  so  that  the 
glandular  vesicles  appear  quite  opaque  and  as  if  entirely  filled  with 
secretion.  The  excretory  ducts,  which,  as  elsewhere,  are  connected 
with  the  glandular  vesicles,  uniting  into  larger  canals  and,  eventually, 
into  the  duct  of  Wirsung,  or  pancreatic  duct,  are  whitish  and  somewhat 
thin  walled.  They  are  composed  of  connective  tissue  and  of  elastic 
fibrils,  and  all  possess  an  epithelium  with  small  cylindrical  cells,  scarcely 
exceeding  0-006-0-008  of  a  line  in  length,  and  0-002  of  a  line  in  breadth. 
In  the  walls  of  the  pancreatic  duct,  and  its  larger  branches,  small 


550  SPECIAL     HISTOLOGY. 

racemose  glands  of  0-06-0-08  of  a  line  with  vesicles  of  0-016-0-02  of 
a  line,  and  a  less  fatty  epithelium,  are  situated  in  considerable  numbers ; 
whether  they  are  mucous  glands  analogous  to  those  of  the  biliary  ducts, 
or  parts  of  the  pancreas  itself,  I  cannot  say.  The  pancreas  possesses 
the  ordinary  investing  tissue  of  the  glands,  with  more  or  less  abundant 
fat-cells,  in  which  the  vessels  and  nerves  of  the  gland  are  distributed. 

Fig.  225. 


The  former  present  exactly  the  same  relations  as  in  the  parotid,  except 
that  the  lymphatics  appear  to  be  more  numerous  ;  the  latter  would  seem 
only  to  accompany  the  vessels  and  arise  from  the  sympathetic,  possess- 
ing fine,  and  a  few  moderately  thick  tubules.  The  secretion  of  the  pancreas 
is  normally  perfectly  fluid,  only  accidentally  containing  formed  constitu- 
ents, as  detached  epithelium  of  the  glandular  vesicles  and  of  the  ducts. 

The  development  of  the  pancreas  commences  by  the  formation  of  a 
diverticulum  of  the  posterior  wall  of  the  duodenum  and  in  its  further 
progress,  exactly  resembles  the  salivary  glands,  except  that  the  rudiment 
of  the  gland  forms,  from  the  first,  a  more  compact  mass  and  thence  is 
not  so  readily  made  out  in  detail. 

The  examination  of  the  pancreas  presents  no  difficulties,  except  that, 
in  Man,  the  fat  in  the  epithelial  cells  of  the  glandular  vesicles  offers 
some  impediment  and  therefore  the  pancreas  of  Mammalia  (Rabbit, 
Mouse),  which  usually  contains  less  fat,  should  be  made  use  of.  The 
glandules  in  the  ducts  are  best  rendered  visible  by  acetic  acid. 

[Literature. — J.  G.  Wirsung,  "Figura  ductus  cujusdam  cum  multi- 
plicibus  suis  ramulis  noviter  in  pancreate  observati,"  Padov.,  1643 ;  J. 

FIG.  225.  Vessels  of  the  pancreas  of  the  Rabbit,  magnified  45  diameters. 


THE    SPLEEN.  551 

Muller,  "De  glandul.  sec.  structura  penitiori;"  Wharton  Jones  in  Philo- 
sophical Transactions,  1848,  II.  p.  227 ;  Yerneuil,  "  Anatomic  du  Pan- 
creas," in  Gazette  Medicale,  1851. — DaC.] 

OF  THE  SPLEEN. 

§  165.  The  spleen,  is  a  so-called  blood-vascular  gland,  which  is  in  some 
way  concerned  in  the  renewal  of  the  blood,  and  probably  with  the  secre- 
tion of  the  bile  also.  It  consists  of  a  fibrous  and  serous  coat  and  of  a  soft 
parenchyma,  the  latter  being  principally  composed  of  reticularly  inter- 
woven solid  bands,  the  splenic  trabeculce,  enclosing  a  red  substance,  the 
splenic  pulp.  In  the  latter  we  find,  in  addition,  many  peculiar  white 
corpuscles,  the  splenic  or  Malpighian  corpuscles,  while  abundant  vessels 
and  a  certain  number  of  nerves  are  distributed  through  its  whole  interior. 

§  166.  Coats  and  Trabecular  Tissue. — The  peritoneal  investment 
covers  the  whole  surface  of  the  spleen,  with  the  exception  of  the  hilus, 
where,  forming  a  sheath  around  the  vessels  and  nerves,  it  passes  on  to 
the  fundus  of  the  stomach  as  the  ligamentum  gastro-lienale,  and  of  the 
upper  extremity,  from  which  it  becomes  detached,  as  the  lig.  phrenico- 
lienale  ;  it  adheres  so  closely  to  the  fibrous  coat  in  Man  (though  not  in 
Ruminants),  that  it  can  only  be  dissected  from  the  organ  in  fragments. 

The  fibrous  coat  (tunica  albuginea  seu  propria)  completely  surrounds 
the  surface  of  the  spleen,  as  a  moderately  thin  and  semi-transparent 
but  very  strong  membrane,  and  at  the  hilus,  passes  into  its  interior,  like 
Glisson's  capsule,  accompanying  the  vessels  in  the  form  of  peculiar 
sheaths,  the  vagince  vasorum.  In  man,  it  is  composed  of  common  connec- 
tive tissue,  with  abundant  networks  of  elastic  fibres,  whilst  in  some 
animals,  the  Dog,  Pig,  Ass,  Cat  (not  in  the  Rabbit,  Horse,  Ox,  Hedge- 
hog, Guiena-pig,  and  Bat),  I  find  it  to  contain  smooth  muscles  in  consi- 
derable numbers.* 

The  trabeculce  of  the  spleen  are  white,  shining,  flattened  or  cylindri- 
cal fibres,  having  on  an  average,  a  diameter  of  io-J  of  a  line,  which 
are  attached  in  great  num- 

F\fr.  226. 

bers  to  the  inner  surface  of 
the  fibrous  coat,  and  less 
frequently  to  the  outer  sur- 
face of  the  sheaths  of  the 
vessels,  and  unite  with  simi- 
lar trabeculce  in  the  interior, 
into  a  network  which  extends 
through  the  whole  organ. 
The  interstices  included  in 

FiG.  226. — Transverse  section  through  the  middle  of  an  Ox-spleen,  washed  out,  to  show 
the  trabeculae  and  their  arrangement.  Natural  size. 

*  [The  existence  of  these  muscles  in  the  ox's  spleen  was  first  pointed  out  by  Dr.  Sharpey. 
See  Quain  and  Sharpey's  Anatomy,  p.  1086  (Vol.  II.,  p.  498.  Am.  Ed.)— TES.] 


552 


SPECIAL    HISTOLOGY. 


Fig.  227. 

A 


it  all  communicate,  contain  the  red  pulp  of  the  spleen  and  the  Malpig- 
hian  corpuscles,  and  although  no  one  exactly  resembles  another,  yet  all 
as  regards  form  and  size,  present  a  certain  similarity. 

The  older  anatomists  considered  them  to  be  regular  cavities  lined  by  a 
membrane,  like  those  of  the  corpora  cavernosa  penis,  to  which,  indeed, 
they  are  very  similar  in  the  arrangement  of  the  limitary  trabeculce,  but 
there  is  nothing  of  this  kind,  as  may  be  best  demonstrated  in  sections 
of  the  spleen,  in  which  pulp  has  been  removed  by  washing.  Such  a 
preparation  is  best  fitted  for  the  study  of  the  relations  and  connections 
of  the  trabeculce  ;  and  it  is  readily  seen,  that  although  very  various  in 
size,  they  do  not  ramify  after  the  fashion  of  vessels,  but  unite  quite 
irregularly.  Where  4,  5,  or  more  of  these  unequally  thick  trabeculce 
unite,  a  flattened  cylindrical  enlargement,  like  a  nervous  ganglion, 
usually  exists  ;  these  are  more  frequent  towards  the  external  surface  of 
the  organ  than  in  its  internal  portions  and  at  the  hilus,  where  the  large 
vessels  already  afford  a  sufficient  support  to  the  parenchyma  and  an 
intimate  union  of  the  trabeculce  is  less  necessary. 

The  structure  of  the  trabeculce  of  the  human  spleen  perfectly  re- 
sembles that  of  the  fibrous  coat ;  they  consist 
of  longitudinally  fibrous  connective  tissue,  with 
intermingled  fine  elastic  fibres.  In  animals, 
on  the  other  hand,  smooth  muscles  exist,  as  I 
showed  in  the  year  1846,  sometimes  in  all  the 
trabeculce  (Pig,  Dog,  Cat),  sometimes  (Ox), 
only  in  the  smaller  ones,  with  respect  to  whose 
distribution  further  particulars  will  be  found 
in  my  "  Mikroskopische  Anatomic,"  II.  2,  p. 
256.  In  the  trabeculce  also,  we  find  peculiar 
spindle-shaped  fibres,  of  0-02-0-03  of  a  line 
in  length,  and  0-002  of  a  line  in  breadth,  with 
undulated  ends  and  prominent  enlargements, 
in  which  rounded  nuclei  are  situated.  They 
are  to  be  met  with  in  great  numbers  in  the 
splenic  pulp  of  Man  (Fig.  227  A\  and  I  for- 
merly, though  as  I  now  believe  wrongly,  took  them  to  be  smooth  mus- 
cles. What  their  nature  is  I  cannot  say,  and  I  can  only  add  that  they 
are  also  found  coiled  up  in  cell-like  bodies*  (Fig.  227  'B). 

§  167.  Malpighian  corpuscles,  i\\Q  splenic  corpuscles,  Malpighian  corpu- 

FiG.  227.— Peculiar  fibres  from  the  pulp  of  the  human  spleen  :  d,  the  same  free;  B,  one 
inclosed  in  a  cell;  magnified  350  diameters. 

*  [According  to  Mr.  Wharton  Jones  ("  British  and  Foreign  Med.  Chir.  Review/'  Jan., 
1853),  these  cells,  containing  "peculiar  fibres,"  are  nothing  but  the  ordinary  nucleated  fibres 
of  the  pulp  "  circularly  coiled,  the  coil  being  maintained  by  a  tenacious  intercellular  substance 
filling  up  the  middle  space." — TRS  ] 


THE     SPLEEN. 


553 


Fig.  228. 


soles  or  vesicles,  are  white  roundish  bodies,  which  are  imbedded  in  the  red 
substance  of  the  spleen  and  are  con- 
nected with  the  smallest  arteries. 
They  are  constant  only  in  quite 
fresh  and  healthy  subjects ;  but 
not  at  all,  or  rarely,  in  those  who 
die  of  disease,  or  after  long  fasting. 
It  hence  becomes  comprehensible 
that  Von  Hessling  found  the  cor- 
puscles only  116  times  in  960 
examinations.  In  subjects  whose 
age  was  between  the  first  and 
second  year,  they  were  present  in 
every  second  individual ;  from  tbe 
second  to  the  tenth  year,  in  every 
third ;  from  the  tenth  to  the  four- 
teenth, in  every  sixteenth ;  and  from 
the  fourteenth  onwards,  only  in 
every  thirty-second.  In  the  bodies 

of  those  who  die  suddenly,  as  in  consequence  of  accidents,  suicide,  or 
judicial  sentence  (of  the  latter  of  whom  I  have  examined  three  cases), 
they  are  probably  never  absent ;  and  it  is  the  same  with  the  majority  of 
children.  In  these  cases  they  are  as  numerous  and  as  distinct  as  in 
Mammalia.  The  size  of  the  splenic  corpuscles  is  liable  to  certain  varia- 
tions in  Man  and  in  animals,  and  has  hitherto,  for  the  most  part,  been 
over-estimated,  in  consequence  of  their  having  been  incompletely  isolated. 
Their  diameter  is  from  1-10-1-3,  on  the  average  1-6  of  a  line  ;  and 
very  probably  depends  upon  the  varying  condition  of  the  chylopoietic 
organs,  so  that  the  corpuscles  are  larger  after  food  has  been  taken 
than  at  other  times  ;  though,  in  confirmation  of  Ecker's  statement,  I 
can  affirm  that  they  are  to  be  met  with,  beautifully  developed,  in  fasting 
animals  also.  We  have  no  data  of  any  kind  with  regard  to  this  point 
in  Man. 

The  Malpigliian  corpuscles,  though  imbedded  in  the  red  pulp  and 
hardly  separable  from  it,  are  nevertheless  always  attached  to  a  branch  of 
an  artery,  in  such  a  manner  that  they  either  rest  laterally  immediately 
upon  a  vessel,  or  are  situated  in  its  angle  of  division,  or  finally  appear 
stalked ;  in  which  latter  case,  however,  the  stalk  itself,  again,  is  usually 
a  small  artery.  Their  number  is  very  considerable,  arterial  twigs  of 
0'02-0'04  of  a  line  carrying  5-10  corpuscles,  so  that  extracted  with 
them  from  the  pulp,  they  present  the  figure  of  an  elegent  raceme  (Fig. 
228).  It  appears  to  me  that  it  would  be  rather  under,  than  over 

FIG.  228. — A  portion  of  a  small  artery,  with  a  branch  covered  with  Malpigliian  corpus- 
cles (Dog),  magnified  10  diameters. 


554 


SPECIAL    HISTOLOGY. 


Fig.  229. 


Fig.  230. 


estimating  the  number  of  the  Malpighian  corpuscles  to  assume  that  every 
1-1J  cubic  line  of  the  pulp  contains  a  corpuscle. 

With  respect  to  its  minute  structure,  every    Malpighian  corpuscle 
possesses  a  special  coat  and  contents,  and  is  therefore  a  vesicle.     The 

membrane  is  colorless  and  transparent, 
0-001-0-002  of  a  line  thick,  and  every- 
where exhibits  a  double  contour,  with 
occasional  intermediate  concentric  lines  ; 
it  is  intimately  connected  with  the  sheath 
of  the  vessel,  with  which  it  also  agrees 
in  structure,  so  far  as  it  contains  homo- 
geneous connective  tissue  and  elastic  fibrils ; 
whilst,  on  the  other  hand,  the  smooth 
muscles  which  are  also  present  as  longi- 
tudinal fibres  in  these  sheaths,  are  entirely 

absent.  In  their  interior,  the  Malpighian  corpuscles  contain  no  epithe- 
lium, but  are  entirely  filled  by  a  viscid,  grayish,  continuous  substance, 
consisting  of  a  small  quantity  of  a  clear,  neutral  fluid,  coagulable  by 
heat,  and  therefore  albuminous ;  of  many,  rounded,  larger  and  smaller 
(from  0-003-0-006  of  a  line),  pale  cells,  which  usually  possess  a  single 
nucleus  and  become  granulated  by  the  action  of  water 
and  of  a  varying  number  of  free  nuclei.  Besides  these 
cells,  which  frequently  contain  single  fat-granules  and 
offer  the  most  distinct  evidence  that  in  the  Malpighian 
corpuscles  a  constant  development  of  cells  is  going  on,  we 
occasionally  meet  with  blood  corpuscles,  either  free  or  in 
cells  and,  as  I  am  inclined  to  believe  from  a  single  observation  in  the 
spleen  of  a  Cat,  with  fine  bloodvessels,  as  in  Peyer's  follicles  (see  §  155). 
The  Malpighian  corpuscles  are  completely  closed,  and  are  not  con- 
nected with  the  lymphatics,  although  this  has  been  assserted  by 
different  authors — among  the  moderns  by  Huschke,  Gerlach,  Polmann 
and  Schaffner.  Anatomically,  they  are  perfectly  similar  to  the  follicles 
of  Peyer's  patches,  and  of  the  solitary  glands,  described  above,  and 
very  closely  agree  with  those  of  the  tonsils  and  lymphatics,  whence 
they  may  for  the  present  be  denominated  gland-like  follicles.* 

FIG.  229. — A  Malpighian  corpuscle  from  the  spleen  of  an  Ox,  magnified  150  diameters: 
a,  wall  of  the  corpuscle  ;  6,  contents;  d,  sheath;  and  e,  wall  of  the  artery  to  which  it  is 
attached. 

FIG.  230. — Contents  of  a  Malpighian  corpuscle  from  the  Ox  :  a,  small ;  &,  large,  cells ;  c, 
free  nuclei. 

*  [In  a  case  of  suicide,  Prof.  Ktflliker  (Wiirzb.  Verhand.  IV.  1)  has  lately  detected  distinct 
capillaries  within  the  Malpighian  corpuscles.  Capillaries  within  the  corpuscles  he  had 
hitherto  only  seen  in  the  spleen  of  a  Cat ;  they  have,  however,  from  independent  obser- 
vations, already  been  described  by  Gerlach  and  Huxley  as  occurring  in  Man. 

The  Malpighian  corpuscles  undergo,  in  some  diseases,  a  peculiar  degeneration.  Thus,  in 
the  disease  termed  "  waxy,"  or  "  colloid"  spleen,  they  present  the  appearance  of  gelatinous 


THE     SPLEEN.  555 

Malpighian  corpuscles  have  been  discovered  in  all  the  Mammalia 
which  have  hitherto  been  examined,  and  also  occur  in  Birds.  Among 
the  scaly  Amphibia  they  were  found  by  Job.  Miiller  in  one  of  the 
Chdonia,  and  by  myself  in  the  Blindworm,  where  the  corpuscles  were 
surrounded  by  an  exceedingly  elegant  network  of  capillaries.  In 
Frogs  and  Toads  they  are,  according  to  Oesterlen,  to  be  met  with  now 
and  then ;  but  I  have  not  yet  succeeded  in  finding  any  trace  of  them 
in  the  naked  Amphibia,  nor  in  the  fresh-water  fishes.  Leydig,  how- 
ever, has  observed  them  in  the  Plagiostomata  (Beitrage  zur  Anat. 
der  Rochen  und  Haie).  Job.  Muller's  supposition  that  the  Mal- 
pighian corpuscles  exist  in  all  Vertebrata,  is,  therefore,  not  borne  out, 
a  fact  which  is  not  without  weight  in  considering  their  physiological 
import.  In  a  few  Mammals  the  Malpighian  corpuscles  contain,  though 
not  constantly,  the  same  forms  of  retrograding  blood  corpuscles  as 
will  be  described  to  occur  in  the  pulp,  in  the  following  section.* 

granules,  and  are  filled  with  a  homogeneous  mass,  consisting  of  soft  concentrically  lami- 
nated bodies.  These  bodies,  which  were  formerly  regarded  as  colloid,  have  recently  been 
found  by  Virchow  (Archiv,  f.  Path.  Anat.  VI.  2)  to  be  the  result  of  a  cellulose  metamorphosis, 
for  a  watery  solution  of  iodine,  and  the  subsequent  addition  of  sulphuric  acid  caused  them  to 
assume  the  peculiar  violet  color  which  is  known  to  belong  to  vegetable  cellulose. — DaC.] 

*  [The  Malpighian  follicles  of  the  spleen  present  three  points  of  importance  to  the  inves- 
tigator. 1.  Whether  they  have  a  capsule,  and  what  is  its  nature?  2.  The  arrangement  of 
their  vessels.  3.  The  structure  of  the  substance  which  they  contain. 

1.  The  capsule  and  its  nature. — We  have  been  quite  unable  to  convince  ourselves  of  the 
existence  of  any  such  capsule  as  that  described  by  Professor  Ko'lliker,  in  the  Malpighian 
follicles  of  Man,  the  Sheep,  the  Pig,  the  Cat  (Kitten),  or  the  Rat;  in  all  of  which  we  have 
made  very  careful  investigations  with  regard  to  this  point.  In  Man,  in  the  Pig,  and  in  the 
Cat,  we  are  unable  to  distinguish  any  boundary  at  all  between  the  follicles  and  the  sur- 
rounding red  pulp — the  substance  of  the  one  appearing  to  pass  into  the  other.  At  the  line 
of  transition,  however,  the  indifferent  tissue  of  the  follicle  underwent  a  partial  metamor- 
phosis and  broke  up,  when  teased  out,  into  spindle-shaped  bodies,  containing  "  nuclei/'  or 
short  delicate  fibres  with  "  nuclei,"  exactly  resembling,  in  Man,  the  structures  described  by 
Professor  Ko'lliker  as  peculiar  fibres,  and  represented  in  Fig.  227. 

In  the  Rat,  this  border  zone  of  metamorphosed  tissue  was  somewhat  broader  and  firmer, 
and  when  the  follicle  was  compressed,  appeared,  particularly  under  a  low  power,  like  an 
indistinctly  fibrous  coat,  such  as  Professor  Ko'lliker  describes ;  but  when  closely  examined, 
it  was  readily  seen  to  be  no  distinct  closed  capsule,  but  to  pass  gradually,  on  the  one  hand, 
into  the  pulp,  and,  on  the  other,  into  the  contents  of  the  follicle.  The  same  is  true  of  the 
Malpighian  follicles  of  the  Sheep,  where  the  appearance  of  a  capsule,  under  a  low  power, 
is  often  very  distinct ;  and  where  imperfect  elastic  fibres  may  be  met  with  in  it. 

In  fact,  our  own  observations  are  perfectly  in  agreement  with  those  of  Mr.  Wharton 
Jones  (British  and  Foreign  Med.  Review,  Jan.,  1853),  and  have  led  us  completely  to  the 
opinion  of  Remak-  (Ueber  runde  Blut-gerinnsel  und  iiber  Pigment  Kugelhaltige  Zellen, 
Muller's  "Archiv,"  1852),  that  the  capsules  of  the  follicles  are  by  no  means  their  essential 
element,  and  that  we  must  consider  the  spleen  to  be  formed  by  two  principal  constituents; 
the  first  being  the  parenchyma,  and  the  second  a  superadded  fabric  of  bloodvessels,  nerves, 
lymphatics,  elastic  and  contractile  elements.  The  manner  in  which  the  latter  are  arranged 
in  and  about  the  parenchyma  is,  in  a  manner,  accidental  and  very  variable.  It  may  be,  as 
Remak  says,  either  inter  capillary,  as  in  the  pulp ;  or  vaginal,  as  in  the  sheaths  of  the  arte- 
ries ;  or  encysted,  as  at  the  angles  of  division  of  the  arteries,  in  the  Malpighian  follicles  of 
the  Sheep. 

To  insist,  therefore,  upon  the  fbllicular  arrangement  of  the  spleen,  or  indeed  of  any  other 


556  SPECIAL    HISTOLOGY. 

§  168.  The  red  substance  of  the  spleen,  the  pulp,  or  parenchyma  of 
the  spleen,  is  a  soft  reddish  substance,  which  fills  up  all  the  interspaces 

of  the  vascular  glands,  as  Sanders  (On  the  Structure  of  the  Spleen,  "  Annals  of  Anatomy 
and  Physiology,"  1850)  and  IvOlliker  do,  seems  to  us  to  mistake  accidental  for  essential 
characters. 

The  results  of  comparative  anatomical  examination  are  strikingly  in  favor  of  this  view 
of  the  matter. 

The  Malpighian  follicles  of  Birds  and  Amphibia  have  no  capsules  (Remak,  Leydig).  In 
Bombinator  igneus,  according  to  Leydig,  a  white  substance,  the  representative  of  the  Mal- 
pighian follicles,  lies  in  the  middle  of  the  spleen,  surrounded  by  a  red  cortical  pulp,  into 
which  it  directly  passes. 

On  the  other  hand,  Coluber  nalrix,  a  Reptile,  presents  the  very  opposite  characters.  Here 
the  red  pulp  is  absent,  and  the  spleen  has,  as  nearly  as  possible,  the  structure  of  an  ordinary 
lymphatic  gland,  consisting  of  a  fibrous  stroma,  containing  cavities  full  of  indifferent  tissue, 
through  which  a  capillary  network,  arising  from  the  vessels  of  the  stroma,  is  distributed 
(Leydig  "  Anatomisch-Histologische  Untersuchungen  fiber  Fische  und  Reptilien,"  1853). 

In  Fishes  the  same  variation  occurs.  In  Hexanchus  there  are  thick-walled  Malpighian 
corpuscles  (Leydig).  In  other  Plagiostomes  and  many  osseous  Fish  there  are  no  distinct 
follicles,  but  the  indifferent  follicular  tissue  follows  the  sheaths  of  the  arteries. 

2.  The  arrangement  of  the  vessels  of  the  Malpighian  follicles. — Johannes  Miiller,  who  gave 
the  first  good  account  of  the  Malpighian  follicles  of  vegetable  feeders  (Mailer's  "  Archiv," 
1834),  not  only  states  that  the  follicles  are,  what  all  recent  researches  have  shown  them  to 
be — the  representatives  of  portions  of  the  sheaths  of  the  arteries,  but  also  that  the  arterial 
twigs  which  supply  them  "  sometimes  run  beside  the  Malpighian  bodies  without  giving 
any  branches  to  them,  sometimes  pass  straight  through  the  corpuscles''  (p.  88).  However,  he 
appears  to  be  inclined  to  the  opinion  that  the  arterial  twigs  pass  "  not  so  much  through  the 
middle  of  the  corpuscles"  as  in  the  thickness  of  their  walls. 

All  subsequent  writers  have  affirmed  that  the  arterial  twigs  pass  over  the  surface  and 
not  through  the  substance  of  the  Malpighian  follicles,  with  the  exception  of  Giinsburg  and 
of  Dr.  Sanders — who  states,  not  in  the  paper  we  have  cited,  but  in  a  subsequent  communi- 
cation to  the  Edinburgh  Physiological  Society  (Jan.  31st,  1851),  that  by  a  peculiar  method  of 
preparation,  he  had  observed  arterial  twigs  passing  diametrically  through  the  substance  of 
the  follicles,  "  stains  of  blood  also,  often  in  linear  arrangement,  indicating  capillaries,  were 
seen  in  the  interior  of  the  sacculi."  With  regard  to  the  latter  point,  it  will  be  observed  that, 
in  the  text,  Professor  Kolliker  also  records  a  single  observation  of  minute  bloodvessels  in  the 
Malpighian  follicles  of  the  Cat. 

In  all  the  Mammalian  spleens  we  have  examined  (Man,  Sheep,  Pig,  Cat,  Rat),  we  have 
observed  the  passage  of  arteries  through  the  Malpighian  follicles  and  the  existence  of  a 
capillary  network  in  them,  with  the  utmost  ease;  we  are,  indeed,  at  a  loss  to  comprehend 
how  it  is  that  previous  observers  have  so  generally  overlooked  facts  so  patent.  The  method 
we  have  pursued  has  been  merely  to  make  a  tolerably  fine  section,  containing  a  Malpighian 
follicle,  with  a  sharp  knife — to  spread  it  out  with  needles,  adding  nothing  but  a  little  weak 
syrup,  and  then,  placing  a  thin  glass  plate  over  it,  we  have  examined  it  with  both  the  simple 
and  the  compound  microscope.  The  use  of  the  former  is  especially  to  be  recommended, 
because  by  manipulating  the  covering  plate,  the  whole  follicle  may  be  readily  rolled  about 
under  the  eye,  and  the  clearest  evidence  thus  obtained  that  the  arterioles  pass  through  and 
not  over  the  surface  of,  the  follicles.  Acetic  acid  should  not  be  used,  as  it  renders  the  con- 
tents of  the  follicle  opaque;  but  the  syrup  is  of  great  service,  as  it  keeps  the  coloring  matter 
of  the  blood  in  the  capillaries  and  renders  them  extremely  obvious.  The  walls  of  the 
capillaries  are  exceedingly  delicate  and  often  indistinguishable  as  distinct  structures.  Both 
the  longitudinal  inner  coat  and  the  transverse  muscular  coat  of  the  arterioles  are  very  well 
developed  in  Man. 

3.  Structure  of  the  "  contents"  of  the  Malpighian  follicles. — We  have  been  unable  to  find 
either  cavity  or  fluid  in  the  contents  of  the  Malpighian  follicles.  So  far  as  we  have  seen, 
they  are  solid  bodies — their  outer  portion  or  "  wall"  being  .constituted  as  above  described  ; 


THE    SPLEEN.  557 

between  the  larger  trabeculae  and  the  coarser  vessels,  and  is  so  soft  as 
to  "be  readily  removed  from  a  fragment  of  the  organ.  It  consists  of 
three  elements;  viz.,  of  the  most  delicate  bloodvessels  of  the  spleen,  of 
microscopic  fibres  and  trabeculce,  and  of  peculiar  cells  of  the  parenchyma. 
In  Man  and  in  Animals  the  occurrence  of  extravasated  blood, in  manifold 
stages  of  metamorphosis,  is  so  frequent,  that  it  may  be  almost  regarded 
as  a  normal  constituent.  According  to  its  amount  and  to  the  disten- 
sion of  the  bloodvessels,  the  pulp  appears  sometimes  of  a  brighter/some- 
times  of  a  darker  blood-red  ;  besides  which,  however,  it  must  be  noted 
that  the  pulp  has  also  its  own  proper  red  coloring  matter. 

The  fibres  of  the  pulp  are  of  two  kinds.  Firstly,  there  are  microscopic 
trabeculce,  answering  completely  to  those  visible  with  the  naked  eye  and 
possessing  the  same  structure,  except  that  in  many  Mammals  they  con- 
tain more  smooth  muscles,  or  are  even  entirely  composed  of  them.  As 
a  general  rule,  their  diameter  varies  between  0-005  and  0-01  of  a  line; 
in  quantity  they  differ  in  different  animals  and  in  different  parts  of  the 
spleen.  In  Man  I  find  them  to  be  more  rare  and  broader  than  in  other 

while  the  inner  is,  to  use  the  accurate  phraseologyof  Mr.  Wharton  Jones,  composed,  of  "  nu- 
cleated granular  corpuscles  and  nucleated  cells,  similar  to  those  of  the  red  substance,  coher- 
ing together  in  a  mass  by  means  of  a  diffluent  intercellular  substance,  and,  interspersed 
among  these,  a  few  somewhat  larger  nucleated  cells"  (1.  c.,  p.  35). 

The  idea  that  the  Malpighian  corpuscles  were  hollow  bodies  originated  with  Malpighi 
himself;  but  Muller,  in  opposition  to  him  and  to  Rudolphi,  asserts  very  justly  that  in  the 
Pig,  Sheep,  and  Ox,  they  are  firm  and  resistant. 

From  all  that  has  been  said,  it  results  very  clearly  that  the  only  difference  between  the 
"  pulp''  and  the  "  Malpighian  follicles"  of  the  spleen  is  one  of  degree,  consisting  in  the  greater 
or  less  development  of  the  vascular  network  and  the  greater  or  less  amount  of  metamor- 
phosis, which  the  elements  of  the  parenchyma  have  undergone.  It  is,  furthermore,  suffi- 
ciently obvious  that  the  anatomical  differences  between  a  solitary  follicle  of  the  intestine,  a 
Peyer's  patch,  a  lymphatic  gland,  and  a  spleen,  are  also  questions  of  degree.  It  is  impos- 
sible to  distinguish,  under  the  microscope,  a  minute  lymphatic1  gland — such  as  may  be  met 
with  in  the  mesentery  of  the  Rat,  for  example — from  one  of  the  follicles  of  the  Peyer's 
patches  of  the  same  animal.  But  as  the  intestinal  follicles  are  aggregated  to  form  the 
Peyer's  patches,  so  the  lymphatic  follicles  are  aggregated  to  form  the  large  lymphatic  glands; 
increase  the  vascularity  of  the  stroma  of  a  lymphatic  gland  and  we  have  a  spleen. 

On  the  other  hand,  we  can  state  decidedly  that  the  follicles  of  the  tonsils,  both  in  Man  and 
in  the  Sheep,  are  traversed  abundantly  by  capillaries,  so  that  they  come  under  the  same 
category ;  differing,  however,  from  the  lymphatic  glands  and  spleen,  in  that  the  follicles  are 
arranged,  not  in  solid  masses,  but  around  diverticula  of  the  intestinal  mucous  membrane, 
which,  in  the  tonsils  (both  in  Man  and  in  ihe  Sheep),  take  the  form  of  more  or  less  irregu- 
larly ramified  ducts.  Starting,  therefore,  from  the  simple  intestinal  follicle,  we  have  two 
series  of  vascular  glands — the  one,  the  solid  series,  reaching  its  utmost  complexity  in  the 
spleen  (and  perhaps  the  supra-renal  bodies  and  thymus)  ;  the  other,  the  diverticular  series. 
Does  the  latter,  however,  reach  its  highest  complication  in  the  tonsils?  or  rather  do  not 
these  lead  in  the  plainest  way  to  the  liver,  which  is,  like  them,  essentially  a  solid  mesh- 
work  of  capillaries,  filled  by  indifferent  tissue  and  arranged  around  a  complex  diverticulum  of 
the  intestine?  It  appears  to  us  that  the  structure  of  the  tonsils  affords,  in  this  way,  an  ana- 
logical basis  for  the  views  of  Dr.  Handfield  Jones;  and  tends  greatly  to  support  the  doctrine, 
that  the  liver  is  essentially  one  of  the  vascular  glands.  While  adding  the  liver,  however, 
we  should  exclude  the  thyroid  ;  its  structure  being  totally  different  from  that  of  the  rest  of 
the  class. — TRS.] 


558  SPECIAL    HISTOLOGY. 

Mammals,  and  perfectly  identical  in  their  structure  with  the  larger  tra- 
beculce. Other  fibres  which  occur  in  the  pulp  are  plainly  the  termina- 
tions of  the  vascular  sheaths.  They  are  very  numerous,  and  usually 
have  the  appearance  of  delicate,  indistinct,  fibrous  membranes,  without 
any  elastic  element,  which  appear  to  connect  the  capillaries,  and  are, 
perhaps,  continuous  with  the  finest  trabeculce. 

The  cells  of  the  pulp,  or  parenchyma-cells  of  the  spleen,  round  cells 
of  0-003-0-005  of  a  line,  with  single  nuclei,  are  for  the  most  part  so 
similar  to  those  in  the  Malpighian  corpuscles,  that  it  is  unnecessary  to 
enter  upon  a  more  minute  description  of  them  ;  intermingled  with  them, 
and,  indeed,  in  larger  quantities  than  in  the  Malpighian  corpuscles,  we 
find  free  nuclei.  Besides  these,  a  few  other  elements  may  be  met  with  : 

1,  pale    round  bodies,   with  a  homogeneous    aspect,  somewhat  larger 
than  the  corpuscles  of  the  blood,  which  appear  either  as  free  nuclei,  or 
as  homogeneous  nuclei,  closely  surrounded  by  a  delicate  investment ; 

2,  larger  cells,  up  to  0-01  of  a  line  in  diameter — both  of  the  completely 
pale  kind,  with  one  or  two  nuclei,  and  also  what  I  have  called  colorless 
granule-cells — that  is,  cells  with  more  or  fewer  colorless,  dark  fat-gra- 
nules.    Each  of  these  elements  exists  in  the  splenic  corpuscles  also,  but 
never  to  so  great  an  amount.     The  quantity  of  the  different  kinds  of 
parenchyma  cells  and  of  free  nuclei  in  the  pulp,  is  so  considerable,  that, 
together  with  a  small  amount  of   a  reddish-yellow  fluid  which  unites 
them,  they  constitute  probably  one-half  of  the  bulk  of  the  spleen.    They 
are  not  collected  in  large  masses,  but  in  small  irregular  aggregations  of 
different  sizes,  which  occupy  the  interspaces  between  all  the  trabeculce 
and  vessels  of  every  description,  and  surround  the  Malpighian  corpus- 
cles.    The  clearest  conception  of  the  arrangement  is  obtained,  if  we 
consider  that  every  segment  of  the  red  substance  included  within  the 
larger  trabeculce  has  the  same  composition,  on  the  small  scale,  as  the 
whole  spleen  has  on  the  large.     In  fact,  the  microscopic  trabeculce,  the 
terminations  of  the  vascular  sheaths  and  the  finest  vessels,  present  the 
same  relations  as  the  large  trabeculce  and  vessels,  while  the  small  masses 
of  parenchyma  cells  correspond  with  the  apparently  homogeneous  masses 
of  pulp,  visible  to  the  naked  eye.     There  are  no  special  investments 
around  the  parenchyma-cells,  but  they  lie  everywhere  in  direct  contact 
with  the  sheaths  of  the  vessels,  the  trabeculce,  and  the  sheaths  of  the 
Malpighian  corpuscles. 

The  red  pulp  of  the  spleen  of  Man  and  of  Animals  has  a  different 
color  at  different  times  ;  or  rather  the  blood-corpuscles  which  it  contains 
and  which,  without  the  participation  of  any  other  element,  give  rise  to 
its  color,  present  different  conditions.  In  some  animals,  for  instance, 
its  color  is  sometimes  paler,  more  grayish-red,  sometimes  brown,  or  even 
blackish-red.  In  the  latter  case,  a  quantity  of  changed  blood-corpuscles 
will  be  met  with  (to  which  we  shall  return  subsequently) ;  in  the  former, 
on  the  other  hand,  it  may  be  microscopically  demonstrated  that  the  red 


THE    SPLEEN.  559 

color  proceeds  from  unchanged  blood-corpuscles,  which  may  also  be 
readily  expressed  from  the  substance  of  the  spleen  and,  on  the  addition 
of  water,  in  a  short  time  lose  all  their  coloring  matter.  In  other  ani- 
mals the  spleen,  although  it  always  has  about  the  same,  usually  dark 
color,  yet  contains  in  addition,  sometimes  only  unchanged  blood-cor- 
puscles, sometimes  multitudes  of  them  in  every  stage  of  metamorphosis. 
These  are  very  striking,  and  in  all  animals  consist  essentially  in  this — 
that,  1,  the  blood-corpuscles,  becoming  smaller  and  darker  and,  in  the 
lower  Vertebrata,  losing  their  elliptical  form  and  taking  a  circular  shape, 
agglomerate  together  into  rounded  masses,  which  either  persist  in  this 
condition,  or,  combined  with  a  certain  amount  of  the  plasma  of  the 
blood,  develop  an  envelope  externally  and  a  nucleus  in  their  interior, 
thus  passing  into  round  blood-corpuscle-  rig.  231. 

holding  sells,  of  0-005-0-015  of  a  line, 
containing  1—20  blood-corpuscles ;  and 
2,  these  masses  and  cells,  their  contained 
blood-corpuscles  gradually  diminishing  ^  $0^0^ 

w 


in  size  and  assuming  a  golden  yellow, 

brownish-red,  or  black  color,  either  in  ^^  JjSfo,  W  /•* 
their  entire  state  or  after  breaking  up 
into  pigment  granules,  change  into  pig- 
ment masses  and  pigmented  granule  cells  ;  and,  finally,  the  latter,  their 
granules  gradually  becoming  pale,  pass  into  perfectly  colorless  cells.  In 
many  cases  the  blood-corpuscles  form  no  masses  or  cells,  but  pass  through 
the  above-described  stages  of  coloration  and  disintegration,  like  the  others.* 

FIG.  231. — Blood-corpuscle-holding  cells  and  their  metamorphoses,  from  the  spleen  of  the 
Rabbit,  magnified  350  diameters  :  a,  two  nucleated  cells,  with  blood-corpuscles ;  b,  similar 
cells  metamorphosed  into  brown  pigment  cells ;  c,  cells  from  which  the  color  has  disappeared 
again;  rf,  pigment  granules  which  have  arisen  from  metamorphosed  free  blood-corpuscles. 

*  [In  his  "  Microscopical  Anatomy,"  Prof.  Kolliker  states,  that  he  has  observed  blood- 
corpuscle-holding  cells,  and  their  breaking  up  into  pigment  granules,  in  the  spleen  of 
almost  all  animals.  In  Mammalia  the  cells  were  generally  seen  with  difficulty.  In  the 
Cat,  Horse,  Ass,  and  Bat,  no  distinct  cells  could  be  detected,  although  the  pigment  masses 
and  the  pigmented  granule-cells  were  easily  observable.  In  Birds  he  met  with  cells  con- 
taining blood-corpuscles  only  in  the  Blackbird  although  in  many  (Fdlco  albicillus,  Cuculus 
canorus)  he  was  able  to  detect  yellow  pigmented  granule-cells  changing  into  black  pigment. 
In  the  naked  Amphibia  and  in  Fishes,  he  frequently  found  cells  enclosing  5  to  20  blood- 
corpuscles,  in  which  the  metamorphosis  into  pigment  could  easily  be  studied. 

The  "  blood-corpuscle-holding  cells"  and  the  supposed  result  of  their  metamorphoses — 
pigment  granules,  are  met  with  in  great  abundance  in  some  of  the  diseases  of  the  spleen. 
Thus  in  atrophy  of  this  organ  the  trabeculse  and  the  parenchymatous  structure  are  filled 
with  masses  of  a  dark  molecular  pigment.  In  the  enlarged  spleen  of  typhoid  and  inter- 
mittent fever,  Heschl  detected  many  pigmented  granule  cells  and  dark  pigment  granules. 
It  is  probable  that  cells  enclosing  blood-corpuscles  exist,  not  only  in  the  spleen,  but  wher- 
ever many  blood-corpuscles  and  large  masses  of  pigment  are  observed.  I  have  seen  cells 
resembling  "  blood-corpuscle-holding  cells"  in  melanosis  of  the  eye,  in  congested  lungs, 
and  as  part  of  the  peculiar  dark  granular  matter,  observed  under  the  microscope,  in  the 
black  vomit  of  yellow  fever.  If  in  this  last-named  instance  the  cells  were  possessed  of 
distinct  membranes  or  not,  I  was  unable  to  determine. — DaC.] 


560  SPECIAL    HISTOLOGY. 

The  changes  undergone  by  the  blood  in  the  spleen,  a  subject  which  is 
more  fully  treated  of  in  my  "  Mikr.  Anat.,"  II.,  2,  pp.  268-270,  and 
which  were  observed  and  interpreted  by  Ecker,  at  the  same  time  and  in 
the  same  manner  as  by  myself,  have  lately  become  the  subject  of  much 
discussion.  Gerlach,  Schaffner,  and  lately  0.  Funke  also  (I.  c.\  who 
are  completely  at  one  with  Ecker  and  myself  as  to  the  facts,  differ  alto- 
gether in  their  interpretation  of  them  ;  and  believe  that,  instead  of  their 
being  the  result  of  a  dissolution  of  the  blood-corpuscles,  they  proceed 
from  a  process  of  development  of  new  corpuscles,  and  that  therefore  the 
spleen — as,  indeed,  was  Hewson's  opinion — is  a  formative  organ  for 
blood-corpuscles. 

I  have  already,  in  another  place  (Zeitsch.  fiir  wiss.  Zool.,  p.  115), 
confuted  Gerlach's  views,  and  I  therefore  consider  it  to  be  unnecessary  to 
enter,  again,  into  this  question,  the  less,  as  Ecker,  after  repeated,  care- 
ful investigations,  quite  agrees  with  me ;  indeed  no  unprejudiced  obser- 
vation can  tend  to  other  conclusions  than  those  at  which  we  have  arrived. 
Kemak  has  recently  brought  forward  an  entirely  new  view  (I.  i.  c.) 
From  the  known  facts,  that  other  pigment  cells  exist  than  those  whose 
coloring  matter  is  derived  from  blood- corpuscles,  and  that  effused  blood 
may  form  cell-like  masses  with  blood-corpuscles,  as  Hasse  and  I  have 
more  particularly  shown — facts  which  he  has  strengthened  by  new  cases 
— Remak  has  allowed  himself  to  be  misled  into  asserting,  not  only  that 
no  cells  with  enclosed  blood-corpuscles  exist  at  all,  but  also,  that  in  the 
spleen  no  blood-corpuscles  are  destroyed,  i.  e.  change  into  pigment  gra- 
nules. This  is  so  strong  an  assertion,  that  I  see  no  necessity  for  my 
contradicting  it ;  one  might  at  last  be  required  to  demonstrate  that  there 
are  such  things  as  cells  and  blood-corpuscles.  It  will  interest  Remak 
to  learn  that  Virchow,  as  he  tells  me,  has  satisfied  himself  of  the  ex- 
istence of  the  cells  in  question,  though  he  explains  their  origin  in  ano- 
ther mode,  believing  that  the  blood-corpuscles  pass  from  without  into 
already  existing  cells — a  supposition  with  which,  at  present,  I  cannot 
exactly  agree. 

An  important  question  arises,  as  to  the  import  of  the  changes  in  the 
blood-corpuscles,  whether  they  are  physiological  or  pathological?  On 
the  one  hand,  very  weighty  reasons  present  themselves  for  considering 
the  phenomena  to  be  normal,  particularly  their  constant  occurrence,  as 
it  may  be  said,  in  so  many  living  animals,  especially  in  those  living 
under  natural  conditions,  as  Amphibia  and  Fishes ;  secondly,  the  appa- 
rent continuance  of  perfect  health,  notwithstanding  the  enormous  quan- 
tity of  disintegrating  blood-corpuscles  ;  thirdly,  the  occurrence  of  blood- 
corpuscle-holding  cells  in  bloodvessels  which  are  not  cut  off  from  the 
general  circulation,  as  may  be  demonstrated  in  the  Amphibia ;  fourthly, 
the  absence  of  similar,  constant  changes  in  the  blood,  repeated  at  short 
intervals,  in  other  organs  in  the  higher  Vertebrata ;  and  much  more 
might  be  added.  To  these  facts,  however,  careful  observation  opposes 


THE    SPLEEN.  561 

many  others,  which  almost  involuntarily  lead  to  the  idea,  that  perhaps 
all  the  changes  of  the  blood-corpuscles  in  the  spleen  are  abnormal,  a 
view  to  which  my  observations  in  Fishes  also  tend.  Here,  1,  the  meta- 
morphoses of  the  blood-corpuscles  in  the  spleen  do  not  go  on  in  the  interior 
of  bloodvessels,  but  in  extravasations  which  resemble  pathological  aneu- 
rismata  spuria  (see  "Mikr.  Anat.,"  II.  2;  and  Todd's  "Cyclopaedia 
of  Anatomy  and  Physiology,"  Art.  Spleen,  fig.  533;  Ecker,  "Icon. 
Phys.,"  tab.  vi.  figs.  15,  16);  2,  extravasations  and  metamorphoses  of 
their  blood-corpuscles  occur,  not  only  in  the  spleen,  but  in  other  organs, 
especially  in  the  kidneys,  where  they  are  constant,  and  frequently  also 
in  the  liver  and  peritoneum. 

If  to  these  facts  we  also  add,  that  in  certain  animals,  e.  g.  the  Cat, 
the  Sheep,  &c.,  the  changes  of  the  blood-corpuscles  in  the  spleen  are 
very  rarely  met  with — furthermore,  that  their  progress  is  not  always 
coincident  with  the  stages  of  digestion — it  becomes  very  difficult  not  to 
believe  that  the  phenomena  are  abnormal,  especially  if  we  consider  that 
similar  phenomena  certainly  not  physiological,  such  as  the  small  effusions 
of  blood  into  the  lungs,  bronchial  glands  and  thyroid  in  Man,  in  the 
lymphatic  glands  of  the  mesentery  of  the  Pig  and  Rabbit,  &c.,  are  also, 
on  the  one  hand,  almost  as  constant  phenomena,  and,  on  the  other  hand, 
are  accompanied  by  perfectly  similar  metamorphoses  of  the  blood-corpus- 
cles. However,  in  the  latter  cases,  the  quantity  of  the  metamorphosed 
blood-corpuscles  is  not  to  be  compared  to  the  immense  number  of  those 
which  are  constantly  undergoing  disintegration  in  the  spleen  ;  and  in 
the  second  place,  it  is  also  possible  that  effusion  of  blood  may  occur  as 
a  physiological  phenomenon,  as  into  the  Graafian  follicles,  and  during 
menstruation  and  the  detachment  of  the  placenta.  And  although  all 
animals  do  not  present  a  microscopically  demonstrable  disintegration  of 
the  blood-corpuscles  in  their  spleen,  yet  it  does  not  follow  that  the  pro- 
cess may  not  occur  and  that  when  it  can  actually  be  demonstrated,  it  is 
pathological.  This  much  is  at  least  certain,  that  congestions  of  blood 
in  the  spleen  occur  in  all  animals,  without  exception;  and  it  is  almost 
certain,  that  these  congestions  are,  in  Mammals,  attended  by  extravasa- 
tion. In  these  stagnations  of  blood,  the  blood-corpuscles  may  be  disin- 
tegrated, in  some  cases  rapidly,  in  others  slowly,  which  would  constitute 
an  important  difference  for  the  observer ;  it  is  also  conceivable  that  they 
and  their  consequences  are  physiological  and  have  some  great  influence 
upon  life,  since  it  is  a  fact,  that  in  many  animals  they  are  constant,  and 
occur  upon  a  very  large  scale. 

For  the  present,  therefore,  so  long  as  the  pathological  character  of 
the  phenomena  in  question  is  not  conclusively  demonstrated,  I  must 
maintain  their  physiological  nature  and  regard  the  disintegration  of 
blood-corpuscles  in  the  spleen  as  a  normal  occurrence. * 

*  [With  respect  to  the  "  bloocl-corpuscle-holding  cells,"  the  reader  will  do  well  to  consult 

36 


562  SPECIAL    HISTOLOGY. 

§  169.  Vessels  and  nerves. — As  they  enter  the  organ,  the  relatively 
very  large  splenic  artery  and  the  still  larger  splenic  vein,  are  accompa- 
nied by  those  processes  of  the  fibrous  membrane,  which  have  been 
referred  to  as  the  vascular  sheaths.  In  Man  these  processes  form  com- 
plete investments  around  the  vessels  and  nerves,  somewhat  after  the 
fashion  of  the  capsule  of  Glisson,  so  that  the  arteries  and  nerves  espe- 
cially, can  be  readily  isolated,  while  the  veins,  which  on  the  side  opposite 
to  the  artery  are  more  intimately  connected  with  the  sheath,  are  less 
easily  separable.  At  first  the  sheaths  are  as  thick  as  the  fibrous  coat 
itself  and  they  retain  this  thickness  so  long  as  they  surround  the  prin- 
cipal branches  of  the  vessels.  The  finer  ramifications  of  the  latter  and 
even  those  small  branches  which  are  given  off  from  the  large  ones,  have 
finer  and  finer  sheaths,  until  at  last,  when  the  vessels  are  quite  minute, 
they  become  lost  as  thin  membranes  in  the  pulp.  The  thickness  of  any 
sheath  is  always  less  than  that  of  the  wall  of  the  artery  to  which  it 
belongs  and  greater  than  that  of  the  vein,  but  after  division  the  sheaths 
become  relatively  stronger.  It  was  remarked  above,  that  a  number  of 
the  trabeculce  are  inserted  into  the  vascular  sheaths  and  they  therefore 
take  a  share,  together  with  the  vessels  wThich  they  inclose,  in  the  forma- 
tion of  the  dense  network  in  the  interior  of  the  spleen.  In  Mammalia, 
as  in  the  Horse,  Ass,  Ox,  Pig,  Sheep,  &c.,  the  sheaths  present  different 
relations,  inasmuch  as  the  smaller  veins  have  none  at  all,  and  the  larger 
possess  them  only  on  the  side  on  which  the  arteries  and  nerves  lie.  Only 
the  two  principal  venous  trunks  near  the  Jiilus  have  perfect  sheaths, 

Remak's  very  valuable  and  elaborate  paper, "  Ueber  runde  Blutgerinnsel  und  iiber  Pigment 
kugel  haltige  Zellen,"  in  Muller's  "  Archiv,"  for  1852,  and  Mr.  Wliarton  Jones's  article  on 
the  same  subject  in  the  "British  and  Foreign  Med.  Chir.  Review,"  for  1853,  to  which  we 
have  already  referred.  Having  carefully  studied  them,  he  will,  we  think,  arrive  very  much 
at  our  own  conclusion,  that  as  the  question  now  stands,  the  very  existence  of  "  blood-cor- 
puscle-holding cells"  must  be  considered  as  highly  problematical. 

Mr.  Wharton  Jones  found  the  blood  of  the  splenic  vein  to  contain  nucleated  corpuscles 
and  fibres  identical  with  those  of  the  pulp,  together  with  free  nuclei  similar  to  those  of  the 
nucleated  corpuscles;  on  the  occurrence  of  which,  he  considers  the  statements  as  to  the 
abundance  of  colorless  corpuscles  in  the  blood  of  the  splenic  vein  are  founded.  Some  of 
these  elements  were  traced  as  far  as  the  vena  portee,  but  in  the  hepatic  veins  they  had  mostly, 
though  not  entirely,  disappeared.  He  appears  to  be  inclined  to  draw  the  conclusion  that 
some  of  the  venous  radicles  of  the  spleen  are  connected  with  the  pulp  in  the  same  way  as 
the  hepatic  ducts  with  the  parenchyma  of  the  liver,  and  that  the  materials  thus  derived  by 
the  blood  from  the  spleen  may  concur  in  fitting  it  for  the  secretion  of  bile.  Moleschott 
(•'Ueber  die  Entwickelung  cler  Blutko'rperchen,"  Muller's  "Archiv,"  1853),  gives  some 
curious  results  obtained  by  extirpating  the  liver  and  spleen  of  Frogs.  Normally,  the  car- 
diac blood  of  Frogs  contains  about  8  red  corpuscles  to  1  colorless ;  after  extirpation  of  the 
liver,  the  proportion  is  2-3  red  corpuscles  to  1  colorless.  The  blood  of  the  spleen  of  Frogs 
contains,  normally,  six  times  fewer  red  corpuscles  in  proportion  to  1  white,  than  that  of  the 
heart.  After  extirpation  of  the  liver,  there  are  1-G  colorless  corpuscles  to  1  red  corpuscle 
in  the  splenic  blood.  When  the  spleen  alone  has  been  extirpated,  the  proportion  of  red 
corpuscles  is  slightly  increased.  Moleschott  concludes  that  the  liver  favors  the  metamorphosis 
of  colorless  into  red  corpuscles.  However,  we  must  confess  that  the  results  of  the  individual 
experiments,  from  the  average  of  which  his  conclusions  are  drawn,  vary  so  widely  as  to 
throw  some  doubt  on  the  latter. — TRS.] 


THE    SPLEEN. 


563 


•whilst  the  arteries,  from  the  main  trunks  to  the  finest  ramifications,  all 
possess  them.  The  structure  of  the  sheaths  is  precisely  that  of  the 
trabeculce,  but  muscles  are  riot  always  found  in  the  former  when  they 
are  contained  in  the  latter — e.  g.  in  the  Ox — while  in  the  Pig  they  are 
also  very  distinct  in  the  sheaths. 

The  splenic  artery,  immediately  it  enters  the  organ,  and  all  its  prin- 
cipal branches,  divide  and  spread  out  into  a  great  number  of  ramifica- 
tions, the  larger  of  which  proceed  towards  the  anterior  margin  of  the 
organ,  the  smaller  towards  the  posterior,  forming  no  anastomoses  with 
those  of  other  principal  branches.  When  they  have  diminished  to  the 
diameter  of  1-5-1-10  of  a  line,  they  separate  from  the  veins,  which  till 
then  had  run  in  the  same  sheath  with  them,  and  become  connected  by 


branches  of  0-01-0-02  of  a  line,  with  the  Malpighian  corpuscles  in  the 
manner  which  has  been  described  above ;  perhaps,  also,  sending  fine 
branches  into  their  interior  (see  §  167).  Then,  often  closely  applied  to 
the  surface  of  the  corpuscles,  but,  so  far  as  I  can  observe,  not  passing 
through  them,  as  Job.  Muller  formerly  supposed,  they  enter  the  red 
pulp  and  immediately  break  up  into  elegant  bundles  of  minute  arteries, 
the  so-called  penicilli  (Fig.  232),  which  finally  subdivide  into  true  capil- 
laries of  0-003-0-005  of  a  line,  which  throughout  the  pulp,  round  the 
Malpighian  corpuscles,  as  well  as  elsewhere,  unite  into  a  somewhat  wider 
network. 

With  respect  to  the  veins,  I  must  especially  express  myself  against 

FIG.  232. — An  artery  with  its  penicillate  ends,  from  the   spleen  of  the  Pig,  magnified  25 
diameters. 


564  SPECIAL     HISTOLOGY. 

the  existence  of  the  venous  tissues  or  spaces  of  ancient  and  modern 
anatomists,  in  the  human  spleen.  The  larger  veins  which  still  accom- 
pany arteries,  present  no  peculiarities,  except  in  their  width  :  all  pos- 
sess a  memhrane,  which  is,  at  least  upon  the  side  of  the  artery,  easy  of 
demonstration,  and,  like  the  vascular  sheath,  gradually  becomes  thinner. 
Apertures  of  more  minute  veins,  the  so-called  stigmata  Malpighii,  exist 
only  in  inconsiderable  numbers  in  the  largest  of  these  veins,  while  in 
the  smaller,  they  are  more  frequent.  From  the  point  of  divarication  of 
the  arteries  and  veins,  the  relations  of  the  latter  become  somewhat  dif- 
ferent. In  the  first  place,  they  give  off  upon  all  sides  a  vast  number  of 
small  veins,  usually  at  right  angles,  whence  their  walls  appear  in  places 
almost  cribriform  ;  and  secondly,  their  membranes  become  completely 
coalescent  with  the  sheaths  of  the  vesse]s,  so  that  ultimately  the  two 
constitute  only  a  single  very  delicate  wall,  which,  however,  may  still  be 
easily  detected  in  the  very  smallest  vessels  that  can  be  isolated  by  dis- 
section. I  find  dilatations  of  any  kind  in  no  part  of  these  veins,  only, 
it  is  to  be  observed  that  they  become  narrowed  more  slowly  than  the 
arteries.  Their  continuity  with  the  capillaries  takes  place  in  exactly 
the  same  manner  as  in  all  other  organs  and  may  be  demonstrated  with- 
out difficulty,  by  injecting  the  veins  of  a  well-preserved  human  spleen, 
especially  of  a  child.  Neither  does  any  trace  of  dilatations  present 
itself  in  this  case. 

The  capillaries  of  the  spleen  have  the  ordinary  structure,  and  a  width 
of  0'003-0'005  of  a  line;  they  are  very  numerous,  and  exist  through- 
out the  pulp,  where,  round  the  Malpighian  corpuscles,  though  not  in 
their  coats,  and  elsewhere,  they  form  a  tolerably  close  network  conti- 
nuous through  the  whole  spleen,  only  interrupted  by  the  minutest  trabe- 
culse  and  by  the  Malpighian  corpuscles. 

The  human  spleen  possesses,  relatively,  very  few  lymphatics.  The 
superficial  set  are  distributed  sparingly  between  the  two  coats,  but  can 
hardly  be  recognized,  except  in  the  neighborhood  of  the  hilus  and  in 
perfectly  healthy  spleens.  The  deep  set  may  be  discovered  in  the  hilus, 
whence  also,  few  in  number  and  small  in  diameter,  they  accompany  the 
arteries,  but  cannot  be  traced  by  any  means  so  far  as  these.  In  the 
hilus  both  sets  of  lymphatics  join,  traverse  a  few  small  glands,  which 
exist  in  this  locality,  and  finally  unite  into  a  trunk  which  opens  into  the 
thoracic  duct  opposite  the  llth  or  12th  dorsal  vertebra.  In  diseased 
spleens  no  trace  of  the  superficial  lymphatics  can  ordinarily  be  detected. 

The  nerves  of  the  spleen,  consisting  of  many  fine  and  a  few  thick 
tubules,  with  a  moderate  proportion  of  Remak's  fibres,  are  derived  from 
the  splenic  plexus,  formed  by  two  or  three  trunks  which  surround  the 
splenic  artery,  and  are  continued  on  the  arteries  into  the  interior  of  the 
organ,  each  dividing  into  one  or  two  branches,  anastomosing  here  and 
there.  In  the  Sheep  and  Ox,  these  splenic  nerves  are  truly  colossal,  so 


THE    SPLEEN.  565 

that,  taken  together,  they  equal  the  empty  and  collapsed  splenic  artery, 
this  size,  however,  heing  attributable  principally  to  the  unusual  quantity 
of  Remak's  fibres. 

In  animals,  these  nerves,  which  never  possess  ganglia,  may  be  followed 
into  the  spleen  further  than  in  Man;  and,  by  the  aid  of  the  microscope, 
I  have  frequently  met  with  them  even  upon  the  arteries  which  support 
the  splenic  corpuscles.  As  to  their  terminations,  I  can  only  state  that 
they  pass  into  the  pulp,  and  are  still  to  be  met  with  upon  the  arterial 
penicilti.  Here  they  ultimately  become  as  delicate  as  the  finest  capilla- 
ries, no  longer  possess  dark-edged  tubules,  and,  according  to  Ecker's 
observations  (1.  c.,  p.  149,  Fig.  10),  probably  end  in  free  dichotomous 
divisions.  In  the  Calf,  the  nerves  upon  arteries  of  1  line  measure 
0-024-0-028,  on  the  penicilli  artertarum  0-0048-0-0056,  in  the  midst 
of  the  pulp  0-003-0-004  of  a  line.  In  branches  of  0-012-0-028  of 
a  line,  I  here  still  found  a  single  dark-edged  nerve-tubule,  whilst  all 
the  rest  consisted  of  a  striated  nucleated  tissue,  which  alone  consti- 
tuted the  finer  threads.  It  is  improbable  that  this  structure  has  here, 
as  in  the  trunks,  the  import  of  Remak's  fibres ;  I  should  rather  with 
Ecker,  consider  it  to  be  embryonic  nervous  tissue,  such  as  we  are 
sufficiently  acquainted  with  in  other  localities;  and  I 'am  inclined  to 
believe  that  the  dark-edged  tubules  of  the  trunks  finally  pass  into  pale 
fibres,  as  such  compose  entirely  or  almost  entirely  the  ultimate  twigs, 
and  then  terminate  by  branching  out.  In  the  trunks  of  the  splenic 
nerves  of  the  Calf,  there  are  found,  before  their  entrance  into  the  spleen 
and  within  it,  numerous  dichotomous  divisions  of  the  dark-edged,  partly-* 
coarser  and  partly  finer  primitive  tubules,  such  as  I  have  not  hitherto 
succeeded  in  detecting  in  Man. 

In  regard  to  the  structure  of  the  veins,  many  of  the  Mammalia  ap- 
pear to  resemble  Man,  while  others,  as  the  Horse,  Ox,  Sheep,  Pig,  pre- 
sent very  wide  differences.  In  these  animals  a  special  venous  membrane 
and  a  vascular  sheath  are  found  only  at  the  origins  of  the  largest 
venous  trunks,  while  further  in,  they  are  visible  only  upon  the  side  of 
the  arteries.  In  all  the  smaller  veins,  which  run  independently  (with- 
out arteries),  no  further  trace  of  two  coats  is  to  be  met  with,  in  fact, 
these  veins  appear  to  be  mere  excavations  in  the  substance  of  the  spleen, 
especially  as  a  number  of  anastomosing  trabeculce  with  red  pulp  often 
forming  projecting  knobs  between  them,  are  apparent  upon  their  walls. 
However,  they  always  have  a  perfectly  smooth  and  shining  surface, 
arising  from  spindle-shaped,  tessellated  epithelium-cells  of  0-005-0-01  of 
a  line,  which  are  only  microscopically  demonstrable.  This  epithelium  cor- 
responds perfectly  with  that  of  the  larger  veins,  only  that  here  it  no 
longer  lies  upon  a  special  wall,  but  immediately  upon,  the  substance  of 
the  spleen,  i.  e.  upon  the  trabeculce  and  upon  a  delicate  membranous 


566  SPECIAL    HISTOLOGY. 

substance  which  bounds  the  pulp  between  them.  Under  these  circum- 
stances we  may,  with  perfect  justice,  speak  of  venous  sinuses  ;  the 
more,  if  we  consider  that  these,  so  to  say,  wall-less  veins  have  a  colos- 
sal width,  and  are  pierced  by  innumerable  veins  which  open  into  them. 
These  smaller  veins,  again,  may  be  traced  for  a  considerable  distance 
with  the  scissors,  but  I  have  as  yet  never  been  able  to  succeed  in  demon- 
strating in  what  manner  they  are  continuous  with  the  capillary  network, 
proceeding  from  the  penicilli  arteriarum,  which  here  also  is  very  dis- 
tinct. I  can  hardly  believe  that  it  will  ever  be  possible  to  make  out  this 
continuity  completely,  for  the  finest  veins,  which  are  often  bounded  by 
but  a  few  traleculce,  and  indeed  for  the  most  part  by  the  red  pulp  alone, 
are  such  delicate  canals,  that  the  slightest  mechanical  force,  as  in  in- 
flating or  injecting  them,  destroys  them ;  and  even  by  the  microscope 
they  are  not  discoverable.  It  may  always  be  observed,  however,  that 
they  eventually  become  very  minute,  so  small  that  it  is  impossible  to 
consider  their  origins  as  enlargements.  For  my  own  part,  I  believe, 
that  here  also,  the  connection  with  the  capillaries  takes  place  quite  in 
the  ordinary  manner,  with  this  distinction,  however,  that  the  veins  in 
arising  from  them  possess  only  one  membrane,  an  epithelium,  and  are 
therefore  perhaps  connected  in  some  other  manner  with  their  structureless 
coat.  Smaller  series  of  more  rounded  epithelial  cells,  which  are  not 
unfrequently  found  on  teasing  out  the  pulp,  probably  belong  to  the 
smallest  veins. 

In  mammalia  the  lymphatics  are  stated  by  all  authors  to  be  extreme- 
4y  numerous,  and  this  is  perfectly  true  for  the  superficial  vessels,  which 
in  the  Calf,  for  example,  are  exceedingly  abundant  and  present  nu- 
merous anastomoses  in  the  subserous  cellular  tissue.  On  the  other  hand, 
I  find  that  the  deeper  lymphatics  are  scanty.  In  ihe-hilus  of  a  calf's 
spleen,  for  instance,  I  found  but  four  lymphatic  trunks  with  a  collective 
diameter  of  0*17  of  a  line.  The  superficial  and  deep  lymphatics  would 
appear  to  be,  to  a  certain  extent,  connected  ;  inasmuch  as  a  few  scattered 
lymphatics,  which  are  probably  connected  with  those  which  proceed  from 
the  hilus,  accompany  the  arteries  which  pass  from  the  interior  of  the 
spleen,  to  be  distributed  in  its  coats,  and  open  into  the  superficial  trunks. 
The  latter  may  readily,  in  the  Ox,  be  traced  for  a  certain  distance  into 
the  interior,  so  far  that  it  can  be  seen  that  they  not  only  at  first,  but 
subsequently,  always  accompany  the  arteries.  Their  origin  is  unknown, 
and  I  can  only  say,  that  in  the  Malpighian  corpuscles  and  in  the  peni- 
cilli,  as  microscopic  investigation  shows,  the  arteries  are  no  longer 
accompanied  by  lymphatics.  They  probably,  as  in  the  liver,  belong 
only  to  the  vascular  sheaths.  In  structure,  the  splenic  lymphatics 
present  no  peculiarities,  and  they  have  valves. 

The  arteries  in,  the  human  spleen  are  exceedingly  muscular,  which 
sufficiently  explains  the  dilatation  and  subsequent  contraction  of  the 


THE     SPLEEN.  567 

organ  observed  5  or  6  hours  after  the  ingestion  of  food,  noticed  by 
many  observers.  In  animals,  besides  these  contractile  elements,  the 
muscles  of  the  coats  and  trabeculce  which  I  have  discovered,  may  take 
some  part  in  this  process,  and  their  presence  further  accounts  for  the 
circumstance  that  the  spleens  of  Animals  contract  by  galvanism,  while 
that  of  man  does  not  (vid.  Mikr.  Anat.  II.  2,  p.  265). 

§  170.  Physiological  remarks. — The  spleen  is  developed  at  the  end 
of  the  second  month,  in  the  foetal  mesogastrium,  at  the  fundus  of  the 
stomach,  from  a  blastema  which,  derived  from  the  middle  layer  of  the 
germ,  independently  of  the  stomach,  the  liver,  or  the  pancreas,  collects 
in  this  situation.  It  is,  at  first,  a  whitish,  often  slightly  lobed  body 
(0-72  of  a  line  in  length,  0*4  of  a  line  in  breadth,  in  the  ninth  to  the 
tenth  week),  which  gradually  becomes  red  and  is  very  soon  as  rich  in 
blood  and  in  vessels  as  in  the  adult.  The  roundish  small  cells,  of  which 
the  spleen  is  at  first  entirely  constituted,  become,  in  the  third  month, 
partly  developed  into  vessels  and  fibres,  whilst  another  portion  remains 
as  parenchyma  cells.  The  Malpighian  corpuscles  are  not  formed  till 
subsequently,  but  may  always  be  found  at  the  end  of  the  foetal  period, 
although  considerably  smaller  than  afterwards.  I  do  not  know  how 
they  are  formed,  but  I  presume  that  they  proceed  from  simple  masses 
of  cells,  whose  external  elements  become  metamorphosed  into  the  coat 
of  connective  tissue,  whilst  the  internal  ones,  partly  persisting  in  their 
original  condition,  partly  becoming  metamorphosed  into  vessels,  form  the 
contents. 

This  is  not  the  place  to  discuss  at  length  the  functions  of  the  spleen ; 
I  must  refer  to  my  "  Mikroskopische  Anatomic,"  II.  2,  p.  282,  and 
content  myself  here  with  stating,  that  I  consider  the  spleen  to  be  an 
organ  into  whose  parenchyma  constituents  of  the  blood  enter  bodily  and 
at  times  in  increased  quantity,  and,  with  the  co-operation  of  cellular 
elements,  which  are  in  a  state  of  continual  formation  and  solution,  un- 
dergo, more  especially  a  retrogressive,  but  partly  also  a  progressive 
metamorphosis,  in  the  end  to  be  taken  up  again  by  the  blood  and 
lymphatics,  in  order  to  be  excreted  from  the  body  or  further  applied  to 
the  purposes  of  the  organism. 

Up  to  a  certain  point  the  investigation  of  the  spleen  presents  no  dif- 
ficulties ;  the  pulp,  the  trabeculce^  and  the  Malpighian  corpuscles,  are 
at  once  obvious.  The  latter  are  most  readily  examined  in  the  Pig  and 
Ox,  where  the  coat  and  the  contents  may  easily  be  isolated,  and  the 
connection  with  the  vessels  is  also  apparent.  To  see  blood-corpuscle- 
holding  cells,  the  addition  of  water  must  be  avoided.  The  muscular 
fibres  are  beautifully  seen  in  the  finer  trabeculce  of  the  Ox,  and  in  the 
trabeculce  of  the  Pig  and  Dog  ;  and  here  maceration  in  nitric  acid,  of 


568  SPECIAL    HISTOLOGY. 

20  per  cent.,  is  of  service.  The  arteries  and  capillaries  are  easily  in- 
jected ;  the  veins  with  great  difficulty ;  most  readily  in  Man.  The 
nerves  are  found  with  ease  on  the  arteries ;  the  lymphatics  may  be  best 
studied  in  the  Ox. 

Literature  of  the  Spleen. — M.  Malpighi,  "  De  liene,"  in  "  Exercit. 
de  vise,  struct.,"  Lond.,  1669 ;  J.  Miiller,  "  Ueber  die  Structur  der 
eigenthiimlichen  Korperchen  in  der  Milz  einiger  pflanzenfr'essenden 
Thiere,"  Miiller's  "Arehiv,"  1834  (the  first  good  anatomical  work 
since  Malpighi) ;  T.  C.  H.  Giesker,  "  Splenologie,  I.  anatomisch.  phy- 
siologische  Untersuchungen  iiber  die  Milz,"  Zurich,  1835  (a  very  ela- 
borate treatise) ;  Schwager-Bardeleben,  "  Observationes  micros,  de  gland, 
ductu  excretorio  carentium  structura,"  Berol.,  1841 ;  Th.  von  Hessling, 
"Untersuchungen  iiber  die  weissen  Korperchen  der  menschlichen  MHz," 
Regensburg,  1842;  A.  Kolliker,  "Ueber  den  Bau  und  die  Verrich- 
tungen  der  Milz,"  in  Mittheil.  "Der  Ziirch.  nat.  Gesellschaft,"  1847, 
p.  120;  "Ueber  Blutkorperchen  haltige  Zellen,"  in  "Zeitsch.  fiir  wiss. 
Zool.,"  Bel.  I.  p.  261,  and  Bd.  II.  p.  115;  art.  "Spleen,"  in  Todd's 
"Cyclopaedia  of  Anatomy,"  June,  1849;  A.  Ecker,  "Ueber  die 
Veranderungen,  welche  die  Blutkorperchen  in  der  Milz  erleiden,"  in 
"Zeitsch.  fiir  Rat.  Medicin,"  VI.  1847,  and  art.  "Blutgefassdrusen," 
in  R.  Wagner's  "Handw.  der  Phys.,"  IV.  1,  1849;  J.  Landis,  "Bei- 
trage  zur  Lehre  iiber  die  Verrichtungen  der  Milz,"  Zurich,  1847  ;  Ger- 
lach,  "Ueber  die  Blutkorperchen  haltenden  Zellen  der  Milz,"  in 
"  Zeitschrift  fiir  Rat.  Medicin,"  VII.  1848;  "  Gewebelehre,"  p.  218  ; 
R.  Sanders,  "On  the  Structure  of  the  Spleen,"  in  Goodsir's  "Annals 
of  Anat.,"  I.  1850;  0.  Funke,  "De  sanguine  vense  lienalis,"  Lips., 
1851. 

[Gray,  "  On  the  Development  of  the  Ductless  Glands  in  the  Chick," 
"  Phil.  Trans.,"  1852.— TRS.] 


OF  THE  RESPIRATORY  ORGANS. 

§  171.  Under  the  head  of  respiratory  organs  are  usually  enumerated 
only  the  larynx,  trachea,  and  lungs  ;  but  I  consider  it  as  most  suitable 
here  to  describe  two  organs  connected  genetically  with  those  respiratory 
organs  of  the  embryo,  which  remain  undeveloped,  that  is  to  say,  the 
branchial  arches  ;  and  which,  physiologically,  perhaps,  belong  to  the 
lungs — the  thyroid  gland  and  the  thymus. 

OF  THE  LUNGS. 

§  172.  The  structure  of  the  lungs  corresponds,  in  all  respects,  with 
that  of  a  compound  racemose  gland,  presenting,  in  the  lobes,  lobules, 
and  air-cells,  the  proper  glandular  parenchyma  ;  whilst  the  bronchice, 


THE    LUNGS.  569 

trachea,  and  larynx,  constitute  the  excretory  apparatus.  They  differ 
from  common  glands  in  this,  that  since  in  the  lungs  a  double  process — 
an  excretion  and  an  absorption  of  matters — is  carried  on,  which  affects 
the  "whole  mass  of  blood,  the  cavities  are  proportionately  more  capa- 
cious, and  also,  on  account  of  the  special  nature  of  their  contents,  of  a 
peculiarly  compact,  and,  at  the  same  time,  elastic  structure. 

§  173.  The  larynx  is  the  most  complex  portion  of  what  are  termed  the 
air-passages,  and  consists,  in  the  first  place,  of  a  firm  framework,  the 
cartilages  of  the  larynx,  together  with  their  ligaments;  secondly,  of  nu- 
merous small  muscles  attached  to  them  ;  and  lastly,  of  a  mucous  mem- 
brane, abounding  in  glands,  with  which  they  are  lined. 

The  cartilages  of  the  larynx  are  not  all  alike  in*  their  structure,  some 
being  composed  of  common  cartilaginous  tissue,  others  of  fibro-cartilage, 
whilst  others,  again,  are  constituted  of  the  so-termed  reticidar  or  yelloio 
cartilage.  To  the  former  belong  the  thyroid-,  cricoid-,  and  arytenoid- 
cartilages ;  all  of  which  present  a  more  homogeneous,  hyaline  matrix, 
with  scattered  cartilage  cells  imbedded  in  it  (Fig.  20),  and  approach 
nearest  to  the  costal  among  the  other  true  cartilages.  Most  externally 
they  contain  flattened  cells,  to  which  succeeds  a  whitish  layer,  with  nu- 
merous large  parent-cells  and  a  more  fibrous  fundamental  substance; 
and,  lastly,  in  the  interior,  a  larger  proportion  of  matrix  and  minute 
radiating  cavities.  The  membranes  of  the  cells  are  thickened,  and,  in 
their  interior,  a  large  oil-drop  is  most  usually  found.  Incrustations  of 
the  cartilage-cells  and  of  the  matrix,  with  minute  calcareous  granules, 
are  very  frequent  in  the  laryngeal  cartilages ;  but  besides  these,  true 
ossifications  occur,  which  are  always  attended  with  the  formation  of 
larger  cavities,  filled  with  a  well-marked,  gelatiniform,  vascular  medulla. 
The  epiglottis  and  the  cartilages  of  Santorini  and  of  Wrisberg,  consist 
of  yelloiv  or  reticular  cartilage  (vide  §  22,  Fig.  21),  presenting  opaque, 
very  closely  interlaced  fibres,  which,  in  animals  (e.  g.  the  Ox),  are  much 
thicker  than  in  Man,  and  clear  cells,  0 -01-0-02  of  a  line  in  size,  in  which 
Henle,  in  one  instance,  noticed  a  concentric  disposition  of  such  a  kind 
that  the  remaining  cavity  of  the  cell  resembled  a  simple  bone-lacuna 
with  a  few  prolongations  (Allg.  Anat.,  Tab.  V.,  Fig.  8).  The  cartilago 
triticea  consists  of  connective  tissue  with  scattered  cartilage-cells,  and 
is,  consequently,  common  fibro-cartilage. 

Of  the  ligaments  of  the  larynx,  the  ligg.  crico-thyreoideum  medium 
and  thyreo-arytcenoidea  inferior  a  contain  a  preponderance  of  elastic  tissue 
and  are  of  a  yellow  color  :  whilst  others,  such  as  the  thyreo-arytwnoidea 
superiora,  hyo-  and  thyreo-epiglottica,  and  the  membr.  hyo-thyreoidea, 
are  characterized,  at  all  events,  by  the  great  abundance»of  that  element 
which  they  present.  The  elastic  fibres  of  the  laryngeal  ligaments  are 
of  the  finer  sort,  scarcely  exceeding  0-001  of  a  line,  and  are  united  in 


570  SPECIAL    HISTOLOGY. 

the  usual  manner  into  a  very  close  elastic  network ;  which,  however, 
even  where  it  is  apparently  most  unmixed,  contains  some  connective 
tissue.  The  muscles  of  the  larynx  are  all  transversely  striated  with 
fibres  of  0*016-0-024  of  a  line,  and  present  the  same  structure  as  those 
of  the  trunk.  They  arise  from  the  cartilages,  and  are  inserted  into  them, 
and  also  into  their  elastic  ligaments;  the  latter  being  the  case  with  the 
thyreo-arytwnoideus,  which  is  for  the  most  part  lost  on  the  concave  side 
of  the  vocal  ligaments. 

The  mucous  membrane  of  the  larynx,  the  continuation  of  that  of  the 
throat  and  mouth,  is  smooth,  whitish  red,  and  connected  with  the  sub- 
jacent parts  by  the  ordinary,  in  some  places  abundant  submucous  con- 
nective tissue.  Except  in  the  glottis,  the  mucous  membrane,  covered 
only  by  a  ciliated  epithelium,  and  presenting  no  papillce,  abounds  in 
finer  elastic  fibrous  networks,  particularly  in  its  deeper  portions  ;  whilst 
the  innermost  layer,  0-03-0-04  of  a  line  thick,  consists  principally  of 
connective  tissue,  and  ceases  in  an  inseparable,  homogeneous  border  of 
0*004  of  a  line.  The  ciliated  epithelium,  in  the  adult,  commences  at  the 
base  of  the  epiglottis  and,  above  the  upper  vocal  ligaments,  is  composed 
of  several  laminae  (vide  §  21),  on  the  whole  0-024-0-04  of  a  line  thick; 
with  the  exception  of  the  vocal  ligaments,  which,  as  was  discovered  by 
H.  Rheiner  and  I  can  confirm,  have  a  squaraose  epithelium,  it  lines  the 
rest  of  the  larynx  throughout.  The  proper  ciliated  cylinders  0-015- 
0-02  of  a  line  long,  and  0-0025-0-004  of  a  line  broad  in  the  mean,  with 
elongated  round  nuclei  of  0-003-0-0045  of  a  line,  and  occasionally  with 
a  few  fat-granules,  are  mostly  much  acuminated,  frequently  even  pro- 
longed into  slender  filaments,  which  may  attain  such  a  length  that  the 
entire  cell  may  equal  0-024-0-027  of  a  line.  The  cilia  are  fine,  trans- 
parent, soft  processes  of  the  cell-membrane,  0-0016-0-0022  of  a  line 
long,  which  arise  from  it  with  a  rather  broader  basis,  and  terminate  in 
a  pointed  extremity.  Most  usually  they  are  placed  close  together,  over 
the  whole  of  the  terminal  surface  of  the  cells,  according  to  Valentin,  on 
the  average,  to  the  number  of  10  to  22,  which  appears  to  be  rather 
under  the  mark ;  more  rarely  they  occur  in  smaller  number,  or  even,  as 
it  is  said,  singly  upon  a  cell.  But  in  this  case,  care  must  be  taken  not 
to  regard  cohering  cilia  as  single  ones,  as  might  happen,  particularly  in 
the  embryo.  In  their  chemical  relations  the  cells  of  the  ciliated  epithe- 
lium correspond  precisely  with  those  of  the  cylinder-epithelium,  and 
especially,  the  separation  of  the  cell  membrane  on  the  addition  of  water, 
may  also  be  remarked  in  them.  The  cilia  are  of  much  more  delicate 
consistence  than  the  cell  membrane  and  are  very  readily  detached  upon 
any  maceration  of  the  epithelium ;  more  or  less  altered  by  almost  all 
reagents,  they  are,  by  many,  at  once  destroyed ;  in  chromic  acid,  how- 
ever, they  may  be  preserved  pretty  well.  In  man,  the  ciliary  motion  is 
directed,  in  the  trachea,  from  below  upwards  and  may  often  be  perceived 


THE    LUNGS. 


571 


fifty-two  or  even  fifty-six  and  seventy-eight  hours  after  death  (Biermer, 
Gosselin).*  There  is  nothing  to  show  the  occurrence,  normally,  of  a 
desquamation  of  the  ciliated  epithelium  of  the  larynx  and  air-passages. 


Fisr.  233. 


Occasionally,  it  is  true,  isolated,  ciliated  cylinders  are  thrown  off  and 
expelled  with  the  mucus  of  the  trachea,  but  of  an  extensive  detachment 
of  the  ciliated  cells  there  is  no  indication.  Even  in  diseases  of  the  re- 
spiratory passages,  the  detachment  of  the  ciliated  cells  is  by  no  means 
so  common  a  phenomenon  as  is  believed  by  many,  and  the  epithelium 
may  be  frequently  found  uninjured  under  puriform  mucus,  or  even  be- 
neath croupose  exudations.  The  mode  in  which  the  ciliated  cylinders 
that  have  been  thrown  off  are  replaced,  is  probably  simply  this  :  that 
the  deep  cells  multiply,  perhaps  by  division  (vide  §  12),  and  succeed 
them,  the  outermost  again  producing  cilia. 

The  laryngeal  mucous  membrane  contains  a  considerable  number  of 

FIG.  233. — Ciliated  epithelium  from  the  human  trachea,  magnified  350  diam.  Jl,  epithelium 
in  situ :  a,  most  external  portion  of  the  elastic  longitudinal  fibres ;  6,  homogeneous,  most  ex- 
ternal layer  of  the  mucous  membrane ;  c,  deepest,  rounded  cells  ;  d,  middle,  elongated  cells ; 
e,  most  superficial  cells,  supporting  cilia.  B,  isolated  cells  from  the  various  layers. 

*  [The  motion  of  the  cilia  is  destroyed  by  many  chemical  and  mechanical  agents,  but 
hitherto,  notwithstanding  the  careful  researches  of  Purkinje  and  Valentin  (De  phenomeno. 
gen.  et  fundam.  motus  vibratorii  continui,  Vratisl.  1835,  pp.  74-7G)  none  have  been  known 
which  possessed  the  power  of  re-exciting  it.  Virchow  (Archiv  f.  path.  Anat.  VI.  1)  has, 
however,  quite  lately,  whilst  examining  the  epithelium  of  a  human  trachea,  discovered 
that  by  the  application  of  a  solution  of  potassa  the  ciliary  motion  may  be  recalled.  Under 
the  action  of  the  potassa,  he  states,  isolated  cilia  begin  at  first  to  exhibit  irregular,  jerking 
movements.  These  gradually  acquire  more  regularity  and  force,  until  at  last  the  rapid, 
rhythmical,  sweeping  movement  of  a  whole  series  of  cells  is  restored.  A  solution  of  soda 
acts  in  the  same  manner  as  one  of  potassa ;  a  solution  of  ammonia  produces,  on  the  other 
hand,  at  once  a  chemical  decomposition.  These  experiments,  Virchow  thinks,  prove  con- 
clusively, that  the  substance  of  the  vibratile  cilia  approximates  the  contractile  substance  of 
muscle  (Syntonin  of  Lehmann). — DaC.] 


572  SPECIAL    HISTOLOGY. 

glandules,  all  of  which  belong  to  the  category  of  minute  racemose  glands  ; 
and,  like  those  of  the  oral  cavity,  pharynx,  &c.,  present  rounded  gland- 
vesicles  of  0-008-0-04  of  a  line  with  a  tessellated  epithelium,  and  excre- 
tory ducts  lined  with  a  cylinder-epithelium.  They  are  situated,  in  part 
scattered  as  minute  glandules  of  T\j-}  of  a  line,  on  the  posterior  surface 
of  the  epiglottis,  where  they  are  frequently  imbedded  in  depressions, 
which  may  even  perforate  the  cartilage,  and  in  the  cavity  of  the 
larynx  itself,  where  their  orifices,  such  as  might  be  produced  by  a 
needle,  are  easily  seen ;  in  part  they  occur  at  the  entrance  of  the 
larynx,  in  front  of  the  arytsenoid  cartilages,  forming  a  large  aggre- 
gate mass,  a  horizontal  division  of  which  envelops  the  cartilage  of 
Wrisberg,  whilst  a  second  dips  down  into  the  cavity  of  the  larynx 
(glandulce  arytwnoidece  later  alee).  Glandules  are  also  placed  upon 
the  arytcenoideus  transversus  and  a  considerable  mass  of  them  pre- 
sents itself  externally,  in  the  ventricles  of  Morgagni,  behind  and 
above  the  sacciform  ligaments.  The  secretion  of  these  glands,  as  of  the 
oral  glands,  is  pure  mucus,  without  any  morphological  elements. 

The  larynx  is  richly  supplied  with  vessels  and  nerves.  The  former, 
in  the  mucous  membrane,  present  the  same  conditions  as  in  the  pharynx 
and  ultimately  breaking  up  into  capillaries,  0*003— 0*004  of  a  line,  form 
a  superficial  plexus.  The  lymphatics  are  numerous  and  are  received  by 
the  deep  cervical  glands.  Of  the  nerves,  we  learn  from  Bidder-Volck- 
mann,  that  the  more  sensitive  laryngeus  superior  contains  a  prepon- 
derance of  fine  fibres,  whilst  the  inferior,  whose  properties  are  more  of 
a  motor  nature,  has  more  thick  fibres.  They  terminate  in  the  muscles, 
the  perichondrium  and,  especially,  in  the  mucous  membrane,  in  which 
they  are  disposed  as  in  the  pharynx;  the  branches  going  to  the  epi- 
glottis are  also  furnished  with  microscopic  ganglia. 

The  glands  of  the  larynx  and  of  the  air-passages  are  frequently 
altered  in  catarrh,  so  that  their  vesicles  measure  as  much  as  0*08,  or 
even  0*15  of  a  line,  and  are  filled  with  minute,  rounded  cells,  which  may 
probably  be  compared  with  the  mucous  corpuscles  formed  on  the  sur- 
faces of  mucous  membranes. 

§  174.  The  trachea  and  its  branches  are  united  to  the  contiguous 
parts  by  a  connective  tissue  abounding  in  well-defined  elastic  fibres; 
they  are  then  surrounded  by  a  tough,  elastic,  fibrous  tissue,  which 
covers  the  cartilaginous  rings,  like  a  perichondrium,  connects  them 
together,  and,  in  a  somewhat  thinner  layer,  invests  the  posterior  mem- 
branous wall  of  the  canal  in  question.  To  this  layer  succeed  the  carti- 
lages, in  front  and  on  the  sides,  while  posteriorly  there  is  a  layer  of 
smooth  muscles.  The  former,  J— J  a  line  thick,  are  constituted  ex- 
actly like  the  larger  cartilages  of  the  larynx,  but  exhibit  no  tendency 
to  become  ossified.  The  muscles,  on  the  contrary,  from  the  trachea 
onwards,  cease  to  be  of  the  striped  kind  and  constitute,  on  the  pos- 


THE     LUNGS. 


573 


terior  wall  of  the  tube,  only  an  incomplete  layer,  0-3  of  a  line  thick, 
composed  of  transverse  fibres  ;  on  the  outer  aspect  of  which  are  isolated 
longitudinal  bundles,  whose  elements,  O03  of  a  line  long  and  0-002-0-004 
of  a  line  wide,  are  united  into  small  fasci- 
culi, which  arise  by  delicate  minute  tendons 
of  elastic  tissue,  in  part  from  the  inner  sur- 
face of  the  ends  of  the  tracheal  rings ;  in 
part,  particularly  the  longitudinal  bundles, 
from  the  external  fibrous  membrane.  (J^id. 
Mikr.  Anat.  II.  2,  Fig.  277.) 

On  the  inner  aspect  of  the  cartilages 
and  muscles,  which,  to  a  certain  extent,  are 
to  be  regarded  as  one  layer,  we  find  a  stra- 
tum about  0-12  of  a  line  thick,  of  more  com- 
mon, close,  connective  tissue,  and  then  the 
true  mucous  membrane.  This  consists  of 
two  layers ;  an  external  composed  of  con- 
nective tissue,  0-12  of  a  line  in  thickness  ; 
and  an  internal,  yellow,  of  0-09-0-1  of  a 
line,  almost  wholly  elastic,  the  plexiform 
fibres  of  which,  0*0015  of  a  line  in  diame- 
ter, run  longitudinally,  and  in  places,  espe- 
cially on  the  posterior  wall,  often  constitute 
flattened  fasciculi  joined  at  acute  angles. 
The  innermost  portion  of  the  elastic  layer, 
0-024-0-03  of  aline  thick,  is,  particularly 
in  the  posterior  wall,  as  in  the  larynx,  fre- 
quently composed  more  of  connective  tissue 
with  fine  elastic  fibrils ;  it  may  also  be  raised 
as  a  thin  pellicle  from  the  thicker  elastic 

layer,  and  internally  always  presents  a  more  homogeneous  layer,  0-005  of 
a  line  thick.  Upon  this  lies  the  ciliated  epithelium,  which  is  laminated 
and  differs  in  no  respect  from  that  of  the  larynx.  Numerous  glands 
exist  in  the  mucous  membrane;  these  are  :  1,  smaller  ones  of  1-10-1-4  of 
a  line,  found  especially  on  the  anterior  wall,  within  the  mucous  mem- 
brane and  immediately  exterior  to  the  elastic  layer ;  and  2,  larger,  of 
J-l  line,  which  occur  more  in  the  posterior  wall,  externally  to  the 
muscles  and  the  whole  mucous  membrane,  or  between  the  cartilages. 
These  glands  differ  from  those  of  the  larynx  only  inasmuch  as  the  larger 
of  them  alone  have  the  usual  tessellated  epithelium  in  their  vesicles ; 

FIG.  234. — Vertical  section  through  the  anterior  wall  of  the  human  trachea,  magnified 
45  diam.:  a,  fibrous  coat;  6.  c,  d,  cartilage;  b,  external  layer,  with  flattened  cells;  d,  inter- 
nal layer,  with  elongated  elements;  e,  submucous  connective  tissue;  /,  portion  of  a  mucous 
gland ;  g,  elastic  longitudinal  fibrous  layer ;  /z,  epithelium,  on  which  the  cilia  are  not  visible  ; 
i,  glandular  orifice. 


574  SPECIAL    HISTOLOGY. 

•whilst  the  smaller,  situated  in  the  mucous  membrane  itself,  and  some 
of  which  are  in  the  strictest  sense  simple,  or  only  bifurcated  coecal  folli- 
cles, present  in  their  oval  gland-vesicles,  0-02-0-03  of  a  line  in  size, 
a  very  narrow  cavity  and  walls  of  0-006-0-01  of  a  line,  a  thickness 
which  may,  perhaps,  be  referred  altogether  to  the  well-marked  cylinder- 
epithelium. 

The  bloodvessels  of  the  trachea  are  very  numerous,  and,  in  the  mucous 
membrane,  are  especially  characterized  by  the  circumstance,  that  the 

larger   branches    run  chiefly 

Fig- 235-  in    a   longitudinal    direction, 

whilst  the  superficial  capillary 
plexus,  which  is  frequently 
met  with  above  the  elastic 
elements,  close  beneath  the 
homogeneous  layer,  more  com- 
monly forms  rounded-angular 
meshes.  The  trachea  is  abun- 
dantly furnished  with  lym- 
phatics; and  in  one  case  I 
found  their  commencement  in 
the  mucous  membrane,  in  the 
form  of  wide-meshed  plexuses 

0'003-0-001  of  a  line  broad,  of  thin-walled  vessels,  from  which,  here 
and  there,  isolated,  caecal  processes  were  given  off  (Fig.  235).  The 
nerves  also  of  the  trachea  are  numerous,  and  present  the  same  condi- 
tions as  those  of  the  larynx. 

§  175.  Lungs. — The  lungs  are  two  large,  compound,  racemose 
glands,  in  which  are  to  be  distinguished :  1,  a  special  serous  coat — 
the  pleura;  2,  the  secreting  parenchyma,  consisting  of  the  ramifica- 
tions of  the  two  bronchi,  with  their  terminations,  the  air-cells,  and 
numerous  vessels  and  nerves  ;  and  3,  an  interstitial  tissue  interposed 
between  these  parts  and  uniting  them  into  larger  and  smaller  lobules. 

The  pleurce,  in  their  structure,  entirely  correspond  with  the  peri- 
toneum, as  in  which,  the  parietal  layer  is  the  thicker,  and  consist  of 
connective  tissue  abounding  in  finer  or  coarser  elastic  elements,  with  a 
tessellated  epithelium,  to  which  constituents,  on  the  walls  of  the  thorax, 
as  on  the  exterior  of  the  pericardium,  a  more  purely  fibrous  lamella  is 
superadded.  Vessels  are  seen  most  abundantly  in  the  pleura  pulmonalis, 
where,  arising  from  the  bronchial  and  pulmonary  arteries,  they  ramify 
in  the  subserous  tissue ;  whilst  the  parietal  lamella  is  more  scantily 
supplied  by  the  intercostal  and  mammary  arteries.  Luschka  found  nerves 

FIG.  235. — Commencement  of  the  lymphatics  in  the  tracheal  mucous  membrane  of  Man, 
magnified  350  diameters. 


THE    LUNGS. 


575 


Fig.  236. 


•with  finer  and  coarser  fibres  and  traced  them,  in  the  outer  portions  of 
the  membrane,  to  the  phrenic  and  to  the  thoracic  divisions  of  the  sympa- 
thetic. In  Man,  I  have  myself  also  seen,  in  the  pleura  pulmonalis, 
nerves,  as  much  as  0'036  of  a  line  in  diameter,  accompanying  the 
branches  of  the  bronchial  arteries,  with  middle-sized  and  thick  fibres 
and  occasionally  large  scattered  ganglion-globules,  which  were  derived 
from  the  plexus  pulmonalis,  and  were  probably  afforded  chiefly  by  the 
vagus. 

§  176.  Air-vessels  and  cells. — When  the  right  and  left  bronchi  have 
reached  the  root  of  the  lungs,  they  begin  to  branch,  like  the  excretory 
ducts  of  one  of  the  larger  glands,  such  as  the  liver,  dividing  for  the 
most  part  dichotomously  and  at  acute  angles,  into  smaller  and  smaller 
branches ;  but  giving  off,  at  the  same  time,  from  the  sides  of  the  larger 
and  middle-sized  branches,  numerous  minute  air-vessels,  at  a  right 
angle,  which  like  the  terminations  of  the  main  ramifications,  subdivide 
in  an  arborescent  manner.  Thus  is  ultimately  constituted  an  extremely 
rich  tree  of  air-vessels,  whose  finest  ter- 
minations, never  anastomosing,  extend 
through  the  entire  lung  and  are  to  be 
found  in  every  part,  on  the  surface  as  well 
as  in  the  interior.  With  them,  also,  are 
connected  the  ultimate  elements  of  the  air- 
passages — the  air-cells  or  pulmonary  vesi- 
cles (vesiculce  s.  cellulce  aerece  s.  Malpig- 
hiance,  alveoli  pulmonum,  Rossignol),  not, 
as  was  formerly  believed,  by  each  finest 
bronchial  twig  terminating  in  a  single 
vesicle,  but  always  by  their  communicating 
with  a  whole  group  of  air-cells.  These 
groups  of  vesicles  correspond  to  the  smallest 
lobules  of  racemose  glands,  and  conse- 
quently there  is  no  occasion  whatever  to  designate  them  under  any 
other  name,  as  was  done  by  Rossignol,  who  calls  them  infundibula, 
although  it  must  be  allowed  that  their  structure,  in  many  respects,  is 
peculiar.  For,  whilst  in  other  glands  the  vesicles,  if  not  quite  so  isolated 
from  each  other  as  has  hitherto  been  supposed,  still  enjoy  a  certain 
degree  of  independence,  the  pulmonary  elements  corresponding  to 
them, — the  air-cells, — are,  to  a  considerable  extent,  confluent  with  each 
other,  so  that  all  the  vesicles  belonging  to  one  lobule  open,  not  into 
ramifications  of  the  finest  bronchial  twig  going  to  it,  but  into  a  common 
space,  from  which  the  air-vessel  is  afterwards  developed.  That  this  is 

FIG.  236. — Two  small  pulmonary  lobules,  a  a,  with  the  air-cells,  b  />,  and  the  finest  bronchial 
twigs,  cc,  upon  which  air-cells  are  also  placed.  From  a  new-born  child;  magnified  25 
diameters.  Half-diagrammatic. 


576  SPECIAL    HISTOLOGY. 

the  true  condition  of  these  parts  is  most  readily  shown  when  sections, 
in  various  directions,  of  an  inflated  and  dried  lung  are  prepared,  or  a 
preparation  injected  with  a  colored  resinous  material  is  corroded  by 
hydrochloric  acid.  In  preparations  of  this  kind,  vesicles  either  termi- 
nal or  otherwise  pedunculated,  or  opening  independently,  are  never  met 
with ;  on  the  contrary,  they  always  open  in  such  a  way,  one  into  the 
other,  and  coalesce  to  such  an  extent,  as,  in  the  aggregate,  to  form, 
most  usually,  a  pyriform  sacculus,  with  sinuous  walls.  These  sacculi, 
which  are  also  identical  with  the  finest  lobules,  or  the  infundibula  of 
Rossignol,  must  not,  however,  be  regarded  as  sacs,  furnished  on  their 
wralls  with  closely  placed  simple  cells  or  alveoli,  the  latter,  on  the  con- 
trary, being  always  grouped  in  such  a  way  that  many  of  them  do  not 
open  directly  in  the  larger  space,  but  first  into  other  alveoli,  and  through 
them  into  the  common  cavity.  An  idea  of  the  whole  relations  of  these 
parts  may  be  best  arrived  at  if  each  pulmonary  lobule  be  viewed  as  an 
amphibian  lung  in  miniature,  or  if  it  be  conceived  that  the  outer  surface 
of  the  dilated  extremities  of  the  bronchial  tubes  is  thickly  beset  with 
numerous  racemose  groups  of  vesicles,  the  constituents  of  which  all 
open  into  one  another  and  into  the  common  cavity.  Understood  in 
this  way  the  structure  of  the  lungs,  then,  does  not  differ  in  the  least, 
in  any  important  respect,  from  that  of  the  other  racemose  glands, 
except  that  in  the  former,  at  all  events  in  the  adult,  a  partial  confluence 
of  the  gland-vesicles  or  air-cells  of  a  lobule,  appears  to  have  taken 
place,  the  dissepiments  between  them  being  here  and  there  broken 
through  and  reduced  to  isolated  trabeculce,  as  Adriani  correctly  observes. 
The  smallest  air-vessels,  0§1— 0*16  of  a  line  in  diameter,  arising  by 
simple  narrowing  from  the  most  minute  lobules,  are  at  first  still  beset 
with  simple  air-cells,  which  may  be  termed  parietal,  and  at  first  also, 
have  sinuous  walls,  a  character,  however,  which  is  soon  lost  to  be  re- 
placed by  the  usual  smooth  appearance  which  is  afterwards  retained. 

The  size  of  the  air-cells  varies  very  considerably  even  in  a  healthy 
lung,  amounting  after  death,  and  when  they  are  wholly  undistended 
with  air,  to  1-6-1-10-1-18  of  a  line.  But  owing  to  its  elasticity,  every 
air-cell  may  be  dilated  to  twice  or  three  times  its  natural  size  without 
rupture,  and  is  capable  afterwards  of  returning  to  its  pristine  condition. 
It  will  not  be  wrong  to  assume,  that,  in  life,  when  the  lungs  are  filled 
with  the  average  quantity  of  air,  the  air-cells  are  at  least  one-third 
larger  than  we  find  them  after  death  ;  and  that,  on  the  deepest  possible 
inspiration,  the  expansion  reaches,  perhaps  to  twice  that  dimension. 
In  emphysema,  dilatations  to  this  and  even  to  a  much  more  considerable 
extent,  are  permanent,  and  ultimately  lead  to  the  rupture  of  the  walls 
of  the  alveoli  belonging  to  a  lobule,  or  even  to  the  confluence  of  the 
lobules  themselves.  The/0r?tt  of  the  alveoli,  in  a  recent  collapsed  lung, 
is  most  usually  rounded  or  oval  and,  in  one  that  has  been  inflated  or 


THE    LUNGS. 


577 


injected,  in  consequence  of  their  mutual  pressure,  rounded-angular ;  the 
air-cells  of  the  surface  of  the  lung  are  invariably  polygonal  and  their 
external  sides  are  almost  always  nearly  plane. 

The  Ululated  structure  of  the  lung  is  not  nearly  so  distinct  in  the 
human  adult  as  in  younger  individuals  and  in  animals.  It  is  therefore 
advisable,  in  the  first  instance,  to  seek  for  these  conditions  in  the  lungs 
of  a  child.  In  this  case  the  separate  lobules  are  still  all  distinctly 
parted  from  each  other  by  connective  tissue  and  admit  of  being  isolated, 
so  that  the  tolerably  regular  pyramidal  form  of  the  superficial,  and  the 
more  irregular  one  of  the  interior  lobules  can  be  satisfactorily  perceived. 
In  the  adult,  also,  these  smallest  lobules,  in  size  J-J-1  line,  still  exist, 
but  are  so  intimately  united,  that,  even  on  the  surface  of  the  lung,  their 
outlines  are  only  perceived  with  difficulty  and  imperfectly  ;  and,  in  the 


Fiff.  237. 


interior  of  the  organ,  a  more  homogeneous  structure,  something  like 
that  of  the  liver,  is  apparently  presented.  Secondary  lobules^  on  the 
other  hand,  of  J-J-1  inch  in  size  (lobules  of  authors)  are,  even  in  the 
adult,  most  usually  evident  and  the  more  so,  because  their  boundaries 
are  indicated  by  streaks  of  pigmentary  matter,  which,  in  course  of 
time,  is  deposited  in  the  continuous  interlobular,  connective  tissue. 
These  lobules  are  ultimately  united  together  by  a  more  abundant  inter- 
stitial tissue,  so  as  to  form  the  large  well-known  lobes. 

Thus  the  lung  consists  entirely  of  larger  and  smaller  groups  of  air- 
cells  and  smallest  bronchial  tubes,  and  accordingly  the  larger  air-vessels 
also  fall  into  certain  definite  groups,  each  of  which  stands  in  relation 
with  only  one  of  the  former. 

FIG.  237. — External  surface  of  the  lung  of  a  Cow,  with  the  air-cells  injected  with  wax, 
magnified  30  diameters;  after  Halting:  a  a,  air-cells;  b  6,  borders  of  the  smallest  lobules  or 
infnndibula  (Rossignol). 

37 


578  SPECIAL    HISTOLOGY. 

§  177.  The  intimate  structure  of  the  bronchice  and  air-cells  is  as  fol- 
lows.    The  bronchice  are  in  general  constituted  in  the  same  way  as  the 
air-tubes  and  their  branches,  although  from  the  very  commencement 
some  differences  are  presented,  which  become  greater  and  greater  in 
their  further  course.     It  is  most  proper  to   distinguish  in  them  two 
membranes,  a  fibrous,  still  in  part  containing  cartilages,  and  a  mucous, 
with  a  smooth  muscular  layer.     The  former,  constituted  of  connective 
tissue  and  elastic  fibrils,  is  at  first  thick,  as  in  the  bronchi,  but  gradually 
becomes  thinner  and  thinner ;  in  bronchice  less  than  J  a  line  in  dia- 
meter, it  is  scarcely  demonstrable  with  the  scalpel;  and  ultimately,  in 
their  terminations,   it   coalesces  with  the  mucous  membrane,  and  the 
more  lax  connective  tissue  uniting  the  bronchia?  with  the  parenchyma 
of  the  lung.     In  this  membrane  are  lodged  the  cartilages  of  the  bron- 
chice, which,  instead  of  being  half-rings,  are  irregular  angular  plates, 
distributed  around  the  entire  circumference  of  the  tubes.     These  carti- 
laginous plates,  at  first  large  and  closely  approximated,  are  soon  more 
widely  separated  at  the  points  of  origin  of  the  branches,  and  become 
smaller  and  smaller,  until  finally  in  tubes  under  J   a  line  in  diameter 
they  usually  cease  to  exist  (Gerlach  would  appear  to  have  noticed  some 
even  in  tubes  of  ^of  a  line  in  diameter).    The  structure  of  these  carti- 
lages, which  are  not  unfrequently  of  a  reddish  hue,  is  at  first  exactly  like 
that  of  the  tracheal  rings,  but  in  the  smaller  and  smallest  of  them  the 
differences  between  the  superficial  and  deeper  cells  disappear  and  the 
tissue  becomes  homogeneous  throughout,  more  like  the  interior  of  the 
larger  cartilages.    In  the  largest  bronchice  the  muscles  present  the  form 
of  circular  flattened  fasciculi,  which,   except  in  old  people,  in  whom 
larger  and  smaller  interstices  occur  between  them,  constitute  a  com- 
pletely continuous  layer,  and  as  they  are  still  seen  in  twigs  of  1-10-1-12 
of  a  line  in  diameter,  probably  exist  even  in  the  pulmonary  lobules.    The 
mucous  membrane  is  intimately  united  with  the  muscles,  and  at  first  is 
of  the  same  thickness  as  in  the  trachea,  but  this  is  gradually  reduced,  so 
that  tubes  of  less  than  J-  a  line  have  only  an  extremely  thin  wall.    This 
everywhere    consists,   externally,    of   elastic,    longitudinal   fibres,   the 
bundles  formed  by  which  give  the  characteristic  longitudinally  striped 
aspect  to  the  inner  surface  of  the  bronchice,  and  also  produce  a  less 
distinct  longitudinal  plication  of  the  mucous  membrane  ;  secondly,  of  a 
homogeneous  layer  0-002-0-003  of  a  line  thick ;  and  thirdly  and  lastly, 
of  a  ciliated  epithelium,  which,  in  the  larger  bronchial  tubes  and  down 
to  those  of  1  line  in  diameter,  is  distinctly  composed  of  several  laminae, 
but  is  gradually  reduced  to  a  single  layer  of  ciliated  cells  0-006  of  a 
line  in  length.     The  bronchise  are  at  first  also  furnished  with  racemose 
glands,  even  in  considerable  number,  which,  however,  are  wanting  in 
tubes  of  1-1 J  lines. 


THE    LUNGS. 


579 


Fig.  238. 


In  the  air-cells,  I  cannot  admit  the  existence  of  more  than  two  layers 
— a  fibrous  membrane  and  an  epithelium.  The  former  is  manifestly  the 
much  attenuated  mucous  membrane  and  fibrous  tunic  of  the  bronchice, 
entirely  deprived  of  the  smooth  muscles,  and  consisting  of  a  homoge- 
neous matrix  of  connective  tissue,  together  with  elastic  fibres  and 
numerous  vessels.  The  elastic  fibres,  0*0005— 0'002  of  a  line  in  size, 
present  the  form  chiefly  of  separate  trabeculse  and  filaments,  running 
especially  at  the  angles  of  the  air-cells,  which  have  been  flattened  in 
the  distended  condition,  as  well  as  around  their  openings  ;  they  anasto- 
mose with  each  other  on  every  side  and  thus  constitute  a  firm  frame,  on 
which  the  softer,  vascular  parts  of  the  air-alveolae,  composed  of  con- 
nective tissue,  are  stretched.  The  structure  of  these  elastic  trabeculce, 
which,  at  the  points  where  the  air-cells  abut  upon  each  other,  mutually 
coalesce,  so  that  the  boundaries  of  the  separate  cells  cannot  for  the 
most  part  be  recognized,  is  al- 
most everywhere  one  of  the 
most  close  elastic  networks 
possible,  the  interstices  of  which 
appear  only  as  extremely  nar- 
row fissures,  although  occasion- 
ally the  fibres  are  more  loosely 
united,  so  that  they  are  plainly 
recognizable  as  elastic  elements 
of  the  usual  kind.  From  the 
trabeculce  also,  but  everywhere 
sparingly,  elastic  fibres,  in  part 
very  fine,  proceed  into  the  re- 
mainder of  the  walls  of  the 
air-cells,  in  which,  by  their 
union,  they  constitute  a  wide 
network.  The  connective  tissue 
of  the  air-cells,  which  appears 
to  be  altogether  homogeneous, 
is  quite  a  subordinate  element 

in  their  composition,  compared  with  the  elastic  elements  and  vessels, 
presenting  itself,  as  it  may  be  said,  only  in  the  walls  of  the  alveola, 
between  the  elastic  trabeculce,  as  a  connective  medium  between  the 
numerous  capillaries. 

The  epithelium  of  the  air-cells  is  of  the  common  tessellated  kind, 
without  cilia,  and  composed  of  polygonal,  pale,  granular  cells,  in  mor- 

FIG.  238. — Human  air-cell,  with  the  surrounding  tissues,  magnified  350  diameters:  a, 
epithelium ;  6,  elastic  trabeculce ;  c,  more  delicate  wall  between  the  latter,  with  finer  elastic 
fibres. 


580  SPECIAL    HISTOLOGY. 

bid  states,  containing  fat,  0-005-0-007  of  a  line  in  diameter,  and 
0'003-0'004  of  a  line  in  thickness,  resting  immediately  upon  the 
fibrous  membrane  of  the  air-cells.  A  regular  detachment  of  this 
epithelium  is  not  to  be  supposed,  any  more  than  with  that  of  the 
trachea  and  bronchia?,  whilst  it  is  indubitable,  that  by  chance,  or  in 
diseases  of  the  air-passages,  its  isolated  elements  may  become  mixed 
with  the  bronchial  mucus.  In  Man,  these  cells  are  detached  with 
remarkable  readiness,  and  then  lie  free  in  the  air-cells  and  finest  ramifi- 
cations of  the  bronchice,  although  in  almost  every  lung,  at  all  events  in 
some  of  the  alveoles,  they  may  still  be  seen  in  situ ;  and  in  animals 
recently  killed,  the  observation  of  their  disposition  presents  no  difficulty 
whatever. 

The  interlobular  connective  tissue  of  the  lungs,  which  is  contained 
sparingly,  even  between  the  secondary  lobules,  and  between  the  primary, 
exists  in  inappreciably  minute  quantity,  consists  of  common  connective 
tissue  with  fine  elastic  fibres,  and  contains,  in  the  adult,  a  larger  or 
smaller  quantity  of  blackish  pigment,  in  the  form  of  irregular,  minute 
granules,  aggregations  of  granules,  arid  also  crystals,  which,  it  may  be 
said,  are  never  enclosed  in  cells.  The  walls  of  the  alveolce  themselves, 
also,  very  frequently  contain  this  pigment,  which,  when  it  is  deposited 
in  smaller  quantity  and  regularly,  marks  out  very  distinctly  the  con- 
tours of  the  secondary  lobules,  and  not  unfrequently,  also,  to  some 
extent,  those  of  the  primary. 

§  178.  Vessels  and  nerves  of  the  lungs. — As  regards  their  blood- 
vessels, the  lungs  occupy  a  unique  position,  inasmuch  as  they  possess 
two  complete  vascular  systems,  for  the  most  part  distinct  from  each 
other — that  of  the  bronchial  vessels,  for  the  nutrition  of  certain  por- 
tions, and  that  of  the  pulmonary  vessels,  for  the  fulfilment  of  their 
proper  function.  The  branches  of  the  pulmonary  artery  follow  pretty 
nearly  the  course  of  the  bronchial  tubes,  which  are  most  usually  placed 
below  and  behind  them,  with  this  difference,  that  they  divide  dichoto- 
inously  with  greater  frequency,  and  consequently  diminish  more  rapidly 
in  diameter.  Ultimately,  a  twig  goes  to  each  secondary  lobule,  which 
then  subdivides  into  still  finer  ramuscules,  in  general  corresponding  in 
number  with  the  smallest  lobules,  and  supplying  the  individual  air-cells. 
The  course  of  these  finest  lobular  arteries,  as  they  may  be  termed,  is 
very  easily  traced  in  injected,  inflated,  and  dried  preparations  ;  and  it 
is  apparent,  that  whilst  traversing  the  uniting  tissue  between  the 
lobules  (infimdibula),  they  supply  not  one  lobule  alone,  but  always  two 
or  even  three  of  them  with  finer  twigs.  These  penetrate  from  without, 
upon  and  between  the  air-cells,  divide  repeatedly  while  running  in  the 
larger  elastic  trabeculw,  anastomosing  also  occasionally,  though  not 


THE    LUNGS. 


581 


regularly,  with  each  other,  or  with  branches  of  other  lobular  arteries, 
and,  finally,  terminate  in  the   capillary  plexus  of  the   air-cells.     This 
plexus,    which  is   one   of  the 
closest   existing    in 
estimated  in   moist 


Fig.  239. 


Man,  as 
prepara- 
tions, presents  rounded  or 
oval  meshes  0-002-0-008  of 
a  line  wide,  and  vessels  of 
0-003-0-005  of  a  line  in 
diameter.  It  lies  in  the  wall 
of  the  air-cells,  at  a  distance 
of  about  0-001  of  a  line  from 
the  epithelium,  in  the  middle 
of  the  fibrous  tissue,  and  is 
continuous,  not  only  over  all 
the  alveola?  of  one  of  the 
smallest  lobules,  but,  also,  at 
all  events,  in  the  adult,  is 

partially  in  connection  with  the  plexuses  of  the  contiguous  lobules. 
The  pulmonary  veins  arise  from  the  above-described  capillary  plexus, 
with  roots  which  lie  more  superficial  than  the  arteries,  and  more  exter- 
nally on  the  smallest  lobules,  then  run  deeply  between  them,  and  unite 
with  other  lobular  veins  into  larger  trunks,  which  proceed  in  part  with 
the  arteries  and  bronchial  tubes,  in  part  more  isolated  by  themselves, 
through  the  pulmonary  parenchyma. 

The  bronchial  arteries  are  distributed,  firstly,  to  the  greater  bronchia, 
whose  vessels  present  the  same  conditions  as  those  of  the  trachea,  then 
to  the  pulmonary  veins  and  arterie?,  the  latter  of  which,  in  particular, 
possess  an  extremely  rich,  vascular  plexus,  which  may  be  traced  as  far 
as  branches  of  -J-  of  a  line,  and  less;  lastly,  to  the  pleura  pulmonalis,  the 
branches  destined  for  which  are,  some  of  them,  given  off  even  at  the 
hilus  and  in  the  fissures  between  the  main  lobes,  some  also  from  the 
vessels  accompanying  the  bronchia*,  coming  out  between  the  secondary 
lobules.  Small  vessels,  moreover,  which  are  not  derived  from  the 
bronchial  arteries,  pass  on  the  pulmonary  ligaments  to  the  pleura. 

The  lymphatics  of  the  lungs  are  very  numerous.  The  superficial 
lymphatic  vessels  run  in  the  subserous  connective  tissue  and  in  the  inter- 
spaces between  the  larger  and  smaller  lobules,  forming  a  superficial, 
finer,  and  a  deep,  coarser,  angular  network,  which  covers  the  entire  sur- 
face of  the  lungs,  and  on  the  one  hand  empties  itself  into  special,  super- 
ficial trunks  accompanying  the  bloodvessels  of  the  pleura  towards  the 
root  of  the  lung,  and,  on  the  other,  opens  into  the  deeper  vessels  by 
numerous  trunks  which  penetrate  between  the  lobules.  These  arise 

FIG.  239. — Capillary  plexus  of  the  human  air-cell,  magnified  GO  diameters. 


582  SPECIAL    HISTOLOGY. 

from  the  walls  of  the  bronchia  and  bloodvessels,  particularly  those  of 
the  pulmonary  arteries,  running  with  those  canals  through  the  substance 
of  the  lung,  and  through  some  minute  lymphatic  glands  (glandulce 
pulmonales),  towards  the  root  of  the  lung,  in  order,  ultimately,  to  com- 
municate with  the  larger  bronchial  glands. 

The  nerves  of  the  lungs  are  derived  from  the  vagus  and  sympathetic, 
form  the  more  scanty  plexus  pulmonalis  anterior,  and  the  richer  plex. 
p.  posterior,  and  are  distributed  principally  with  the  bronchia?  and  the 
pulmonary  artery,  occasionally,  however,  accompanying  the  pulmonary 
veins  and  vasa  bronchialia.  In  the  interior  of  the  lung  they  are  also 
furnished  with  microscopic  ganglia,  and  may  be  traced  nearly  to  the 
termination  of  the  bronchice. 

It  is  very  remarkable,  that  besides  the  air-cells,  some  other  parts  of 
the  lungs  are  also  supplied  by  the  vasa  pidmonalia,  such  as  the  surface 
of  the  lungs  and  the  finer  bronchia*.  With  respect  to  the  former,  even 
in  uninjected  lungs,  minute  ramuscules  of  the  pulmonary  artery  are 
apparent  in  various  situations  on  the  surface  of  the  lungs,  ramifying 
under  the  pleura.  Reisseisen  (p.  17)  describes  these  vessels,  and  figures 
them  very  beautifully  (Table  IV.,  Y.) ;  recently,  Adriani  has  traced 
them  in  injected  lungs  and  states  that  they  penetrate  into  the  interior, 
much  convoluted  and  frequently  anastomosing ;  they  are  considerably 
thicker,  however,  and  form  wider  plexuses  than  those  of  the  alveoli. 
The  blood  from  these  plexuses  is  conveyed  away,  on  the  one  hand,  by 
the  superficial  roots  of  the  pulmonary  veins,  and,  on  the  other,  through 
anastomoses  with  the  ramifications  of  the  vasa  bronchialia  in  the  pleura 
pulmonalis.  That  the  pulmonary  artery  also  supplies  the  bronchice  to 
some  extent  was  stated  by  Arnold  (Anat.  II.,  p.  171) ;  and  to  Adriani 
we  are  indebted  for  more  precise  information  on  this  interesting  subject. 
According  to  them,  the  pulmonary  artery  and  veins  chiefly  participate 
in  the  formation  of  the  capillary  plexus  on  the  surface  of  the  bronchice, 
which  is  characterized  by  the  elongated  form  of  its  meshes,  and  is  con- 
stituted by  vessels  almost  as  fine  as  those  of  the  air-cells  (in  Man,  of 
0-004-0-006  of  a  line),  whilst  the  bronchial  vessels  are  specially  destined 
for  the  supply  of  the  muscular  and  fibrous  coats  of  those  canals.  It  is 
comprehensible,  also,  that  in  this  situation  the  two  vascular  systems  are, 
to  a  certain  extent,  connected ;  and  consequently  the  older  anatomists, 
such  as  Haller,  Sommering,  and  Reisseisen,  who  speak  of  a  connection 
between  the  two  vascular  systems  of  the  lungs,  were  quite  right.  Ac- 
cording to  Adriani  and  Rossignol,  the  bronchial  arteries  and  veins  may 
be  injected  from  the  pulmonary  veins,  and  inversely,  the  pulmonary 
veins  from  the  bronchial  arteries ;  but  the  bronchial  vessels  cannot  be 
filled  from  the  pulmonary  arteries. 

In  accordance  with  these  facts,  a  participation  in  the  interchange  of 
gases  may  be  ascribed  also  to  the  finest  bronchice,  but,  on  account  of  the 


THE    LUNGS.  583 

already  somewhat  increased  thickness  of  the  epithelium  in  them,  and  the 
rather  wider  capillary  plexus,  to  a  less  extent  than  in  the  air-cells. 
Here,  also,  we  might  recall  to  mind  the  dilatation  of  the  bronchial  arte- 
ries and  extension  of  their  zone  of  distribution,  in  cases  where  the  circu- 
lation through  the  pulmonary  arteries  is  interrupted  (vide  Virchow,  in 
his  "  Archiv."  III.,  3,  p.  456),  in  which  cases  the  bronchial  arteries 
frequently  wholly  replace  branches  of  the  pulmonary  artery,  and  become 
respiratory  vessels ;  conditions  which,  from  the  occurrence  of  numerous 
normal  anastomoses  between  the  two  vascular  systems,  it  is  not  difficult 
to  explain. 

§  179.  Development  of  tlie  lungs. — In  the  Mammalia,  the  lungs  ap- 
pear a  little  after  the  liver,  in  the  form  of  two  hollow  protrusions  of  the 
anterior  wall  of  the  pharynx,  which  are  in  close  apposition,  and  soon 
become  furnished  with  a  common  peduncle — the  rudiment  of  the  larynx 
and  trachea — and  in  the  composition  of  which  the  epithelial  tube  and 
the  fibrous  membrane  of  the  intestine  take  an  equal  share. 

In  the  further  course  of  development,  there  springs  from  the  extre- 
mities of  the  original  protrusions,  a  continually  increasing  number  of 
arborescent  processes,  which  differ  entirely  from  what  may  be  observed 
in  most  other  glands.  From  their  first  formation  they  are  always  hollow, 
and  in  the  sixth  month  the  air-cells  are  developed  from  their  invariably 
clavate,  dilated  extremities.  During  this  growth  of  the  glandular  ele- 
ments, the  interior  epithelium  extends  itself  by  spontaneous  multiplica- 
tion of  its  cylindrical  cells  (probably  by  division),  whilst,  at  the  same 
time,  the  fibrous  layer  surrounding  them  also  grows,  and  finally  consti- 
tutes the  fibrous  membrane  of  the  bronchioe  and  air-cells,  together  with 
the  vessels  and  nerves.  In  the  second  month,  in  the  human  embryo, 
the  large  pulmonary  lobes  are  already  formed,  and  besides  them,  smaller 
divisions  also,  0-16  of  a  line  in  size,  may  be  recognized,  originating  in 
the  dilated  extremities  of  the  bronchia*,  which,  even  at  this  time,  are 
considerably  ramified.  As  development  proceeds  and  the  ramifications 
of  the  bronchice  are  multiplied,  these  gland-granules,  as  I  have  termed 
them,  become  more  and  more  numerous,  and  ultimately,  in  the  fifth 
month,  are  aggregated  so  as  to  form  smaller  lobules,  of  0-24-0-48  of  a 
line  in  size,  each  of  which,  in  all  probability,  is  produced  from  a  single 
gland-granule,  or  bronchial  termination  of  the  second  month.  Each  of 
the  gland-granules  of  these  lobules,  which  correspond  with  the  secondary 
lobules  of  the  future  lung,  by  continued  budding,  finally  constitutes  a 
primary  lobule,  which,  with  air-cells  of  0-025-0-3  of  a  line  in  size,  first 
becomes  distinctly  visible  in  the  sixth  month,  although,  up  to  the  time 
of  birth,  new  alveoli  are  constantly  superadded  (vide  "Mikr.  Anat." 
II.  2,  p.  323).  In  the  new-born  child  the  secondary  lobules  measure 
2-3-4  lines  ;  the  alveoli,  before  they  are  filled  with  air,  0-03,  and  after 


584  SPECIAL    HISTOLOGY. 

the  first  inspiration,  O-Oo-OO-l-O-OG  of  a  line  ;  the  latter,  at  this  time, 
•appear  to  exist  in  the  same  number  as  in  the  adult,  the  further  increase 
of  the  lungs  proceeding  only  from  the  expansion  of  all  its  parts. 

[The  pathological  changes  occurring  in  the  tissue  of  the  lung  are 
numerous.  An  atrophy  of  the  parenchyma  takes  place  in  old  age  and 
in  emphysema.  In  the  former,  a  thinning  of  the  walls  of  the  air-cells, 
and  a  partial  obliteration  of  the  capillaries  exists.  In  emphysema  the 
alveoli  of  the  cells  are  enlarged,  but  the  walls  much  attenuated;  some- 
times their  rupture  ensues  and  a  communication  between  the  sepa- 
rate cells  is  established.  Hypertrophy  of  the  air-cells,  with  ejilarge- 
ment  of  the  capillaries,  is  observed  in  the  hypertrophy  of  the  lung 
which  occurs  from  increased  functional  action.  Obliteration  of  the  air- 
cells  is  mostly  caused  by  exudation  or  deposit  into  the  air-vesicles  or 
the  interstitial  tissue.  In  pneumonia  this  exudation  occurs  mainly 
into  the  alveoli,  sometimes,  however,  into  the  walls  of  the  cell,  the 
interstitial,  or  even  into  the  interlobular  tissue  (interlobular  pneumonia). 
The  granular  appearance  of  red  hepatization  is  owing  to  a  complete  ex- 
pansion of  the  air-cells  by  the  plastic  exudation.  In  gray  hepatization 
the  walls  of  the  cells  and  the  interstitial  tissue  become  softened,  and 
undergo  a  fatty  metamorphosis. 

Deposits  of  pigment  occur  as  a  consequence  of  hepatization,  or  from 
a  simple  congestion  of  the  lung.  The  pigment  is  found  in  the  inter- 
stitial tissue,  and  sometimes  exists  in  sufficient  quantity  to  compress 
the  air-vesicles  and  produce  their  atrophy.  It  is  formed  either  from 
the  coloring  matter  of  the  blood,  or  else  by  the  blood  corpuscles  break- 
ing up  into  distinct  pigment-cells  and  granules  (Yirchow).  Tubercle 
is  most  generally  deposited  in  the  air-cells ;  cancer  more  frequently  in 
the  interstitial  tissue. 

Effusions  of  serum,  or  of  blood,  occur  either  into  the  interstitial 
tissue,  or  into  the  air-vesicles.  In  oedema  the  effused  serum  has  its 
seat  in  the  air-cells,  whilst  in  apoplexy  of  the  lung,  the  blood  is  effused 
in  the  interstitial  tissue.  A.  fatty  degeneration  of  the  epithelial  cells  is 
observed  in  portions  of  lung,  compressed  by  a  pleuritic  effusion,  in  ate- 
lectasis  (Reinhardt),  and  in  splenization.  Accidental  formations  (bone, 
cartilage)  and  cysts  have  their  seats  generally  in  the  interstitial  tissue. 
Destruction  of  the  parenchyma  of  the  lung  is  the  result  of  inflammation, 
gangrene,  tubercle,  or  cancer.  A  microscopical  examination  of  the  de- 
stroyed parts  shows  them  to  be  infiltrated  with  fine  fatty  molecules;  the 
elastic  elements  of  the  air-cells  are  generally  found  well  preserved. — DaC.] 

The  investigation  of  the  lungs  presents  no  real  difficulty,  except  in 
one  point ;  that  is,  with  respect  to  the  relation  of  the  pulmonary  cells 
to  the  terminations  of  the  bronchice,  but  here  the  difficulties  are  very 


THE    THYROID    GLAND.  ,      585 

considerable.  In  recent  preparations  it  is  obvious  that  the  air-cells 
communicate  in  many  ways,  and  in  any  case,  that  they  are  not  merely 
terminal  on  the  extremities  of  the  branchiae.  If  it  be  desired  to  investi- 
gate the  whole  subject,  inflated  and  dried  lungs  (it  is  better  in  an 
inflated  lung  to  tie  off  an  end  and  dry  it  by  itself),  or  corroded  prepara- 
tions, or  lungs  injected  with  uncolored  substances  (wax  and  resin)  are 
most  suitable,  and  with  such,  a  definite  result  will  be  obtained,  after  a 
series  of  observations. 

Before  the  injection  of  the  bronchice  is  proceeded  with,  the  air  must 
be  exhausted  in  the  air-pump,  for  which  purpose,  also,  though  less  con- 
veniently, a  well-fitted  syringe  may  be  employed.  The  injection  of  the 
bloodvessels  is  readily  effected  and  the  preparations  should  be  kept 
wet;  sometimes,  when  injected  with  opaque  material,  sometimes,  follow- 
ing the  processes  of  Schroder  and  Halting,  with  transparent  substances 
(Prussian  blue,  &c.),  dried  preparations  are  to  be  preferred.  The  air- 
cells  and  bronchia?,  the  larynx  and  trachea,  are  readily  examined.  The 
epithelium  of  the  air-cells  is  obtained  in  large  quantity  in  every  section 
through  the  lung,  as  well  as  ciliated  cells.  If  it  be  wished  to  study  the 
alveoli,  the  air  must  previously  be  carefully  removed.  These  are  best 
displayed  in  Man,  in  whom,  also,  all  the  other  parts,  such  as  cartilage, 
elastic  elements,  muscles,  and  glands,  are  easily  obtainable. 

Literature. — M.  Malpighi,  "De  pulmonibus  epistolse  II  adBorellum." 
Bonon.  1661;  F.  D.  Reisseisen,  "  Ueber  den  Bau  der  Lungen,  eine 
gekrbnte  Preisschrift,"  Berlin,  1822;  [Magendie,  "  Mdm  sur  la  struc- 
ture du  poumon,  in  <  Journ.  de  Phys.  exper. ;'  "  Rainey,  "  On  the  minute 
structure  of  the  lungs,"  Philosoph.  Transact.  1845;]  J.  Moleschott,  "De 
Malpighianis  pulmonurn  vesiculis,"  Heidi.  1845,  Diss.  and,  "  Ueber  die 
letzten  Endigungen  der  feinsten  Bronchien,"  in  the  Hollandischen 
Beitragen,  I.  p.  7  ;  Rossignol,  "  Recherches  sur  la  structure  intime  du 
Poumon,  Brux.,"  1846;  A.  Adrian!,  "De  subtiliori  pulrnonum  struc- 
tura."  Trajecti  ad  Rhen.  1847,  Diss.;  Kostlin,  "  Zur  normalem  und 
patholog.  Anatomic  der  Lungen,"  in  Gries.  "  Archiv,"  1848,  Heft.  IV. 
p.  282,  and  1849,  Heft  II.  p.  167  ;  E.  Schultz,  "  Disquisitiones  de  struc- 
tura  et  textura  canalium  aeriferorum,"  cum  tab.,  DorpatiLiv.  1850. 
Dissert. 

OF  THE  THYROID  GLAND. 

§  180.  The  thyroid  gland,  or  body  (glandula  thyroidea),  is  a  so-termed 
"  ductless  gland,"  which  in  its  external  aspect  much  resembles  the  race- 
mose glands,  seeing  that  its  round,  closed  gland-vesicles,  ^-oV  of  a  ^ne 
in  size,  are  surrounded  by  a  fibrous  stroma  and  subdivided  into  rounded 
or  elongated,  often  slightly  polygonal  lobules,  J-J  of  a  line  in  size, — 
the  gland- granules  of  authors  ; — and  these  again  are  associated  into 
larger,  though  not  completely  separated,  lobes,  out  of  which  the  main 


586 


SPECIAL    HISTOLOGY. 


divisions  of  the  organ  are  then  constituted ;  these  have  special,  and 
indeed  thicker  coats,  with  which,  lastly,  a  fibrous  membrane  investing 
the  whole  organ  is  conjoined. 

§  181.  With  respect  to  its  intimate  structure,  there  is  not  much  to 
be  said  about  the  fibrous  tissue  or  stroma  of  the  thyroid  gland,  inasmuch 
as  it  consists  of  common  interlaced  bundles  of  connective  tissue,  inter- 
mixed with  fine  elastic  fibres  and  also,  on  the  surface,  contains  a  certain 
quantity  of  fat-cells.  The  gland  vesicles  themselves,  in  Man,  present 
such  varied  conditions  of  structure,  that  it  is  not  easy  to  say  what  is 
their  normal  state.  According  to  what  I  have  observed  in  Man  and 
also  in  animals,  I  must,  with  regard  to  this  point,  declare  that,  analo- 
gous to  the  true  gland  vesicles,  for  instance,  of  the  mucous  glands,  they 
consist  of  a  membrana  propria,  an  epithelium,  and  fluid  contents.  The 
membrane  is  quite  homogeneous,  transparent,  and  delicate,  0*0008  of  a 
line  thick  ;  and,  like  all  membranes  of  the  sort,  is  rendered  more  distinct 
by  caustic  alkalies,  in  which  it  swells  up.  On  its  inner  surface  lies  a 
single  layer  of  epithelium,  composed  of  polygonal,  finely  granular,  trans- 
parent cells  of  0-004-0-006  of  a  line,  with  simple  nuclei ;  whilst  the 
space  surrounded  by  these  cells  is  occupied  with  a  clear,  somewhat  vis- 
cous fluid,  with  a  tinge  of  yellow 
in  its  color,  the  behavior  of  which 
towards  alcohol  and  nitric  acid 
and  when  the  gland  is  boiled, 
clearly  manifests  the  presence  of 
much  albumen.  This  is  the  cha- 
racter of  the  contents  in  the  healthy 
thyroid  gland  of  Man,  particularly 
in  children  ;  if  the  organ,  how- 
ever, is  but  very  little  altered, 
conditions,  in  many  respects  dif- 
ferent, are  presented.  Very  fre- 
quently, instead  of  a  regular 
epithelium,  nothing  is  met  with 
but  a  fluid  mixed  with  minute, 


f 


clearer  or  darker  granules  and  free 


nuclei ;  although  I  am  ignorant  whether  this  condition  of  the  contents 
does  not  take  place  till  after  death,  or  whether  it  is  to  be  regarded  as 
abnormal.  For  we  so  frequently  observe,  in  the  granular  fluid,  a  greater 
or  less  number  of  the  same  cells,  which  at  other  times  exist  as  epithe- 
lium, often  pale  and  as  if  half  dissolved,  that  it  is  impossible  to  avoid 
the  conclusion,  that  in  these  cells  we  have  an  instance  of  that  post-mor- 
tem decomposition,  so  frequently  observed  in  the  human  subject.  On 
the  other  hand,  the  pathological  nature  of  the  change  in  the  thyroid 


FIG.  240. — Some  gland-vesicles  from  the  thyroid  gland  of  a  Child,  magnified  250  diam. : 
cr,  connective  tissue  between  them;  b,  membrane  of  the  gland-vesicles;  c,  their  epithelium. 


THE    THYROID     GLAND. 


587 


Fig.  241. 


body  and  its  vesicles,  termed  colloid,  cannot  be  doubted,  although  this 
morbid  condition  is  so  frequent,  in  certain  minor  degrees,  that  many 
authors  enumerate  it  under  the  physiological  occurrences.  In  this  de- 
generation, there  is  deposited  in  the  gland  vesicles,  which  increase  in 
size  at  the  same  time,  the 
colloid  substance,  which  also 
occurs  in  other  situations,  in 
the  form  of  transparent,  amor- 
phous, light  yellowish,  soft, 
solid,  masses,  by  which  they 
are  more  or  less  filled.  In  the 
lesser  degrees  of  this  change, 
the  vesicles  are  but  little  en- 
larged, to  as  much  as  0-05  of 
a  line  in  a  transverse  section, 
presenting  the  appearance 
of  transparent  yellowish-white 
spots  or  granules,  which  have 
been  very  aptly  compared,  by  Ecker,  with  boiled  sago,  and  otherwise 
retaining  the  usual  structure.  In  a  higher  degree,  the  vesicles  contain- 
ing colloid  are  transformed  into  larger  cysts,  of  yo-J  of  a  ^ne?  in  which 
the  epithelium  is  rarely  any  longer  distinct,  but,  together  with  the  ab- 
normal contents,  rounded,  pale  cells,  filled  with  colloid  matter  or  gra- 
nules, and  nuclei,  may  occur  ;  these  cysts  compress  the  stroma  and 
ultimately,  owing  to  a  partial  absorption  of  the  walls,  coalesce  into  still 
larger  sinuous  cavities,  the  contents  of  which  are  afterwards  frequently 
altered  in  various  ways,  by  extravasations  and  their  metamorphoses. 
In  Mammalia  and  Birds,  the  thyroid  body  also  occasionally  contains 
gland-vesicles  slightly  distended  with  colloid  matter. 

The  bloodvessels  of  the  thyroid  gland  are,  as  is  well  known,  dispro- 
portionately numerous,  but  in  their  coarser  ramifications  present  nothing 
worthy  of  remark.  Each  gland-vesicle  is  provided  with  some  smaller 
arteries,  the  subordinate  branches  of  which  are  distributed  and  sub- 
divided in  the  stroma  between  the  vesicles,  finally  constituting  around 
each  of  them  a  delicate  capillary  plexus,  with  rounded-angular  and 
elongated  meshes  of  0-008-0-016  of  a  line,  and  vessels  of  0-003-0-005 
of  a  line,  resembling  that  of  the  air-cells,  except  that  the  interstices  are 
wider.  From  this  plexus  the  veins  arise,  which,  in  their  further  course, 
only  partially  accompany  the  arteries,  which  they  much  exceed  in 
number.  Lymphatics  also  occur  in  considerable  number  in  the  thyroid 
gland;  the  relations  of  which,  however,  in  the  interior,  are  unknown. 
The  few  nerves,  lastly,  are  only  vascular  nerves,  and  are  derived  from 
the  cervical  portions  of  the  sympathetic. 

FIG.  241. — Gland-vesicles  of  the  thyroid  gland,  filled  with  colloid  matter,  magnified  50 
diameters. 


588  SPECIAL    HISTOLOGY. 

Ecker  distinguishes  the  struma,  which  is  by  far  the  most  frequent 
degeneration  of  the  thyroid,  into  a  vascular  and  a  glandular.  In  the 
latter,  the  above-described  changes  of  the  gland-vesicles  take  place, 
whilst  in  the  vascular  struma,  which  is  not  regarded  by  Rokitansky  as 
a  special  form,  besides  a  hyperoemiated  condition,  numerous  aneurismal 
dilatations  of  the  smaller  vessels,  for  the  most  part  of  those  0*030-0-040 
of  a  line  in  size,  which  Ecker  looks  upon  as  arteries  and  larger  capilla- 
ries, are  met  with.  From  the  bursting  of  these  dilatations,  apoplectic 
cysts,  of  various  sizes,  subsequently  ensue,  which  may  exhibit  phases  of 
the  most  various  kinds,  as  the  blood  undergoes  changes  of  one  kind  or 
another ;  fresh  extravasations,  and  also  exudations,  are  superadded,  and 
even  'normal  tissue  becomes  involved  in  them.  In  vascular  struma, 
Ecker  also  very  frequently  met  with  a  Gratification  of  the  vessels,  con- 
sisting in  the  deposition  of  numerous  scattered  calcareous  particles  in 
the  walls  of  the  smaller  and  smallest,  dilated  or  normal  vessels,  so  that 
they  appeared  quite  white;  and  when  the  affection  had  advanced  to  the 
highest  stage,  were  obliterated  and  became  concretions.  In  a  certain 
form  of  scrofula,  Rokitansky  describes  an  hypertrophy  of  the  thyroid 
gland,  due  to  a  multiplication  of  the  normal  glandular  elements,  taking 
place  by  the  production  of  new  gland-vesicles,  sometimes  independent, 
sometimes  occurring  in  enlarged  gland-vesicles,  in  growths  inwards  of 
their  walls. 

According  to  Remak,  the  thyroid  body  is  developed  by  the  constric- 
tion of  a  portion  of  the  anterior  wall  of  the  pharynx,  and  the  division 
of  this  into  two  halves.  In  a  human  embryo,  at  the  third  month,  I 
found  that  the  thyroid  body  was  already  composed  of  isolated  vesicles 
0-016-0-05  of  a  line  in  size,  consisting  of  a  homogeneous  envelop  and 
rounded-angular  cells  in  the  interior,  and  I  think  I  perceived  that  this 
follicle  was  multiplied  by  the  formation  of  rounded  buds  and  their  sepa- 
ration by  constriction.  If  this  really  be  the  case,  the  entire  develop- 
ment, probably,  of  the  thyroid  gland  would  have  to  be  regarded  as  a 
continued  growth  and  division  of  the  glandular  follicles,  of  which  the 
fission  of  the  primary  vesicular  rudiment,  observed  by  Remak,  would  be 
merely  the  first  phase.  In  this  respect,  also,  a  certain  resemblance 
with  the  tJiymus  would  be  established,  only  that  in  the  latter,  both  the 
buds  of  the  primary  rudiment,  as  well  as  the  later  ones,  are  not  de- 
tached, but  all  remain  in  connection.  The  follicles  of  the  thyroid 
gland,  therefore,  would  not  be  any  kind  of  enlarged  cells,  and  still  less 
metamorphosed  nuclei  (Rokitansky),  but  be  equivalent  to  true  gland- 
follicles. 

The  investigation  of  the  vesicles  of  the  thyroid  gland  has  mainly  been 
pursued  in  animals,  especially  in  Birds,  Amphibia,  and  in  children; 
and  sections  obtained  by  means  of  the  double-bladed  knife,  or  glands 
that  have  been  hardened,  are  most  suitable  for  the  purpose  of  studying 


THE    THY  M  US.  589 

the  vesicles  in  detail,  and  in  their  mutual  relations ;  but  the  same  object 
may  also  be  attained  by  minute  dissection,  and  the  teasing  out  of  the 
structure.  Injections  are  very  easily  made  and  run  very  finely  in 
children  ;  they  best  exhibit  the  plexuses  around  the  vesicles,  in  sections 
taken  from  the  surface. 

Literature.  —  Schwager-Bardeleben,  "  Obs.  micr.  de  glandularum 
ductu  excret.  carentium  structura,"  Berol.  1841,  Diss. ;  Panagiotides 
and  K.  Wagener,  "Einige  Beobachtungen  uber  die  Schilddriise,"  in 
Froriep's  "N.  Notiz."  Bd.  XL.,  p.  193-  and  Panagiotides,  "De  gland, 
thyreoidese  structura,  penitiori,"  Diss.  Berol.,  184T ;  A.  Ecker,  "Ver- 
such  einer  Anatomic  der  primitiven  Formen  des  Kropfes,  &c.,"  in 
"Henle  and  Pfeuifer's  Zeitschrift,"  f.  rat.  Med.  VI.,  Bd.,  p.  123,  and 
Article  "  Blood-vascular  glands,"  in  Wagner's  "  Handw.  d.  Physiol." 
III.;  Rokitansky,  in  "  Zeitsch.  d.  Wiener  Aerzte,"  1847,  and  "  Zur 
Anatomic  des  Kropfes,"  in  "  Denkschriften  der  kaiserl.  Akad.  zu 
Wien,"  Bd.  L,  Wien,  1849. 

OF  THE  THYMUS. 

§  182.  The  internal  thoracic  gland  or  thymus,  also  one  of  the  so- 
termed  blood-vascular  glands,  is  a  bilobate,  elongated,  flattened  organ, 
broad  iriferiorly,  invested  and  united  to  the  surrounding  parts  by  a  lax 
connective  tissue.  Larger  lobules,  measuring  on  the  average  2-5  lines, 
and  of  a  rounded,  oval,  or  pyriform  shape,  though  for  the  most  part 
flattened  figure,  are  very  distinctly  apparent,  even  on  superficial  in- 
spection ;  these,  although  pretty  closely  approximated,  are  still  united 
merely  by  a  yielding  connective  tissue,  and  may  be  separated  without 
difficulty.  If  these  lobules  be  traced  from  without  inwards,  it  is  easily 
perceived  that  they  have  no  further  mutual  connection,  although  they 
are  invariably  attached  by  a  more  slender  portion,  to  a  canal,  which 
traverses  the  interior  of  the  gland,  and  is,  in  general,  spirally  convo- 
luted, though  not  quite  regularly  so.  When  this  canal,  normally  J-1J 
lines  in  diameter,  is  opened,  there  are  found  on  its  inner  surface  a  great 
number  of  oval  fissures  or  apertures,  each  of  which  leads  to  a  lobule  and 
constitutes  the  outlet  of  a  cavity  contained  in  it.  The  resemblance  of 
this  canal  of  the  thymus  and  of  the  closely  approximated  lobules  open- 
ing into  it,  to  the  excretory  duct  and  the  lobules  of  a  true  gland,  is  still 
further  heightened  by  the  circumstance,  that  the  lobules  are  composed 
of  smaller,  also  hollow  subdivisions  and  the  latter  of  rounded  cor- 
puscles, 1-5-1-3  of  a  line  in  size,  like  gland-vesicles,  the  gland-granules 
(acini  of  authors),  which  may  be  recognized  even  on  the  exterior,  and, 
from  their  polygonal  shape,  give  the  surface  of  the  lobules  a  delicate 
mosaic  aspect,  not  unlike  that  of  the  lungs.  These  gland-granules, 
however,  are  not  vesicles  at  all,  such  as  the  air-cells,  which,  among  the 


590 


SPECIAL    HISTOLOGY. 


elements  of  the  true  glands,  approach  nearest  to  them  in  size,  but  solid 
bodies,  which,  towards  the  cavity  of  the  lobules  or  its  accessory  cavities, 
are  intimately  coherent,  whilst  on  the  outer  side  they  are  separated 


Fig.  242. 


Fiff.  243. 


from  each  other.  Each  lobule  may  also  be  regarded  as  a  thick-walled 
vesicle,  with  protrusions,  whose  inner  surface  is  even  and  continuous, 
whilst  the  outer  is  subdivided  into  the  above-mentioned  gland-granules, 
by  more  or  less  deep  fissures. 

In  many  cases,  a  condition  different  from  that  just  described  is  met 
with,  inasmuch  as,  instead  of  a  contracted  canal,  into  which  the  cavities 
of  the  gland-lobules  open,  each  thymus  contains  a  larger  though  con- 
tracted cavity^  J-l  inch  wide,  with  which  the  gland-lobules  communi- 
cate by  larger  fissure-like  openings.  Many  anatomists,  and  among  the 
more  modern,  particularly  Sir  A.  Cooper,  consider  the  existence  of  this 
cavity  as  normal ;  whilst  others,  at  the  head  of  whom  is  Simon,  are  dis- 
posed to  regard  it  as  produced  by  the  methods  of  investigation  employed 

FIG.  242. — Portion  of  the  thymus  of  a  Calf,  unfolded  :  a,  main  canal ;  b:  glandular  lobules  5 
c,  isolated  gland-granules,  seated  upon  the  main  canal.  Natural  size. 

FIG.  243. — Half  of  the  human  thymus,  with  a  large  cavity  in  the  inferior  wide  portion 
and  numerous  orifices  leading  into  the  lobules. 


THE    THYMUS. 


591 


Fig.  244. 


(injections,  inflation).  I  believe  that  Simon  is  correct,  when  he  asserts 
that  in  such  a  delicate  structure  as  the  thymus^  injection  or  inflation, 
unless  effected  with  the  greatest  care,  necessarily  leads  to  error,  and  I  am 
also  satisfied,  that  many  of  the  observed  "  reservoirs"  in  the  tliymus 
are  only  artificially  produced  ;  but,  nevertheless,  I  am  of  opinion,  that 
there  really  "are  thymus  glands,  containing,  in  life,  a  central  cavity 
because  I  have  seen  such  cavities  extending  through  the  entire  tliymus 
or  only  through  separate  segments  of  it,  and  this  in  cases  where  no  pre- 
paration of  any  kind  or  injection  had  been  used.  I  look  upon  the  oc- 
currence of  a  narrow  central  canal,  as  the  original  and  usual  condition, 
but  believe,  that  in  certain  cases  it  may  be  expanded  by  a  more  abun- 
dant formation  of  the  secretion,  and  ultimately  be  converted  into  a  large 
cavity. 

§  183.  Intimate  structure  of  the  thymus. — When  a  lobule  is  stripped 
of  its  investing  coat,  consisting  of  common  connective  tissue,  with  fine 
elastic  fibres  of  the  finer  sort  and  fre- 
quently with  scattered  fat-cells,  its  ex- 
ternal surface,  fissured  in  correspon- 
dence with  the  separate  gland-granules, 
comes  into  view.  Under  strong  mag- 
nifying powers,  there  is  now  presented 
a  very  thin  (0-0005-0-001  of  a  line), 
indistinctly  fibrous,  or  almost  homo- 
geneous membrane,  quite  correctly  de- 
scribed by  Simon,  which  is  continuous 
over  an  entire  lobule  or  even  the  whole 
gland,  and  must  be  placed  in  the  same 
category  with  the  wall  of  the  follicles 
in  Peyer's  patches,  the  tonsils,  &c. 
Within  this  envelop,  between  it  and 
the  cavity  of  the  lobule,  lies  a  grayish- 
white,  soft,  easily  lacerable  substance, 
i~i  °f  a  line  thick,  which,  when  ex- 
amined microscopically,  appears  to  consist  of  nothing  but  free  nuclei 
and  minute  cells,  and  on  this  account  has,  by  agreement  of  all  obser- 
vers, hitherto  been  regarded  as  the  secretion  of  the  supposed  gland- 
vesicles.  But  this  substance  cannot  be  washed  away,  which  would  have 
been  the  case  had  it  lain  loosely  in  the  space  enclosed  by  the  delicate 
membrane ;  on  the  contrary,  it  exhibits  a  considerable  degree  of  tough- 
ness and  resistance.  When  examined  more  closely,  it  is,  by  degrees, 

FIG.  244. — Transverse  section  through  the  summit  of  an  injected  lobule  of  the  thymus  in 
a  Child,  magnified  SOdiarn.:  cr,  membrane  of  the  lobule  ;  6,  membrane  of  the  gland-granules; 
c,  cavity  of  the  lobule  from  which  the  larger  vessels  branch  out  into  the  granules,  on  the 
surface  of  which  they  terminate,  occasionally  forming  loops. 


592  SPECIAL    HISTOLOGY. 

apparent  that  other  elements,  to  some  extent  of  quite  an  unexpected 
kind,  enter  into  its  composition  ;  as  for  instance,  bloodvessels,  and  also 
a  smaller  quantity  of  a,  fibrous  substance  of  the  nature  of  connective  tis- 
sue, so  that  a  structure  not  unlike  that  of  the  contents  of  the  Peyerian 
follicles  is  presented. 

Of  the  elements  of  the  walls  of  the  thymus-lobules,  the  vesicular, 
together  with  a  small  quantity  of  a  connecting  fluid,  constitute  the  main 
bulk.  Among  these,  free  nuclei  0-002-0-005  of  a  line  in  size,  of  a 
round  slightly  flattened  shape,  with  homogeneous,  clear  contents,  which 
become  troubled  and  granular  in  soda  and  acetic  acid  and  with  or  with- 
out a  micleolus,  are  always  present  in  very  great  numbers.  Secondly, 
as  I  find,  agreeing  with  Ecker  but  in  opposition  to  Simon,  cells  also  are 
never  wanting,  though  existing  of  very  various  sizes,  from  0-004  to  0-01 
of  a  line,  and,  though  varying  in  number  as  well,  still  much  less  nu- 
merous than  the  nuclei.  Their  nuclei  are  for  the  most  part  simple  and 
distinct,  and  the  contents  pale  or  with  scattered  fat-granules,  or,  and 
this  Ecker  says  that  he  has  noticed  after  the  complete  development  of 
the  organ,  they  are  without  nuclei  and  entirely  filled  with  fat.  In  the 
midst  of  these  elements  run  numerous  bloodvessels  of  larger  and  smaller 
size.  The  main  trunks  running  on  the  outer  aspect  and  close  upon  the 
central  cavity  in  the  longitudinal  direction  of  the  organ,  give  off  a  large 
number  of  branches  to  the  central  cavity,  which,  penetrating  its  walls, 
reach  its  internal  surface,  and  there  ramify  minutely  in  a  delicate  pelli- 
cle, composed  of  connective  tissue,  with  which  it  is  lined,  anastomosing 
and  also  forming  tolerably  close  capillary  plexuses.  From  these  arterial 
plexuses,  at  every  point  where  the  lobules  open,  numerous  vessels  arise 
and  enter  them,  taking  their  course  in  the  innermost  portion  of  the 
thick  boundary  wall,  and  then  ramify  towards  the  exterior  in  the  sepa- 
rate gland-granules,  so  as  to  constitute  a  capillary  plexus  entirely  filling 
them,  composed  of  vessels  0-003-0-005  of  a  line  in  diameter,  and  with 
meshes  of  0-01-0-02  of  a  line  (Fig.  244).  The  distribution  of  these 
vessels,  in  Man,  is  so  limited  to  the  interior  of  the  gland-granules,  that, 
even  when  these  have  been  most  completely  displayed,  not  a  single  vessel 
is  found  on  the  outer  aspect  of  their  structureless  investing  membrane ; 
on  the  contrary  they  are  all  seen  terminating  in  loops  close  upon  it. 
Besides  these  bloodvessels  a  small  quantity  of  connective  tissue  also  ap- 
pears to  enter  into  the  formation  of  the  thick  walls  of  the  glandular 
lobes  ;  at  all  events,  in  their  innermost  portions,  where  the  larger 
vessels  are  situated,  we  find,  often  with  tolerable  distinctness,  a  mem- 
brane supporting  them,  analogous  to  that  lining  the  central  cavity.  In 
other  cases,  hewever,  and  especially  in  animals,  an  internal  limitary 
membrane  of  this  kind  cannot  be  demonstrated,  and  the  cavities  of  the 
lobules  are  bounded  immediately  by  the  granular  substance  connecting 
the  vessels,  between  which,  only  some  delicate  indications  of  fibres  are 


THE    TIIYMUS.  593 

apparent.  In  no  case  does  there  exist  any  epithelium  lining  the  cavi- 
ties and  consequently,  the  comparison  of  the  innermost  part  of  their  wall 
with  a  mucous  membrane  is  untenable. 

The  common  cavity  or  central  canal  of  the  thymus,  presents  the  same 
structure  as  the  lobules,  except  that  externally  there  is  a  thicker  fibrous 
layer,  and  internally  a  less  thick  granular  stratum,  with  rather  larger 
vessels.  In  a  fully  developed  thymus  it,  as  well  as  all  the  secondary  cavi- 
ties, contains  a  grayish-white  or  milky,  faintly  acid  fluid,  often  in  large 
quantity,  in  which,  together  with  a  clear  fluid  abounding  in  albumen, 
numerous  nuclei,  isolated  cells  and,  under  certain  circumstances,  also 
concentrical  corpuscles  (vide  infra)  are  contained.  The  lymphatics  of 
the  thymus  are  numerous  and  nerves  may  be  readily  demonstrated  upon 
the  arteries,  although  they  cannot  be  traced  as  far  as  their  terminations. 

Besides  the  above-described  normal  elements,  there  occur,  especially 
at  the  period  of  involution  of  the  organ,  other  peculiar  spherical  struc- 
tures, which,  with  Ecker,  I  would  term  the  concentric  corpuscles  of  the 
thymus.  They  present  very  various  forms,  which,  however,  it  seems  to 
me  may  conveniently  be  reduced  to  two;  viz.  1,  simple,  O'OOG-OOl  of 
a  line  in  size,  with  a  thick  concentrically  striated  membrane  and  a  granu- 
lar substance  in  the  interior,  sometimes  appearing  like  a  nucleus,  some- 
times as  a  cell ;  and  2,  compound,  as  much  as  0*04  or  even  0*08  of  a 
line  in  size,  arid  consisting  of  several  simple  corpuscle^,  surrounded  by 
a  common  laminated  envelop.  These  bodies,  which  were  first  noticed 
by  Hassall  and  Virchow,  and  were  further  investigated  by  Ecker  and 
Bruch,  it  appears  to  me  arise  not  from  a  direct  metamorphosis  of  the 
nuclei  and  cells  in  the  wall  of  the  glandular  lobule,  but  from  the  succes- 
sive deposition  of  an  amorphous  material  around  them ;  and  conse- 
quently that  they  are  analogous  in  their  mode  of  formation  to  the  cor- 
puscula  amylacea  of  the  brain,  the  prostatic  concretions,  &c.  The  lami- 
nated portion  consists  of  a  substance  certainly  not  of  a  fatty  nature 
which  offers  considerable  resistance  to  alkalies,  approaching  the  colloid 
substance  and  the  substance  of  the  prostatic  concretions  and  corpuscula 
amylacea,  being  probably  formed  from  a  change  in  the  albumen  in  the 
glandular  walls.  The  situation  of  these  concentric  corpuscles  is  ex- 
ternal to  the  secretion  of  the  thymus,  and  principally  in  the  innermost 
part  of  the  glandular  parietes,  where  the  larger  vessels  occur.* 

§  184.  Development  of  the  Thymus. — According  to  Remak,  the  thymus 
of  the  Chicken  originates  in  the  separation,  by  constriction,  of  the  bor- 
ders of  the  last  two  (third  and  fourth)  branchial  fissures,  which  are  lined 

*  [Whatever  may  be  the  true  nature  of  the  Hassallian  corpuscles,  they  do  not  seem  to  be 
an  essential  element  of  the  thymus  or  its  secretion,  as  they  are  not  found  in  that  body  in 
Fishes  (Skate,  Ray,  Sturgeon,  Zeusfabcr)-  although  present  in  the  Reptilia.  Ley  dig,  ':  Amu. 
histol.  Untersuchung.  ti.  Fische  und  Reptilien,"  pp.  21  and  GO. — TRS.] 


594  SPECIAL    HISTOLOGY. 

by  the  intestinal  epithelium  ;  and  at  the  period  when  the  last  three  aortic 
arches  become  detached  from  the  walls  of  the  pharynx,  these  follow 
them,  and  eventually  lie  as  two  elongated  sacculi,  on  each  side,  between 
them. 

In  the  earliest  state  observed  in  Mammalia,  e.  g.,  in  the  foetal  Calf,  1 
line  long,  according  to  BischofF  the  gland  represents  two  delicate  tracts 
of  blastema,  which  descend  from  the  larynx  as  far  as  the  thorax  and  ap- 
pear to  be  connected  above  with  the  thyroid  body.  Simon  gives  a  simi- 
lar description  of  the  tJiymus  in  the  foetal  Calf  and  Swine,  j— 1 J  inches 
long,  except  that  he  makes  no  mention  of  any  connection  with  the  thy- 
roid body,  figuring  the  tract  as  a  tube  bounded  by  a  delicate  structure- 
less membrane  and  filled  with  nuclei  and  a  granular  substance,  which  is 
further  developed  by  becoming  thicker  and  longer,  whilst  at  the  same 
time  it  pushes  out,  at  first,  simple  and  afterwards,  more  and  more  widely 
ramifying  buds.  Thus  in  foetal  calves,  2J-3  inches  long,  wart-like  and 
spherical,  in  part  even  shortly  pedunculated  offsets  already  existed, 
which  subsequently  increased  in  number,  becoming  produced,  at  first  into 
two  and  four  and  afterwards,  successively,  into  still  more  globular  bodies, 
until  ultimately  the  lobules  were  completed.  In  this  way  the  primitive 
tube  would  be  converted  into  the  central  cavity  of  the  tliymus  and  each 
offset  of  it,  in  course  of  time,  into  an  entire  lobule  of  the  organ.  In 
the  human  subject,  as  early  as  in  the  seventh  week,  I  have  seen  the 
tliymus  lobate  at  the  lower  end  and  single  above.  In  an  embryo  ten 
weeks  old,  the  upper  extremity  was  a  delicate  walled  tube,  0%04— 0*06  of 
a  line  in  diameter,  filled  with  polygonal  cells ;  the  lower  portion,  0-16  of 
a  line  thick,  presented  several  rounded  outgrowths,  in  part  isolated,  in 
part  grouped,  to  the  number  of  from  two  to  five  together.  The  thicker, 
inferior  portion  of  the  gland,  was  entirely  covered  with  further  developed 
lobules  0-08-O1  of  a  line  in  size,  of  which,  again,  more  simple  gland- 
granules,  each  with  a  structureless  membrane  and  contained  cells,  were 
visible.  In  the  twelfth  week  I  found  the  tliymus  not  much  larger,  but 
the  horns  broader,  and,  like  the  rest  of  the  organ,  covered  with  lobules 
0*12— 0*24  of  a  line  in  size.  From  this,  although  the  first  stages  have 
not  yet  been  observed  in  Man,  there  can  be  no  doubt  that  the  mode  of 
development  is  the  same  as  that  observed  by  Simon  in  other  Mammalia. 

The  later  development  of  the  thymus  affords  other  interesting  con- 
ditions. In  the  embryo  it  continues  to  grow  slowly  from  the  third 
month  ;  in  the  sixth  it  extends  as  far  as  to  the  thyroid  gland ;  and 
from  and  after  the  seventh  month  begins  to  contain  a  whitish  secretion. 
After  birth  it  is  not  stationary,  as  was  formerly  believed,  but  usually 
continues  to  grow  until  the  second  year,  and,  indeed,  at  first  very  con- 
siderably. After  that  period  its  growth  ceases,  though  it  still  usually 
remains  for  some  time  longer  unchanged,  until  ultimately  it  becomes 
atrophied,  and  finally  disappears.  The  period  at  which  these  changes 


THE  URINARY  ORGANS.  595 

take  place  varies  very  much.  Simon  places  the  commencement  of  the 
atrophy  between  the  eighth  to  the  twelfth  years,  a  statement  which, 
from  my  own  observations,  and  in  accordance  with  those  of  Ecker,  I 
cannot  consider  as  universally  correct ;  because,  up  to  the  twentieth 
year,  the  thymus  is  frequently  met  with  in  a  good  state  of  nutrition, 
distended  with  fluid,  without  any  fatty  metamorphosis,  and  presenting 
the  same  structure  as  in  children.  It  is  still  more  difficult  to  assign  the 
time  of  its  complete  disappearance,  for  which  no  determinate  age  can 
be  indicated,  although  it  is  true  that  the  thymus  is  usually  not  to  be 
found  after  the  fortieth  year.  The  disappearance  takes  place  in  con- 
sequence of  a  gradual  absorption,  with  a  simultaneous  development  of 
fat  in  the  gland-granules,  and  of  fat-cells  in  the  interlobular  connective 
tissue.  At  the  same  time,  also,  the  concentric  corpuscles  multiply 
more  and  more,  and  ultimately,  according  to  Ecker,  even  connective 
tissue  is  developed  in  the  lobules,  the  glandular  structure  being  com- 
pletely lost. 

% 

The  investigation  of  the  thymus  is  not  easy.  I  recommend,  in  the 
first  place,  boiled  preparations,  which  of  themselves  are  very  well 
adapted  for  the  investigation  of  the  connection  of  the  lobes  with  the 
central  canal,  and  the  cavities  in  the  lobules,  and  when  hardened  in 
spirit  are  convenient  for  the  making  of  fine  sections.  Besides  this,  the 
hardening  of  recent  preparations  in  alcohol,  pyroligneous  and  chromic 
acid,  and  the  boiling  of  them  in  acetic  acid,  are  advisable.  The  thy- 
mus, also,  of  small  Mammalia,  which  is  membranous  at  the  edges,  is 
well  adapted  to  afford  a  general  knowledge.  But,  moreover,  and  above 
all,  are  injections  cf  the  human  thymus  indispensably  requisite,  without 
which  no  satisfactory  conclusions  can  be  arrived  at. 

Literature. — S.  C.  Lucae,  "  Anat.  Untersuchung.  d.  Thymus  im 
Menschen  und  in  Thieren,"  Frankfurt  am  M.  1811  u.  12,  4to,  und 
"Anat.  Bemerk.  iiber  die  Divertikel  am  Darm.  u.  die  Hohlen  des 
Thymus,"  Nurnb.  1813,  4 to  ;  F.  C.  Haugsted,  "  Thymi  in  horn,  et  per 
ser.  animal  descrip.,"  Hafn.,  1832,  8vo ;  A.  Cooper,  "  Anatomy  of  the 
Thymus  Gland,"  Lond.,  1832,  4to ;  J.  Simon,  "A  Physiological  Essay 
on  the  Thymus  Gland,"  Lond.,  1845,  4to  ;  Ecker,  Art.  "  Blutgef ass- 
driisen,"  in  Wagner's  "  Handw.  der  Phys."  III. 

OF  THE  URINARY  ORGANS. 

§  185.  The  urinary  organs  consist  of  the  two  kidneys — true  glands, 
having  a  tubular  structure,  which  secrete  the  urine — and  of  the  secre- 
tory urinary  passages,  the  ureters,  bladder,  and  urethra. 

§  186.  In  the  kidneys,  are  to  be  distinguished  the  coats  and  the  secre- 


596  SPECIAL    HISTOLOGY. 

ting  parenchyma.  To  the  former  belong  the  adipose  capsule,  as  it  is 
termed  (capsula  s.  tunica  adiposd),  constituted  of  lax  connective  tissue 
abounding  in  fat  cells,  scarcely  deserving  the  name  of  a  special  mem- 
brane, and  the  fibrous  tunic  (tunica propria  s.  albuginea),  a  thin  but  strong 
coat,  of  a  whitish  color,  composed  of  common  connective  tissue  and 
numerous  fine  elastic  networks,  which  closely  invests  the  kidney,  and,  at 
the  hiluSj  is  in  apposition  with  the  pelvis  of  the  gland  and  the  vessels, 
but  does  not  penetrate  into  the  interior  of  the  organ. 

The  secreting  parenchyma,  which  is  abruptly  defined  from  the  fibrous 
membrane,  consists,  as  seen  by  the  naked  eye,  of  two  portions,  the 
medullary  and  the  cortical  substance,  the  former  of  which  constitutes  8-15, 
isolated,  conical,  masses  converging  towards  the  hilus,  the  pyramids  of 
Malpiglii  ;  whilst  the  latter  forms  the  entire  cortical  part  of  the  organ, 
and  moreover,  sends  processes  between  the  separate  pyramids  which 
extend  as  far  as  the  hilus, — the  columnar  Bertini, — and  is  apparently 
continuous  throughout  the  gland.  Examined  microscopically,  however, 
the  cortical  substance  is  found  to  be  divided  into  as  many  segments  as 
there  are  pyramids,  and  the  kidneys,  therefore,  may  be  regarded  as  made 
up  of  a  certain  number  of  large,  though  closely  connected  lobes. 

§  187.  Composition  of  the  Renal  Substance. — Both  portions  of  the  kid- 
neys consist,  essentially,  of  the  uriniferous  canals  (tubuli  uriniferi\ 
cylindrical  tubules,  measuring,  on  the  average,  0'016-0*025  of  a  line. 
They  commence  in  each  renal  lobe  or  segment,  in  those  portions  of  the 
pyramids  which  are  surrounded  by  the  calices  renales,  or  on  the  renal 
papillae,  by,  on  the  average,  from  200  to  500  orifices,  0 -024-0 •!  of  a  line 
wide,  scattered  over  the  surface  of  those  processes  ;  they  traverse  the 
pyramids  in  nearly  a  straight  line  and  in  close  contiguity,  whence  they 
are  termed  in  that  situation,  tubuli  recti  (or  Belliniani)  (Fig.  245  k). 
In  this  course,  each  of  the  straight  canals  divides  repeatedly,  most  usually 
under  very  acute  angles  and  at  first  with  a  considerable  diminution  of 
size,  either  into  two  (Fig.  245  Z),  or  more  rarely  into  three  or  four,  so  that, 
ultimately,  a  complete  bundle  of  finer  tubules  is  produced  from  them  ;  and 
in  this  way  the  continued  increase  in  breadth  of  the  pyramids  towards 
the  exterior  is  accounted  for.  At  the  same  time,  towards  the  base  of 
the  pyramids,  the  connection  of  the  ducts  of  Bellini  is  rendered  less 
close,  by  the  interpolation  between  them,  at  regular  distances,  of  large 
vascular  bundles  (arteriolce  and  venulce  rectcd),  and  they  become  sepa- 
rated on  all  sides  from  each  other,  so  that,  in  perpendicular  sec- 
tions, the  pyramids  (the  papilla?  of  course  excepted)  in  the  entire 
circumference  appear  to  spread  out  into  numerous  small  bundles  or 
pencils — the  pyramids  of  Ferrein  of  authors — but  which,  as  sections 
across  them  show,  are  only  to  be  regarded  as  separate,  sharply-defined 
fasciculi.  The  tubuli  uriniferi,  even  here,  assume  a  slightly  undulating 


THE    URINARY    ORGANS. 


597 


Fig.  245. 


course,  but  this  becomes  much  more  manifest  in  the  cortical  substance, 
where  they  constitute  the  convoluted  uriniferous  tubules  (tubuli  contorti 
s.  corticales),  which  at  first  sight,  appear  to  be  inextricably  and  irregu- 
larly interwoven,  each  terminating,  ulti- 
mately, as  Bowman  discovered  in  the 
year  1842,  in  a  vesicular,  dilated  ex- 
tremity, 0-06-0-01  of  a  line  in  dia- 
meter, containing  a  vascular  plexus  of 
a  peculiar  kind — the  so-called  Mal- 
pighian  body.  Upon  more  minute  ob- 
servation, however,  it  is  easy  to  perceive 
the  convoluted  tubuli  are  arranged  in 
columnar  masses,  J—J  of  a  line  wide, 
extending  through  the  entire  thick- 
ness of  the  cortical  substance  and  in 
close  apposition,  which,  notwithstand- 
ing their  incomplete  limitation  from 
each  other,  may  nevertheless  be  desig- 
nated fasciculi  corticales,  or  lobuli  re- 
num  (or  the  "pyramids  of  Ferrein"  of 
the  older  anatomists).  In  these  co- 
lumns (Fig.  245),  the  tubuli  uriniferi 
are  disposed,  in  miniature,  in  the  same 
way  as  in  a  renal  lobe,  so  that  in  their 
interior,  more  especially  at  the  peri- 
phery, convoluted  canals  may  be  dis- 
tinguished. When  the  arrangement  of 
these  parts  is  accurately  investigated, 
it  is  seen  that  the  ducts  of  Bellini,  en- 
tering a  cortical  lobule  in  a  fascicular 
manner,  at  first  run  in  perfectly  straight 
lines  (Fig.  245  o).  Soon,  however, 
some,  and  further  on,  more  and  more, 
of  the  canals  are  curved  laterally  (Fig. 
245  ra),  in  order  to  reach,  in  a  ser- 


m 


FIG.  245.— Vertical  section  through  a  portion  of  a  pyramid  and  the  cortical  substance 
belonging  to  it,  of  an  injected  Rabbit's  kidney.  The  figure  is  half-diagrammatic  ;  magnified 
30  cliam.  The  vessels  are  rspresented  on  the  left  side,  and  on  the  right  the  course  of  the 
tubuli  uriniferi :  a,  arteries  interlobulares,  with  the  glomcruli  Malpighiani,  6,  and  their  vasa  cffe- 
rentia  :  c,  vasa  efferentia  ;  d,  cortical  capillaries  ;  e.  vasa  efferentia  of  the  outermost  corpuscles, 
proceeding  to  the  superficial  capillaries  ;  /,  vasa  efferentia  of  the  innermost  glomeruli,  continu- 
ous with  the  arteriolce  rectce,  g  g  g  ;  h,  capillaries  of  the  pyramids  which  are  formed  out  of 
the  latter ;  i,  a  venula  recta,  commencing  at  the  papilla  ;  k,  commencement  of  a  straight 
canal  at  the  papilla  •  Z,  divisions  of  the  same  ;  m,  convoluted  tubules  in  the  cortex,  their  whole 
course  not  shown ;  n,  the  same  at  the  surface  of  the  gland;  o,  their  continuation  in  the 
straight  tubules  of  the  cortex  ;p,  their  connection  with  the  Malpighian  capsules. 


598  SPECIAL    HISTOLOGY. 

pentine  course,  the  arterial  twigs  surrounding  the  cortical  lobules  ;  until, 
at  last,  .the  entire  bundle  of  tubules  is  broken  up,  at  some  distance  from 
the  surface  of  the  kidney  (or  of  the  centre  of  the  columnoe  Bertini\ 
into  convoluted  canaliculi.  The  Malpighian  bodies  (Fig.  245  5),  from 
which  the  tubuli  uriniferi  arise,  are  found  throughout  the  entire  thick- 
ness of  the  cortical  substance,  from  the  pyramids  to  within  -^  of  a  line 
from  the  surface,  as  well  as  in  the  septa  Bertini,  down  to  the  sinus  of 
the  kidney  and  are  disposed  so  regularly  and  in  such  numbers,  around 
the  cortical  lobules,  that  every  transverse  section  through  the  cortex 
always  displays  a  red  streak,  caused  by  these  corpuscles,  between  each 
two  lobules.  Usually  each  of  these  streaks  consists  of  a  minute  artery, 
with  from  two  to  four,  of  Malpighian  bodies  supported  by  it,  but  not  in 
regular  series,  some  of  which  stand  more  in  relation  with  the  one,  and 
others  with  the  other  cortical  bundle.  Each  fasciculus  of  tubuli  urini- 
feri, therefore,  upon  entering  the  cortical  substance,  is,  from  the  first 
entirely  encompassed  by  the  Malpighian  bodies,  and  it  is  obvious  that 
some  of  the  tubuli  quit  it  soon  and  others  later,  in  order  to  reach  their 
appropriate  Malpighian  bodies.-.  For  the  rest,  each  corticaf  tubule,  after 
its  origin,  is  much  convoluted,  runs  at  first  somewhat  outwardly,  and 
then  returns  upon  itself,  to  join  the  straight  tubules  of  the  cortical 
fasciculus. 

The  number  of  the  convoluted  tubuli  uriniferi  corresponds  with  that 
of  the  Malpighian  bodies  and  is  consequently,  in  every  instance,  very 
considerable.  According  to  Huschke,  200  tubuli  exist  in  each  fasciculus 
corticaliSj  and  700  such  fasciculi  in  a  pyramid  ;  which  calculation  gives, 
in  fifteen  pyramids,  more  than  two  millions  of  commencements  of  tubuli 
and  Malpighian  bodies.  Since  each  papilla  has  about  500  or  even  more 
orifices,  it  is  possible  that  each  cortical  fasciculus  proceeds  from  a  single 
"duct  of  Bellini;"  in  any  case,  it  is  evident  that  in  every  straight 
tubule  the  divisions  are  repeated  at  least  ten  times.* 

x§  188.  The  tubuli  uriniferi,  are  everywhere  composed  of  the  same 
elements ;  viz.  of  a  membrana  propria,  and  a  tessellated  epithelium.  The 
former  is  a  perfectly  structureless,  transparent,  thin  (0-0004-0-0008 
of  a  line),  but  proportionately  strong  and  elastic  coat,  which,  particu- 
larly in  the  straight  tubules,  may  be  very  easily  isolated  for  a  considera- 
ble extent,  when  it  is  very  prone  to  fall  into  folds,  which  often  present 
the  striated  aspect  of  connective  tissue.  On  the  inner  surface  of  this 

*  [It  would  scarcely  be  deduced,  from  what  is  said  in  the  text,  that  the  tubuli  uriniferi,  in 
the  cortical  part  of  the  kidney,  anastomose  very  freely  and  frequently,  although  the  fact  of 
their  doing  so  has  been  long  well  known  and  often  described.  These  anastomoses,  how- 
ever, and  the  general  disposition  of  the  tubules,  are  more  particularly  adverted  to  and  well 
depicted  by  Toynbee  (:4  Med.  Chir.  Transact.,"  2d  ser.,  vol.  XI.  p.  308,  pi.  7).— TBS.] 


THE    URINARY    ORGANS. 


599 


coat,  which  in  its  chemical  characters  is  very  closely  allied  to  the  sarco- 
lemma  (vid.  §  58),  lies  a  single  layer  of  polygonal,  moderately  thick 
cells,  surrounding  the  cavity  of  the  tubulus,  which,  from  the  readiness 
with  which  they  alter,  have  given  rise  to  many  erroneous  representations 
respecting  the  structure  of  the  urinary  ducts  and  their  contents.  For 
instance,  in  the  usual  mode  of  examination  in  water,  they  expand, 
owing  to  its  absorption  and  become  vesicularly  distended,  so  that  their 
polygonal  form  and  regular  arrangement  are  lost ;  the  renal  ducts, 
within  the  structureless  membrane,  appearing  to  be  entirely  filled  with 


Fig.  246. 


Fis.  247. 


rounded  larger  cells  and  no  longer  to  possess  any  cavity.  The  cells, 
also,  frequently  burst,  in  which  case  the  tubuli  contain  nothing  but  a 
fine  granular  substance,  with  nuclei  and  clear  albuminous  drops  escaped 
from  the  cells.  In  kidneys  not  quite  fresh,  these  changes  proceed 
spontaneously  ;  and,  therefore,  it  is,  above  all  things,  necessary  to  exa- 
mine the  organ  as  soon  as  possible  after  death  and  to  avoid  all  additions 
capable  of  producing  change.  The  contents  of  the  epithelium  cells 
are,  besides  round  nuclei  of  the  usual  kind,  a  most  usually,  very  finely- 
granular  substance,  which,  on  the  addition  of  water,  affords  clear,  light- 
yellowish  drops,  probably  of  albumen,  but  is  not  otherwise  changed  ; 

Fig.  24G. — Two  straight  tubuli  uriniferi  of  Man,  one  with  perfect  epithelium,  the  other 
half  empty :  a,  membrana  propria  ;  6,  epithelium. 

Fig.  247. — 1,  a  Malpighian  corpuscle,  A,  with  the  tubulus  uriniferus  springing  from  it, 
J9,  C-  Human;  magnified  300  diam. ;  figure  half-diagrammatic:  a,  membrane  of  the  Mal- 
pighian body,  continuous  at  6,  with  the  membrana  propria  of  the  convoluted  tubule ;  c,  epi- 
thelium of  the  Malpighian  body;  d,  that  of  the  tubule;  e,  detached  epithelium  ;/,  vas  afferens  ; 
g,  vas  effcrens;  h,  glomcndus  Malpighianus.  2,  three  epithelial  cells  from  the  convoluted 
tubule,  magnified  350  diam.;  one  with  oil  drops. 


600  SPECIAL    HISTOLOGY. 

under  acetic  acid  the  contents,  together  with  the  cell-membrane,  are 
rendered  pale,  and  soon  dissolve  ;  whilst  the  nuclei  at  the  same  time 
soon  become  pale,  and  finally,  on  the  application  of  caustic  alkalies, 
disappear  in  the  same  manner  as  the  membrane.  Besides  these  gra- 
nules, which  I  do  not  hesitate  to  declare  are  a  protein  substance,  and 
the  albumen  in  solution  in  the  contents,  the  cells  very  commonly  contain 
some  dark  oil-drops,  and  more  rarely  one  or  another,  exhibits  granules 
of  yellow  pigment. 

The  straight  and  convoluted  canals,  together  with  the  general  cha- 
racters just  described,  present  some  differences.  The  former,  although 
originally  of  the  considerable  width  of  even  0*06-0*1  of  a  line,  soon 
diminish,  in  consequence  of  the  divisions  they  undergo,  to  a  diameter  of 
0*01-0*014-0*018  of  aline,  but  in  the  "bundles  of  Ferrein,"  again 
acquire  the  size  of  0*02-0*24  of  a  line.  With  this  diameter  they  enter 
the  cortical  substance,  but  subsequently,  in  the  proper  convoluted 
tubules,  attain  one  of  0*033  of  a  line,  though  again  somewhat  constricted 
close  to  their  commencement.  The  membrana  propria  in  the  convoluted 
tubules  is  more  delicate  (0-0003-0*0004  of  a  line)  and  isolated  with 
more  difficulty,  the  epithelium,  on  the  contrary,  is  usually  thicker,  with 
cells  measuring  0*008-0*012  of  a  line  in  width,  and  0-004-0*005  of  a 
line  in  thickness;  whilst  in  the  straight  tubules  the  cells  are  not  more 
than  0*004-0*006  of  a  line  wide,  and  0*004  of  a  line  thick.  Physiolo- 
gically, it  also  seems  to  me  worthy  of  remark,  that  the  last  cells  have 
clear,  non-granular  contents,  whence,  also,  the  medullary  substance,  in 
the  bloodless  condition,  appears  whitish,  whilst  the  cortical  exhibits  a 
yellowish  hue. 

The  Malpighian  bodies  present  a  very  peculiar  structure.  They  are 
to  be  regarded  as  appendages  of  the  convoluted  tubuli  uriniferi,  and 
contain  imbedded  in  their  epithelium,  and,  as  it  may  be  said,  entirely 
filling  their  cavity,  a  compact,  rounded  vascular  plexus — the  glomerulus 
Malpigliianus,  the  structure  of  which  will  be  afterwards  described.  The 
same  membrana  propria,  which  surrounds  the  tubuli  uriniferi,  also 
somewhat  thickened  (0*0005—0*0008  of  a  line)  invests  these  bodies  (Fig. 
247  a);  and  the  epithelium  is  likewise  continued  into  the  capsules  thus 
formed,  only  that  its  cells  are  smaller  and  less  distinct,  and  invest  the 
vascular  coil  on  the  side  directed  towards  the  canal  of  the  emergent 
tubulus  uriniferus.  This  latter,  generally  somewhat  constricted  (Fig. 
247,  jB),  is  inserted  into  the  Malpighian  capsule,  most  usually  on  the 
opposite  side  to  the  afferent  and  efferent  vessels ;  but  in  accordance  with 
what  has  been  said,  its  cavity  penetrates  into  the  capsule,  only  to  an 
inconsiderable  extent ;  inasmuch  as  the  latter  is  almost  entirely  occupied 
by  the  vessels  and  the  epithelium  surrounding  them.* 

*  [With  respect  to  the  question  of  the  csecal  termination,  or  commencement,  as  it  might 
more  properly  be  termed,  of  the  tubuli  uriniferi  in  the  Malpighian  capsules,  there  is  an 


THE    URINARY    ORGANS.  601 

The  ciliary  motion  discovered  by  Bowman  in  the  neck  of  the  Mal- 
pighian  bodies  of  the  Frog,  and  in  the  commencement  of  the  tubuli 
uriniferi,  with  the  direction  of  the  stream  towards  the  ureter,  is  readily 
confirmed,  when  the  addition  of  water  is  avoided.  It  is  absent,  how- 
ever, in  Birds  (Gerlach  thinks  he  has  seen  it  on  one  occasion  in  the 
Fowl)  and  other  Mammalia,  and  was  not  noticed  by  me  in  the  cases  of 
two  executed  criminals,  examined  especially  with  respect  to  this  point, 
whilst  it  is  found  in  Serpents,  in  the  Salamander,  Triton,  Bombinator, 
Bufo,  and  is  very  well  marked  in  Fishes,  and  also,  according  to 
Remak's  and  my  own  observations,  in  the  Wolffian  bodies,  which  have 
the  structure  of  kidneys,  in  the  embryo  of  the  Lizard ;  in  the  last  two 
instances  they  are  also  met  with  in  the  uriniferous  ducts  at  a  greater 
distance  from  the  Malpighian  bodies. 

Of  the  very  numerous  pathological  degenerations  of  the  tubuli  urini- 
feri,  I  will  notice  only  the  following  :  The  membrana  propria  is  fre- 
quently thickened  to  O'OOl,  or  even  0*002  of  a  line,  when  it  often 
presents,  on  the  inner  aspect,  very  delicate,  closely  approximated  trans- 
verse striee.  The  epithelial  cells,  particularly  in  the  cortical  substance, 
frequently  contain  oil-drops  in  considerable  quantity,  so  as  often  to 
present  a  deceptive  resemblance  to  the  cells  of  a  fatty  liver,  and  at  the 
same  time  they  are  usually  enlarged  to  a  diameter  of  0'02  of  a  line. 
Together  with  the  oil,  pigment  granules  (of  the  coloring  matter  of 
urine  ?)  occur  in  them  (also  in  the  straight  canals),  whereas  the  concre- 
tions of  uric  acid  and  calcareous  salts,  which  are  so  frequently  met 
with  in  the  canals  of  the  tubules  in  the  Vertebrata  have  not  as  yet 
been  demonstrated  with  certainty  in  the  cells  themselves  (in  Fishes, 
Simon,  "  Thy mus"  p.  69,  often  found  crystals  in  the  renal  cells). 
Colloid-like,  bright  yellow  masses  are  frequent  in  the  epithelial  cells, 
which  then  most  usually  increase  in  size,  dilate  into  slender  cysts  as 

apparent  discrepancy  of  opinion  among  anatomists.  Bowman  states  that  each  tube  com- 
mences in  a  Malpighian  capsule;  whilst  Gerlach  says  that  the  capsules  do  not  form  the 
extremities  of  the  uriniferous  tubes,  but  are  merely  diverticula,  which  communicate  by  a 
small  neck  with  the  angle  formed  by  the  uriniferous  tubes,  winding  through  the  cortical 
part  of  the  kidneys;  or,  as  the  same  thing  is  described  by  Leydig  (1.  c.,  p.  32),  with  respect 
to  the  kidney  of  the  Sturgeon,  two  closely  contiguous,  uriniferous  tubules,  are  connected  with 
the  (Malpighian)  capsule  and  continuous  with  it;  in  other  words,  the  tubules  join  in  a  loop, 
at  the  apex  of  which  is  a  globose  diverticulum,  in  which  the  glomerulus  is  lodged  ;  and 
according  to  him,  the  same  arrangement  obtains  in  the  Reptilia.  Now  it  seerns  that  this 
discrepancy  admits  of  an  easy  explanation,  for  if  we  suppose  the  constricted  neck  of  the 
diverticulum  to  be  lengthened  into  a  tube,  we  have  at  once  the  disposition  described  by 
Bowman,  viz. :  a  tube  commencing  in  a  dilatation  containing  the  glomerulus  and  afterwards 
anastomosing  with  another  or  with  other  tubules;  and  if  the  neck  of  the  so-called  diverti- 
culum be  very  short,  or,  in  other  words,  if  the  Malpighian  capsule  be  sessile,  we  have  the 
arrangement  described  by  Gerlach,  &c.  Mr.  Toynbee's  notion  that  the  tubulus  uriniferus 
merely  passes  through  the  Malpighian  capsule,  forming  a  coil  within  it,  appears  to  us  to  be 
wholly  inadmissible;  but  many  of  the  appearances  depicted  in  his  very  carefully-executed 
figures  (1.  c.)  would  serve  to  support  the  opinion  that  the  Malpighian  body  is  more  often 
sessile  than  it  would  seem  to  be  from  Bowman's  account. — TRS.] 


602  SPECIAL    HISTOLOGY. 

much  as  0-05-0-072  of  a  line  long,  and  finally,  by  bursting,  empty 
themselves  of  the  colloid  substance,  whence  the  latter  is  found  free  in 
the  uriniferous  ducts,  and  also  in  the  urine.  A  development  of  the 
epithelial  cells  into  other  cysts,  as  is  stated  to  take  place  by  J.  Simon, 
and  also  by  Gildemeester  (Tijdschr.  d.  Nederl.  Maatsch.  1850)  has  not 
yet  occurred  to  my  observation,  whilst  I  have  noticed,  as  did  Johnson, 
very  distinctly,  in  an  atrophied  kidney,  a  partition  of  the  convoluted 
tubules  into  closed  cysts,  to  all  appearance  by  a  connective  tissue 
developed  between  and  constricting  them.  These  cysts  had  the  same 
structure  as  the  tubules,  and  were  either  of  the  same  diameter,  or  dis- 
tended into  vesicles,  0-1  of  a  line  in  width.  The  Malpighian  bodies 
also  may  expand  into  cysts,  in  which,  together  with  a  clear  fluid,  the 
atrophied  glomerulus  is  often  visible  on  the  wall.  As  abnormal  con- 
tents, the  tubuli  uriniferi  present :  1,  blood,  most  frequently  in  the 
commencement  of  the  convoluted  tubules,  especially  the  superficial, 
often  in  such  quantity  as  to  produce  bloody  points  as  big  as  a  pin's 
head,  and  visible  to  the  naked  eye,  which  were  formerly  erroneously 
regarded  as  distended  Malpighian  bodies  ;  2,  fibrine,  in  cylindrical 
masses,  corresponding  to  the  cavity  of  the  tubules ;  3,  the  above- 
mentioned  colloid-like  substance;  4,  concretions  in  the  ducts  of  Bellini, 
consisting,  in  the  adult,  chiefly  of  carbonate  and  phosphate  of  lime 
("  Kalkinfarct") ;  in  new-born  infants,  of  uric  acid-salts  ("  Harnsau- 
reinfarct,"  Virchow),  which  give  the  pyramids  a  brilliant  gold-yellow 
color,  and,  if  not  exclusively,  still  usually  occur  only  in  children  who 
have  already  respired  (between  the  third  and  twentieth  day  after  birth). 
In  the  later  stages  of  "  Bright's  disease,"  many  tubuli,  which  have  lost 
their  epithelium  in  consequence  of  the  exudations  poured  out  in  them, 
become  atrophied,  and  ultimately  disappear  altogether,  whilst  groups  of 
others  are  seen,  filled  with  a  fatty,  broken-up  exudation,  and  dilated 
into  minute  nodosities  (granulations,  Christison). 

§  189.  Vessels  and  Nerves. — The  large  renal  artery  divides,  in  the 
pelvis  of  the  kidney,  into  a  certain  number  of  branches,  which,  after  sup- 
plying the  parts  lying  in  the  hilus,  enter,  above  and  below  the  renal 
veins,  the  cortical  substance  interposed  between  the  pyramids  (the 
columnce  Bertini}.  From  this  point  they  are  continued,  repeatedly 
dividing,  close  upon  the  boundary  of  the  two  renal  substances,  so  that 
around  each  pyramid  a  delicate  ramification,  but  without  any  anasto- 
moses, usually  afforded  only  by  two  large  arteries,  is  formed.  From 
this  ramification,  on  the  side  looking  towards  the  cortical  substance, 
there  arise,  with  great  regularity,  and  for  the  most  part  at  right  angles, 
smaller  arteries,  which  after  a  few  or  more  repeated  divisions  give  off 
fine  twigs,  O'06-O'l  of  a  line  in  diameter,  which  run  outwardly  in  a 
straight  course  between  the  cortical  fasciculi  or  lobules,  and  are  most 


THE    URINARY    ORGANS. 


603 


fitly  termed  arterice  interlobulares  (Fig.  245  a).  It  is  these  twigs  which 
support  the  Malpighian  bodies,  and,  with  the  exception  of  some  branches 
to  the  coats  of  the  organ,  they  terminate  exclusively  in  the  formation  of 
their  vascular  coils.  In  fact,  each  interlobular  artery  gives  off,  in  its 
whole  length,  on  two,  three,  or  four  sides,  a  great  number  of  fine  twigs 
possessing  the  structure  of  arteries  and  0-008-0-02  of  a  line  in  diameter, 


Fig.  248. 


which,  after  running  a  short  distance,  either  directly  or  after  dividing 
once,  penetrate  the  tunic  of  the  Malpighian  body,  becoming  the  vasa 
afferentia  of  its  vascular  coil.  Each  of  these  (Fig.  247,  248)  consists 
of  a  close  convolution  of  fine  vessels  0-004-0-008  of  a  line  in  diameter, 
having  the  usual  structure  of  capillaries  (structureless  coat  and  nuclei) 
and  possesses,  besides  the  afferent  artery,  an  efferent  vessel,  the  vas 
efferent.  The  mode  in  which  these  two  vessels  are  connected  is  not 
that  which  usually  obtains  in  arteries  and  veins,  but  corresponds  with 

FIG.  248. — From  the  Human  kidney,  after  Bowman:  a,  extremity  of  an  interlobular 
artery;  6,  afferent  arteries;  c,  naked  glomerulus ;  d,  efferent  vessel;  e,  glomeruli,  surrounded 
by  the  Malpighian  capsules;  /,  tubuli  uriniferi  springing  from  them. — Magnified  43 
diameters. 

FIG.  249. — Glomerulus  from  the  innermost  part  of  the  cortex  of  the  kidney  of  the  Horse, 
after  Bowman:  a,  arter.  interlobularis  •  of,  vas  afferens  •  m  m,  glomerulus;  ef,  vas  efferens  s. 
arteriola  recta;  b,  divisions  of  the  same  in  the  medullary  substance. — Magnified  70  diameters. 


604  SPECIAL    HISTOLOGY. 

the  arrangement  presented  in  the  bipolar  retia  mirabilia^  as  they  are 
termed;  the  vas  afferens,  immediately  after  its  entrance  into  the  coil, 
dividing  into  5-8  branches  and  each  of  these  into  a  bundle  of  capillaries, 
which  are  much  convoluted  and  interlaced,  without  anastomosing,  and 
ultimately,  in  the  same  way  as  that  in  which  they  were  formed,  reunite 
into  a  single  trunk.  Usually  the  two  main  vessels  enter  and  quit  the 
glomerulus  near  together,  opposite  the  origin  of  the  urinifero  us  duct, 
and  its  finest  vessels  of  0-003-0.004  of  a  line,  the  peripheral  loops  as  it 
were,  are  invariably  situated  exactly  at  the  commencement  of  the  duct. 
In  Birds,  Amphibia,  and  Fishes,  each  glomerulus  consists  of  a  single  con- 
voluted vessel. 

The  vasa  efferentia,  although  composed  of  capillaries,  are  not  veins, 
but  in  their  nature,  and  to  some  extent  in  their  structure,  minute  arte- 
ries, a  character  that  they  retain  until,  in  their  further  course,  they  are 
merged  in  the  capillary  plexus  of  the  kidney.  This  plexus  exists  in  the 
cortical  substance  and  in  the  pyramids,  presenting  somewhat  different 
characters  in  these  two  situations.  In  the  former  (Fig.  245,  d)  the 
vasa  efferentia  0-004-0-008  of  a  line  in  size,  after  a  short  course,  ter- 
minate in  a  very  rich  plexus  of  capillaries  0-002—0-004-0-006  of  a  line 
in  diameter,  the  rounded-angular  meshes  of  which,  0-005—0*015  of  a 
line  wide,  encompass  the  convoluted  tubuli  on  all  sides  arid  must  be  re- 
garded as  continuous  throughout  the  whole  cortical  substance.  The 
efferent  vessels  of  the  glomeruli  in.  nearest  contiguity  to  the  Malpighian 
pyramids  alone  present  an  exception  to  this  condition,  inasmuch  as, 
characterized  by  their  more  considerable  size  (0-01-0-016  of  a  line), 
they  are  distributed  not  in  the  cortical  substance,  but  in  the  pyramids, 
and  are  distinguished  by  their  long,  straight  course,  and  upon  the  whole, 
scanty  ramifications.  These  vessels  (Fig.  245  g\  which,  with  Arnold, 
I  would  term  arteriolce  reccet,  penetrate  around  the  entire  circumference 
of  the  pyramids,  in  a  straight  course,  between  the  ducts  of  Bellini,  and 
descend,  repeatedly  dividing  at  acute  angles,  and  gradually  attenuated 
to  the  diameter  of  0-004-0-01  of  a  line,  towards  the  papittce,  in  which,  as 
in  the  interior  of  the  medullary  substance  (in  the  latter  situation,  either 
by  their  extremities  or  by  twigs  given  off  at  right  angles),  they  are  con- 
tinuous with  the  capillaries  in  those  regions,  measuring  from  0-002  to 
0-004  of  a  line.  These  capillaries  are  very  importantly  distinguished 
from  those  of  the  cortical  substance  by  their  less  number  and  the  elon- 
gated figure  of  the  meshes  of  the  plexus  which  they  form,  although  at 
the  boundary  of  the  pyramids  the  two  sets  are  continuous  with  each 
other.  The  renal  veins  commence  in  two  situations,  viz.,  at  the  sur- 
face of  the  organ  and  at  the  apices  of  the  papillae.  In  that  situation, 
minute  venous  radicles  collect  together  from  the  outermost  portions  of 
the  capillary  plexus  of  the  cortical  substance,'  which  either  regularly 
surround  each  cortical  lobule,  and  between  them  unite  in  a  stellate 


THE    URINARY    ORGANS.  605 

manner  (stellulce  Verheynii)  into  somewhat  larger  roots,  or,  extending 
over  several  or  numerous  lobules,  collect  into  larger  trunks.  These  two 
sets  of  veins,  forming  the  vence  interlobulares,  then  penetrate  more 
deeply  in  company  with  the  arteries  of  the  same  name,  between  the 
cortical  fasciculi,  where  they  are  enlarged  by  the  accession  of  nume- 
rous other  venous  radicles  from  the  interior  of  the  cortical  substance, 
and  proceed  to  join  the  larger  veins,  either  directly  or  united  into  some- 
what larger  trunks,  and  for  the  most  part  at  right  angles.  These  lie, 
together  with  the  larger  arteries,  around  the  periphery  of  the  pyramids, 
ultimately  opening  into  large  veins  without  valves,  as  are  all  the  renal 
veins,  and  which  lying  singly  close  to  the  arteries,  quit  the  kidney  in 
the  same  way.  Previously  to  this,  however,  besides  those  of  the  columnce 
Bertini,  they  receive  the  veins  of  the  pyramids,  which  commence  in  a 
beautiful  plexus  surrounding  the  orifices  of  the  tubuli  uriniferi  on  the 
papillae,  and  ascend  between  the  tubuli  recti,  being  strengthened  by  ad- 
ditional radicles  ;  these  united  with  the  arteries  of  the  pyramids,  the 
vasa  efferentia  of  the  innermost  glomeruli  or  the  arteriolce  rectce,  into 
larger  vascular  bundles,  lying  between  the  "  pyramids  of  Ferrein," 
open  into  the  arched,  wider,  venous  ramification  which  encompasses  the 
pyramids. 

The  vessels  of  the  membranes  of  the  kidney,  arise  in  part  from  the 
art.  renalis,  before  it  enters  the  hilus,  and  from  the  suprarenal  and 
lumbar  arteries,  in  part,  also,  they  are  branches  of  the  arteries  inter- 
lobulares, which,  after  supplying  the  Malpighian  bodies,  send  on  fine 
twigs  to  the  fibrous  coat,  forming  in  it  a  wide-meshed  capillary  plexus, 
which  is  also  continuous  with  that  of  the  capsula  adiposa. 

The  kidneys  present,  proportionally,  but  few  lymphatics  They  run, 
in  the  interior,  along  the  larger  vessels,  and  do  not  appear  to  extend 
further  than  the  vasa  interlobularia.  In  the  hilus,  they  unite  into  a 
few  small  trunks,  which  also  receive  lymphatic  vessels  from  the  pelvis 
of  the  kidney  and  then  open  into  the  lumbar  glands.  Superficial 
lymphatics,  which  have  been  described  by  the  older  anatomists  (Nuck, 
Cruikshank,  Mascagni,  &c.),  I  have  as  yet  not  seen,  except  in  the  cap- 
sula adiposa,  but  I  am  unwilling  positively  to  deny  their  existence. 

The  renal  nerves,  from  the  cseliac  plexus  of  the  sympathetic  are  tole- 
rably numerous,  form  a  plexus  around  the  arteries,  continue  to  present 
a  few  ganglia  in  the  hilus,  and  may  be  traced,  in  company  with  the 
vessels,  as  far  as  the  interlobular  arteries.  Where  and  how  they  ter- 
minate is  unknown.* 

*  [With  respect  to  the  termination  of  the  nerves  in  the  kidney,  Mr.  Toynbee  (1.  c.,  p.  805) 
makes  the  remarkable  and  very  important  observation,  that  "the  filaments  end  by  becoming 
continuous  with  the  parenchyma  of  the  organ,  precisely  in  the  same  way,"  he  goes  on  to 
say,  "as  lie  has  observed  those  in  the  tail  of  a  Tadpole  to  become  directly  continuous  with 
the  radiating  fibres  of  stellated  corpuscles,  and  the  filaments  from  the  corpuscles  to  commu- 
nicate with  each  other." — TRS.] 


606 


SPECIAL    HISTOLOGY. 


All  these  vessels  and  nerves  are  supported  by  a  connective  tissue, 
which,  at  the  same  time,  serves  as  a  stroma  for  the  secreting  elements, 
and  is  much  more  developed  in  the  medullary  substance  than  in  the 
cortical.  At  the  surface  of  the  gland,  it  is  condensed  into  a  membrane, 
often  very  distinct,  0-01-0-02  of  a  line  thick,  which  is  but  loosely  con- 
nected with  the  fibrous  tunic,  partly  supports  the  superficial  capillary 
plexus,  and  is  continuous  with  the  internal  stroma  by  numerous  delicate 
processes. 

Fig.  250. 


In  inflammations  and  exudations,  the  stroma  is  frequently  so  much 
condensed  as  to  be  apparent  on  the  most  superficial  inspection,  or  even, 
more  or  less  to  compress  the  tubuli  uriniferi.  The  additional  elements 
consist  chiefly  of  a  fibrinous  exudation,  presenting  various  stages  of 
transition  into  connective  tissue,  partly  also  of  such  forms  as  are  pecu- 
liar to  immature  normal  connective  tissue,  as  fusiform  cells,  &c.  In  the 
case  of  the  Malpighian  bodies,  these  new  formations  present  the  form 
of  concentric,  often  very  thick  deposits,  which  constrict  the  afferent  and 
efferent  vessels,  thus  inducing  atrophy  of  the  glomerulus,  and  very 
essentially  and  prejudicially  affecting  the  secretion  of  urine.  In  other 
cases  the  increase  of  the  stroma  is  only  apparent,  and  depends  upon  the 
atrophy  of  the  secreting  elements. 

FIG.  250. — Transverse  section  through  some  straight  cortical  tubules,  magnified  350 
diameters ;  from  Man :  a,  transverse  section  of  tubuli  urinifcri,  the  membrana  propria  only  of 
which  remains  ;  6,  similar  tubules,  with  the  epithelium  still  remaining;  c,  stroma  of  connec- 
tive tissue,  with  elongated  nuclei ;  d,  cavity  in  which  a  Malpighian  corpuscle  was  con- 
tained. 

FIG.  251. — Epithelium  of  the  pelvis  of  the  Human  kidney,  magnified  350  diameters:  »4, 
isolated  cells;  B,  the  same  in  situ:  a,  small;  6,  large  tessellated  cells;  c,  the  same  with 
nucleated  corpuscles  in  the  interior;  d,  cylindrical  and  conical  cells  from  the  deeper  layers; 
c,  transitional  forms. 


THE    URINARY    ORGANS.  607 

§  190.  Excretory  urinary  passages. — The  ureters,  the  pelvis,  and 
calices  of  the  kidney,  are  all  composed  of  an  external  fibrous  membrane, 
a  smooth  muscular  layer,  and  a  mucous  membrane.  The  first,  formed 
of  common  connective  tissue  and  elastic  fibres,  chiefly  of  the  finer  kind, 
is  continuous,  at  the  point  where  the  calices  surround  the  papilla*,  with 
the  fibrous  tunic  of  the  kidney.  The  muscular  layer  in  the  ureters  is 
very  distinct,  with  external,  longitudinal,  and  internal  transverse  fibres, 
to  which,  towards  the  bladder,  internal  longitudinal  fibres  also  are 
superadded.  In  the  pelvis  of  the  kidney  the  two  muscular  layers  are 
quite  as  thick  as  in  the  ureter,  whilst  in  the  calices  they  become  thinner 
and  thinner,  ceasing  where  the  latter  are  inserted  into  the  papilla. 
The  mucous  membrane  of  all  these  parts  is  thin,  tolerably  vascular, 
without  glands  or  papillce,  and  becoming  very  much  thinner  (O-005-O'Ol 
of  a  line,  without  epithelium),  is  also  continued  upon  the  renal  papillae, 
being  likewise  connected  with  their  interior  stroma.  Its  epithelium, 
0-02-0-04  of  a  line  thick,  is  laminated  and  characterized  by  the  variety 
of  form  and  size  of  its  elements,  of  which  the  most  deeply-seated  cells 
are  rounded  and  small,  those  in  the  middle  cylindrical  or  conical,  O'Ol— 
0-02  of  a  line  in  length,  and  the  superficial,  rounded-polygonal  scales 
0-006-0-04  of  a  line  in  size,  or  more  flattened,  and  reaching  a  diameter 
of  0'02  of  a  line.  The  frequent  occurrence  of  two  nuclei  in  these  cells 
is  a  striking  fact,  as  well  as  of  clear,  darkish-colored  round  granules 
0-001-0-002  of  a  line  in  size,  which  often  almost  assume  the  aspect  of 
nuclei. 

The  urinary  bladder,  besides  its  peritoneal  investment,  possesses  the 
same  membrane  as  the  ureters.  The  muscular  coat  presents,  exter- 
nally, the  well-known  longitudinal  fibrous  layer  (detrusor  urince),  with 
parallel  bundles,  from  which  isolated  fibres  are  continued  upon  the 
urachus ;  beneath  these  is  a  plexiform  arrangement  of  oblique  and 
transverse,  stronger  and  slender  fasciculi,  interwoven  into  a  true  plexus, 
which  do  not  completely  cover  the  entire  mucous  membrane,  and,  at  the 
neck  of  the  bladder,  constitute  a  strong  continuous  circular  fibrous  layer 
(sphincter  vesicce).  The  corpus  trigonum,  in  the  fundus  of  the  bladder, 
is  a  thick  layer  of  whitish-yellow  fibres,  lying  immediately  beneath  the 
mucous  membrane,  continuous  with  the  longitudinal  muscular  fibres  of 
the  ureters  passing  through  the  muscular  coat  of  the  bladder,  and  con- 
tains chiefly  longitudinal,  but  also  some  transverse  fine  elastic  elements, 
connective  tissue,  and  smooth  muscular  fibres.  The  mucous  membrane, 
pale,  smooth,  and  tolerably  thick,  except  where  the  corpus  trigonum  is 
situated,  presents  an  abundant  submucous  layer,  and  consequently,  when 
the  bladder  contracts,  is  thrown  into  numerous  folds.  It  presents  no 
villi,  is  tolerably  rich  in  vessels,  especially  at  the  fundus  and  neck,  less 
so  in  nerves,  which,  however,  especially  in  those  two  situations  where 
they  are  more  abundant,  may  be  recognized  as  dark-bordered,  fine  and 


608  SPECIAL    HISTOLOGY. 

medium-sized  fibres,  and  is  covered  with  a  laminated  epithelium  0§03— 
0'05  of  a  line  thick,  whose  deeper  elements  are  usually  fusiform,  conical 
or  cylindrical,  the  more  superficial,  rounded-polygonal,  or  flattened. 
They  exhibit  the  same  want  of  uniformity  in  size  as  those  of  the  pelvis 
of  the  kidney,  to  which  irregularity  the  numerous  depressions  of  various 
depths  on  the  under  surface  of  the  uppermost  cells,  for  the  reception  of 
the  ends  of  the  deeper,  elongated  cells,  much  contribute ;  peculiar 
stellate  and  dentate  forms  being  thence  produced.  In  the  neck  of  the 
bladder  and  towards  i\\Q  fundus,  there  occur  minute  glands,  in  the  form 
of  simple  pyriform  follicles,  or  small  aggregations  of  these  (simple 
racemose  glands).  These  glands,  0-04-0-24  of  a  line  in  size,  have 
orifices  of  0-02-0-05  of  a  line,  a  cylindrical  epithelium,  and  contain  a 
clear  mucus.  In  pathological  conditions,  as  Virchow  informs  me,  they 
are  occasionally  enlarged  and  filled  with  whitish  mucous  plugs. 

The  male  urethra  will  be  described  with  the  sexual  organs.  That  of 
the  female  presents  a  reddish  mucous  membrane  with  numerous  vessels, 
especially  in  the  form  of  much-developed  venous  plexuses  in  the  sub- 
mucous  tissue  (which  Kobelt,  without  any  reason,  has  described  as  a 
corpus  spongiosum),  and  a  squamous  epithelium,  the  deeper-seated  cells 
of  which  are  elongated,  as  in  the  bladder.  There  is  an  external  mus- 
cular tunic  united  with  the  mucous  membrane,  consisting  of  a  thin 
layer  of  longitudinal  and  transverse  smooth  muscles,  intermixed  with 
much  connective  tissue  and  elastic  fibres,  and  of  the  thick  substance  of 
the  musculus  urethralis,  the  direction  of  the  fibres  in  which  is  chiefly 
transverse.  A  certain  number  of  larger  and  smaller  racemose  mucous 
glandules  ("glands  of  Littre"),  resembling  in  their  structure  those  of 
the  bladder,  except  that  they  are  usually  somewhat  larger  and  more 
closely  placed,  pour  their  secretion  into  the  urethra.  Occasionally 
these  glands  occur  of  larger  size  (as  much  as  2  lines),  and  prominent, 
containing  a  colloid-like  material  in  the  distended  vesicles. 

§  191.  Physiological  remarks.  Development  of  the  urinary  organs. 
— According  to  Remak,  the  kidneys  in  the  Chicken  are  formed  as  two 
protrusions  of  the  intestine,  in  the  constitution  of  which  the  epithelial 
and  the  fibrous  layers  both  take  part,  and,  like  the  lungs,  grow  by  the 
ramification  of  their  epithelial  tube,  and  the  augmentation  in  bulk  of 
the  fibrous  layer  (Unters.  z.  Entw.  d.  Wirbelth.  Tab.  II.,  fig.  83-85). 
In  the  Mammalia,  the  earliest  stage  of  the  development  of  the  kidneys 
has  not  yet  been  observed ;  but  what  we  do  know  from  the  labors  of 
Rathke,  J.  Miiller,  Valentin,  and  Bischoif,  with  respect  to  its  subse- 
quent conditions,  perfectly  accords  with  the  statements  of  Remak, 
except  that,  in  this  case,  the  glandular  canals  appear  to  be  developed 
upon  the  type  of  the  salivary  glands,  and  are  not  hollow  from  the  com- 
mencement. The  rudimentary  kidneys  in  the  Mammalia,  at  first, 


THE  URINARY  ORGANS.  609 

present  nothing  but  the  pelvis  and  a  certain  number  of  clavate  hollow 
protrusions  continuous  with  it — the  calices.  From  each  of  the  latter  is 
subsequently  formed,  by  continued  budding,  a  bundle  of  tubuli  uriniferi, 
each  of  which  bundles  ultimately  constitutes  a  Malpighian  pyramid  and 
the  cortical  substance  appertaining  to  it ;  whilst,  at  the  same  time,  the 
kidney  expands  into  a  corresponding  number  of  lobes.  The  tubuli 
uriniferi  are  at  first  solid,  composed  solely  of  cells,  and  without  any 
membrana  propria.  In  the  course  of  development  the  latter  arises, 
probably  from  a  plasma  afforded  by  the  cells,  and  the  cavity  of  the 
canal  is  formed,  in  consequence,  it  may  be  supposed,  of  the  connection 
of  a  fluid  between  the  cells  ;  simultaneously  with  which  the  tubules 
begin  to  grow  rapidly  in  length,  and  to  become  convoluted.  The  Mal- 
pighian bodies  are  originally  nothing  more  than  solid,  clavate,  thick- 
ened extremities  of  the  rudimentary  tubuli  uriniferi.  The  interior 
cells  of  these  pyriform  or  rounded  bodies,  subsequently  become  capil- 
laries, which  are  continuous  at  two  points,  with  the  vessels  outside, 
whilst  the  most  exterior  form  the  epithelium,  which  joins  that  of  the 
tubulus  uriniferus,  and,  like  it,  is  invested  with  a  membrana  propria, 
which  is,  of  course,  deficient  where  the  afferent  and  efferent  vessels 
enter  and  emerge,  at  which  point  it  may  be  said  to  be  perforated.  In 
the  newborn  child,  according  to  Harting,  the  renal  canals  are  three 
times  more  slender  than  in  the  adult,  whence,  as  the  kidney  of  the 
latter  is  only  twice  the  size  of  that  of  the  child,  it  is  obvious  that,  at 
any  rate  after  birth,  no  tubules  are  formed. 

With  respect  to  the  physiological  relations,  I  would  merely  offer  the 
following  remarks.  There  can  be  no  question  that  the  peculiar  vascular 
conditions  in  the  kidney,  in  accordance  with  which  the  blood  circulates 
in  special  coils  projecting  into  the  commencement  of  the  tubuli  urini- 
feri, before  it  passes  into  the  proper  capillary  plexus  of  the  organ,  are 
most  intimately  connected  with  the  secretion  of  a  large  proportion  of 
water  in  the  urine.  The  hindrance  to  the  flow  of  the  blood  gives  rise 
to  a  considerable  lateral  pressure  in  the  glomeruli,  and  a  large  quantity 
of  blood-plasma  is  forced  through  the  thin  opposing  membrane  (the  walls 
of  the  capillaries  and  the  epithelium}.  Since  all  the  elements  of  the 
plasma  are  not  found  in  the  urine,  and  those  that  are,  present  in  it 
totally  different  proportions  to  those  in  which  they  exist  in  the  blood,  it 
is  obvious  that  the  membrane  in  question  does  not  act  simply  as  a  filter, 
but  also,  for  reasons  at  present  unknown,  retains  certain  substances 
(protein-compounds,  fat),  whilst  it  allows  others  (urea,  &c.)  to  pass 
through  with  peculiar  facility.  In  this  way  there  is  formed  in  the  com- 
mencements of  the  tubuli  uriniferi,  probably  a  very  diluted  urine,  which 
afterwards,  as  it  flows  towards  the  pelvis  of  the  kidney,  reciprocally 
acts  and  is  acted  upon  by  the  blood  circulating  around  the  tubuli  urini- 
feri, receiving  additional  substances  from  it  (perhaps  more  urea),  but 

39 


610  SPECIAL     HISTOLOGY. 

also  yielding  up  certain  of  its  own  constituents  (water  and  salts),  and 
thus,  at  last,  becomes  true  urine. 

As  regards  the  chemical  composition  of  the  kidney,  we  know  very 
little.  Frerichs  (1.  c.  p.  42)  found,  in  a  healthy  kidney,  16-30-18&  solid 
matter,  72-73-70  water.  Of  the  former,  the  fat  amounted  to  0-63-0-lS, 
although,  according  to  Owen  Rees,  it  may  amount  to  1-86 ;  the  greater 
portion,  however,  is  probably  albumen,  with  regard  to  which,  Ludwig 
especially  has  shown,  that  it  exists  in  large  quantity  in  the  kidney,  a 
fact  that,  from  the  micro-chemical  characters  of  the  epithelial  cells  of 
the  tubuli  uriniferi,  cannot  be  wondered  at. 

In  the  higher  animals,  the  secretion  of  the  urine  takes  place  without 
any  formation  or  dissolution  of  cells,  and  consequently  the  normal  urine 
just  evacuated  contains  no  morphological  elements.     It  is  only  occa- 
sionally that  ejrithelial  cells  from  the  urinary  passages,  especially  from 
the  bladder  and  urethra,  occur  in  it ;  but  we  almost  always  find  mucus 
from  the  same  localities,  forming  clouds  or  a  light  sediment,  occasionally 
with  mucous  corpuscles;  hnd  lastly,  spermatic  filaments  after  emissions. 
In  inflammations,  hemorrhages,  exudations,  fatty  kidney,  we  find  pus 
corpuscles,  oil  drops,  blood  globules,  blood,  and  fibrinous  coagula,  moulded 
in  the  tubuli  uriniferi,  in  the  form  of  cylindrical  casts,  and  epithelium 
from  the  tubuli,  isolated  or  in  continuous  strings  or  tubes.   Sedimentary 
deposits  of  the  salts  of  the  urine  are  readily  formed  as  the  products  of 
decomposition.    All  normal  urine  without  sediment,  at  a  mean  tempera- 
ture, undergoes  an  acid  fermentation,  under  the  influence  of  the  mucus 
contained  in  it;  and  whilst  fermentation  and  filamentary/^?^'  are  de- 
veloped, forms,  from  the  decomposition  of  the  urinary  coloring  matter, 
lactic  or  acetic  acid,  in  consequence  of  which  uric  acid  is  set  free  from 
its  compounds  and  deposited,  in  the  form  of  rhombic  or  prismatic  crys- 
tals, colored  yellow  or  reddish  by  the  coloring  matter  of  the  urine. 
Sooner  or  later  the  acid  disappears,  and  from  the  decomposition  of  the 
urea,  perhaps  also  of  the  coloring  matter,  the  urine  becomes  ammoniacal 
and  alkaline,  with  large  colorless  pyramidal  prisms,  or  needles  grouped 
in  a  stellate  fashion  and  soluble  in  acetic  acid,  of  the  triple  phosphate  of 
magnesia  and   ammonia,   which,   intermixed  with   numerous   infusoria 
(vibriones  and  monades)  form  a  superficial  pellicle,  and  with  granules  of 
urate  of  ammonia,  and   also,  it  may  be,  of  carbonate  of  lime,  a  white 
sediment.     Under  conditions  not  as  yet  known,  and  rarely,  hexahedral 
prisms  of  cystin  appear  in  the  urine ;  more  frequently,  after  the  use  of 
drinks  containing  carbonic  acid,  and  also  in  pregnant  women,  we  find 
the  octohedrons  of  oxalate  of  lime  insoluble  in  acetic  acid.    If  the  quan- 
tity of  uric  acid  be  augmented,  as  after  the  inordinate  use  of  nitrogenous 
food  with  deficient  exercise,  in  impaired  digestion,  fevers,  &c.  a  more  or 
less  abundant  yellowish  precipitate  of  urate  of  soda,  in  the  form  of 


THE     URINARY     ORGANS.  611 

isolated  or  aggregated  granules,  is  formed  as  soon  as  the  urine  cools, 
and  becomes  redissolved  when  it  is  again  warmed.  If,  under  these  cir- 
cumstances, the  acid  fermentation  is  set  up,  very  considerable  sediments 
of  colored  crystals  of  uric  acid  (brickdust  sediment)  are  often  thrown 
down.  In  injuries  of  the  bladder,  the  urine  frequently  becomes  alkales- 
cent with  great  rapidity,  when  the  above-mentioned  crystals  of  triple 
phosphate  at  once  make  their  appearance ;  they  are  also  very  frequent 
in  pregnancy ;  and  when  assuming  the  pellicular  form  above  described, 
were  at  one  time  regarded  as  a  peculiar  substance  (Kiesteine). 

The  occurrence  of  albumen,  fibrin,  and  fat,  within  the  tubuli  urini- 
feri, is,  in  my  opinion,  easily  explained,  upon  the  supposition,  that  in 
such  cases  the  circulation  is  obstructed,  and  an  increased  secretion  of 
the  elements  of  the  blood  takes  place  in  the  Malpighian  bodies  and 
tubuli  uriniferi,  in  consequence  of  which  the  epithelium  of  those  parts 
which,  as  is  well  known,  is  found  in  these  cases  in  considerable  quantity 
in  the  urine,  is  washed  away,  whence,  of  course,  any  further  hindrance 
to  the  continued  passage  of  the  above  substances  is  removed.  A  per- 
meation of  fibrin  through  the  epithelium  is  also  conceivable,  just  as 
much,  for  instance,  as  upon  the  mucous  membrane  of  the  respiratory 
organs,  although  I  do  not  believe  that  an  increased  pressure  of  such  a 
kind  as  to  induce  a  transudation  of  fibrin  could  fail  to  affect  the  deli- 
cate epithelium.  When  the  epithelium  is  once  removed,  it  becomes  an 
important  question  whether  it  is  quickly  restored ;  and  it  appears  to 
me,  that  the  frequent  occurrence  of  small  quantities  of  albuminous 
matter  in  the  urine  often  depends  simply  upon  local  deficiencies  of  the 
epithelium  caused  in  one  way  or  another. 

Investigation  of  the  kidney. — The  tubuli  uriniferi  are  readily  isolated 
when  the  tissue  of  the  organ  is  teased  out ;  the  epithelium,  membrana 
propria,  and  canal  being  distinctly  recognizable  if  blood-serum,  or  a 
solution  of  albumen  be  employed  to  moisten  it.  Together  with  entire 
tubules,  there  will  be  found  in  every  preparation  numerous  epithelial 
cells,  separate,  or  in  groups,  or  even,  as  especially  in  the  pyramids,  in 
the  form  of  long  continuous  tubules.  The  latter  often  present  a  pecu- 
liar aspect,  for  the  most  part  collapsing,  exhibiting  somewhat  flattened 
cells,  and  resembling  vessels.  Equally  frequent  are  longer  or  shorter 
tubes  of  the  membrana  propria,  which,  when  much  plicated,  cannot 
always  at  once  be  recognized.  In  the  examination  of  the  pyramids, 
the  extremely  numerous  vessels  must  not  be  confounded  with  the 
"  ducts  of  Bellini,"  or  the  epithelial  casts  that  have  escaped  from  them. 
The  connection  of  the  tubuli  uriniferi  with  the  Malpighian  bodies  is 
easily  discerned  in  the  kidney  of  the  Frog  and  of  Fishes,  upon  careful 
teasing  out  of  the  structure ;  but  in  Mammalia,  also,  it  will  rarely  be 


612  SPECIAL    HISTOLOGY. 

missed  in  fine,  hardened  sections,  and  especially  in  injected  prepara- 
tions. The  glomeruli  themselves  may  frequently  be  recognized  when 
naturally  injected,  and  still  better  when  artificially  filled,  which  we  may 
very  readily  succeed  in  doing  with  any  fine  material  thrown  in  by  the 
arteries.  Similar  injections,  also,  when  successful,  fill  the  whole  capil- 
lary plexus  of  the  cortical  substance  and  of  the  pyramids ;  when  this 
portion  of  the  circulatory  apparatus,  especially  in  perpendicular  sec- 
tions, may  be  very  satisfactorily  made  out.  For  the  same  purpose, 
kidneys  injected  from  the  veins  are  employed,  in  which  not  only  the 
capillary  plexus,  but  the  glomeruli  are  filled  ;*  and  for  the  study  of  the 
vasa  efferentia.)  preparations  not  completely  filled  from  the  arteries  are 
suitable.  The  course  of  the  tubuli  uriniferi  should  be  studied  in  fine 
sections  of  kidneys  hardened  by  immersion  in  alcohol,  by  boiling  in 
dilute  nitric  acid  and  drying  (Wittich),  or  by  chromic  acid,  and  ren- 
dered transparent  by  acetic  acid  ;  or  in  sections,  made  with  the  double- 
bladed  knife,  of  recent,  as  well  as  of  injected  kidneys,  in  which  the 
most  important  conditions,  even  the  divisions  of  the  "  ducts  of  Bellini," 
may  be  observed.  Nevertheless,  it  is  always  expedient  to  inject  the 
tubuli  uriniferi ;  and  for  this  purpose,  among  the  Mammalia,  the 
Horse  appears  to  be  best  adapted.  This  filling  may  happen,  in  conse- 
quence of  accidental  extravasation  into  the  Malpighian  capsules ;  in 
the  injection  of  the  arteries  by  this  means,  however,  rarely  more  than 
the  convoluted  tubuli  are  filled ;  or  it  may  be  effected  by  injection  from 
the  ureter  with  the  aid  of  the  air-pump  (Huschke,  Isis,  1826),  or  the 
pelvis  of  the  kidney  being  kept  filled,  if  an  endeavor  be  made  by  the 
kneading  of  it  with  the  hand,  to  force  the  material  into  the  "  ducts  of 
Bellini,"  and  beyond  them  (Cayla).  By  means  of  a  very  fine  canula, 
the  individual  tubuli  may  also  be  injected  directly  from  the  papillce. 

Literature. — M.  Malpighi,  "De  Renibus,  in  Exercit.  de  vise,  struct. ;" 
Al.  Schumlansky,  "  Diss.  de  structura  renum,"  c.  tab.  Argentor.  1782, 
4to  ;  W.  Bowman,  "  On  the  structure  and  use  of  the  Malpighian  Bodies 
of  the  Kidney,"  in  "Phil.  Trans.,"  1842.  I.  p.  57;  C.  Ludwig,  "Beit- 
rage  zur  Lehre  vom  Mechanismus  der  Harnsecretion,"  Marburg,  1843 ; 
and  Art.  "Mere,"  in  Wagner's  "  Handw.  d.  Physic-log.,"  II.  p.  628; 
J.  Gerlach,  in  "  Mailer's  Archiv.,"  1845  and  1848  ;  Kolliker,  in  "  Mull. 
Archiv.,"  1845;  Remak,  in  "Froriep's  N.  Notiz.,"  No.  786,  1845,  p. 
308  ;  F.  Bidder,  in  "Mull.  Archiv.,"  1845,  and  "  Untersuch.  uber  die 
Geschlechts-  und  Harnwerkzeuge  der  Amphibien,"  Dorpat,  1846;  J. 
Hyrtl,  in  "Zeits.  d.  Wien.  Aerzte,"  1846  ;  [Jos.  Toynbee,  "  On  the  In- 
timate Structure  of  the  Human  Kidney,"  "Med.  Chirur.  Transact.,"  2d 
Ser.  vol.  II.,  p.  303,  1846;]  C.  v.  Patruban,  "Beitrage  zur  Anatomic 

*  [I  have  found  that  the  Malpighian  corpuscles  are  filled  with  much  more  difficulty,  and 
always  imperfectly  by  injections  thrown  in  by  the  veins. — DaC.] 


THE    SUPRARENAL    GLANDS.        .  613 

der  menschlichen  Niere,"  in  "Prag.  Viertelj."  1847,  III. ;  Gr.  Johnson, 
Art.  "  Ren,"  in  "  Cyclop,  of  Anat.,"  May,  1848  ;  V.  Cams,  in  "  Zeitsch. 
f.  wiss.  Zool.,"  II.,  p.  61 ;  v.  Wittich,  in  "  Arch,  fur  path.  Anat."  III., 
1,  1849  ;  v.  Hessling,  in  "  Froriep's  N.  Notiz.,"  1849,  p.  264,  and  "  His- 
tologische  Beitrage  zur  Lehre  von  der  Harnsecretiop,"  Jena,  1851.  Be- 
sides which  should  be  consulted  the  usual  Manuals  of  Anatomy,  espe- 
cially those  of  Henle,  Valentin,  J.  Muller,  and  myself;  the  "Memoirs 
on  Development,"  particularly  of  Valentin,  Rathke,  "Abhand  zur 
Entw."  II.,  p.  97;  J.  Muller,  "  De  Gland,  sec.  structura";"  and  lastly, 
the  "  Annual  Reports  of  Reichert,"  1846  and  1849. 

OF  THE  SUPRARENAL  GLANDS. 

§  192.  The  suprarenal  glands  or  capsules,  glandulce  suprarenales,  are 
a  pair  of  organs,  in  their  structure  approaching  nearest  to  the  blood-vas- 
cular glands,  but  whose  function  is  as  yet  altogether  unknown.  Each 
consists  of  a  moderately  firm  but  thin  coat  composed  of  connective 
tissue,  which  closely  invests  the  entire  organ  and  is  connected  by  numer- 
ous processes  with  the  proper  parenchyma,  composed  of  a  cortical  and  a 
medullary  substance.  The  former,  substantia  corticalis,  is  more  com- 
pact, J— J  a  line  thick,  tearing  readily  in  the  direction  of  its  thickness, 
and,  when  torn,  presenting  a  fibrous  aspect.  Its  color  is  for  the  most  part 
whitish-yellow,  or  yellow,  in  the  innermost  third,  however,  usually  pass- 
ing into  brownish  yellow  or  brown,  so  that  in  a  transverse  section,  two 
layers  may  be  distinguished,  an  external,  bright-colored  layer  and  an 
internal,  narrow,  dark  border.  The  medullary  substance  is,  normally, 
of  a  brighter  color  than  the  cortical,  being  of  a  grayish-white  with  a 
tinge  of  red,  although  when  its  numerous  veins  are  full  of  blood,  it  may 
assume  a  darker  and  more  venous  hue.  Its  consistence  is  softer  than 
that  of  the  cortical  substance,  though  not  so  much  so  as  is  usually  be- 
lieved, and  with  respect  to  its  thickness,  it  is  very  inconsiderable  (|— J 
of  a  line)  at  the  thin  borders  and  at  the  upper  and  outer  extremity  of 
the  organ,  whilst  in  the*  middle,  and  in  the  lower  and  inner  half,  it 
amounts  to  as  much  as  1  or  even  1J  lines.  In  the  dead  human  subject, 
the  cortical  substance  very  readily  becomes  detached  from  the  medullary, 
when  the  suprarenal  gland  presents  a  cavity,  frequently  occupying  the 
entire  organ,  and  containing  a  dirty,  pultaceous  substance  derived  from 
the  half  disintegrated  brown  layer  of  the  cortex,  mixed  with  blood,  to- 
gether with  the  less  altered  medullary  substance ;  which,  however,  in 
more  rare  instances,  also  becomes  broken  up. 

§  193.  Intimate  structure. —  The  cortical  substance  presents  as  a  foun- 
dation, a  delicate  meshwork  of  connective  tissue,  which,  in  connection 
with  the  tunic  and  the  thin,  mutually  connected  lamina?  proceeding  from 


614  SPECIAL    HISTOLOGY. 

it,  pervades  the  entire  layer,  and  forms  the  boundaries  of  very  nume- 
rous, closely-approximated  compartments,  0-016-0-02,  or  even  0-03  of 
a  line  in  diameter,  which  extend  in  a  vertical  direction  from  without  to 
within,  through  the  entire  thickness  of  the  cortex.  In  these  compart- 
ments is  lodged  a  granular  substance,  subdivided  by  delicate,  oblique  or 
transverse  dissepiments,  into  larger  and  smaller  aggregations,  which 
Ecker  describes  as  gland-follicles,  and  as  containing,  within  a  structure- 
less membrane,  a  granular  material  mixed  with  nuclei  or  even  cells. 
But  in  these  " cortical  cylinders,"  as  I  would  term  them,  I  have,  in 
most  instances,  noticed  nothing  but  rounded-angular  cells,  0-006-0-012 
of  a  line  in  size,  and  believe  that  Ecker,  from  the  more  rare  occurrence 
of  true  follicles,  has  been  induced  to  regard  the  compact  aggregations 

Fig.  253. 


of  so-termed  cells  which  occur  in  the  interior  of  the  cortex,  and  which 
are  0-024—0-048—0-06  of  a  line  long,  as  special  follicles.  In  fact,  the 
cortical  cells,  which,  on  the  external  and  internal  portions  of  the  cortex, 
are  to  be  met  with  more  isolated  in  the  compartments,  are  in  its  inte- 
rior, closely  united  into  oval  or  cylindrical  masses,  in  which  the  outlines 
of  the  cells  have  frequently  coalesced  into  a  single,  general  contour-line. 
I  have  never  been  able  to  detect  any  other  membrane  surrounding  the 
cells  besides  the  connective  tissue  of  the  corresponding  compartment, 
and  I  have  almost  always  succeeded,  by  pressure,  or  the  addition  of 
alkalies,  in  isolating  the  cells,  without  bringing  into  view  any  special 
sac.  True  follicles,  I  have  hitherto  seen  only  in  the  inner  portions  of 
the  cortex,  in  the  form  of  round  or  oval  vesicles  0-02-0*8  of  a  line  in 
diameter,  within  which  no  cells  like  those  of  the  cortical  cylinders  are 
formed,  but  only  a  collection  of  oil-drops  could  be  recognized,  arid  which 

FIG.  252. — Portion  of  a  vertical  section  through  the  cortex  of  the  suprarenal  body  in  Man : 
a,  septa  of  connective  tissue;  6,  cortical  cylinder,  whose  composition  out  of  cells  is  more  or 
less  distinctly  manifest. — Magnified  300  diameters. 

FIG.  253. — From  the  suprarenal  body  of  Man :  a,  five  cells  filled  with  pale  contents,  from 
the  summit  of  a  cortical  cylinder;  6,  pigment-cells  from  the  innermost  layer  of  the  cortex; 
c,  fat-containing  cells,  from  the  yellow  cortical  layer;  d,  a  larger  cyst  filled  with  fat,  from  a 
cortex  of  that  kind  (gland-follicle,  Ecker)  ;  e,  cells  from  the  medullary  substance,  some  with 
processes. — Magnified  300  diameters. 


THE     SUPRARENAL    GLANDS.  G15 

I  have  been  inclined  to  regard  as  enlarged  cells.  The  contents  of  the 
cortical  cells  normally  consist  of  fine  granules  of  a  nitrogenous  sub- 
stance ;  but  to  these  are  almost  always  added  solitary  fat-granules,  which 
in  many  cases  (in  the  yellow  cortical  substance),  exist  in  such  quantity, 
as  entirely  to  fill  the  cells,  which  then  assume  a  deceptive  resemblance 
to  those  of  a  fatty  liver.  In  the  brown  layer  of  the  cortex,  the  cells  are 
entirely  filled  with  brown  pigment  granules. 

The  medullary  substance  also  has  a  stroma  of  connective  tissue,  which, 
prolonged  from  the  cortical  lamellse,  pervades  the  whole  interior,  for  the 
most  part,  in  more  delicate  fasciculi,  constituting  a  network  with  rather 
narrow,  rounded  meshes.  In  this  network  lies  a  pale,  fine-granular  sub- 
stance, in  which,  in  Man,  by  careful  manipulation,  and  in  recent  prepa- 
rations, I  have  almost  always  noticed  pale  cells  of  0-008-0-016  of  a  line, 
which,  in  their  fine-granular  contents,  occasionally  presenting  a  few  fat, 
or  pigment  granules,  their  frequently  very  distinct  nucleus  with  large 
nucleoli,  their  angular  form,  and  occasionally  single  or  multiple,  or  even 
branched  processes,  resemble  the  nerve-cells  of  the  central  organs, 
although  they  cannot  definitively  be  declared  to  be  such. 

§  194.  Vessels  and  nerves. — The  bloodvessels  of  the  suprarenal 
glands  are  numerous,  lie  in  the  stroma  of  connective  tissue,  and  forni 
two  kinds  of  capillary  plexuses  ;  one  in  the  cortex  with  elongated 
meshes,  and  one  in  the  medullary  substance  with  more  rounded  inter- 
stices. The  arteries  arise  as  numerous  (amounting  to  twenty)  small  ves- 
sels from  the  neighboring  larger  trunks  (phrenic,  eseliac,  aortic,  renal), 
and  either  penetrate  directly  into  the  medullary  substance  or  ramify  in 
the  cortical.  The  latter,  which  are  the  more  numerous,  cover  the  outer 
surface  of  the  organ  with  their  multiplied  ramifications,  and  form  a 
wide  capillary  plexus  even  in  the  outer  tunic.  They  then  subdivide  into 
numerous  fine  twigs,  and  dip  down  into  the  dissepiment  of  the  cortex, 
in  which,  becoming  more  and  more  attenuated,  they  run  straight  to- 
wards the  medulla,  being  mutually  connected  in  their  course  by  pretty 
numerous  transverse  anastomoses,  so  that  the  cortical  cylinders  are  sur- 
rounded by  blood  on  all  sides.  The  extremities  of  these  vessels  extend 
to  the  interior  of  the  medulla,  where,  in  common  with  the  arteries 
which  penetrate  directly  to  the  same  point  (of  which,  however,  accord- 
ing to  Nagel,  in  the  Sheep,  some  proceed  from  the  medulla  entirely  to 
the  cortex)  they  form  a  rich  capillary  plexus  of  rather  large  vessels. 
The  veins  arise  chiefly  from  this  latter  plexus,  and,  within  the  medul- 
lary substance,  join  the  principal  vein  of  the  organ, — the  v.  suprarenalis 
— which  comes  out  on  the  anterior  surface,  at  the  so-termed  Mlus, 
emptying  itself,  on  the  right  side,  into  the  vena  cava  and  on  the  left, 
into  the  renal  vein.  Besides  these,  a  good  many  smaller  veins  arise 
from  the  cortex,  which  either  accompany  the  arteries  in  pairs,  or  pro- 


616 


SPECIAL    HISTOLOGY. 


Fig.  254. 


ceed  independently  and  open  into  the  renal  and  phrenic  veins,  and  into 
the  inferior  vena  cava.  Of  lymphatics,  I  have  as  yet  noticed  only  a 
few  small  trunks  on  the  surface  of  the  organ,  but  none  in  the  interior 
or  corning  out  from  it.  The  nerves  of  the  suprarenal  glands  are,  as 
was  correctly  stated  by  Bergmann,  extremely  numerous,  arising  from 
the  semilunar  ganglion  and  the  renal  plexus ;  according  to  Bergmann 
also,  to  a  small  extent,  from  the  vagus  and  phrenic  nerves.  In  Man, 
in  the  right  suprarenal  gland,  I  have  counted  thirty-three  trunks,  8  of 
1-5-1-10,  5  of  1-14-1-20,  7  of  1-25-1-33,  and 
13  of  1-45-1-50  of  a  line,  and  found  that,  with- 
out exception,  or  at  all  events  in  a  very  prepon- 
derating proportion,  they  were  constituted  of 
dark-bordered,  finer  and  medium-sized,  or  even 
thick  fibres  ;  were  whitish  or  white  and  furnished 
with  isolated,  larger  or  smaller  ganglia.  They 
are  especially  apparent  on  the  inferior  half  and 
inner  border  of  the  organ,  and  appear  to  be  all 
destined  for  the  medullary  substance,  in  which,  at 
least  in  the  Mammalia,  an  extremely  rich  plexus 
of  dark-bordered,  finer  fibres  occurs,  inclosed  in 
the  trabeculce.  and  connective  tissue,  their  termi- 
nations, however,  being  nowhere  perceptible.  In 
man,  the  medullary  substance  is,  in  most  in- 
stances, so  altered,  that  the  nerves  cannot  be 
traced  farther  than  to  their  entrance  into  it,  it  be- 
ing impossible  to  follow  their  farther  distribution. 

§  195.  Physiological  remarks. — The  suprarenal  glands  are  developed 
simultaneously  with  the  kidneys  and  independently  of  them,  from  a 
blastema  derived  from  the  middle  germinal  lamella  (Remak),  the  first 
appearance  and  growth  of  which  is  unknown,  and  are  originally  larger 
than  the  kidneys.  In  the  third  month  the  two  organs  are  of  equal  size  ; 
in  the  embryo  at  six  months,  the  weight  of  the  suprarenal  capsule  is,  to 
that  of  the  kidney,  as  2  to  5,  in  the  mature  embryo  as  1  to  3,  in  the 
child  at  birth  as  1  to  8  (Meckel).  In  other  Mammalia  the  suprarenal 
glands  are,  from  the  first,  smaller  than  the  kidneys,  and  increase  in  the 
same  proportion  with  them.  Little  is  known  with  respect  to  the  histo- 
logical  development  of  the  organ.  I  have,  hitherto,  investigated  this 
only  in  an  embryo  of  three  months,  in  which,  like  Ecker,  I  found  the 
cortex  whitish,  the  medulla  whitish-red,  and  both  constituted  of  cells  and 
fibres.  The  cells  measured  0-012-0-02  of  a  line,  had  well  marked  in  part 
colossal  nuclei,  with  distinct  nucleoli,  and  in  the  cortical  part  also  fatty 

FIG.  254. — Transverse  section  of  the  suprarenal  body  of  the  Calf,  magnified  about  15 
diameters:  treated  with  soda:  a,  cortex ;  6,  medulla;  c,  central  vein  surrounded  with  some 
cortical  substance ;  </,  three  entering  nerves ;  e.  nerves,  and  their  distribution  in  the  interior. 


THE  SUPRARENAL  GLANDS.  617 

molecules.  Of  the  nerves  at  that  period  I  saw  nothing.  In  a  newly-born 
Rabbit,  Ecker  observed  no  appearance  of  follicles,  whilst  in  a  foetal  Calf, 
1  foot  6  inches  long,  he  found  them  very  distinct,  but  small  (O05-0'15mm). 
As  regards  the  functions  of  the  suprarenal  glands,  in  the  absence  of 
all  physiological  indications,  arid  so  long  as  the  course  of  the  nerves  in 
them  is  not  much  more  accurately  known,  only  very  general  observa- 
tions can  at'present  be  offered.  I  consider  the  cortical  and  medullary 
substances  as  physiologically  distinct.  The  former  may,  provisionally, 
be  placed  with  the  so-termed  "blood-vascular  glands,"  and  a  relation 
to  secretion  assigned  to  it ;  whilst  the  latter,  on  account  of  its  extremely 
abundant  supply  of  nerves,  must  be  regarded  as  an  apparatus  apper- 
taining to  the  nervous  system,  in  which  the  cellular  elements  and  the 
nervous  plexus  either  exert  the  same  reciprocal  action  as  they  do  in  the 
gray  nerve-substance,  or  stand  in  a  relation  as  yet  wholly  unascertained, 
towards  each  other.  (For  a  more  detailed  account  vid.  Mikros.  Anat. 
II.  2,  zw.  Halfte.)* 

*  [The  former  and  more  recent  researches  of  Leydig  ("  Anatomisch-histologische  Unters.  tib. 
Fische  u.  Reptilien,"  1853)  appear  satisfactorily  to  show  the  identity  of  the  suprarenal  glands 
of  the  Mammalia,  with  the  yellow,  vascular  bodies  seated,  either  on  the  kidney  itself  and 
its  ernulgent  veins,  or  at  a  greater  distance  from  those  glands,  on  the  veins  near  the  epididy- 
mis  or  ovaries,  or  upon  the  sympathetic  nerve.  The  study  of  these  more  simple  forms  has 
also  thrown  very  considerable  light  upon  the  structure  and  true  import  of  the  more  compli- 
cated organ  in  the  Mammalia.  In  the  Salamander,  the  ganglia  of  the  sympathetic  have  a 
very  remarkable  structure,  and  contain  cellular  elements  of  two  very  distinct  kinds.  Each 
ganglion  has  a  tunic  of  connective  tissue  which  sends  septa  into,  the  interior,  which  is  thus 
divided  into  distinct  and  occasionally,  perfectly  separate  compartments.  The  cells  of  both 
kinds  are  enclosed  in  these  compartments,  and  are  never  intermixed  in  one  and  the  same. 
In  some  of  the  compartments,  or  as  they  might  almost  be  termed,  vesicles,  the  cells  are 
large,  clear,  and  finely  granular,  with  a  vesicular  nucleus  and  very  transparent  nudeolus. 
From  some  of  these  cells,  nerve-fibres  are  distinctly  seen  to  proceed,  and  they  would  appear 
to  be  of  the  bipolar  kind  of  ganglion-  or  nerve-cells.  The  other  kind  of  cells,  contained  in 
perfectly  distinct  compartments,  are  much  smaller  and  their  contents  of  a  peculiar  dirty 
yellow  color,  owing  to  which  the  perfectly  transparent  nucleus  is  rendered  very  distinct. 

These  two  kinds  of  cells  occur  in  very  variable  proportions  in  different  ganglia.  Now,  if 
the  dirty  yellow-colored  ganglion-globules  of  one  of  these  sympathetic  ganglia  be  compared, 
side  by  side,  with  the  contents  of  one  of  the  yellow  bodies  on  the  veins,  or  of  the  yellow 
granular  masses  on  the  kidney,  it  will  be  at  once  apparent,  that  by  a  gradual  transforma- 
tion, they  directly  pass  into  the  fatty,  granular  cells  of  the  so-termed  suprarenes.  And  the 
same  transformation  may  take  place  even  in  the  sympathetic  ganglia. 

According  to  'Leydig,  the  cortical  substance  of  the  suprarenal  capsules  of  the  Mammalia 
corresponds  to  the  yellow,  granular  and  striped  suprarenal  bodies  of  Fishes  and  Amphibia; 
whilst  the  medullary  substance  of  the  Mammalian  organ,  which  is  abundantly  supplied  with 
nerves  and  cells,  very  like  the  ganglion-globules,  represents  the  other  divisions  of  the  sym- 
pathetic ganglia:  whence  he  concludes  that  Bergmann's  view,  according  to  which  the 
suprarenal  capsules  are  closely  related  to  the  nervous  system,  is  undoubtedly  correct,  and 
that  those  organs  bear  the  same  relation  to  the  ganglia  of  the  sympathetic  nerves,  as  the 
pituitary  body  bears  towards  the  brain.  Besides  this  relation  to  the  nervous  system,  how- 
ever, they  have  an  intimate  one  with  the  vascular;  and  are,  therefore,  always  pervaded  by  a 
very  close  capillary  plexus.  But  in  any  case,  he  says,  the  supi'arenal  bodies  must  be  re- 
moved from  the  category  of  the  so-termed  blood- vascular  glands,  which  would  then  include 
only  the  thyroid  and  thymus,  or  should  probably  be  abolished  altogether,  as  an  unmeaning 
term. — TRS.] 


618  SPECIAL     HISTOLOGY. 

In  the  investigation  of  the  suprarenal  glands,  the  larger  Mammalia 
ought,  in  the  first  place,  to  be  chosen,  and  not  till  afterwards  should 
they  be  studied  in  Man.  The  cortical  portion  is  readily  examined  when 
its  elements  contain  but  little  fat,  and,  above  all,  perpendicular  sections 
of  fresh  specimens,  or  of  such  as  have  been  hardened  in  alcohol  and  in 
chromic  acid,  which  are  afterwards  to  be  rendered  transparent  by  soda, 
are  to  be  recommended.  The  medullary  substance,  even  in  animals,  is 
very  easily  disintegrated,  so  that  its  elements  are  either  not  to  be  seen 
at  all  in  the  normal  state,  or  only  partially,  although  they  are  occa- 
sionally very  beautifully  displayed  without  any  addition,  as  well  as  in 
chromic-acid  preparations.  In  animals,  the  nerves  are  very  easily  dis- 
cerned in  fine  sections,  after  the  addition  of  soda;  and  when  their  ex- 
ternal visible  points  of  entrance  are  exactly  hit  upon  in  the  making  of 
the  section,  their  course  through  the  cortical  substance  is  readily  brought 
into  view.  For  the  vessels,  injections  should  be  employed,  which  are 
best  effected  in  the  Sheep  or  sucking  Pig,  and  which  readily  succeed 
when  made,  as  well  from  the  arteries  as  from  the  non-valvular  veins. 

Literature. — Nagel.  "  Diss.  sistens  ren.  succent.  mammal,  descript.," 
Berol.,  1838,*  and  Mull.  "  Arch.,"  1836;  C.  Bergmarm,  "  Diss.  de 
glandulis  suprarenal,"  c.  tab.  Gott.,  1839  ;  A.  Ecker,  "  Der  feinere 
Bau  der  Nebennieren  beim  Menschen,"  u.  den  4  "  Wirbelthierclassen," 
Braunschweig,  1846,  und  Art.  "Blutgefassdrusen,"  in  Wagner's 
"  Handw.  d.  Physiologic,"  Bd.  IV.  1849  ;  H.  Frey,  Art.  "  Suprarenal 
Capsules,"  in  Todd's  "  Cyclop,  of  Anat.,"  Oct.,  1849. 

[H.  Gray,  "  On  the  development  of  the  ductless  Glands  in  the  Chick," 
"  Phil.  Trans."  1852.— TRS.] 


OF    THE    SEXUAL    ORGANS. 
A.     MALE  SEXUAL  ORGANS. 

§  196.  The  male  sexual  organs  consist,  1,  of  two  glands  for  the  se- 
cretion of  the  semen,  the  testes,  which,  together  with  special  tunics,  the 
tunicce  vaginales,  are  contained  in  the  scrotum  ;  2,  of  their  efferent 
canals,  the  vasa  deferentia  and  ejaculatory  ducts  with  their  appendages, 
the  vesicular  seminales;  3,  of  the  copulatory  organs,  the  penis  and  its 
muscles ;  4,  and  lastly,  of  special  accessory  glands,  the  prostate  and 
Cowpers  glands. 

§  197.  The  testicles,  testes,  are  a  couple  of  true  glands,  containing 
within  a  special  tunic,  the  tunica  albuginea  s.  fibrosa,  the  secreting  ele- 
ments, in  the  form  of  complexly  convoluted  tubules,  the  spermatic  tubes 
or  tubuli  seminiferi.  The  tunic  is  a  white,  dense  and  thick  membrane, 


THE     SEXUAL     ORGANS. 


619 


corresponding  in  structure,  in  all  respects,  with  other  fibrous  membranes 
(the  dura  mater  especially),  and  everywhere  surrounding  the  paren- 
chyma of  the  testis  as  a  closed  capsule.  Its  external  surface,  except 
where  the  epididymis  is  attached  to  the  testis,  is  rendered  smooth  and 
glistening  by  a  special  covering,  the  tunica  adnata,  whilst  the  internal 
is  united  with  the  substance  of  the  gland  by  a  thin  layer  of  loose  con- 
nective tissue,  and  moreover,  sends  a  considerable  number  of  processes 
into  the  interior;  of  which,  the  most  important  is  the  corpus  Highmori 


Fig.  257. 


s.  mediastinum  test-is,  a  vertical  lamella  of  dense  connective  tissue  f— 1 
inch  long,  and  thick  at  its  commencement,  which  extends  from  the  pos- 
terior border  of  the  testis  to  a  depth  of  3-4  lines  into  the  interior  (Fig. 

FIG.  255. — Transverse  section  through  the  right  testis  and  its  tunics,  in  Man :  cr,  t.  vaginalis 
communis  ;  6,  t.  vaginalis  propria,  outer  lamella;  c,  cavity  of  the  t.  v.  propria,  which  does  not 
exist  in  life;  d,  inner  lamella  of  the  t.  v.  propria  (adnata),  coalescent  with  e,  the  t.  albuginea; 
/,  continuation  of  the  t.  propria  on  the  epididymis,  g  ;  h,  corpus  Highmorianum  ;  i  i  i,  branches 
of  the  spermatic  artery;  k,  vena  spermalica  interna;  I,  vas  defercns  ;  m,  artery  of  the  vas  defc- 
rens;  n,  lobuli  testis ;  s,  seplula. 

FIG.  25G. — Diagram  of  the  course  of  a  spermatic  tubule. 

FIG.  257. — Human  testis  and  epididymis,  after  Arnold:  a,  testis ;  b,  lobes;  c,  ductuli  recti  • 
d,  rele  vasculosum  •  e,  vascula  ejferentia  ;  f,  coni  vasculosi ;  g,  epididymis;  h,vas  deferens ;  i,  vas 
aberrans  •  m,  branches  of  the  spermatica  interna  of  the  testis  arid  epididymis  •  n:  ramification  on 
the  testis ;  o,  art.  defcrentialis  •  p,  anastomosis  with  a  branch  of  the  spermatic. 


620  SPECIAL    HISTOLOGY. 

255  h) ;  but  besides  this,  there  are  numerous  lamellar  processes  (septula 
testis)  (Fig.  255  s)  arising  from  the  internal  surface  of  the  tunica  albu- 
ginea,  composed  of  more  lax  connective  tissue,  which,  separating  the 
divisions  of  the  glandular  structure  from  each  other,  and  conveying  the 
vessels  belonging  to  them,  converge  from  all  sides  towards  the  corpus  Higli- 
mori,  and  are  attached  by  their  acuminate  terminations  to  its  surfaces. 
The  glandular  substance  of  the  testis  is  not  absolutely  homogeneous, 
but  consists  of  a  certain  number  (100—250)  of  pyriform  lobules,  lobuli 
testis,  which  are  not,  however,  everywhere  wholly  separated  from  each 
other,  and  all  converge  with  their  points  towards  the  corpus  Highmo- 
rianum,  close  to  which  they  are  shortest,  whilst  those  between  the 
borders  of  the  organ  are  the  longest  (Fig.  255  n,  257  b).  Each  of  these 
lobules  is  formed  of  from  1  to  3  seminal  tubules  or  canaliculi,  1-8-1-15 
of  a  line  in  diameter.  These  tubules,  much  convoluted,  pretty  frequently 
dividing  and  also,  perhaps,  anastomosing,  in  their  course,  form  a  com- 
pact substance  and  ultimately  terminate  at  the  thick  end  of  the  lobule, 
at  a  greater  or  less  distance  from  the  surface,  either  in  csecal  ends  or  in 
loops  (Fig.  256  g).  The  spermatic  canals  of  each  particular  lobule, 
although  joined  to  each  other  by  some  connective  tissue  and  vessels,  may 
nevertheless,  by  careful  dissection,  be  separated  to  a  great  extent,  or 
even  wholly  isolated.  Their  length,  according  to  Lauth,  is  from  13  to 
33  inches.  At  the  pointed  extremity  of  each  lobule  the  spermatic  canals 
become  straighter,  when  each  by  itself,  or  the  two  or  three  arising  in 
one  lobule  united  into  a  simple  canal,  enter  as  the  ductuli  recti,  1-10  of 
a  line  in  diameter  (Fig.  257  c),  the  base  of  the  corpus  Higlimori,  where 
they  form  a  very  close  plexus,  2-3  lines  broad  and  1J  lines  thick,  and 
extending  the  whole  length  of  that  body, — the  rete  testis  (r.  vasculosum 
Halleri]  (Fig.  257  d).  From  the  upper  end  of  this  plexus,  the  canals  in 
which  measure  from  1-12  to  1-33  of  a  line  (0-03-0-08  of  a  line),  proceed 
7-15  efferent  canals,  vasa  efferentia  testis  s.  Grraafiana,  of  J-J  of  a  line 
(0*16-0-18  of  a  line)  (Fig.  257  e),  which,  traversing  the  t.  albuginea,  are 
continued  into  the  epididymis.  Here  they  contract  to  1-8  and  1-10  of 
a  line,  are  convoluted  in  exactly  the  same  way  as  the  spermatic  canals 
in  the  lobuli  testis,  but  without  presenting  divisions  or  anastomoses,  and 
thus  produce  a  certain  number  of  conical  bodies,  the  apices  of  which  are 
directed  towards  the  testis, — the  spermatic  cones  (coni  vasculosi  s.  cor- 
pora pyramidalid)  (Fig.  257 /).  These  cones,  united  together  by  con- 
nective tissue,  constitute  the  head  (globus  major)  of  the  epididymis,  at 
the  upper  and  posterior  border  of  which  their  canals  gradually  coalesce ; 
and  thus  is  formed  the  simple  thick  duct  of  the  epididymis,  0*16-0-2  of 
a  line  in  diameter  (Fig.  257,  g).  This  duct,  convoluted  in  a  well-known 
manner,  forms  the  body  and  tail  (globus  minor)  of  the  epididymis, 
usually  giving  off  at  its  inferior  extremity  a  coscal  prolongation,  vas 
aberrans  Halleri  (Fig.  257,  i)  and  is  ultimately  continuous  with  the 


T  H  E    S  E  X  U  A  L     0  R  G  A  N  S.  621 

spermatic  duct  or  vas  deferens,  which  at  first  J— J  of  a  line  in  diameter 
and  convoluted,  soon  increases  to  a  size  of  f-1  line,  and  becomes 
straight  (Fig.  257,  h).  The  epididymis,  moreover,  has  an  extremely 
delicate  fibrous  tunic  (J  of  a  line)  of  a  grayish-white  color. 

§  198.  Structure  of  the  seminiferous  tubes. — The  seminal  tubes  of 
the  testis  are,  in  proportion  to  their  diameter,  rather  more  firmly  con- 
structed than  other  glandular  canals  and  consist  of  a  fibrous  membrane 
and  an  epithelium.  The  former,  from  0-0024-0-005,  or  in  the  mean 
0-003-0-004  of  a  line  thick,  composed  of  an  indistinctly  fibrous  connec- 
tive tissue  with  longitudinal  nuclei,  without  muscular  fibres  and  rarely 
presenting  an  indication  of  elastic  fibrils,  is  tolerably  firm  and  exten- 
sible. A  simple  layer  of  roundish,  polygonal  Fig  258 
cells,  of  0-005-0-008  of  a  line,  occasionally 
with  an  indication  of  a  membrana  propria  as 
a  substratum,  on  the  inner  surface  of  this 
fibrous  membrane,  completes  the  vascular  ca- 
nal, which  thus  obtains  a  wall,  0-007-0-01  of  a 
line  in  entire  thickness.  In  younger  subjects, 
these  cells  are  pale  and  finely  granular,  but 
as  age  advances,  a  continually  increasing  num- 
ber of  fatty  granules  is  collected  in  them, 
whence  the  seminiferous  tubes  sometimes  ac- 
quire a  light  yellowish,  partially  brownish 
color,  which  is  manifest  very  frequently  in  men  even  at  the  middle 
period  of  life,  and  invariably  in  old  age.  The  ductuli  recti  present  the 
same  structure  as  the  tubes ;  whilst  in  the  rete  test-is,  no  special  fibrous 
tunic  can  be  distinguished,  the  canals  in  this  portion  of  the  gland  ap- 
pearing to  be  nothing  more  than  cavities  in  the  dense  fibrous  tissue  of 
the  corpus  Highmorianum,  lined  by  an  epithelium.  In  the  coni  vas- 
culosi  the  fibrous  coat  again  makes  its  appearance,  and  to  it  there  is 
now,  also,  added  a  layer  of  smooth  muscles,  which,  in  the  form  of  trans- 
verse and  longitudinal  fibres,  are  recognizable  even  in  canals  of  j  to  -J 
of  a  line  in  diameter.  The  thicker  portions  of  the  canal  of  the  epididy- 
mis  are  constructed  in  the  same  way  as  the  vasa  deferentia  (vid.  infra], 
with  a  cylindrical  epithelium,  which,  moreover,  commences  even  in  the 
head  of  the  epididymis. 

The  contents  of  the  seminiferous  tubes  vary  according  to  age.  In 
Boys  and  young  Animals  the  slender  tubuli  contain  nothing  but  minute, 
clear  cells,  the  most  external  of  which  might  be  regarded  as  epithelial 
cells,  although  not  always  clearly  distinguishable  from  the  others.  At 
the  age  of  puberty,  together  with  the  increased  size  of  the  tubuli  semini- 

FiG.  258. — Portion  of  a  spermatic  tube  in  Man,  magnified  350  diameters:  a,  fibrous  coat 
with  longitudinal  nuclei;  6,  clear  border,  probably  a  membrana  propria  ;  c,  epithelium. 


622 


SPECIAL    HISTOLOGY. 


feri,  the  elements  contained  in  them  also  increase  in  circumference ; 
and  when  the  formation  of  semen  has  actually  commenced,  they  appear 
as  clear,  round  cells  and  cysts  of  0-005— 0-03  of  a  line,  which,  according 
to  their  size,  enclose  a  variable  number  of,  from  1  to  10,  or  even  20, 
clear  nuclei  of  0-0025-0-0035  of  a  line  with  nucleoli.  At  this  time,  in 
many  cases,  an  epithelium  is  not  manifest,  the  seminal  tubes  rather 
appearing  to  be  occupied  entirely  and  solely  by  the  cells  in  question ; 
at  other  times,  and  particularly  in  advanced  years,  an  epithelium  is 
presented  containing  fat,  or  pigment-cells,  and  surrounding  the  other 
elements.  The  latter,  whether  they  occur  in  the  one  way  or  the  other, 
are  the  precursors  of  the  semen,  which,  in  the  mature  condition,  entirely 
consists  of  an  extremely  small  quantity  of  a  viscid  fluid,  and  of  innu- 


Fig.  259. 
t  .   *•' 


Fig.  200. 


\ 


\ 


merable  minute,  linear  corpuscles  having  a  peculiar  movement,  the 
spermatic  filaments  or  animalcules,  fila  spermatica,  spermatozoa  (also 
sperniatozoidd).  These  spermatic  filaments  are  perfectly  homogeneous, 
soft  corpuscles,  in  which  are  distinguishable  a  thicker  portion — the  body 
or  head, — and  a  filamentary  appendage, — the  filament  or  tail.  The 
former  is  flattened  and,  viewed  on  the  side,  pyriform,  with  the  acute 
end  in  front ;  on  the  surface  oval,  or  even  rounded  anteriorly,  and  also, 
though  more  towards  the  anterior  part,  slightly  cupped  ;  so  that  it 
sometimes  appears  clear  in  the  middle,  sometimes  opaque.  It  is  0*0016— 
0-0024  of  a  line  long,  0-008-0-0015  of  a  line  wide,  0-0005-0-0008  of  a 
line  thick,  and  according  as  it  lies  on  the  surface  or  edge,  does  it  appeal- 
clearer  or  more  opaque,  always  presenting  a  peculiar  fat-like,  glistening 

FIG.  259. — Spermatic  filaments  (human);  1,  magnified  350  diameters;  2,  magnified  800 
diameters;  a,  viewed  on  the  edge;  6,  on  the  flat  surface. 

FIG.  200. — Development  of  the  spermatic  filaments  in  the  Rabbit:  a,  parent-cell  (cyst) 
with  five  nuclei:  i,  one  with  ten  nuclei,  each  of  which  contains  a  convoluted  spermatic  fila- 
ment; c,  an  isolated  nucleus  with  nucleoli;  d,  one  with  the  spermatic  filament;  e,  a  cyst  with 
a  bundle  of  spermatic  filaments;  //,  gg,  immature  spermatic  filaments,  with  enlargements 
in  the  filamentary  portion ;  h,  a  perfect  spermatic  filament,  a,  6.  c.  magnified  350  diameters ; 
d — /i,  magnified  500  diameters. 


THE     SEXUAL     ORGANS.  623 

aspect,  and,  particularly  in  a  lateral  view,  dark  borders.  The  pale 
filamentary  portion  has  an  average  length  of  0'02  of  a  line,  and  at  its 
anterior  end,  where  it  joins  the  broader  extremity  of  the  body,  with  a 
slight  constriction,  it  is  wider  (0-0003-0-0005  of  a  line,  and  also  flat- 
tened, being  gradually  prolonged  into  an  extremely  fine  point,  scarcely 
visible  even  under  the  highest  magnifying  powers.  In  vigorous  men 
the  semen,  throughout  the  vas  deferens  and  in  the  globus  minor  of  the 
epididymis  is  composed  of  these  corpuscles,  occasionally  intermixed 
with  isolated  granules,  nuclei,  and  cells,  whilst  in  the  upper  part  of  the 
epididymis  and  in  the  body  of  the  testis  other  elements,  such  as  the  above- 
described  cells  and  cysts,  preponderate  more  and  more,  and  finally  con- 
stitute the  entire  secretion.  These  spermatic  cells  and  cysts,  as  I  term 
them,  have  a  definite  relation  to  the  spermatic  filaments,  for  in  each 
nucleus,  as  was  first  shown  by  me,  a  spermatic  filament  is  developed  on 
the  inner  wall,  in  the  form  of  a  spiral  corpuscle  with  two  or  three  turns. 
How  this  really  arises  is  unknown;  very  probably  as  a  sort  of  deposit 
from  the  contents  of  the  nucleus,  which  at  the  same  time  become  clear, 
in  the  same  way  as  the  spiral  filaments  of  the  vegetable  cell  are  formed ; 
but  it  may  at  all  events  be  asserted  as  a  positive  fact,  that  the  testis 
itself  is  the  proper  site  of  this  development,  so  that,  under  normal  condi- 
tions, developed,  spermatic  filaments  may  always  be  found  in  the  nuclei, 
in  the  internal  portions  of  the  gland,  and  frequently  in  every  seminiferous 
tube  without  exception.  But  in  the  normal  course  of  things  the  sper- 
matic filaments  in  the  testis  itself  do  not  become  liberated  at  all,  or  in 
very  small  proportion,  and  the  tubuli  seminiferi,  consequently,  are  by 
no  means  the  situation  in  which  spermatic  filaments  are  to  be  sought 
for,  although  even  here,  on  the  addition  of  water,  which  causes  the  sub- 
stance by  which  they  are  enclosed  to  burst,  they  will  always  be  found. 
They  do  not  occur  in  the  free  state  before  reaching  the  rete  testis  and 
coni  vasculosi.  First,  the  nuclei  burst,  and  the  filaments  remain  in  the 
spermatic  cells,  in  which,  when  numerous  (10—20),  they  are  very  regu- 
larly disposed  in  close  apposition,  with  the  heads  and  tails  together,  in 
a  curved  bundle,  or  when  in  less  number,  confusedly  aggregated.  Ulti- 
mately these  cells  and  cysts  also  burst,  the  filaments  are  liberated,  and, 
forming  a  dense  entangled  crowd,  entirely  fill  the  epididymis,  still  in 
part  associated  in  bundles,  which,  however,  also  are  soon  broken  up,  in 
part  isolated.  In  the  lower  portion  of  the  epididymis,  the  entire  pro- 
cess of  development  is  usually  concluded,  though  it  happens,  not  unfre- 
quently,  that  isolated  transitional  forms  are  conveyed  still  farther,  and 
are  not  completely  developed  before  reaching  the  vas  deferens. 

The  semen,  regarded  as  a  whole,  as  it  is  found  in  the  vas  deferens,  is 
a  whitish,  viscid,  inodorous  material,  consisting  almost  entirely  of  sper- 
matic filaments,  and  containing  between  those  bodies  an  extremely 
minute  quantity  of  a  connective  fluid.  The  chemical  composition  of 


624  SPECIAL    HISTOLOGY. 

this  unmixed  semen  has  not  yet  been  investigated  in  Man ;  but  we 
know  through  Frerichs,  with  regard  to  the  semen  of  the  Carp,  that  the 
spermatic  fluid  contains  no  albumen,  some  little  mucus,  and,  of  salts, 
chloride  of  sodium,  and  a  small  quantity  of  alkaline  sulphates  and 
phosphates ;  whilst  the  spermatozoa  consist  of  a  protein  compound 
(according  to  Frerichs,  binoxide  of  protein),  and  contain  besides  4'05ol  of 
a  yellowish,  butyraceous  fat,  and  5*21{}  of  phosphate  of  lime.  The 
semen,  as  ejaculated,  is  a  mixture  of  pure  semen,  and  of  the  secretions 
of  the  vesiculce  seminales,  the  prostate  and  Cowpers  glands.  It  is,  in 
this  condition,  colorless,  opalescent,  with  an  alkaline  reaction  and  pecu- 
liar odor ;  when  emitted,  it  is  viscid  and  glutinous,  like  albumen,  but  on 
cooling  becomes  gelatinous,  and  after  some  time  again  thinner  and 
fluid.  When  examined  microscopically  it  presents,  besides  the  sperma- 
tozoa, a  moderate  quantity  of  a  clear  fluid,  which,  on  the  addition  of 
water,  presents  irregular-sized  whitish  flocculi  and  fragments,  and  is 
undoubtedly  derived  principally  from  the  vesiculce  seminales.  This 
gelatinizing  substance,  which  Henle  described  as  fibrin,  and  Lehmann 
regards  as  an  albuminate  of  soda,  has  been  described  by  Vauquelin, 
who  analyzed  human  emitted  semen,  together  with  the  substance  of  the 
spermatic  filaments,  as  spermatin,  of  which  he  found  6",  whilst  besides 
it  there  were  present  OOo1  water,  3$  earthy  phosphates,  and  1$  soda. 
When  semen  is  dried,  innumerable  crystals  of  the  triple  phosphate  of 
magnesia  and  ammonia  are  formed  among  the  undestroyed  spermatozoa, 
which  generally,  owing  probably  to  the  considerable  quantity  of  car- 
bonate of  lime  contained  in  them,  are  not  easily  destructible.  They 
may  be  demonstrated  in  seminal  spots  even  after  a  long  time,  when 
they  are  moistened;  resist  putrefaction  for  a  lengthened  period  in 
water  and  animal  fluids  (Donne  observed  them  even  after  three  months 
in  putrid  urine),  and  retain  their  form  unchanged  even  after  incinera- 
tion (Valentin).  Acetic  acid  has  but  little  effect  upon  the  spermatic 
filaments.  Caustic  potassa  and  soda  render  them  pale,  and  dissolve 
them,  after  from  15  to  30  minutes.  Nitric  acid  (20$)  at  first  produces 
scarcely  any  change,  afterwards  dissolving  them.  In  sulphuric  acid 
their  outline  becomes  extremely  faint,  and  they  swell  up,  but  are  not 
entirely  dissolved,  as  are,  for  instance,  the  epithelial  cells  of  the  seminal 
tubes.  They  are  not  colored  yellow  by  nitric  acid  and  potassa,  nor  red 
by  sugar  and  sulphuric  acid.  Nitrate  of  potassa  in  a  solution  contain- 
ing 6  per  cent,  does  not  dissolve  them.  In  the  pure  semen  the  fila- 
ments exhibit  no  movements,  or  scarcely  any,  when  it  is  too  much  con- 
centrated. Their  movements  are  first  visible  in  the  contents  of  the 
vesiculce  seminales,  and  in  ejaculated  semen,  or  when  pure  semen  is 
diluted.  The  movement  of  these  bodies  is  effected  solely  by  the  alter- 
nate flexure  and  extension,  or  serpentine  motion  of  the  filamentary 
portion,  in  which  way  are  produced  such  lively  and  various  undulating, 


THE    SEXUAL    ORGANS.  625 

rotatory,  quivering  changes  of  place,  during  which  the  head  or  body 
always  precedes,  that  these  elements  of  the  semen  were  formerly 
regarded  as  animals.  The  duration  of  the  movements  depends  upon 
various  circumstances.  In  the  dead  body  they  are  not  unfrequently 
perceptible,  even  12-24  hours  after  death  (on  one  occasion  Valentin 
noticed  faint  motion  at  the  end  of  even  84  hours),  and  in  the  female 
genital  organs  in  the  Mammalia,  they  exhibit  motion  even  after  seven 
or  eight  days.  Water  at  first  renders  the  motions  more  lively,  but  they 
soon  cease,  and  the  filaments  are  not  unfrequently  curved  in  a  loop- 
like  form.  Blood,  milk,  mucus,  pus,  syrup,  and  a  diluted  saline  solu- 
tion usually  have  no  injurious  effect ;  but  it  is  otherwise  with  urine  and 
bile,  the  former  particularly,  when  it  is  strongly  acid  or  much  diluted. 
All  chemical  reagents,  acids,  metallic  salts,  caustic  alkalies,  &c.,  cause 
the  motion  to  cease,  as  do  narcotics  when  they  act  chemically  upon  the 
filaments,  or  are  too  much  diluted.* 

The  formation  of  the  spermatic  filaments  and  of  the  semen,  it  is  true, 
usually  ceases  in  old  age,  although  they  are  not  unfrequently  found  in 
men  of  60,  70,  or  even  80  years  of  age,  and  even  accompanied — though 
this,  it  must  be  confessed,  is  an  unusual  phenomenon — with  the  procrea- 
tive  faculty.  After  diseases,  the  spermatic  filaments  are  as  often  found 
to  be  present  as  absent ;  and,  with  respect  to  the  cause  of  their  defi- 
ciency, only  this  much  can  be  stated,  that  it  appears  to  depend  princi- 
pally upon  impaired  nutrition. f 

*  [Chloroform  exerts  the  same  influence  upon  the  spermatozoa  as  it  does  upon  all 
motile  tissues  in  animals  and  plants.  The  spermatozoa  of  the  Frog,  when  exposed  to  the 
dilute  vapor  of  chloroform,  gradually  cease  to  move,  regaining  their  motile  property  upon 
exposure  of  the  fluid  to  the  air  (at  any  rate  many  of  them),  and  the  filaments  thus  re- 
vivified, appear  to  retain  all  their  impregnating  power. — T&S.J 

t  [The  origin  and  development  of  the  spermatic  filaments  have  lately  been  accurately  inves- 
tigated by  Dr.  Burnett  (vid.  Mem.  of  Americ.  Acad.  of  Arts  and  Sciences,  v.  i.,  1853).  From 
an  extensive  series  of  researches  in  the  vertebrate  animals,  Dr.  Burnett  concludes  that  the 
morphological  changes  in  the  sperm-cell,  preceding  the  formation  of  the  spermatic  filaments, 
are  identical  in  their  character  with  the  changes  in  the  ovum,  which  are  antecedent  to  the 
formation  of  the  new  being.  When  the  generative  function  begins  to  be  developed, 
the  character  of  the  epithelial  cells,  lining  the  tubules,  is  modified.  The  cells  pass  to 
a  higher  degree  in  function,  but  do  not  undergo  any  change  in  structure,  except  a  slight 
increase  in  size.  In  this  condition,  they  divide  and  subdivide,  by  a  process  similar  to  the 
segmentation  of  the  yelk,  until  they  are  entirely  converted  into  a  mulberry  mass.  A  lique- 
faction of  the  segmented  contents  into  a  minute  granular  blastema  then  ensues,  and  from 
this  the  spermatic  filaments  are  developed.  In  the  Plagiostomes,  Dr.  Burnett  was  able 
to  observe  the  disappearance  of  the  mulberry  mass,  and  its  replacement  by  a  fasciculus 
of  spermatic  filaments,  although  the  exact  metamorphosis  by  which  the  granular  cellular 
mass  formed  the  bodies  of  the  spermatozoids  could  not  be  detected.  The  spermatic  filaments, 
Dr.  Burnett  thinks,  are  not  formed,  as  stated  by  Koiliker,  by  a  deposit  from  the  contents  of 
the  sperm-cell  or  nucleus,  but  by  an  elongation  of  the  cell  or  nucleus  itself.  The  body  of 
the  spermatozoid  is  developed  from  the  cell,  whilst  the  tail  is  probably  subsequently  formed 
by  an  accumulation  of  minute  granules. 

The  absence  of  these  spermatic  particles  does  not  always,  as  above  stated,  depend  upon 
impaired  nutrition.  M.  Gosselin  (Archives  Generates  de  Medicine,  Sept.,  1853)  has  noticed 

40 


626  SPECIAL    HISTOLOGY. 

§  199.  Membranes,  vessels,  and  nerves  of  the  testis. — The  testes, 
together  with  their  fibrous  tunic,  and  a  portion  of  the  epididymis,  are 
immediately  invested  by  the  tunica  vaginalis  propria  (Fig.  255,  b,  d,  /), 
a  delicate  serous  membrane,  which,  at  one  time,  was  a  part  of  the  peri- 
toneum, and  corresponds  with  it  in  structure.  Its  epithelium,  constituted 
of  a  layer  0-005  of  a  line  thick,  of  clear,  polygonal  cells,  0-005-0-008 
of  a  line  in  size,  with  distinct  nuclei,  and  occasionally  with  isolated,  yel- 
lowish pigment-granules  rests  on  the  testis,  immediately  upon  the  fibrous 
membrane,  or,  at  all  events,  in  this  situation,  is  inseparably  united  with 
the  fibrous  coat  constituting  the  tunica  adnata  testis,  or  the  visceral 
lamella  of  the  t.  v.  propria;  whilst,  on  the  epididymis,  the  serous  coat 
may  be  distinctly  separated,  and,  like  its  parietal  portion,  consists  of 
dense  connective  tissue  containing  elongated  nuclei.  The  tunica  vagi- 
nalis communis,  is  a  dense,  tolerably  thick  membrane,  consisting,  on  the 
testis,  of  firm  connective  tissue,  and  higher  up,  of  a  more  lax  reticulated 
tissue  with  elastic  fibres  ;  it  closely  surrounds  the  tunica  vaginalis  propria, 
and  also  invests  the  spermatic  cord,  and  the  lower  end  of  the  epididymis. 
Between  it,  the  tunica  propria,  and  the  e-pididymis,  and  firmly  con- 
nected with  both  tissues,  is  placed  a  layer  of  smooth  muscles,  usually 
corresponding  to  the  two  lower  thirds  of  the  testis, — the  internal  mus- 
cular tunic  of  the  testis ;  whilst  on  its  outer  side  is  inserted  the  cremaster, 
composed  of  transversely  striated  fibres.  The  scrotum,  lastly,  is  formed 
by  the  external  muscular  tunic  of  the  testis,  which  is  more  laxly  con- 
nected with  the  t.  v.  communis, — the  tunica  dartos ;  with  respect  to 
which,  vid.  §  34  ;  and  by  the  external  integument,  which  is  characterized 
by  its  thinness,  the  absence  of  fat,  the  color  of  its  epidermis,  and  its, 
mostly,  large  sebaceous  and  sweat-glands. 

The  bloodvessels  of  the  testis  and  epididymis  are  derived  from  the 
long  and  slender  a.  spermatica  interna,  which,  running  in  the  spermatic 
cord,  proceeds  from  its  posterior  aspect  to  the  testis,  and  sometimes 
entering  at  once  the  corpus  Higlimorianum,  sometimes  divided  into  nume- 
rous branches,  ramifies  in  the  fibrous  tunic  of  the  testis,  and  on  its  inner 
surface,  proceeding  towards  the  anterior  border  of  the  gland.  The 
coarser  ramification  in  the  parenchyma  of  the  testis  proceeds  partly  from 
the  corpus  Highmorianum,  partly  from  the  points  of  origin  of  the  septula 
testis,  from  the  tunica  albuginea,  into  the  septula,  from  which,  again, 
numerous  more  minute  vessels  penetrate  into  the  interior  of  the  lobules, 
constituting  a  rather  wide-meshed  plexus  of  capillaries,  0-003-0-008  of 
a  line  in  diameter,  around  the  tubuli  seminiferi.  In  the  epididymis 

that  in  the  semen  of  patients  who  had  suffered  attacks  of  double  epididymitis,  the  spermato- 
zoids  remained  absent  for  months,  even  for  years,  after  a  complete  restoration  of  the  general 
health.  In  some  diseases,  the  spermatozoids  themselves  are  changed.  Thus,  Lallemand 
(Annales  des  Sciences  Nat,  torn.  xv..  p.  30),  states,  that  in  patients  broken  down  by  seminal 
losses,  they  appear  imperfectly  formed,  the  tails  being  rough,  irregular,  and  indistinct. — 
DaC.] 


THE    SEXUAL    ORGANS.  627 

there  is  a  similar  though  less  abundant  plexus,  in  the  formation  of  which 
the  artery  of  the  vas  deferens  also  participates  (Fig.  257),  whilst  the 
scrotum  and  the  t.  vaginalis  are  richly  supplied  with  vessels  from  the 
aa.  scrotales  and  spermatica  externa.  The  veins  accompany  the  arte- 
ries, and  with  respect  to  the  lymphatics,  not  only  are  those  of  the 
scrotum  and  vaginal  tunics  extremely  numerous,  but,  according  to  the 
beautiful  researches  of  Panizza  ("  Osservazioni,"  Tab.  VIII.),  confirmed 
by  Arnold,  those  of  the  testis  are  also  very  much  developed.  They  pro- 
ceed partly  from  the  interior,  partly  from  the  surface  of  the  testis  and 
epididymis,  form  beneath  the  tunica  adnata  beautiful  plexuses,  ulti- 
mately connected  by  several  trunks  in  the  spermatic  cord,  and,  together 
with  those  of  the  vaginal  tunics,  communicate  with  the  lumbar  glands. 

The  few  nerves  of  the  testis  are  derived  from  the  internal  spermatic 
plexus,  and  accompany  the  arteries  to  the  gland.  I  have  in  vain  endea- 
vored to  follow  their  course  in  the  interior,  where  it  but  rarely  happens 
that  dark-bordered  nerves  are  seen,  even  accompanying  the  larger  arte- 
ries of  the  parenchyma. 

§  200.  Vasa  deferentia,  vesiculce  seminales,  accessory  glands. — The 
spermatic  ducts,  or  vasa  deferentia,  are  cylindrical  canals,  having  a  mean 
width  of  1-1J  lines,  the  walls  being  J-f  of  a  line  thick,  and  the  cavity 
J-J  of  a  line  in  diameter,  and  composed,  most  externally,  of  a  thin 
fibrous  membrane,  then  of  a  strong,  smooth-muscular  layer,  and  most, 
internally,  of  a  mucous  membrane.  The  muscular  tunic,  which  is  0-38 
—0*6  of  a  line  thick,  consists  of  an  external,  strong  layer  of  longitudinal 
fibres,  a  middle  one,  also  strong,  of  transverse  and  oblique  fibres,  and 
an  internal  thinner  longitudinal  layer,  constituting  not  more  than  Jth  of 
the  whole  muscular  tunic.  The  tissue  is  constituted  of  stiff  and  pale 
fibre-cells,  as  much  as  0-1  of  a  line  in  length,  and  having  an  average 
width  of  0-004-0-006  of  a  line,  intermixed  with  some  connective  tissue, 
and  a  very  few  pale  elastic  fibrils.  The  mucous  membrane,  0-12  of  a  line 
thick,  is  white,  longitudinally  plicated,  and  in  the  last,  broadest  and 
widest  portions  of  the  duct,  presents  numerous  larger  and  sm&ller  fossce, 
disposed  in  a  reticular  manner.  Its  external  two-thirds  are  whiter,  and 
contain  one  of  the  closest  felted  tissues  of  elastic  fibrils  with  which  I  am 
acquainted;  whilst  towards  the  interior  is  found  a  more  transparent, 
thinner  layer,  composed  of  an  indistinctly  fibrous  connective  tissue,  with 
nuclei,  upon  which  rests  a  single  layer  of  tessellated  epithelium,  consti- 
tuted of  cells  0-005-0-008  of  a  line  in  size,  and  which  almost  invariably 
contain  a  certain  number  of  brownish  pigment-granules,  from  which  the 
internal  surface  of  the  mucous  membrane  acquires  a  yellowish  hue.  The 
vessels  of  the  vas  deferens  are  very  distinct  in  the  external  fibrous  tunic, 
but  also  penetrate  into  the  muscular  and  mucous  coats,  constituting  in 
each,  loose  plexuses  of  capillaries  0-003-0-005  of  a  line  in  diameter. 


628  SPECIAL    HISTOLOGY. 

According  to  Swan  ("Nerves  of  the  Human  Body,"  PI.  V.,  82;  VI., 
81),  the  vas  deferens  within  the  pelvis  is  surrounded  by  numerous,  but 
fine  nerves,  which  are  in  connection  with  those  of  the  lateral  and  me- 
dian, vesical  and  rectal  nerves,  as  well  as  with  those  of  the  hypogastric 
plexuses.  I  have  myself  also  seen  these  nerves,  which  contain  fine 
fibres,  and  "fibres  of  Remak,"  but  have  been  unable  to  trace  them  in 
the  interior. 

The  structure  of  the  ejaculatory  ducts  and  vesieulce  seminales  appears 
to  be  the  same  as  that  of  the  vasa  deferentia  ;  the  seminal  vesicles,  as  is 
•well  known,  being  nothing  more  than  appendages  of  the  latter,  furnished 
with  wart-like,  saccular,  or  even  branched  processes.  The  ejaculatory 
ducts,  in  their  upper  portions,  present  the  same  muscular  structure  as 
the  spermatic  canal,  only  that  their  walls  are  more  delicate.  As  they 
approach  the  prostate,  their  membranes  become  still  thinner,  but  never- 
theless, even  at  the  ultimate  extremity,  exhibit  muscular  fibres,  mixed 
with  a  considerable  quantity  of  connective  tissue  and  elastic  fibrils.  The 
walls  of  the  vesieulce  seminales  are  much  thinner  than  those  of  the  vas 
deferens,  although  they  possess  the  same  structure,  except  that  the  mani- 
festly vascular  mucous  membrane  is  furnished  throughout  with  reticular 
fossce.  Externally,  the  vesieulce  seminales  are  invested  with  a  membrane, 
in  part  composed  solely  of  connective  tissue,  in  part,  as  on  the  posterior 
surface,  distinctly  muscular,  which  is  continued  between  the  separate 
convolutions  of  its  canal,  connecting  them  together ;  and,  at  the  inferior 
end,  passes  from  one  vesicula  seminalis  to  the  other,  in  the  form  of  a 
broad  muscular  band.  The  contents  of  the  vesieulce  seminales  are,  nor- 
mally, a  clear,  rather  viscid  fluid,  which  after  death  acquires  a  soft  gela- 
tinous 'Consistence,  though  subsequently  it  becomes  perfectly  fluid ;  it 
contains  a  protein-compound  very  readily  soluble  in  acetic  acid  and 
which  is  obviously  identical  with  that  contained  in  the  ejaculated  semen. 
With  many  other  observers,  I  have  so  frequently  seen  spermatic  fila- 
ments in  the  vesieulce  seminales,  that  I  should  describe  their  occurrence 
there  as  normal,  and  assign  a  double  function  to  the  seminal  vesicles ; 
together  with  its  principal  one,  of  afibrding  a  special  secretion,  that  of 
also  performing  the  part  of  seminal  receptacles.  The  nerves  of  the  vesi- 
culce  seminales  are  derived  from  the  sympathetic,  and  spinal  cord,  imme- 
diately from  the  rich  plexus  seminalis,  the  filaments  of  which,  in  part, 
penetrate  the  membranes  of  the  vesicles,  though  they  cannot  be  traced 
further,  in  part  proceed  to  the  prostate,  whose  plexus — plexus  prostati- 
cus — receives  additions  also  from  the  vesical  and  inferior  pelvic  plexuses. 

The  prostate,  according  to  my  observations,  is  a  very  muscular  organ, 
so  much  so,  that  the  glandular  substance  does  not  constitute  more  than 
one  third  or  a  half  of  the  whole  mass.  Proceeding  from  within  to  with- 
out, there  is  presented  in  intimate  connection  with  the  thin  mucous  mem- 
brane, the  epithelium  of  which  is  always  in  two  layers,  though  possess- 


THE    SEXUAL    ORGANS.  629 

ing  a  superficial  lamella  composed  of  cylindrical  cells,  a  yellowish  longi- 
tudinally fibrous  layer,  which  extends  from  the  trigonum  vesicce  to  the 
caput  gallinaginis,  is,  in  fact,  unconnected  with  the  muscles  of  the  blad- 
der, and  is  composed,  in  equal  proportions,  of  connective  tissue  with 
elastic  fibres,  and  of  smooth  muscles.  To  this  succeeds  a  strong  layer 
of  circular  fibres  of  a  similar  structure,  continuous  with  the  sphincter 
vesicce,  extending  as  far  as  the  caput  gallinaginis,  and  which  I  term  the 
sphincter  prostatce.  Beyond  these  different  muscular  layers,  we  come 
at  last  to  the  proper  glandular  tissue  of  the  prostate,  which  consequently 
occupies,  principally,  the  more  external  portions  of  the  organ,  although 
it  is  true  that  isolated  lobules  encroach  upon  the  circular  fibres;  its 
numerous  excretory  ducts  penetrate  the  longitudinal  and  transverse 
fibres,  and  open  on  both  sides  of  the  caput  gallinaginis.  The  latter 
consists  of  a  grayish-red,  tolerably  dense  substance,  which  may  be  very 
readily  split  into  fibres  in  the  direction  of  the  transverse  diameter  of 
the  organ,  or  more  accurately  described,  radiates  on  all  sides  of  the 
upper  surface  of  the  organ,  and  is  composed,  in  the  first  place,  of  vari- 
ously-sized bundles  of  evidently  smooth  muscle,  and  secondly  of  the 
glands  of  the  prostate.  The  latter  are  30-50  compound,  racemose 
glands,  whose  aggregate  form  is  conical  or  pyriform,  and  which  are  dis- 
tinguished from  the  usual  kind  of  racemose  glands  by  their  more  lax 
structure,  their  evident  composition  of  numerous,  pedunculate,  glandu- 
lar vesicles,  and  the  slight  development  of  the  extremely  minute  glan- 
dular lobules,  a  condition  which  is  partly  connected  with  the  abundant 
fibrous  tissue  interposed  between  the  glandular  elements.  The  glandu- 
lar vesicles  are  pyriform  or  roundish,  0-05-0-1  of  a  line  in  size,  and 
lined  with  polygonal  or  short,  cylindrical  epithelial  cells,  0-004-0-005 
of  a  line  long,  with  brown  pigment  granules;  whilst  in  the  excretory 
ducts,  the  same  cylinders  are  met  with  as  exist  in  the  prostatic  portion 
of  the  urethra.  The  secretion  of  the  prostate  appears  to  be  similar  to 
that  of  the  vesiculce  seminales  ;  at  all  events,  according  to  Virchow,  the 
prostatic  concretions,  or  stones,  as  they  are  termed — round,  concentric 
concretions,  O-03-O'l  of  a  line,  and  more,  in  size,  which  are  formed  in 
the  glandular  vesicles — consist  of  the  same  protein-compound,  soluble 
in  acetic  acid,  which  is  found  in  the  vesicular  seminales.  The  prostate 
possesses  a  fibrous  coat,  abounding  in  bundles  of  smooth  muscles,  and 
closely  investing  the  glandular  tissue,  and  tolerably  numerous  vessels, 
among  which  numerous  capillaries  surrounding  the  glandular  elements, 
and  a  rich  venous  plexus  under  the  mucous  membrane  of  the  urethra, 
are  deserving  of  notice.  The  course  of  the  nerves  above  described,  in 
the  interior  of  the  prostate,  is  unknown. 

The  uterus  masculinus,  or  vesicula  prostatica,  situated  in  the  caput 
gallinaginis,  in  the  middle,  between  the  ductus  ejaculatorii,  presents  in 
its  whitish-yellow  walls,  lined  with  a  cylinder-epithelium,  principally 


630  SPECIAL    HISTOLOGY. 

connective  tissue  and  elastic  fibrils,  with  which,  in  the  neck  of  the  blad- 
der, a  few,  and,  at  its  base,  pretty  numerous  flat,  smooth  muscles  are 
intermixed. 

The  glands  of  Cowper  are  compact,  compound,  racemose  glands, 
whose  ultimate  vesicles,  0-02-0-05  of  a  line  in  size,  are  lined  with  a 
tessellated  epithelium,  whilst  a  cylindrical  epithelium  is  found  in  the 
excretory  canals.  The  delicate  membrane  with  which  the  whole  gland 
is  invested,  as  well  as  the  fibrous  stroma  in  its  interior,  is  tolerably  rich 
in  smooth  muscles,  which  have  lately  been  also  found  by  me  in  the  ex- 
cretory canals,  J  of  a  line  wide,  as  a  delicate  longitudinal  layer.  The 
secretion  of  these  glands,  which  may  be  readily  obtained  from  the  ex- 
cretory ducts,  is  common  mucus. 

§  201.  The  organ  of  copulation,  in  Man,  consists  of  the  penis,  an 
organ  which  is  composed  of  three  erectile,  highly  vascular  bodies — the 
corpora  spongiosa  s.  cavernosa  ;  it  is  attached  to  the  pelvis,  and  traversed 
by  the  urethra,  invested  by  special  fasciae  and  by  the  external  integu- 
ment, and  furnished  with  three  proper  muscles. 

The  corpora  cavernosa  penis  are  two  cylindrical  bodies  separated 
posteriorly,  united  anteriorly,  and  parted  only  by  a  single  incomplete 
septum,  in  which  are  to  be  distinguished  a  special  fibrous  membrane 
(tunica  albuginea  s.  fibrosa),  and  the  internal  spongy  tissue.  The 
former,  which  is  a  white,  glistening,  very  strong  membrane,  J  a  line 
in  thickness,  constitutes  both  the  external  tunic  of  the  spongy  bodies, 
and  also,  in  its  anterior  half — as  a  thin  lamella,  partially  broken  up  into 
separate  fibres  and  laminae — the  septum  between  them  ;  it  consists  of 
common  fibrous  tissue,  like  that  of  tendons  and  ligaments,  with  nume- 
rous, well-developed,  fine,  elastic  fibres.  Within  it  lies  the  reddish 
spongy  substance,  consisting  of  innumerable  fibres,  bars,  and  laminae, 
united  into  a  fine  meshwork — the  trabeculce  corp.  cavernosorum  ;  and 
with  its  minute,  rounded-angular  cavities,  which  anastomose  on  all  sides, 
and,  in  life,  are  filled  with  venous  blood,  the  venous  sinuses  of  the 
spongy  body,  bears  the  most  deceptive  resemblance  to  a  sponge.  All 
the  trabeculce,  without  exception,  present  precisely  the  same  structure. 
Externally  they  are  covered  by  a  simple  layer  of  intimately  connected 
tessellated  epithelium,  the  cells  of  which  frequently  do  not  admit  of 
being  separated, — the  epithelium  of  the  venous  spaces  ;  to  this  succeeds 
the  proper  fibrous  tissue,  which  is  composed  on  the  one  hand  of  almost 
equal  proportions  of  connective  tissue  and  fine  elastic  fibres,  and  on  the 
other  of  smooth  muscles,  and  in  many,  but  by  no  means  in  all,  the  tra- 
beculce, encloses  larger  or  smaller  arteries  and  nerves.  The  elements  of 
the  trabecular  muscles  are  not  only  at  once  distinctly  recognizable  from 
their  wholly  characteristic  nuclei,  on  the  addition  of  acetic  acid,  but 
may  also  be  isolated  in  great  numbers,  and  especially  after  treatment 


THE    SEXUAL    ORGANS.  631 

with  nitric  acid  of  20g,  appearing  as  fibre-cells  0-02-0-03  of  a  line  long, 
0-002-0-0025  of  a  line  broad. 

The  corpus  cavernosum  urethrce  (corpus  spongiosum)  is  constructed 
essentially  in  the  same  way  as  that  of  the  penis,  except  that,  1,  the 
fibrous  membrane,  which  in  the  bulb  also  forms  the  rudiment  of  a  septum, 
is  much  thinner,  less  white,  and  more  abundantly  supplied  with  elastic 
elements  ;  2,  the  intertrabecular  spaces  are  smaller,  being  smallest  in  the 
glans ;  3,  and  lastly,  the  trabeculce  are  more  delicate,  and,  beneath  the 
epithelium,  richer  in  elastic  fibrils ;  having,  however,  in  other  respects, 
the  same  structure  as  elsewhere. 

This  is  the  place  also  to  speak  of  the  male  urethra,  which  at  the 
isthmus  is  an  independent  canal,  whilst  at  its  commencement  and  termi- 
nation it  consists  merely  of  a  canal  of  mucous  membrane,  supported  by 
the  prostate  and  corpus  cavernosum  urethrce.  The  proper  mucous  mem- 
brane, beneath  a  longitudinal  layer  of  connective  tissue  abounding  in 
elastic  fibres,  presents  not  only,  as  already  mentioned,  in  the  prostatic 
portion,  but  -also  in  the  membranous  parts,  although  less  developed, 
smooth  muscles  mixed  with  the  usual  fibrous  tissue,  disposed  longitudi- 
nally and  transversely ;  to  which  again  succeed  the  animal  fibres  of  the 
musculus  urethralis.  In  the  pars  cavernosa,  also,  the  submucous  tissue 
still  presents,  here  and  there,  muscles  of  the  same  kind,  and  at  a  certain 
depth  longitudinal  fibres  are  always  found,  with  a  greater  or  less  inter- 
mixture of  such,  which,  however,  cannot  be  referred  to  the  corpus  caver- 
nosum, seeing  that  there  are  no  venous  spaces  between  them ;  but  which 
rather  form  a  continuous  membrane,  bounding  the  true  corpora  caver- 
nosa,* on  the  side  towards  the  mucous  membrane  of  the  urethra.  The 
epithelium  of  the  urethra  is  formed  of  pale  cylinders,  0-012  of  a  line  in 
size ;  beneath  which,  however,  are  found  one,  or  perhaps  two,  layers  of 
round  or  oval  cells.  In  the  anterior 
half  of  the  fossa  of  Malpighi  exist  Fiff.  aei. 

papillce  0-03  of  a  line  long,  and  a 
tessellated  epithelium,  0-04  of  a  line 
thick.  In  the  isthmus  and  pars  caver- 
nosa urethrce  are  found,  in  conside- 
rable number,  the  so-termed  "  glands 
of  Littre,"  J— J  a  line  in  size,  which, 
speaking  generally,  rank  with  the 
racemose  glands,  although  distin- 
guished from  them  by  their  tubular 
form,  and  the  frequently  much  con- 
voluted course  of  the  glandular  vesi- 

FIG.  261. — "Gland  of  Littre,;'  from  the/ossa  Morgagni,  in  Man;  magnified  500  diameters. 

*  [Mr.  Hancock  published,  in  1851,  an  account  of  the  distribution  of  the  organic  muscular 
fibres  of  the  urtthra,  essentially  agreeing  with  the  above.  He  states  that  this  internal  mus- 
cular coat  of  the  corpus  spongiosum^  or,  as  Mr.  Hancock  prefers  to  call  it,  muscular  coat  of  the 


632  SPECIAL    HIStOLOGY. 

cles,  which  are  0-04-0-08  of  a  line  wide.  More  simple  forms  of  glands 
of  this  kind  (Fig.  161)  are  occasionally  met  with  intermixed  with  the 
others;  and  in  the  pars  prostatica,  instead  of  them,  we  find  minute 
mucous  follicles,  similar  to  those  which  have  been  before  described  as 
occurring  in  the  cervix  vesicce.  The  epithelium,  both  in  the  vesicles  of 
the  "glands  of  Littre"  and  in  the  excretory  ducts,  1-2  lines  long, 
which  are  directed  forwards,  penetrating  the  mucous  membrane  obliquely, 
is  cylindrical ;  in  the  former  situation,  however,  more  or  less  approach- 
ing the  tessellated  form  (Fig.  261);  the  secretion  is  common  mucus, 
which  in  dilatations  of  the  glandular  follicles  is,  not  unfrequently,  col- 
lected in  some  quantity.  Some  minute,  inconstant  fossae  of  the  mucous 
membrane  have  been  termed  lacunce  Morgagni,  in  which  I  have  been 
unable  to  detect  anything  of  a  glandular  nature.  The  fascia  penis,  a 
tissue  abounding  in  finer  elastic  fibres,  surrounds  the  penis,  from  the 
root  to  the  glans,  being,  in  the  former  situation,  in  connection  with  the 
perineal  fascia,  and  that  of  the  inguinal  region,  and  also  contributes  to 
the  formation  of  the  suspensory  ligament  of  the  penis,  a  structure  very 
rich  in  true  elastic  tissue,  which  extends  from  the  sympliysis  to  the 
dorsum  penis.  Externally  it  is  continuous,  without  any  line  of  demar- 
cation, with  the  skin  of  the  penis,  which,  up  to  the  free  border  of  the 
prepuce,  a  simple  duplicature  of  it,  possesses  the  nature  of  the  common 
integument ;  though  certainly  characterized  by  its  delicacy,  and  the  pre- 
sence of  a  layer  of  smooth  muscles  in  the  abundant,  fatless,  subcutaneous 
tissue,  a  continuation  of  the  tunica  dartos  (vid.  §  34),  which  extends  as 
far  as  into  the  prepuce.  At  the  border  of  the  prepuce  the  integument 
of  the  penis  assumes  more  of  the  nature  of  a  mucous  membrane,  and  is 
no  longer  furnished  with  hairs  and  sudoriparous  glands,  although  it  has 
well-developed  papillce ;  it  is  still  thinner  than  before,  and  on  the  glans 
is  intimately  connected  with  the  spongy  body,  and  covered  with  a  softer 
cuticle  (§  42,  Fig.  56,  4),  always,  however  0-035-0-056  of  a  line  thick. 
With  respect  to  the  sebaceous  glands  (gl.  Tysoniance),  which  exist  in 
this  situation,  and  the  formation  of  the  preputial  smegma,  consult  §§ 
46,  74. 

The  arteries  of  the  penis  are  derived  from  the  pudic,  and  are  pecu- 
liar only  in  the  way  in  which  they  supply  the  corpora  spongiosa.  In 
the  corp.  cav.  penis,  except  a  few  small  twigs  from  the  a.  dorsalis,  the 

urethra,  unites  with  the  external  coat,  at  the  lips  of  the  urethra,  so  as  to  form  a  sort  of  sphincter. 
Mr.  Hancock  also  discovered  and  described  the  abundant  organic  muscles  surrounding  the 
vesicles  and  ducts  of  the  prostate,  which,  though  admitted  in  the  text,  were  denied  by  Prof. 
Kolliker,  in  his  Essay  upon  the  distribution  of  the  organic  muscles  in  Siebold  and  Kolliker, 
Zeitschrift.  Mr.  Hancock  further  states  that  the  muscular  fibres  of  the  membranous  portion 
of  the  urethra  are  continued  over  the  inner  and  outer  surfaces  of  the  prostate,  into  the  mus- 
cular coat  of  the  bladder,  so  that,  according  to  his  view,  there  is  one  continuous  muscular 
coat,  from  the  bladder  to  the  end  of  the  penis,  which  twice  separates  into  two  layers;  pos- 
teriorly, to  enclose  the  prostate,  anteriorly,  to  envelop  the  spongy  tissue  of  the  corpus  spon- 
giosum. — See  Hancock  on  the  "Anatomy  and  Physiology  of  the  Urethra,"  1852. — TRS.] 


THE     SEXUAL    ORGANS.  633 

a.  profundce  penis  alone  run  near  the  septum,  surrounded  by  a  sheath 
of  connective  tissue  continuous  with  the  trabecular  network,  in  fact 
directly  forwards,  but  giving  off  a  small  twig  to  the  bulbs  of  the  crura. 
In  this  course  they  afford  numerous,  occasionally  anastomosing  branches 
to  the  spongy  substance,  which,  running  in  a  convoluted  manner  (except 
at  the  time  of  erection)  in  the  axis  of  the  traleculce,  ramify  in  them,  and 
ultimately,  without  the  formation  of  capillary  plexuses  open  into  the 
venous  spaces,  by  capillaries  of  0-006-0*01  of  a  line  in  diameter.  In 
the  posterior  part  of  the  penis  there  are  numerous  minute  arterial 
trunks,  measuring  0-04—0*08  of  a  line  in  diameter,  and  for  the  most 
part  lying  from  3-10  together,  as  was  first  observed  by  J.  Muller  ;  they 
are  contorted  and  convoluted  in  a  peculiar,  tendril-like  manner  (arterice 
helicince),  and  do  not  terminate  in  csecal  ends,  but,  as  I  have  ascertained, 
give  off  from  their  clavate  extremities  minute  vessels  of  0-006-0-01  of  a 
line,  which,  like  the  other  arterial  prolongations,  are  continued  further,  and 
terminate  in  the  venous  spaces.  The  arterial  ramification  is  precisely 

Fig.  262. 


similar,  in  the  corpus  cavernosum  urethrce,  which  is  furnished  with  its 
supply  from  art.  bulbosce,  bulbo-urethrales,  and  dorsales,  and  in  the  bulb 
there  also  exist  art.  lielicince.  The  veins  commence,  as  it  may  be  said, 
in  the  venous  spaces  which  intercommunicate  throughout ;  and  from 
which,  though  not  universally  from  the  same  situations,  short  efferent 
canals,  or  emissaria,  receive  the  blood  and  convey  it  into  the  external 
veins,  furnished  with  special  walls  (vena  dorsalis,  v.  v.  profundse,  and 
lullosce  in  particular).  The  lymphatics  form  very  close  and  delicate 
plexuses  in  the  skin  of  the  glans,  the  prepuce,  and  in  the  remainder  of 

FIG.  262. — Arteries  from  the  corpora  cavernosa  penis  of  Man,  injected  ;  magnified  30  diame- 
ters. 1,  one  of  the  smaller  arteries,  with  a  lateral  branch,  dividing  into  two  helicine  arteries, 
from  the  extremities  of  which  two  very  small  vessels  proceed,  and  are  continued  into  the 
delicate  trabecula  ;  2,  five  helicine  arteries  placed  on  a  short  stem  of  a  larger  arterial  divi- 
sion; from  two  of  these,  fine  vessels  are  seen  to  be  given  oft",  the  others  appear  to  terminate 
in  caeca!  ends :  a,  trabecular  tissue,  here  presenting  the  form  of  sheaths  to  the  arterial  trunks 
and  helicine  arteries ;  6,  wall  of  the  arteries. 


634  SPECIAL    HISTOLOGY. 

the  integument,  and  communicate  with  the  superficial  inguinal  glands 
through  trunks  accompanying  the  dorsal  vessels.  According  to  Mas- 
cagni,  Fohmann,  and  Panizza,  there  are  also  numerous  lymphatics  in  the 
glans  surrounding  the  urethra,  which  run  backwards  on  that  canal,  and 
proceed  to  the  pelvic  glands. 

The  nerves  of  the  penis  are  derived  from  the  pudendal  and  the  plexus 
cavernosus  of  the  sympathetic,  the  former  of  which  are  distributed 
principally  to  the  skin  and  the  mucous  membrane  of  the  urethra,  and, 
in  a  small  proportion  only,  to  the  corpora  cavernosa,  to  which  alone  the 
latter  set  of  nerves  is  destined.  The  terminations  of  the  former  nerves 
present  the  same  conditions  as  those  of  the  integuments  ;  numerous 
divisions,  in  particular,  and  faint  indications  of  axile  corpuscles,  occur  in 
the  glans  penis ;  those  of  the  latter  nerves  are  not  as  yet  known, 
although,  in  the  trabeculce  of  the  corpora  cavernosa,  nerves  with  fine 
fibres,  and  "fibres  of  Remak,"  are  readily  demonstrated. 

The  smooth  muscles  of  the  corpora  cavernosa  are  very  distinctly 
shown  in  the  penis  of  the  Horse  and  Elephant,  but  are  also  not  want- 
ing in  those  of  other  Mammalia.  The  art.  lielicince,  since  Valentin  and 
Henle  have  declared  them  to  be  produced  artificially,  and  to  arise  from 
the  inrolling  of  trabeculce  which  have  been  cut  across,  or  from  the  spon- 
taneous retraction  of  certain  arteries  in  stretched  trabeculce,  have  been 
generally  rejected/ but  incorrectly.  They  do  exist ;  only  I  am  satisfied 
that  the  circumstance,  noticed  even  by  J.  Miiller,  of  the  extremity  of 
one  of  these  arteries,  giving  off  an  excessively  delicate,  almost  capillary 
vessel,  occurs  very  frequently,  and  consequently,  that  the  caecal  termi- 
nations are  merely  apparently  such.  That  similar  terminations  do  not 
exist  at  all,  cannot  however,  be  definitively  proved,  and  it  is  very  pos- 
sible that  Miiller,  in  this  respect  also,  may  still  be  right.  The  art. 
lielicince,  therefore,  are  not  simple  vascular  loops,  as  which  they  are 
described  by  Arnold,  although,  in  one  instance,  I  have  noticed  such  an 
arrangement  in  place  of  them. 

§  202.  Physiological  remarks. — The  development  of  the  testes,  com- 
mencing in  the  second  month,  takes  place,  according  to  all  that  we 
know,  from  a  blastema  which  appears  independently  on  the  inner  side 
of  the  Wolffian  body ;  and,  at  first,  the  form  of  the  male  sexual  glands 
entirely  resembles  that  of  the  ovaries.  At  a  subsequent  period,  when 
the  Wolffian  body  begins  to  waste,  a  portion  of  its  fine  canals,  the 
Malpighian  corpuscles  of  which  disappear,  become  connected  with  the 
testes,  and  are  formed  into  the  epididymis,  whilst  at  the  same  time  the 
excretory  duct  of  the  Wolffian  body  constitutes  the  vas  deferens.*  Then, 

*  [It  is  a  curious  fact  connected  with  this  alleged  origin  of  the  epididymis  distinctly  from 
the  rest  of  the  gland,  that,  in  cystic  disease  of  the  testicle,  either  of  the  innocent  or  rnalig- 


THE    SEXUAL     ORGANS.  635 

by  a  process  not  as  yet  accurately  explained,  the  testes,  with  its  perito- 
neal investment,  descends  into  the  scrotum  under  the  agency  of  the 
gubernaculum,  a  process  composed  of  transversely  striated  and  smooth 
muscles  ;  and  by  the  growing  together  of  the  peritoneal  protrusion 
contained  in  the  gubernaculum — the  processus  vaginalis  peritoncei, — 
with  its  own  proper  serous  coat,  acquires  its  tunica  vaginalis  propria. 
The  vesicula  prostatica,  the  analogue  of  the  uterus,  and  probably  of 
the  vagina,  is  the  remainder  of  the  "  Mullerian  ducts,"  two  canals, 
descending  on  the  external  border  of  the  Wolffian  body,  which,  in  the 
female,  form  the  oviduct  and  by  the  coalescence  of  their  extremities, 
the  uterus  and  vagina ;  but  in  the  male  disappear,  except  the  com- 
mencement, which  becomes  the  "  hydatids  of  Morgagni,"  and  the  last 
portion.  The  vesiculce  seminales  are  protrusions  of  the  v.  defer entia ; 
and  the  prostate,  Coivpers,  and  the  smaller  glands,  are  most  probably 
formed,  in  analogy  with  other  similar  glands,  from  the  epithelium  of  the 
urethra.  The  penis  is  developed  from  the  pelvic  bones  outwards,  and 
does  not,  till  subsequently,  include  the  urethra  which  is  formed  by  the 
closure  of  a  groove  on  its  inferior  surface. 

With  respect  to  the  histological  development  of  these  parts  little  is 
known.  The  testes  are  constituted  originally  of  a  uniform  cellular  sub- 
stance, which,  however,  soon  begins  to  divide  into  transverse  rows,  form- 
ing the  rudiments  of  the  seminal  tubes.  These  are,  at  first,  straight 
csecal  canals,  extending  from  the  outer  border  of  the  testis  to  the  inte- 
rior, which  most  probably  originate  as  solid  tracts  of  cells,  and  only 
subsequently  acquire  a  cavity  and  membrana  propria.  From  the  con- 
tinued growth,  especially  in  length,  of  these  primary  channels,  and  the 
production  of  offsets  from  them,  the  later,  convoluted  and  very  long 
seminal  tubes  arise ;  it  appearing,  in  fact,  that  an  entire  lobule  of  the 
testis  is  formed  from  each  of  them.  The  tunica  albuginea  of  the  testis 
and  its  internal  prolongations  arise  from  the  primary  blastema  of  the 
gland,  and  make  their  appearance  at  the  same  time  with  the  seminal 
tubes. 

With  regard  to  the  physiological  relations  of  the  male  sexual  organs, 
in  the  adult,  I  would  here  notice  the  following  points.  The  secretion  of 
semen,  in  animals,  does  not  go  on  continuously,  like  that  of  the  urine, 
but  is  intermittent,  taking  place  only  at  the  time  of  rutting  or  heat.  In 
Man,  the  capability  of  producing  semen,  assuredly,  always  exists, 
although  it  does  not  appear  to  follow  from  this,  that  semen  is  being  con- 
tinually formed,  and  that  what  is  not  emitted  undergoes  absorption  ;  and 
consequently  it  seems  justifiable  to  suppose  that  the  seminal  tubes  secrete 
semen  only  when  the  secretion  has  been  partially  evacuated  externally, 
either  in  consequence  of  sexual  congress,  or  of  seminal  emissions,  and 

nant  type,  the  affection  is  "  the  result  of  morbid  changes  in  the  ducts  of  the  rete  testis  ;  this 
part  of  the  gland  being  the  sole  seat  of  the  disease."  (Curling,  "  Med.  Chir.  Transact.," 
XXXVI.  p.  456,  1853).— TRS.] 


636  SPECIAL    HISTOLOGY. 

an  excitement  of  the  nervous  system  has  caused  an  increased  flow  of 
blood  to  the  testis.  There  are  no  certain  facts  in  favor  of  an  absorption 
of  the  semen  when  formed,  which  could  only  take  place  in  the  vasa  de- 
ferentia  and  vesiculce  seminales  ;  for  what  is  observed  in  animals,  after 
the  rutting  season  is  over,  has  no  reference  to  this  point ;  and  the  very 
circumstance,  that  in  the  situations  above-mentioned,  no  traces  of  disin- 
tegration of  the  semen  are  ever  found,  appears  to  be  very  much  opposed 
to  such  a  supposition.  At  the  same  time,  however,  it  is  perhaps  unques- 
tionable, that  without  seminal  evacuations,  a  formation  of  semen  may  be 
possible ;  for  it  is  sufficiently  established,  that  a  rich,  heating  diet,  and 
an  unsatisfied  sexual  excitement,  often  produce  a  turgescence  of  these 
organs,  attended  with  painful  sensations,  and  most  probably  with  a  for- 
mation of  semen.  The  subsequent  removal  of  this  fulness  does  not, 
however,  appear  to  me  incontestably  to  prove  any  absorption,  because  a 
difference  in  the  quantity  of  blood  in  the  testis,  and  the  passing  of  the 
semen  into  the  v.  deferentia  are  sufficient  to  account  for  the  restoration 
of  the  usual  condition.  The  fluid  constituting  a  seminal  emission  is  not 
pure  semen,  but  in  great  part  the  secretion  of  the  vesiculce  seminales  and 
prostate,  and  affords  no  criterion  by  which  to  estimate  the  energy  of  the 
secretion  of  the  testes.  The  formation  of  the  semen  itself  certainly  does 
not  proceed  rapidly  and  copiously,  as  might  be  concluded  from  the  rela- 
tively small  quantity  of  blood  contained  in  the  testes,  and  from  its  slow 
motion  in  them,  necessarily  consequent  upon  the  anatomical  conditions; 
and  as  is  also  evident  from  the  fact,  that  after  a  few  previous  emissions, 
even  in  the  most  vigorous  organisms,  a  certain  time  is  requisite  for  the 
preparation  of  a  fresh  secretion.  The  secretions  of  the  accessory  glands 
are  perhaps  simply  intended  for  the  dilution  of  the  semen. 

That  the  seminal  filaments  are  not  animalcules,  but  elementary  parts 
of  the  male  organism,  it  is  useless  at  the  present  time  to  attempt  to  de- 
monstrate ;  although  it  is  still  as  much  as  ever  unknown,  and  will  not 
easily  soon  be  ascertained,  what  is  effected  by  their  curious  movements, 
which  are  obviously  intended  to  convey  them  to  the  ovum,  from  the  ute- 
rus, which  they  probably  reach  in  fruitful  congress.  Nor,  from  the  ex- 
periments of  Prevost,  Dumas,  Schwann,  and  Leuckart,  and  the  later 
researches  of  Newport  (Phil.  Trans.  1851,  1),  can  the  least  doubt  be  en- 
tertained that  they  are  the  true  impregnating  agent,  and  for  the  purpose 
of  impregnation  must  necessarily  come  in  contact  with  the  ovum.  The 
circumstance  that  motile  spermatic  filaments  alone  possess  the  fertilizing 
property,  and,  according  to  Newport,  that  the  effect  upon  the  ovum  takes 
place  immediately  upon  the  contact,  although  a  short  duration  of  the 
contact  of  the  spermatic  filament  with  the  ovum  is  necessary  to  render  it 
efficient,  also  shows,  as  it  appears  to  me,  that  they  do  not  act  by  afford- 
ing any  material  substance  to  the  egg,  but  in  consequence  of  their  ex- 
citing actions  in  it,  as  bodies  in  a  state  of  peculiar  activity.  In  my  first 


THE    SEXUAL    ORGANS.  637 

work  upon  the  spermatic  fluid,  in  which  I  expressed  this  view,  in  order 
to  indicate  a  ground  for  discussion,  I  compared  its  influence  upon  the 
ovum  to  that  of  a  nerve-fibre  upon  a  nerve-cell,  or  of  a  magnet  upon 
iron ;  and  these  comparisons,  to  which  might  be  added  the  influence 
which  a  part  of  an  organism  exerts  upon  a  self-organizing  exudation,  or 
an  entire  organism  upon  a  part  in  a  state  of  self-regeneration,  still  appear 
to  me  the  most  suitable,  if  impregnation  is  in  any  way  to  be  assimilated 
with  other  processes ;  but  I  have  no  objection  to  offer,  should  the  chemi- 
cal side  of  the  question  be  advocated  in  preference,  as  by  Bischoff,  and 
the  functions  of  the  semen  be  referred  to  the  category  of  catalytic  phe- 
nomena.* 

In  the  act  of  copulation,  various  motile  phenomena  are  presented,  of 
which  we  need  discuss  only  those  conducive  to  ejaculation  and  erection. 
In  the  former  the  vasa  deferentia,  provided  as  they  are  with  a  colossal 
muscular  apparatus,  are  chiefly  operative ;  these  organs,  as  Virchow 
and  I  found  in  an  executed  criminal,  shorten  and  contract  with  remark- 
able energy  when  excited  by  galvanism ;  as  also  do  the  vesicular  semi- 
nales,  the  highly  muscular  prostate,  and,  of  course,  the  transversely 
striated  muscular  tissue  of  the  urethra  and  penis.  JErection  is  caused, 
as  I  have  shown  ("Wurzb.  Verh."  Bd.  II.),  by  a  relaxation  of  the 
muscular  elements  in  the  trabeculce  of  the  cavernous  and  spongy 
bodies,  and  of  the  tunica  media  of  the  arteries  of  those  parts ;  in  con- 
sequence of  which  the  tissue,  like  a  sponge  which  has  been  compressed, 
expands  and  becomes  filled  with  blood.  The  rigidity  ensues  so  soon  as 
the  muscles  are  completely  relaxed,  and  the  sinuses  filled  to  the  utmost, 
without  there  being  any  necessity  that  the  return  of  the  blood  should 
be  impeded,  and  the  circulation  stopped.  It  ceases  when  the  muscles 
again  contract,  the  venous  spaces  become  narrowed,  and  the  blood  is 
expressed  from  them.  In  the  act  of  ejaculation,  the  ischio-cavernosi, 

*  [The  later,  most  important  researches  of  Dr.  Neilson,  respecting  the  impregnation  of  the 
ovum  in  Jlscaris  mystax  ('l  Phil.  Transact.,"  1852),  and  of  Mr.  Newport  (op.  cit.),  with  regard 
to  that  of  the  Frog,  in  which  he  has  been  compelled  to  abandon  his  former  opinion,  that  the 
spermatozoa  did  not  penetrate  through  the  vitelline  membrane,  and  has  shown  that,  in  that 
case,  as  in  the  one  so  ably  described  by  Dr.  Neilson,  those  bodies  penetrated  into  the  sub- 
stance of  the  vitellus  in  large  numbers,  where  they  underwent  changes,  and  finally  disap- 
peared— render  much  of  the  above  speculation  on  the  subject  of  their  influence  in  impreg- 
nation futile.  Whatever  may  be  the  nature  of  the  influence  conveyed  to  the  vitellus  by  the 
spermatic  filaments,  it  must  now  perhaps  be  regarded  as  an  established  fact,  that  it  cannot 
be  communicated  except  by  an  immediate  contact  between  the  motile  filaments  and  the  sub- 
stance of  the  vitellus,  which  thereupon  undergoes  segmentation,  and  the  series  of  changes  is 
commenced,  to  terminate  in  the  evolution  of  the  embryo.  Additional  confirmation  of  the 
same  fact  would  be  afforded  by  Dr.  Keber  s  researches  on  the  entrance  of  the  spermatozoon 
into  the  ovum  of  Unio  ("De  introitu  Spermatozoorum,"  &c.,  1852),  could  full  reliance  be 
placed  upon  his  results ;  but  this,  from  some  investigations  of  our  own  on  the  same  subject 
— both  in  Unio  and  in  Pholas — we  consider  extremely  doubtful.  The  appearances  he  de- 
scribes, much  more  resemble  those  noticed  by  Von  Wittich  and  Carus  in  the  ovum  of  Spi- 
ders.— TRS  J 


638  SPECIAL    HISTOLOGY. 

and  the  bulbo-cavernosus  muscles,  which  are  formed  of  transversely 
striated  fibres,  increase  the  rigidity  of  the  anterior  parts  by  the  com- 
pression of  the  root  of  the  penis  and  dorsal  veins  ;  but  under  no 
circumstances  can  they,  of  themselves  alone,  contribute  to  the  bringing 
about  of  the  erection.  I  am  not  aware  that  any  more  important  func- 
tion can  be  assigned  to  the  helicine  arteries ;  this  much  being  certain, 
that  the  erection  does  not  depend  upon  them,  because  they  do  not  occur 
in  every  part  of  the  human  penis,  and  are  wanting  in  many  animals. 

The  investigation  of  the  male  sexual  organs  presents,  generally 
speaking,  no  great  difficulties.  The  tubuli  seminiferi  are  very  readily 
isolated,  and  when  they  are  carefully  unfolded  some  divisions  are 
always  met  with.  In  order  to  trace  their  entire  course,  they  must  be 
injected  according  to  the  directions  of  Lauth  or  Cooper,  which  may  be 
found  quoted  in  all  Manuals  of  anatomy.  Lauth  places  the  testicle  for 
two  or  three  hours  in  lukewarm  water,  then  expresses  the  semen  as 
completely  as  possible  from  the  epididymis,  and  immerses  the  gland 
for  3-4  hours  in  a  solution  of  carbonate  of  ammonia,  or  for  8-12  hours 
in  a  saturated  solution  of  carbonate  of  potassa,  or  a  weak  solution  of 
caustic  potassa,  which  reagents  partly  dissolve  the  spermatic  cells  and 
epitlielia ;  the  testis  is  then  again  compressed,  laid  in  alkaline  water, 
and  injected  with  quicksilver,  at  first  under  a  weak  and  afterwards 
under  a  strong  pressure,  a  process  requiring  from  1J  to  2  hours.  So 
soon  as  the  quicksilver  has  penetrated  into  the  vas  deferens,  the  column 
must  be  lowered  to  5  inches,  for  otherwise  the  tubuli  seminiferi,  the 
filling  of  which  demands  some  hours  more,  burst.  Cooper  injected 
from  the  vasa  efferentia,  into  which  he  introduced  a  fine  canula.  For 
microscopical  investigation,  Gerlach  recommends  a  solution  of  gelatine, 
with  carmine  or  chromate  of  lead.  The  vas  deferens  is  best  studied  in 
transverse  sections,  after  it  has  been  hardened  or  dried,  as  are  also  the 
prostatic  glands  ;  whilst  the  muscles  of  the  prostate  and  the  corpora 
cavernosa  can  be  distinctly  made  out  only  in  the  recent  state,  or  after 
the  application  of  nitric  acid.  The  helicine  arteries  may  be  seen,  even 
in  fresh  preparations,  close  to  the  larger  arterial  trunks,  but  still  better 
after  injection  with  fine  materials. 

Literature. — A.  Cooper,  "  Obs.  on  the  structure  and  diseases  of  the 
testis,"  London,  1830,  with  twenty-four  plates;  E.  A.  Lauth,  "Mem. 
sur  le  testicule  humain,"  in  "  Mem.  de  la  socie'te'  d'histoire  naturelle  de 
Strasbourg,"  torn.  I,  1833;  C.  Krause,  "Verm.  Beobachtungen" 
(various  observations),  in  Mull.  "Arch."  1837,  p.  20;  E.  H.  Weber, 
"  De  arteria/  spermatica  deferente,  de  vesica  prostatica  et  vesiculis  semi- 
nalibus,"  Progr.,  1836,  editum  in  Progr.  collecta,  II.  1851,  p.  178; 
"  Zusatze  zur  Lehre  vom  Bau  und  den  Verrichtungen  der  Geschlechtsor- 
gane"  (Contributions  to  the  knowledge  of  the  structure  and  functions  of 


THE     SEXUAL    ORGANS.  639 

the  sexual  organs),  Leipsic,  1846  ;  C.  J.  Lampferhoff,  "  De  vesieularum 
seminalium  natura  et  usu,"  Berol.,  1835  ;  Kolliker,  "  Ueber  die  glatten 
Muskeln  der  Harn-  und  Geschlechtsorgane,"  in  "  Beitrage  zur  Kenntniss 
der  glatten  Muskeln"  (On  the  smooth  muscles  of  the  urinary  and  genital 
Organs,  in  Contributions  to  the  knowledge  of  the  smooth  muscles),  in 
"Zeitsch.  f.  wiss.  Zoologie,"  I.  ;  Fr.  Leydig,  "Zur  Anatomie  der  mann- 
lichen  Geschlechtsorgane  und  Analdriisen  der  Saugethiere"  (On  the 
Anatomy  of  the  male  sexual  Organs  and  anal  glands  of  the  Mammalia), 
in  "  Zeits.  f.  wiss.  Zoologie,"  II. ;  A.  v.  Leeuwenhoek,  "  Arcana 
Nature,"  p.  59;  Provost  and  Dumas,  "  Ann.  d.  Sc.  Nat.,"  III.  1824, 
and  "Mem.  de  la  Soc.  d'Hist.  Nat.  de  Geneve,"  torn.  I.  p.  180;  K. 
Wagner,  "Die  Genesis  der  Samenthierchen"  (The  genesis  of  the  Sper- 
matozoa), in  Mull.  "  Archiv,"  1836,  and  "  Fragmente  zur  Physiologie 
der  Zeugung"  (Fragments  on  the  physiology  of  Generation),  Munich, 
1836;  A.  Donne,  "Nouv.  ExpeV.  sur  les  animalcules  spermatiques," 
Paris,  1837,  and  "Cours  de  Microscopic,"  Paris,  1844;  A.  Kolliker, 
"  Beitrage  zur  Kenntniss  der  Geschlechtsverhaltriisse  und  der  Samen- 
flussigkeit  wirbelloser  Thiere"  (Contributions  to  the  knowledge  of  the 
sexual  relations  and  the  seminal  fluid  of  the  Invertebrata),  Berlin,  1841, 
and  "  Die  Bildung  der  Samenfaden  in  Blaschen  als  allgemeines 
Entwicklungsgesetz"  (The  formation  of  the  spermatic  filaments  in  cells, 
as  a  general  law  of  Development),  in  "  Denkschr.  d.  schweiz.  naturf. 
Gesellsch.,"  Bd.  VIII.  1846;  Kramer,  "  Obs.  microsc.  et  experimenta 
de  motu  spermatozoorum,"  Gott.,  1842;  Fr.  Will,  "Ueber  die  Secre- 
tion des  thierischen  Sam  ens"  (On  the  secretion  of  the  semen  of  animals), 
Erlangen,  1849  ;  K.  Wagner  and  Leuckart,  art.  "  Semen"  in  Todd's 
"Cycl.  of  Anat."  Jan.  1849;  Newport,  "On  the  impregnation  of  the 
ovum  of  the  Amphibia,"  in  "Phil.  Trans."  1851,  I.;  B.  Panizza, 
"  Osservazioni  anthropo-zootomico-fisiologische,"  Pavia,  1836;  J.  Muller, 
"  Entdeckung  der  bei  der  Erection  wirksamen  Arterien"  (Discovery  of 
the  Arteries  which  effect  Erection),  "Arch."  1835,  p.  202;  G.Valentin, 
"  Ueber  den  Verlauf  der  Blutgefasse  in  dem  Penis  des  Menschen"  (On 
the  course  of  the  bloodvessels  in  the  human  penis),  Mull.  "Arch."  1838  ; 
Kobelt,  "  Die  Mannlichen  und  Weiblichen  Wollustorgane"  (The  male 
and  female  sexual  organs),  Freiburg,  1844  ;  Herberg,  "  De  erectione 
penis,"  Lips.  1844  ;  Kolliker,  "  Ueber  das  Anat.  und  Phys.  Verhalten 
der  Cavernosen  Korper  der  Mannlichen  Sexualorgane"  (On  the  ana- 
tomical and  physiological  relations  of  the  corpora  cavernosa  of  the  male 
sexual  organs),  in  "Verhandl.  der  Wurzb.  Med.  Phys."  Ges.  1851. 
[H.  Hancock,  "  On  the  Anatomy  and  Physiology  of  the  Male  Urethra, 
1852;"  Fr.  Leydig,  "  Zur  Anat.  d.  mannl,  Geschlechtsorgane  u.  Anal- 
driisen  der  Saugethiere,"  in  "  Zeitschrift  fur  wiss.  Zool."  Bd.  II. ;  Waldo 
J.  Burnett,  "  Researches  upon  the  origin,  mode  of  development,  and 
nature  of  the  Spermatic  Particles  among  the  four  classes  of  Vertebrated 


640  SPECIAL    HISTOLOGY. 

Animals,  in  Mem.  of  Americ.  Acad.  of  Arts  and  Sciences,"  V.  part  1, 
1853;  H.  Luschka,  "  Die  Append  ienlargebilde  des  Hoden,"  in  "Vir- 
chow's  Archiv,"  VI.  3,  1854.— DaC.] 

B.     FEMALE  SEXUAL  ORGANS. 

§  203.  The  female  sexual  organs  consist :  1,  of  two  follicular  glands, 
in  which  the  ova  are  formed — the  ovaries — with  the  parovaria,  and  the 
two  excretory  ducts,  which,  however,  are  not  directly  connected  with 
them, — the  oviducts,  or  Fallopian  tubes ;  2,  of  the  uterus,  for  the  re- 
ception and  nourishment  of  the  foetus  ;  and  3,  of  the  parts  subservient 
to  the  expulsion  of  the  foetus,  as  well  as  to  copulation — the  vagina 
and  external  genitals. 

§  204.  Ovary,  parovarium. — The  ovaries,  ovaria,  are  constituted  of 
special  tunics,  and  of  a  stroma  containing  the  ova,  or  the  parenchyma. 
The  former  consist  of  a  peritoneal  coat,  which  covers  all  but  the  inferior 
border,  and  of  a  firm,  white,  fibrous  coat,  the  tunica  albuginea  s.  propria, 
J  of  a  line  thick,  which  closely  invests  the  whole  parenchyma,  and  is 
intimately  connected  with  it  without  any  abrupt  line  of  demarcation  ; 
but  does  not  send  any  processes  into  the  interior,  like  the  correspond- 
ing coat  of  the  testes,  with  which,  otherwise,  it  precisely  corresponds 
in  structure.  The  stroma  is  a  grayish-red  substance,  of  tolerably  firm 
consistence,  composed  of  a  nucleated,  tough,  fibrous, 
though  not  distinctly  fibrillar,  connective  tissue,  in 
which  are  lodged  the  ovisacs  and  the  vessels  of  the 
organ.  From  the  inferior  border  of  the  ovary,  where 
the  vessels  enter,  and  ovisacs  are  never  situated,  the 
stroma  extends,  in  the  form  of  a  compact  lamella,  into 
the  interior  of  the  ovary,  from  which  it  then  radiates, 
in  larger  and  more  slender  bundles,  towards  both  sur- 
faces and  the  free  border  of  the  organ,  so  that,  in  a 
transverse  section,  a  penicillar  arrangement  is  pre- 
sented by  them.  The  ovisacs  or  follicles,  usually  termed  Cf-raafian  vesicles, 
folliculi  ovarii  s.  G-rafiani,  s.  ovi-sacci,  entirely  closed,  round  follicles, 
from  J  to  3  lines  in  mean  size  (Fig.  263  a,  b),  are  imbedded  in  the  more 
peripheral  portions  of  the  stroma,  so  that,  in  a  section,  at  all  events,  of 
well-developed  and  normal  ovaries,  the  parenchyma  separates,  as  it 
were,  into  a  medullary  and  cortical  substance,  the  latter  of  which  only 
as  it  may  be  said,  contains  the  follicles.  Ovaries  in  that  condition, 
also,  should  alone  be  made  use  of,  for  the  obtaining  of  a  correct  notion 

FIG.  263. — Transverse  section  through  the  ovary  of  a  woman  dead  in  the  fifth  month  of 
pregnancy :  a,  Graafian  follicle  of  inferior,  and  6,  of  the  superior  surface,  c,  peritoneal 
lamella  of  the  lig.  latum,  continued  upon  the  ovary,  and  coalescing  with  d,  the  t.  albuginea  ; 
in  the  interior,  two  corpora  albicantia  (old  corpora  lutea]  are  visible ;  e,  stroma  of  the  ovary. 


THE    SEXUAL    ORGANS.  641 

of  the  size,  position,  and  number  of  the  Graafian  follicles.  The  latter 
amounts  to  30-50-100  in  each  ovary,  and  in  many  cases  may  reach 
200  ;  whilst  in  arrested  or  degenerated  ovaries,  such  as  are  frequent 
especially  in  old  women,  not  more  than  2  to  10,  or  even  none  at  all, 
are  often  met  with. 

Each  follicle,  in  the  fully  formed  condition,  consists  of  a  membrane 
and  contents.  The  former  may  be  most  aptly  compared  with  a  mucous 
membrane  and  presents  :  1,  a  highly  vascular  fibrous  layer,  tliecafolli- 
culi  v.  Baer,  s.  tunica  iibrosa,  of  a  proportionately  not  inconsiderable 
thickness,  which  is  united  to  the  stroma  of  the  ovary  by  a  rather  loose 
connective  tissue,  and  consequently  can  be  readily  stripped  off  in  its 
totality.  Its  external,  somewhat  firmer,  reddish-white  layer  (Fig.  264 
a),  has  been  distinguished  by  v.  Baer  from  the  internal,  thicker,  softer, 
and  redder  portion  (Fig.  264  b) ;  but  at  the  same 
time  it  should  be  remarked,  that  the  inner  layer 
also  may  be  again  divided,  and  that  both  lamince 
are  composed  of  the  same  undeveloped,  nucleated 
connective  tissue,  intermixed  with  numerous, 
mostly  fusiform,  formative  cells.  In  young  folli- 
cles a  delicate,  structureless,  membrana  propria, 
bounds  the  fibrous  coat  on  the  inner  aspect  and 
may,  by  the  use  of  alkalies,  even  at  a  later 
period,  frequently  be  demonstrated  as  a  distinct  membrane.  2,  an 
epithelium  (granular  layer,  membrana  granulosa  of  authors),  (Fig.  264 
b,  c).  This  membrane,  0-008-0-012  of  a  line  or  more,  in  thickness, 
lines  the  entire  follicle,  and  on  the  side  looking  towards  the  surface 
of  the  ovary,  where  the  ovum  is  situated,  presents  a  wart-like  thicken- 
ing, projecting  towards  the  interior  and  enveloping  the  ovum — the  ger- 
minal eminence,  cumulus  proligerus,  J  of  a  line  broad  (Fig.  264  e). 
Its  roundish,  polygonal  cells,  0-003-0-004  of  a  line  in  size,  with  pro- 
portionately large  nuclei,  and,  frequently,  some  yellowish  fatty  granules 
disposed  in  several  layers,  are  extremely  delicate,  and  after  death  soon, 
become  indistinct,  in  consequence  of  which  the  whole  epithelium  pre- 
sents the  appearance  of  a  fine  granular  membrane  with  numerous 
nuclei.  The  interior  of  the  follicles  is  occupied  by  a  clear,  light-yel- 
lowish fluid — liquor  folliculi — of  the  density  of  the  serum  of  the  blood, 
containing,  almost  always,  isolated  granules,  nuclei,  and  cells,  which  are 
scarcely  anything  more  than  detached  portions  of  the  membrana  granu- 
losa, and  do  not  originate  in  the  fluid. 

In  the  germinal  eminence,  close  upon  the  fibrous  membrane  of  the 
follicle,  and  therefore  in  the  most  prominent  part  of  it,  is  placed  the 

FIG.  204. — Graafian  follicle  of  the  Sow,  magnified  about  10  diameters:  a,  external ;  6, 
internal,  layer  of  the  fibrous  membrane  of  the  follicle:  c,  membrana  granulosa;  d,  liquor 
folliculi  •  e,  germinal  eminence,  a  projection  of  the  membrana  granulosa  ;/,  ovum  with  a  zona 
pellucida,  vitellus,  and  germinal  vesicle. 

41 


642  SPECIAL    HISTOLOGY. 

egg  (ovulum},  imbedded  in  the  cells  of  which  the  eminence  is  composed, 
and  retained  in  its  position  by  them.  When  the  follicle  bursts,  or  is 
ruptured,  the  ovulum  escapes,  surrounded  by  the  cells  of  the  cumulus, 
and  the  contiguous  part  of  the  epithelium,  which  encompass  it,  as  a  sort 
of  ring  or  disc  (discus  proligerus,  germinal  disc,  v.  Baer),  enclosing  it, 
however,  entirely,  and  by  no  means  only  attached  to  it  in  its  greatest 
breadth.  The  ovulum  itself  is  a  spherical  vesicle,  measuring  when 
mature  1-8-1-10  of  a  line,  which,  though  in  certain  respects  peculiar, 
nevertheless  possesses  the  nature  and  constitution  of  a  simple  cell.  The 
cell-membrane,  or  vitelline  membrane,  membrana  vitellina,  has  the  un- 
usual thickness  of  0-004-0-005  of  a  line,  and,  in  microscopical  figures, 
surrounds  the  contents,  or  yelk  (vitellus),  as  a 
clear,  transparent  ring,  whence  it  has  received 
the  name  of  zona  pellucida.  It  is  structureless, 
very  elastic,  and  firm,  so  as  to  support  a  consi- 
derable degree  of  extension  without,  being  torn ; 
and  in  chemical  characters  corresponds,  in  every 
particular,  with  the  membranes  proprice,  §  16. 
The  light-yellow  yelk,  which  in  recent  ovula  com- 
pletely fills  the  vitelline  membrane,  is  composed  of  viscid  fluid,  having 
numerous  minute,  pale  granules  dispersed  in  it,  with  which,  in  the 
mature  ova,  some  fatty  granules  are  also  associated,  and,  in  the  fully- 
formed  ovum,  contains,  excentrically,  a  well-marked  vesicular  nucleus, 
0*02  of  a  line,  with  clear  contents,  and  a  homogeneous,  round,  parietal 
nucleolus,  0*003  of  a  line  in  size,  the  germinal  vesicle,  vesicula  germina- 
tiva  (the  "vesicle  of  Purkinje"),  and  the  germinal  spot,  macula  ger- 
minativa  (or  "  spot  of  Wagner")  as  they  are  here  termed. 

The  parovarium  (Nebeneierstock)-  a  rudiment  of  the  Wolifian  body  of 
the  embryo,  consists  of  a  certain  number  of  canals,  0-15-0-2  of  a  line 
in  diameter,  diverging  from  the  hilus  ovarii  into  the  "  bat's  wring," 
which  in  Man  neither  open  into  the  ovarium  nor  are  connected  with 
any  other  parts,  and  contain  nothing  but  a  little  clear  fluid.  The  tubes 
are  formed  of  a  fibrous  membrane,  0-020-0-024  of  a  line  thick,  and  of  a 
single  layer  of  pale,  cylindrical,  probably  ciliated  cells,  and  are  of  in- 
terest only  as  the  remains  of  an  embryonic  structure. 

The  arteries  of  the  ovary,  derived  from  the  aa.  spermatica  and  uterina, 
and  forming  numerous  minute  trunks  between  the  lamellae  of  the  broad 
ligaments,  enter  from  the  inferior  border  of  the  ovary,  run  in  a  serpen- 
tine course  in  the  internal  portion  of  the  stroma,  and  terminate  partly 
in  the  stroma  itself  and  in  the  t.  albuginea,  but  chiefly  in  the  walls  of 
the  Graafian  follicles,  where  they  form  an  exterior  more  coarse,  and  an 

FIG.  265. — Human  ovulum,  from  a  follicle  of  the  average  size,  magnified  250  diam. :  a, 
vitelline  membrane  (zona  pellucida)  •  6,  external  boundary  of  the  yelk,  and  also  internal 
boundary  of  the  yelk-membrane ;  c,  germinal  vesicle,  with  the  germinal  spot. 


THE    SEXUAL    ORGANS.  643 

inner  finer  plexus,  which  extends  as  far  as  the  membrana  granulosa. 
The  veins  arise  in  the  same  situation,  are  in  Man,  for  the  most  part, 
very  beautifully  displayed  in  the  walls  of  the  larger  follicles,  and  ter- 
minate in  the  uterine  and  internal  spermatic  veins.  A  few  lymphatic 
vessels  come  out  from  the  liilus  ovarii,  and  proceed,  in  company  with  the 
bloodvessels,  to  the  lumbar,  and  pelvic  glands.  And  with  respect  to 
the  nerves,  they  arise  from  the  spermatic  plexus,  enter  as  minute  trunks 
with  fine  fibres,  and  "  fibres  of  Remak,"  together  with  the  arteries, 
into  the  ovary ;  but  as  respects  their  ultimate  condition,  they  have  not 
yet  been  investigated. 

§  205.  Detachment  and  re-formation  of  the  ova, — corpora  lutea. 
From  the  commencement  of  puberty  up  to.  the  period  of  involution,  the 
ovaries  are  the  seat  of  a  continual  detachment  of  the  ova  ly  dehiscence 
of  the  Grraafian  vesicles,  which,  independently  of  sexual  congress,  takes 
place  in  women  and  virgins,  above  all  at  the  menstrual  period,  although 
it  may  and  does  frequently  occur  at  other  times,  under  conditions  not 
yet  accurately  determined.  In  animals  the  same  process  is  exhibited 
at  the  time  of  "  heat,"  although  sexual  congress  appears  to  afford  a 
necessary  impetus  to  its  completion  ;  and  in  them  the  anatomical  pro- 
cesses may  be  more  completely  traced,  whilst,  in  Man,  the  opportunity 
for  such  observations  is  much  more  rarely  afforded. 

When  the  Graafian  follicles  approach  the  time  of  bursting,  they  gra- 
dually enlarge  to  a  circumference  of  4  to  6  lines  and  more,  and  are 
continually  brought  more  and  more  near  to  the  surface,  until  they 
project  beyond  it,  as  wartlike  or  hemispherical  elevations,  covered  only 
by  a  thin  pellicle  of  the  much  attenuated  t.  albuginea,  with  its  peritoneal 
lamella.  At  the  same  time  their  vessels  are  remarkably  multiplied,  and 
by  the  continual  exudation  from  them,  the  liquor  folliculi  is  rendered 
more  and  more  abundant,  whilst  the  fibrous  coat  of  the  follicle,  at  the 
bottom  and  sides,  but  not  where  the  ovulum  is  situated,  becomes  thick- 
ened towards  the  interior ;  the  membrana  granulosa  also  swells  a  little, 
and  contains  larger  cells  (up  to  0-01  of  a  line.)  When  these  processes 
have  advanced  to  a  certain  point,  the  thin,  opposing  coats  can  no  longer 
withstand  the  continued  and  ever-increasing  pressure  from  the  interior 
of  the  follicle ;  they  give  way  at  the  most  elevated,  and  most  thinned 
point,  exactly  where  the  ovulum  is  situated,  and  this  body,  surrounded 
by  the  cells  of  the  germinal  eminence,  if  the  oviduct  has  applied  itself 
exactly  over  the  follicle,  escapes  into  it.  But  the  vital  course  of  the 
Graafian  follicle  is  not  hereupon  concluded,  for  now  a  series  of  partly 
new  formations  is  presented  in  it,  in  consequence  of  which  it  at  first 
becomes  a  corpus  luteum,  as  it  is  termed,  and  ultimately  disappears 
altogether. 

These  corpora  lutea  are  displayed  in  the  most  complete  state,  when 


644  SPECIAL    HISTOLOGY. 

conception  and  pregnancy  ensue  upon  the  detachment  of  the  ovum,  and, 
when  in  perfection,  appear  as  roundish  or  oval,  firm  bodies,  mostly 
rather  larger  than  the  former  follicles,  and  are  usually  visible  even  on  the 
exterior  as  projections,  exhibiting  on  the  summit  a  stellate  cicatrix, 
arising  from  the  rupture  of  the  Graafian  follicle.  Exteriorly,  these 
bodies  are  bounded,  towards  the  stroma  of  the  ovary,  by  a  thin  whitish 
fibrous  membrane  (Fig.  266,  2  /),  succeeded  by  a  yellowish  vascular 
lamella,  which  is  much  plicated,  and  consequently  appears  thicker  (Fig. 
266  c);  and  in  the  interior  is  a  larger  or'smaller  cavity  filled,  either  with 
coagulated  blood  (blood-clot),  or  with  a  somewhat  gelatinous  fluid  tinged 
with  blood  (Fig.  266  d  e).  With  respect  to  the  origin  of  these  bodies, 
it  is  easily  perceptible,  that  their  "nucleus"  or  contents  consist  of  the 
blood  poured  out  upon  the  rupture  of  the  follicle,  frequently  mixed  with 
some  remains  of  the  liquor  foUiculiy  and  that  the  outer  fibrous  mem- 
brane is  the  external  layer  of  the  original  fibrous  coat  of  the  follicle ; 
and  as  regards  the  yellow  plicated  cortical  layer,  this  is  referable  for 

the  most  part  to  the  internal  layer  of  the 
fibrous  membrane  of  the  original  follicle, 
which,  even  before  the  expulsion  of  the 
ovum,  becomes  loosened  in  texture,  and 
afterwards  rapidly  expanded  to  the  thick- 
ness of  J-J  a  line  and  more.  The  remains 
of  the  epithelium,  or  membrana  granulosa, 
which  were  not  expelled  with  the  ovum  from 
the  follicle,  also  seem  to  contribute  to  this 
thickening,  though  in  a  subordinate  degree, 
and  by  no  means  in  the  same  proportion  as 
the  layer  in  question;  the  increased  thick- 
ness of  which  is  accompanied  by  the  deve- 
lopment of  a  vast  number  of  smaller  and 
larger  cells,  which  are,  in  part,  transformed 
into  immature  connective  tissue  arid  vessels,  in  part  remain  in  the  con- 
dition of  cells,  characterized  by  their  size,  which  reaches  as  much  as 
0  01-0-2  of  a  line,  their  well-marked,  vesicular  nuclei  with  nucleoli,  and 
a  greater  or  less  number  of  yellow  oil-drops  in  the  interior.  The  corpus 
luteum,  thus  constituted,  retains  its  original  size  for  some  time,  up  to 
the  second  or  third  month  of  pregnancy  ;  because,  whilst  the  contents 
(whether  these  are  a  blood-clot,  or  a  reddish  gelatinous  substance  with 
a  small  cavity  in  the  interior)  gradually  diminish  and  lose  their  color, 
the  yellow  cortical  layer  continues  to  increase  in  thickness,  and,  at  the 

FIG.  266. — Two  corpora  lutea,  of  the  natural  size,  in  a  transverse  section.  1,  quite  recent, 
eight  days  after  conception;  2,  at  the  fifth  month  of  pregnancy:  a,  t,albuginea;  6,  stroma 
ovariifc,  thickened  and  plicated  fibrous  membrane  of  the  follicle  (inner  layer);  d,  blood-clot 
within  it;  e,  discolored  blood-clot;  /,  fibrous  coat  bounding  the  corpus  luteum. 


THE    SEXUAL     ORGANS.  645 

same  time,  its  tissue  to  become  more  organized  and  more  compact ;  this 
change  taking  place  by  the  transformation,  on  the  one  side,  of  the  in- 
ternal substance  into  fibrous  tissue,  and  on  the  other  by  the  more 
intimate  fusion  of  the  yellow  cortex  with  it,  and  the  more  abundant 
development  of  immature  connective  tissue  in  the  former.  In  the  fourth 
and  fifth  months  the  atrophy  of  the  corpus  luteum  commences,  and  is 
slowly  continued  to  the  end  of  pregnancy ;  so  that  in  persons  dead  in 
childbed,  it  still  measures  4  lines  on  the  average,  but  afterwards  more 
rapidly,  until  ultimately,  after  some  months,  the  metamorphosed  Graa- 
fian  follicle  has  entirely  disappeared,  or  become  reduced  to  a  diminutive, 
variously  colored  corpuscle,  which  undoubtedly  may  still  exist  for  a  long 
time,  and,  perhaps,  is  not  removed  altogether  for  some  years.  Such 
arrested  corpora  lutea  (corpora  albicantia  and  nigra,  of  authors)  at  first 
retain  a  distinct  limitation,  a  dentate  nucleus,  containing  a  minute 
cavity  of  a  grayish  white,  or  red-brown,  even  black  color  depending  upon 
altered  hematin,  and  a  cortical  substance  presenting  various  tints  of 
yellow  or  yellowish-white,  or  even  quite  white,  and  often  still  distinctly 
plicated,  but  subsequently  they  become  mere  amorphous  spots,  coales- 
cent  with  the  stroma  of  the  ovary.  Their  elements  are  fibres,  more  of 
an  embryonic  character,  such  as  also  form  the  ovarian  stroma,  together 
with  various  pigmentary  molecules  and  colored  crystals  (hsematoidin), 
and  a  whitish-yellow  fat,  which  latter  at  first  occurs  in  the  cortical  sub- 
stance still  contained  in  larger,  round,  elongated,  or  fusiform  cells,  but 
is  ultimately  liberated  by  their  rupture,  and  at  last  subjected  to  a  more 
or  less  complete  absorption. 

In  the  corpora  lutea,  which  are  not  formed  at  the  time  of  a  preg- 
nancy, the  same  processes,  in  general,  take  place  as  in  the  others,  but 
with  much  greater  rapidity ;  so  that  these  bodies  have  usually  entirely 
disappeared  in  the  space  of  one  or  two  months,  or  left  only  the  merest 
trace,  whence  they  never  possess  the  peculiar  conformation  of  the 
others,  which  have  been  termed  the  true  corpora  lutea.* 

The  place  of  the  numerous  follicles  which  disappear  from  the  ovaries 
during  the  whole  of  the  vigorous  periods  of  life,  is  supplied  by  the 
constant  production,  even  in  the  adult,  of  new  ovisacs,  which  are 
developed  into  Graafian  follicles.  In  animals,  these  new  formations 
which  take  place  at  the  time  of  heat,  and  were  first  noticed  by  Barry, 
Bischoff,  and  Steinlin,  are  very  abundant,  and  very  easily  observed, 

*  [Besides  the  difference  in  size  and  the  rapidity  of  their  metamorphoses,  the  true  corpora 
lutea  are  distinguishable  from  the  corpora  lutea  formed  in  the  non-pregnant  state  by  the 
thickness  of  the  wall,  and  by  their  different  color.  The  convoluted  wall  of  the  true  corpus 
luteum  is  almost  always  twice  as  thick,  whilst  its  color  and  that  of  the  central  coagulum, 
is  never  of  so  decided  a  yellow,  but  has  generally  more  of  a  dusky  and  indefinite  hue  ;  a 
difference  which  is  probably  owing  to  a  less  number  of  yellow  oil-globules.  (Vide  Dalton's 
Prize  Essay,  "  On  the  Corpus  Luteum  of  Menstruation  and  Pregnancy,"  Transactions  of  the 
American  Medical  Association  for  1851.) — DaC.] 


646  SPECIAL    HISTOLOGY. 

whilst  in  Man  no  opportunity  has  as  yet  Jbeen  afforded  of  noticing 
them,  and  it  is  only  from  the  circumstance,  that  in  this  case  also  in 
normal  ovaries,  follicles  of  the  most  various  sizes  are  always  met  with, 
that  a  continual  formation  of  them  may  be  concluded  to  take  place. 
In  Man,  it  is  also  probable,  that  the  times  of  conception  and  of  men- 
struation are  those  in  which,  especially,  these  productions  take  place, 
which  in  animals,  as  respects  their  histology,  originate  in  exactly  the 
same  way,  as  will  be  afterwards  described  when  we  speak  of  the  first 
follicles  of  the  embryo.  [See  Appendix,  §  corpora  lutea. — TRS.] 

§  206.  Oviducts  and  uterus. — Of  the  three  coats  of  the  oviduct,  the 
most  external,  which  belongs  to  the  peritoneum,  presents  nothing 
worthy  of  remark.  The  middle,  or  smooth  muscular  coat,  is  of  tolera- 
ble thickness,  especially  in  the  internal  half  of  the  duct ;  and  consists 
of  external,  longitudinal,  and  internal  transverse  fibres,  the  elements  of 
which,  even  at  the  time  of  pregnancy,  can  be  isolated  with  some  diffi- 
culty, and  are  intermixed  with  much  more  undeveloped  connective 
tissue  of  the  same  form  as  in  the  stroma  of  the  ovary.  The  innermost 
coat  is  the  mucous  membrane,  a  thin,  whitish-red,  soft  layer,  which  is 
connected  with  the  muscular  tunic  by  a  small  quantity  of  submucous 
connective  tissue,  presents  no  glands  or  villi,  though  it  has  a  few  lon- 
gitudinal folds,  and  consists  of  undeveloped  connective  tissue,  with 
many  fusiform  formative  cells.  On  its  inner  surface,  from  the  uterus 
to  the  free  border  of  the  fimbrice,  lies  a  single  layer  of  conical  or 
filiform,  ciliated  cells,  of  0*006— O'Ol  of  a  line,  whose  distinct  cilia 
effect  a  current  running  from  the  ostium  abdominale  to  the  ost.  uteri- 
num,  which  probably  assists  in  the  locomotion  of  the  ovula,  but  not  of 
the  spermatic  fluid. 

The  uterus  is  constituted  in  the  same  way  as  the  oviducts,  except 
that  the  muscular  coat  and  mucous  membrane  are  much  stronger,  and, 
in  some  respects,  differently  constructed.  In  the  pale  red  muscular 
coat,  three  layers  may,  most  conveniently,  be  distinguished,  which, 
however,  cannot,  as  elsewhere  (in  the  intestine  for  instance),  be  sharply 
defined  from  each  other.  The  external  layer  is  composed  of  longitudi- 
nal and  transverse  fibres,  the  former  of  which,  forming  a  continuous, 
thin  stratum,  intimately  united  to  the  serous  coat,  extend  over  the 
fundus  and  the  anterior  and  posterior  surfaces,  as  far  as  the  cervix, 
whilst  the  stronger  transverse  fibres  surround  the  organ,  and  are  also, 
to  some  extent,  continued  beyond  the  uterus,  into  the  ligg.  rotunda, 
ovarii,  and  lata,  and  upon  the  oviducts.  The  middle  layer  is  the 
strongest,  presents  transverse,  longitudinal,  and  oblique,  flat  bundles, 
which  are  interlaced  in  a  complex  manner,  and  contains  larger  vessels, 
chiefly  veins,  whence,  especially  in  the  pregnant  uterus,  it  presents  a 
spongy  appearance.  The  innermost  layer,  lastly,  is  again  thinner,  and 


THE    SEXUAL    ORGANS.  647 

formed  of  a  network  of  more  slender,  longitudinal,  and  of  stronger, 
transverse,  and  oblique  fibres,  which,  at  the  openings  of  the  oviducts, 
frequently  form  very  distinct  rings.  In  the  fundus,  where  the  uterus 
is  thickest,  the  middle  layer  is  strongest,  and  often  appears  to  be  com- 
posed of  several  laminae ;  whilst,  at  the  thinner  cervix,  transverse  fibres 
especially,  intermixed  with  isolated  longitudinal  ones,  are  met  with. 
In  the  neighborhood  of  the  external  os  uteri,  and  in  that  part  itself, 
highly  developed  transverse  fibres  lie  immediately  beneath  the  mucous 
membrane,  and  may  be  described  as  an  occlusor  of  it — sphincter  uteri. 
As  to  the  elements,  all  these  layers  consist  of  short  (0- 02-0-03  of  a 
line)  fusiform  fibre-cells,  with  elongated  oval  nuclei,  which,  on  account 
of  the  great  quantity  of  the  nucleated  embryonic  connective  tissue,  of  the 
same  constitution  as  in  the  stroma  ovarii,  by  which  the  layers  are  per- 
vaded, can  only  with  difficulty  be  isolated,  and  even  with  the  aid  of  nitric 
acid,  of  20$,  are  not  brought  into  view  so  distinctly  as  elsewhere. 

The  mucous  membrane  of  the  uterus  is  of  a  white  or  whitish-red 
color ;  it  is  closely  united  with  the  muscular  coat,  from  which  it  cannot 
be  raised ;  in  transverse  sections,  however,  it  is  distinguishable  from  it 
by  its,  mostly,  brighter  color,  though  rarely  presenting  any  marked  line 
of  demarcation.  Except  in  its  fundamental  substance,  consisting  of  the 
connective  tissue  which  exists  everywhere  in  the  female  genital  organs, 
containing  undeveloped  nuclei  and  fibre-cells  without  elastic  elements, 
and  the  epithelium^  which  throughout  appears  as  a  ciliated  epithelium 
with  pale  cells,  as  much  as  0-016  of  a  line  in  size,  and  delicate  cilia 
which  vibrate  from  without  to  within,  the  mucous  membrane  is  differ- 
ently constituted  in  the  body  &nd.fundus,  and  in  the  canal  of  the  cervix. 
In  the  former  situations  it  is  more  delicate,  redder,  and  thinner  (from 
J-l  line),  smooth  on  the  inner  aspect,  and  without  papillce,  but  occa- 
sionally presenting  a  few  large  folds.  Ill  it  are  found  very  numerous 
minute  glands,  the  utricular  glands  of  the  uterus,  or  uterine  glands 
(glandulce  utriculares  s.  uterince),  which  bear  the  closest  resemblance 
to  the  Lieberklihnian  glands  of  the  intestine ;  they  exhibit  the  form  of 
thickly  placed  follicles,  either  simple  or  bifurcated,  and  not  unfrequently 
spirally  contorted  at  the  end,  and  in  length  correspond  with  the  thick- 
ness of  the  mucous  membrane,  being  0-02-0-03  of  a  line  broad.  They 
consist  of  a  very  delicate  structureless  membrane,  and  a  uniform  cylin- 
der-epithelium, and  open  either  singly  or  two  or  three  together,  with 
orifices  l-30th  of  a  line  wide.  Normally,  these  glands  contain  no  mor- 
phological elements  at  all,  but  it  is  probable  that  their  epithelium  is 
very  easily  detached,  and  may  appear  as  a  grayish-white  secretion  fill- 
ing them. 

In  the  cervix  the  mucous  membrane  is  whiter,  denser,  and  thicker 
(1-1J  lines),  particularly  on  the  anterior  and  posterior  walls,  where  the 
well-known  plicce  palmatce  are  situated ;  between  which  are  found  larger 


648  SPECIAL    HISTOLOGY. 

and  smaller,  sinuous  fossae  lined  with  cylinder-epithelium,  and  as  much 
as  1  line  and  more  in  depth,  and  differing  very  essentially  from  common 
mucous  follicles,  although,  as  the  secreting  organs  of  the  viscid,  crys- 
talline mucus  of  the  cervix  uteri,  they  may  be  designated  the  mucous 
follicles  of  the  uterus.  In  this  region  also  occur,  in  great  abundance, 
closed  vesicles,  J-l-2  lines  and  more  in  size,  filled  with  the  same  secre- 
tion, and  composed  of  a  layer  of  connective  tissue  and  short  cylinder- 
cells,  the  so-termed  ovula  Nabothi^  which,  like  the  Graafian  follicles, 
might  perhaps  be  regarded  as  closed  glandular  vesicles,  bursting  periodi- 
cally, but  which  probably  are  nothing  more  than  dilated  and  closed 
mucous  follicles,  and  in  part  also  pathological  new  formations ;  they 
are  likewise  occasionally  found  in  the  mucous  membrane  of  the  body  of 
the  uterus.  The  inferior  third  or  half  of  the  cervical  canal  contains 
verrucose  or  filiform  papillae,  0-1-0-3  of  a  line  long,  clothed  with  ciliated 
cylinders,  containing  a  single  or  several  vascular  loops,  with  very  nu- 
merous minute  nuclei,  and  also,  perhaps,  pale  oil-drops  in  their  interior. 

The  distribution  of  the  vessels  in  the  unimpregnated  uterus,  does  not 
present  much  of  a  special  nature.  The  larger  arterial  branches  run  in 
the  muscular  substance,  and  ramify  thence  on  both  sides  in  the  muscular 
and  mucous  coats.  The  latter,  as  everywhere,  has  larger  vessels  in  the 
deeper,  and  finer  in  the  superficial  portion,  and  these,  after  they  have 
surrounded  the  glands  with  smaller  capillaries,  form  an  extremely  rich 
and  delicate  plexus  of  larger  vessels  (0-006-0-01  of  a  line)  on  the  sur- 
face, from  which  arise  the  wide,  thin-walled  veins,  unfurnished  with 
valves,  which  follow  the  course  of  the  arteries  towards  the  exterior. 
The  lymphatics,  probably  commencing  in  the  mucous  membrane,  are 
remarkably  numerous,  form  coarser  or  finer  networks  under  the  peri- 
toneal investment  and  proceed,  in  numerous,  considerable  trunks?  ac- 
companying the  blood-vessels,  in  part  to  the  pelvic  glands,  in  part,  with 
the  vasa  spermatica,  to  the  lumbar  plexus.  The  nerves  of  the  uterus, 
containing  numerous  fine,  and  some  thick  nerve-fibres  coming  from  the 
hypogastric  and  pudendal  plexuses,  and  united  in  a  plexiform  manner, 
reach  the  uterus  through  the  broad  ligaments,  and  ramify,  following 
principally  the  course  of  the  vessels  in  the  muscular  substance,  from 
the  fundus  to  the  cervix,  in  which  latter  situation  they  are  the  most 
abundant.  They  are  white  and,  in  the  uterus,  are  not  furnished  with 
any  ganglia ;  their  condition  in  the  mucous  membrane,  and  their  termi- 
nations elsewhere,  are  unknown. 

Of  the  ligaments  of  the  uterus,  the  ligg.  lata,  anteriora,  and  poste- 
riora,  are  duplicatures  of  the  peritoneum,  which  contain,  together  with 
the  vessels  and  nerves  passing  to  and  from  the  uterus,  a  considerable 
number  of  smooth  muscular  fibres  continued  into  them  from  the  uterus. 
The  same  tissue  also  arising  from  the  uterus,  occurs  more  sparingly  in 
the  ligg.  ovarii,  and  in  very  considerable  number  in  the  ligg.  rotunda, 


THE    SEXUAL    ORGANS. 


649 


in  the  form  of  longitudinal  bundles  surrounded  by  connective  tissue, 
with  which  at  the  internal  abdominal  ring  a  good  many  transversely 
striated  muscular  fibres,  often  extending  nearly  to  the  uterus,  are 
associated. 


Fig.  267. 


§  207.  Changes  in  the  uterus  at  the  menstrual  period  and  in  preg- 
nancy.— At  the  menstrual  period,  the  whole  uterus  enlarges,  and  its 
texture  expands,  which  is  perhaps  to  be  attributed,  chiefly,  to  the  dis- 
tension of  the  vessels,  and  the  considerable  infiltration  of  the  entire 
organ  with  blood-plasma ;  at  all  events,  beyond  a  greater  facility  in  the 
demonstration  of  its  elements.  I  have  been  unable  to  perceive  any  fur- 
ther alteration  in  the  muscular  coat.  The  mucous  membrane,  -on  the 
other  hand,  in  many  cases  really  increases,  being  thickened  to  1—2, 
even  3,  or,  in  its  projecting  folds,  even  to  5—6  lines ;  it  becomes  softer 
and  presents,  in  its  tissue,  well-marked,  easily  isolated,  utricular  glands, 
1—8  lines  long,  and  0'036— 0*04  of  a  line  broad,  and  numerous  immature, 
round  and  fusiform  cells.  The  bloodvessels  of  the  mucous  membrane, 
which  chiefly  afford  the  menstrual  flux,  are  throughout  the  uterus,  and 
particularly  in  its  body  and  fundus,  extremely  numerous  and  much  dis- 
tended, and  this  is  especially  the  case 
with  the  superficial  capillary  plexus ; 
whence  also,  the  mucous  membrane 
presents  a  bright  red  color.  With  the 
escape  of  the  blood  from  the  superfi-^ 
cial,  ruptured  capillaries,  the  epithe- 
lium of  the  mucous  membrane  is,  in 
great  measure,  thrown  off,  except  that 
of  the  cervix,  and  may  always  be  found 
in  large  quantity  in  the  mucus  mixed 
with  blood,  which  fills  the  cavity  of  the 
uterus  ;  it  is  not,  however,  to  be  re- 
garded as  normal,  if,  after  the  men- 
strual period,  or  during  it,  the  whole 
uterine  mucous  membrane  or  portions 
of  it  are  detached.  After  the  menstrual 
period,  the  parts  rapidly  regain  their 
pristine  condition,  and  the  epithelium 
is  restored. 

Changes  of  a  totally  different  kind 
are  induced  in  the  uterus  by  preg- 
nancy, among  which,  however,  in  a 
microscopical  point  of  view,  the  in- 

FIG.  267. — Muscular  elements  from  the  uterus,  in  the  fifth  month  of  pregnancy ;  a,  formative 
cells  of  the  muscular  fibres;  6,  younger;  c,  developed,  fibre-cells. — Magnified  350  diameters. 


650 


SPECIAL     HISTOLOGY. 


Fig.  268. 


creased  bulk  of  the  organ  only,  is  of  interest.  This  enlargement,  as 
is  well  known,  depends  upon  the  great  augmentation  of 
the  circumference  and  of  the  cavity ;  at  first  with  in- 
creased, and  afterwards  (usually  from  the  fifth  month 
onwards)  with  a  diminished  thickness  of  the  walls,  and 
an  increase  in  bulk,  amounting  on  the  average  to  twenty- 
four  times  the  original  size  ( J.  F.  Meckel,  "Anat.,"  IV. 
691).  The  mode  in  which  this  change  is  brought  about 
was,  as  regards  the  histological  conditions,  until  a  recent 
period,  it  may  be  said,  entirely  unknown  ;  but,  in  the 
main  point,  is  now  sufficiently  made  out.  The  principal 
changes  occur  in  the  muscular  coat,  to  which  the  in- 
creased volume  of  the  uterus  is  chiefly  to  be  assigned, 
and  there  are  two  processes  which  participate  in 
common  in  its  production :  in  the  first  place,  an  en- 
largement of  the  pre-existing  elements  ;  and  secondly, 
a  new  formation  of  them.  The  former  is  so  conside- 
rable, that  the  contractile  fibre-cells, 
instead  of  a  length  of  0-002-0-003 
of  a  line,  and  width  of  0-002  of  a 
line,  as  elsewhere,  in  the  fifth  month 
present  a  length  of  0-06-0-12,  and 
width  of  0-0025-0-006,  or  even  0-01 
of  a  line,  and  in  the  second  half  of 
the  sixth  month,  a  length  of  0-1- 
0-25,  a  width  of  0-004-0-006,  and 
a  thickness  of  0-002-0-0028  of  a 
line;  consequently,  their  length  is 
increased  from  seven  to  eleven  times, 
and  their  width  from  twice  to  five 
times.  The  new  formation  of  mus- 
cles may  be  observed  in  the  first  half 
of  pregnancy,  especially  in  the  in- 
nermost layers  of  the  muscular  coat, 
where  newly  originating  cells,  0*01- 
0-018  of  a  line  in  size,  in  all  stages 
of  transition  into  fibre-cells  of  0-02 
-0-03  of  a  line,  always  occur  in  great 
quantity  ;  but  it  takes  place  also  in 


FIG.  268. — a,  muscular  fibre-cell  from  a  gra- 
vid uterus,  at  the  sixth  month  ;  6,  its  middle 
portion,  after  treatment  with  acetic  acid,  and 
exhibiting  the  appearance  of  a  membrane  ;   c,  nucleus  of  the  fibre-cell. — Magnified  350 
diameters. 
FIG.  269.— A  uterine  gland  from  a  woman  in  the  first  pregnancy,  eight  days  after  conception. 


THE    SEXUAL    ORGANS.  651 

the  outer  layers.  After  the  sixth  month,  this  origination  of  muscles 
seems  to  cease  ;  at  least  in  the  twenty-sixth  week,  in  the  whole  uterus  I 
have  found  nothing  but  the  above-mentioned  colossal  fibre-cells,  and 
no  longer  any  trace  of  their  earlier  forms.  Like  the  muscles,  the 
fibrous  tissue  which  unites  them  also  increases,  and  towards  the  end  of 
pregnancy,  occasionally  exhibits  distinct  fibrils.  Whilst  the  muscular 
coat  grows  in  this  way,  the  mucous  membrane  has  also  undergone  mani- 
fold changes.  It  is  in  it,  especially,  that  the  metamorphoses  of  the  gravid 
uterus  commence,  seeing  that  as  early  as  the  second  week,  it  becomes 
thickened  to  2-3  lines,  is  softer,  more  lax,  and  redder,  acquires  more  promi- 
nent plicce,  and  is  more  distinctly  defined  from  the  muscular  coat ;  pecu- 
liarities which,  as  time  goes  on,  become  more  and  more  marked.  Examined 
microscopically,  it  is  apparent,  that  not  only  are  the  vessels  more  dis- 
tended, but  also  that  an  abundant  new  formation  of  connective  tissue 
has  taken  place  in  its  parenchyma,  and  a  considerable  enlargement  of 
the  utricular  glands,  which  latter  are,  at  this  time,  2-3  lines  long, 
and  0-04-0-11,  or,  on  the  average,  0-08  of  a  line  broad.  As  these 
changes  proceed,  the  greater  part  of  the  hypertrophied  mucous  mem- 
brane is  transformed  into  the  well-known  decidua  vera,  whilst  another  por- 
tion, at  the  point  of  attachment  of  the  ovum,  is  converted  into  the  pla- 
centa uterina,  and  by  a  growth  from  the  border  of  this  part,  the  reflexa 
is  produced  around  the  ovum  ;  processes  of  which  this  is  not  the  place 
to  speak  farther.  It  can  only  be  remarked  that  the  utricular  glands,  in 
the  decidua  vera,  are  gradually  converted  into  wider  follicles,  the  orifices 
of  which  give  rise  to  the  appearance,  as  it  were,  of  a  cribriform  perfora- 
tion in  that  membrane  and  the  border  of  the  reflexa;  and  moreover, 
that  the  deciduce,  from  the  second  month  onwards,  though  gradually 
diminishing,  it  is  true,  in  thickness,  nevertheless,  on  account  of  the 
enlargement  of  the  internal  surface  of  the  uterus,  are  still  far  from 
ceasing  to  increase  in  bulk ;  and  lastly,  that  their  tissue  at  all  times 
consists  of  larger  and  smaller,  round  cells,  with  large,  often  compound 
nuclei,  in  part  of  colossal  fibre-cells  with  well-formed  large  nuclei,  and, 
particularly  in  the  decidua  vera,  of  vessels  ;  whilst  in  epithelium,  except 
in  the  first  month,  is  no  longer  to  be  found  upon  the  deciduce.  The 
mucous  membrane  of  the  cervix  takes  no  part  in  the  formation  of  the 
deciduce,  and  retains  its  epithelium  (without  cilia)  during  the  whole  time 
of  pregnancy.  It  also,  however,  swells,  and  its  mucous  follicles,  espe- 
cially, enlarge  and  secrete  the  well-known  mucous  plug  which  fills  up 
the  entire  canal  of  the  cervix. 

The  serous  coat  also  increases  considerably  in  thickness,  though  not 
to  the  same  extent  as  the  mucous  membrane  :  whilst  the  thickening  of 
the  uterine  ligaments,  particularly  of  the  round  ligaments,  is  very  evi- 
dent, and  also  depends  upon  changes  in  their  smooth  muscles  similar  to 
those  described  in  the  muscles  of  the  uterus,  and  probably  also,  upon  an 
increase  of  the  transversely  striated  bundles.  The  growth  of  the 


652 


SPECIAL    HISTOLOGY. 


Fig.  270. 


bloodvessels  and  lymphatics,  in  length  and  calibre,  is  also  very  evident, 
and  is,  in  great  part,  to  be  referred  to  the  enlargement  and  new  forma- 
tion of  muscular  elements,  which,  in  the  veins,  are  also  demonstrable  in 
the  t.  adventitia  and  intima.  With  respect  to  the  nerves,  they  also 
become  thickened,  although  it  is  doubtful  whether  new  nerve-fibres  are 
really  produced  in  them.  On  the  other  hand,  it  is  certain  that  the  pre- 
existing elements  increase  in  width  and  length,  retain  their  dark  bor- 
ders for  a  greater  distance,  and  may  be  traced  further  into  the  interior 
than  at  other  times. 

The  lessening  of  the  uterus  after  parturition,  and  its  restoration  to  a 
condition,  not,  indeed,  similar  to  the  previous  state,  though  closely  ap- 
proximated to  it,  does  not  take  place  in  its  various  portions  exactly  in 
the  same  way.  In  the  muscular  coat,  an  atrophy  of  the  contractile 
fibrous  elements  manifestly  plays  a  principal  part,  since,  as  early  as 
three  weeks  after  parturition,  these  fibres  are  again  as 
short  (0-03  of  a  line)  as  in  the  virgin  uterus,  fat,  at  the 
same  time,  being  developed  in  their  interior;  but  a 
complete  absorption  of  certain  muscular  fibres  is  also 
probably  superadded  to  this.  A  different  process  takes 
place  in  the  mucous  membrane,  which,  in  the  form  of 
the  deciduce  and  placenta  uterina,  is  completely  thrown 
off  after  parturition,  and  consequently  has  to  be  entirely 
formed  anew.  The  intimate  nature  of  the  processes 
accompanying  this  unique  kind  of  regeneration  has  not 
yet  been  traced,  though  it  is  more  than  probable  that 
it  is  completed  as  early  as  within  the  first  two  or  three 
months  after  parturition.  It  is  evident  that,  besides 
this,  the  serous  coat,  the  vessels  and  nerves  of  the 
uterus,  return  to  their  former  condition,  but  the  precise 
nature  of  this  change  in  them  has  not  yet  been  inves- 
tigated. 

It  has  been  generally  assumed,  since  Tiedemann, 
that  the  nerves  of  the  gravid  uterus  are  thicker  than  in 
the  virgin  state ;  but  quite  recently  this  has  been  alto, 
gether  disputed  by  Dr.  Snow-Beck,  and  is  only  par- 
tially admitted  by  Jobert  de  Lamballe  ("  Compt.  rend.," 
1841,  Mai),  inasmuch  as  that  he  states  that  it  is  the  in- 
vesting connective  tissue,  but  not  the  nerves  themselves, 
that  is  thickened.  It  is  evident  that  very  accurate  mi- 
croscopic investigations  are  alone  competent  to  decide 
this  question ;  but  such  investigations  are  wanting.  No 

FIG.  270. — Muscular  fibre-cell  of  the  uterus,  three  weeks  after  parturition,  four  of  them 
treated  with  acetic  acid,  and  pale:  «,  nuclei;  g,  fat-granules. — Magnified  350  diameters. 


THE    SEXUAL    ORGANS.  653 

conclusion,  in  the  first  place,  can  be  drawn  from  Remak's  statement 
(1.  c.),  that  the  nerves,  at  the  time  of  pregnancy,  enlarge  and  acquire  a 
gray  color,  a  change  depending  upon  an  increase  of  nucleated  fibres, 
because  no  grounds  exist  upon  which  it  can  be  decided  whether  these 
nucleated  fibres  are  embryonic  nerve-fibres,  or  a  form  of  connective 
tissue.  On  the  other  hand,  we  are  indebted  to  Kilian  for  careful  re- 
searches in  animals,  which  prove  with  certainty  that  the  uterine  nerves, 
at  the  time  of  pregnancy,  may  be  traced  further  into  the  substance  of  the 
uterus,  in  the  form  of  dark-bordered  fibres ;  whilst  at  an  earlier  period, 
in  part  even  before  they  enter  the  uterus,  in  part  when  they  have  scarcely 
reached  it,  they  possess  the  nature  of  embryonic  non-medullated  fibres. 
For  this  reason,  Kilian  succeeded  also  in  tracing  the  nerves  in  the  gravid 
uterus  much  further  into  the  parenchyma  than  at  other  times.  He  perceived 
no  evidence  of  a  formation  of  new  nerve-fibres  in  the  trunks,  and  regards 
such  an  occurrence  as  improbable ;  for  otherwise  a  new  formation  of 
ganglionic  substance  must  also  be  assumed,  which  is  unlikely.  Some- 
thing of  the  kind  appears  to  me  by  no  means  impossible,  because  the 
multiplication  of  the  ganglion-cells  and  of  the  fibres  would  only  take 
place  once — in  the  first  pregnancy  ;  it  is  also  conceivable  that  newly 
formed  nerve-fibres  are  added  to  the  others  simply  as  branches,  and 
consequently  it  will  be  more  prudent  to  wait  and  see  upon  which  side 
Remak's  statements,  with  respect  to  the  human  subject,  incline.  Upon 
this,  however,  I  would  also  remark,  that  a  thickening  of  the  nerves  may 
undoubtedly  be  produced  by  an  increased  size  of  the  already  existing 
fibres  and  an  augmentation  of  the  neurilemma,  and  that  the  nerves,  by 
a  multiplication  of  their  ultimate  divisions,  are  fully  enabled  to  ramify 
over  larger  spaces  than  at  other  times. 

The  increased  size  of  the  vessels,  both  of  the  arteries,  and,  above  all, 
of  the  veins,  at  the  time  of  pregnancy,  is  very  considerable ;  owing  to 
which,  at  this  period,  the  middle  layer  of  the  muscular  substance,  con- 
taining the  larger  vessels,  is  much  more  distinct  from  the  other  two. 
The  alteration  which  takes  place  in  the  vessels  of  the  mucous  membrane, 
at  the  point  where  the  placenta  is  formed,  cannot  here  be  entered  upon  ; 
and  I  will  only  remark  that  I  agree  with  those  who  believe  that  large 
vascular  trunks  exist  in  the  human  uterine  placenta,  at  the  border  and 
on  the  convex  surface,  whilst  in  the  interior  there  are  only  lacunce  with- 
out walls,  between  the  villi  of  the  chorion  (vide  Kiwisch,  "  Geburtskunde," 
I.  p.  151,  et  seq. ;  C.  Wild,  "Zur  Physiologie  d.  Placenta,"  Wurzb., 
1849;  Virchow,  "  Archiv,"  III.  p.  449;  Schroder  v.  d.  Kolk,  in  the 
"Verb.  d.  Nied.  Instituts,"  1851).  In  the  rest  of  the  decidua,  the 
capillaries  are  frequently  excessively  enlarged ;  according  to  Virchow 
("Archiv.  f.  path.  Anat.,"  III.  p.  436),  its  superficial  capillaries,  in  the 
sixth  week  of  pregnancy,  reach  the  size  of  0-027-0-045  of  a  line,  and 
become  extremely  thin-walled,  as  are,  probably,  also  those  in  the  part 


654  SPECIAL    HISTOLOGY. 

where  the  placenta  is  situated,  before  their  walls  disappear  and  their 
cavity  is  thrown  into  that  of  tHe  lacunce.  In  the  venous  trunks  of  the 
gravid  uterus,  besides  the  circular  muscular  layer,  with  much  enlarged 
fibre-cells,  which  exist,  also  in  other  situations,  I  have  found  an  external 
and  internal  longitudinal  muscular  layer  with  similar  colossal  elements ; 
so  that  here  the  increase  of  the  walls  may  be  directly  demonstrated 
("Zeitsch.  f.  wiss.  Zool."  I.  84). 

§  208.  Vagina  and  external  sexual  parts.  The  walls  of  the  vagina, 
1  line  thick,  consist  of  an  external  fibrous  coat,  a  middle  muscular  layer, 
and  a  mucous  membrane.  The  thin  white  fibrous  coat  presents  externally 
a  more  lax,  towards  the  interior  a  more  dense  connective  tissue,  with 
numerous  elastic  fibres  arid  venous  plexuses,  and  passes,  without  any 
line  of  demarcation,  into  the  second,  redder  layer,  which,  together  with 
connective  tissue  and  numerous  veins,  contains,  particularly  during 
pregnancy,  a  good  many,  developed,  smooth  muscular  fibres,  which,  with 
their  transverse  and  longitudinal  bundles  of  fibre-cells,  0*04,  0*08  of  a 
line  long,  constitute  a  true  muscular  membrane.  The  mucous  membrane 
is  of  a  pale  red  color,  with  numerous  larger  and  smaller  folds  and  eleva- 
tions— the  columnar  rugosce  ;  it  is  composed  of  a  dense  connective  tissue, 
without  glands,  and  containing  elastic  elements  in  extreme  abundance, 
to  which  its  great  firmness  and  extensibility  are  due.  Its  inner  surface 
presents  numerous  conical  or  filiform  papillae,  from  0-06  to  0-08  of  a  line 
in  length,  and  0-025  to  0-03  of  a  line  in  breadth,  which  are  entirely 
imbedded  in  a  tessellated  epithelium,  0-07-0-09  of  a  line  thick,  of  the 
same  kind  as  that  in  the  oesophagus,  the  uppermost  scales  of  which, 
having  a  diameter  of  0-01-0-015  of  a  line,  contain  nuclei  of  0-003  of  a 
line.  The  hymen  is  a  duplicature  of  the  mucous  membrane  of  the  vagina, 
and  contains  the  same  elements. 

From  the  vayina  the  mucous  membrane  is  also  continued  upon  the 
external  genitals,  invests  the  glans  clitoridis  and  the  vestibule,  with  the 
orifice  of  the  urethra;  folds  of  it  constituting  the  preputium  clitoridis 
and  labia  minora.  On  the  labia  majora,  it  is  continuous  uninterruptedly 
with  the  external  integument,  which,  on  their  inner  side,  and  at  the 
commissura  labiorum,  still  bears  a  close  resemblance  to  a  mucous  mem- 
brane ;  whilst  on  their  border  and  outer  surface,  and  on  the  mons  veneris, 
it  resembles  the  cutis  in  all  respects.  The  matrix  of  the  mucous  mem- 
brane of  the  external  genital  organs,  is  a  spongy,  highly  vascular,  fatless 
connective  tissue,  containing,  however,  a  good  many  elastic  fibres,  and 
which,  in  its  condensed  external  layer,  i-|  of  a  line  thick,  correspond- 
ing to  the  corium,  is  everywhere  furnished  with  much-developed  papillce, 
in  the  labia  minora  1-10-1-20,  and  on  the  clitoris  1-24-1-33  of  a  line 
in  length;  and  with  a  squamose  epithelium  of  0-04-0-12  of  a  line,  the 
most  superficial  cells  of  which  are  0-01-0-02  of  a  line  in  size  (Fig. 


THE     SEXUAL    ORGANS.  655 

56,  4).  The  Idbia  majora,  in  the  structure  of  their  coverings,  corres- 
pond partly  with  the  mucous  membrane,  in  part  approach  the  cutis,  and 
contain,  in  the  interior,  common  adipose  tissue. 

The  external  genital  organs  are  furnished  with  various  smaller  and 
larger  glands.  Sebaceous  glands,  mostly  of  a  rosette-form  and  consi- 
derable size  (J-l  line),  occur  in  the  Idbia  majora,  on  the  external  and 
internal  aspects,  in  connection  with  larger  and  smaller  hair-follicles; 
moreover,  in  larger  quantity  in  the  Idbia  minora,  for  the  most  part 
without  hairs  and  rather  smaller  (from  ^  to  J  a  line) ;  occasionally, 
also,  around  the  orifice  of  the  urethra,  and  laterally  at  the  entrance  of 
the  vagina.  Common  racemose  mucous  glands,  J— 1 J  lines  in  size,  with 
scarcely  visible  or  tolerably  wide  openings,  and  having  excretory  ducts, 
either  short,  or  as  much  as  6  lines  long,  exist  in  very  various  number 
around  the  orifice  of  the  urethra,  in  the  vestibule,  and  in  the  lateral 
portions  of  the  entrance  of  the  vagina.  Lastly,  the  two  "glands  of 
Bartholini,"  corresponding  to  Cowper's  glands  in  the  male,  are  situated 
at  the  inferior  extremity  of  the  bulbi  vestibuli;  they  are  common  race- 
mose mucous  glands,  6  lines  in  size,  with  pyriform  gland-vesicles  lined 
with  a  tessellated  epithelium,  0-02-0-05  of  a  line  in  diameter,  and  lodged 
in  a  compact  nucleated  connective  tissue  without  muscular  fibres.  The 
excretory  ducts  of  these  glands,  7-8  lines  long,  and  J  a  line  wide,  have, 
external  to  their  mucous  membrane,  invested  with  a  cylinder  epithelium 
0-01  of  a  line  thick,  a  delicate  longitudinal  layer  of  smooth  muscles,  and 
always  contain  a  viscous,  amorphous,  clear,  yellowish  mucus. 

The  clitoris,  with  its  two  corpora  cavernosa  and  glans  attached  to  the 
bulbi  vestibuli,  the  divided  corpus  cavernosum  urethrce  of  the  female, 
present,  on  a  small  scale,  precisely  the  same  conditions  as  the  corre- 
sponding parts  and  corpora  cavernosa  of  the  male ;  and  in  them  the 
muscular  elements  are  even  more  readily  isolated  than  in  man. 

The  bloodvessels  of  the  vagina  and  of  the  external  genital  organs, 
present,  upon  the  whole,  nothing  much  worthy  of  remark.  In  the 
papillce  of  the  various  situations  where  they  occur,  we  find,  for  the 
most  part,  simple  vascular  loops ;  it  is  only  when  the  papillae  are  larger 
or  compound,  such  as  abound  around  the  orifice  of  the  urethra,  that 
more  complex  loops  occur.  The  corpora  cavernosa  have  the  same  struc- 
ture as  in  man ;  and,  according  to  Valentin,  helicine  arteries  also  ap- 
pear to  exist  in  the  clitoris.  The  venous  plexuses  in  the  walls  of  the 
vagina,  above  the  bulbi  vestibuli,  are  extremely  rich ;  but  by  no  means, 
as  Kobelt  assumes,  represent  true  corpora  cavernosa.  The  lymphatics 
of  the  external  genital  organs,  and  of  the  vagina,  are  numerous,  and 
communicate  partly  with  the  inguinal  glands,  partly  with  the  pelvic 
plexus.  The  nerves,  lastly,  are  derived  in  part  from  the  sympathetic, 
in  part  from  the  pudendal  plexus,  and  are  extremely  numerous,  espe- 
cially in  the  clitoris,  but  are  also  found  without  difficulty  in  the  mucous 


656 


SPECIAL    HISTOLOGY. 


membrane  of  the  vagina.  In  the  latter  situations  they  present  divi- 
sions, and  their  terminations  have  as  yet  been  but  little  investigated.  I 
have  never  found  nerves  in  papillae  containing  vessels,  whilst,  in  the 
clitoris,  I  have  sometimes  met  with  them  in  non-vascular,  minute  verru- 
cosities,  which  also  contained  rudimentary  axile  corpuscles  ;  and  I  think 
I  have  noticed  here,  as  well  as  on  the  surface  of  the  mucous  membrane 
itself,  finer  and  coarser  looplike  terminations  of  nerves  lying  buried  in 
the  bodies  resembling  axile  corpuscles,  which  are  also  occasionally  met 
with  in  these  situations.  In  the  clitoris  of  the  Sow,  Dr.  Nylander,  of 
Helsingfors,  found  Pacinian  bodies,  which  I  have  also  seen ;  and  looped 
terminations  of  the  nerves  in  the  papillce. 

§  209.  Physiological  remarks. — In  their  development,  the  internal 
female  genital  organs,  as  was  noticed  above  in  §  202,  entirely  correspond, 
originally,  with  those  of  the  male ;  and  it  is  not  till  after  some  time 
that  a  difference  in  the  histological  development  of  the  sexual  glands  is 
manifested,  consisting  in  this,  that  in  the  female,  the  Wolffian  body, 
except  that  it  forms  the  parovarium,  stands  in  no  farther  relation  to  the 
genital  apparatus,  whilst  the  "ducts  of  Miiller"  are  formed  into  the 
oviducts,  uterus,  and  vagina.  As  regards  the  histological  conditions, 
the  ovaries  alone  seem  to  present  any  great  interest.  These  bodies  are 
composed  at  first  of  common  formative  cells,  0-005-0-009  of  a  line  in 

size,  which  afterwards  pass,  in  part,  into 
fibres  and  vessels,  in  part  persist  as  cells, 
multiply  spontaneously,  probably  by  divi- 
sion, and  serve  for  the  formation  of  the 
Graafian  follicles.  These,  according  to 
Barry,  at  first  appear  as  spherical  agglome- 
rations, 0-01  of  a  line  in  size,  of  some  few 
cells,  which  contain,  in  the  interior,  a  clear 
vesicle — the  germinal  vesicle;  but,  by  the 
formation  of  a  delicate,  structureless  mem- 
brane on  the  exterior,  around  the  cells, 

which  then  represent  an  epithelium,  soon  assume  the  nature  of  follicles. 
Very  young  Graafian  follicles  of  this  kind  (ovisacs,  Barry)  occur  by 
thousands  in  the  ovaries  of  nearly  mature  embryos,  and  of  new-born 
children,  in  which  the  further  development  is  very  easily  traced.  Whilst 
the  follicle  increases  by  the  multiplication  of  the  cells  of  its  epithelium 
(the  membrana  granulosd),  and  at  the  same  time  acquires  an  external 
vascular,  fibrous  coat;  a  clear  substance,  in  Man  containing  but  few 
granules,  is  collected  in  the  interior,  detaching  the  germinal  vesicle, 

FIG.  271. — Three  Graafian  follicles  from  the  ovary  of  a  newly-born  female  child,  magni- 
fied 350  diameters.  1,  without;  2,  with,  acetic  acid:  a,  structureless  membrane  of  the 
follicle ;  b,  epithelium  (membrana  granulosa] ;  c,  yelk ;  d,  germinal  vesicle  with  spot ;  e,  nucleus 
of  the  epithelial  cells ;  /,  vitelline  membrane,  very  delicate. 


Fig.  271. 


THE    SEXUAL    ORGANS.  657 

0-0065-0-008  of  a  line  in  size,  with  a  germinal  spot  of  0-001^0-0015  of 
a  line,  from  the  epithelium,  to  which  at  first  it  was  closely  applied,  and 
forcing  it  into  the  centre  of  the  follicle.  When  this  has  attained  the 
size  of  0-02  of  a  line,  a  membrane  in  close  apposition  with  the  membrana 
granulosa,  and  surrounding  the  germinal  vesicle  and  the  whole  contents 
of  the  follicle — the  vitelline  membrane — becomes  evident ;  which  is  re- 
garded by  all  authors  as  a  secondary  formation,  although  it  probably 
exists,  even  in  the  very  earliest  rudiment  of  the  follicle,  as  an  extremely 
delicate  membrane,  closely  surrounding  the  germinal  vesicle.  At  first 
excessively  delicate,  and  scarcely  perceptible,  the  vitelline  membrane, 
when  the  follicle  has  increased  in  size  and  contains  more  fluid,  becomes 
more  distinct,  owing  to  its  removal  from  the  wall  of  the  follicle,  and 
rapidly  thickens.  In  follicles  of  0-04—0-05  of  a  line,  the  ova  are  per- 
fectly distinct  and  disproportionately  large,  with  a  delicate  zona  pellu- 
cida,  and  still  lying  very  close  to  the  walls  of  the  follicle.  The  further 
development  is  apparent  of  itself;  and  I  will  only  remark  that,  in  the 
new-born  child,  follicles  visible  to  the  naked  eye  will  be  more  rarely 
found  ;  whilst  such  make  their  appearance  even  before  puberty,  although 
they  undergo  no  considerable  development  before  that  period. 

According  to  what  has  been  said,  the  mode  of  origin  of  the  Graafian 
follicle  ranks  in  every  respect  with  that  of  the  tubular  glands.  The  for- 
mer is  an  agglomeration  of  cells,  at  first,  perhaps,  without  cavity  or  con- 
tents, to  which  the  structureless  membrane  is  added,  not  by  the  coales- 
cence of  the  outermost  cells,  but  probably  as  an  excretion  from  them, 
and  thus  is  formed  the  follicle,  which  therefore  exactly  corresponds  with 
a  closed  gland-vesicle,  or  a  section  of  a  tubular  gland  canal.  How  the 
germinal  vesicle,  and  the  vitelline  membrane  arise,  is  doubtful ;  the  for- 
mer is  either  a  nucleus  of  new  formation,  originating  in  the  minute  cavity 
of  the  follicle,  about  which  a  certain  amount  of  vitellus  is  subsequently 
collected,  the  cell,  or  vitelline  membrane  not  being  formed  until  after 
this,  from  a  sort  of  cell  formation  "around  portions  of  contents;"  or 
the  whole  ovum,  with  the  germinal  vesicle,  is  nothing  else  than  the  cen- 
tral cell  of  the  primordial  rudiment  of  the  Graafian  follicle,  and  conse- 
quently co-existent  with  it.  In  any  case  it  corresponds  to  a  cell,  and  the 
germinal  vesicle  is  nothing  but  the  cell-nucleus. 

With  respect  to  the  physiological  conditions  of  the  mature,  female 
sexual  organs,  much  has  already  been  remarked  in  the  preceding  pages  ; 
and  it  will,  therefore,  here  be  sufficient  to  say  something  about  their 
movements  and  secretions.  In  the  ovaries,  whose  stroma  frequently  pre- 
sents a  deceptive  appearance  of  muscularity,  I  have  in  vain  sought  for 
muscles,  with  nitric  acid  of  202,  although  in  recent  preparations  micro- 
scopical appearances  are  occasionally  obtained,  which  one  is  inclined  to 
explain  as  belonging  to  that  tissue.  That  the  oviducts  are  capable  of 

42 


658  SPECIAL     HISTOLOGY. 

very  active  movements  cannot  be  doubted,  from  the  results  of  vivisec- 
tions  in  animals,  and  microscopical  researches  in  Man ;  and  in  opposi- 
tion to  V.  Kiwisch  ("  Geburtskunde,"  p.  96)  I  do  not  understand  why 
their  application  to  the  ovaries  should  not  be  brought  about  by  move- 
ments in  them,  together  with  a  kind  of  erection  dependent  upon  increased 
fulness  of  the  vessels,  as  has  also  been  established  by  the  experiments  of 
Gendrin  and  Raciborski  (1.  c.  p.  412-417),  in  two  women  dead  during 
menstruation,  and  of  Laahr  ("De  mutat.  gen.  mul.  brevi  post  concept." 
Halis,  1843)  in  the  case  of  one  who  was  killed  shortly  after  coitus.  As 
regards  the  movements  of  the  uterus,  they  are,  at  all  events  during  par- 
turition,  very  energetic,  but  take  place  even  at  other  times.  The  mus- 
cular tissue  is  so  disposed,  that  at  first  a  universal  contraction  of  the 
uterine  cavity,  but  afterwards  local,  more  or  less  extensive  contractions, 
also  may  be  performed  with  great  ease.  Thus,  in  the  act  of  parturition, 
the  cervix  and  the  os  uteri  are  at  rest,  whilst  the  fundus  and  body  con- 
tract, contractions  of  the  former  parts  and  of  the  vagina  not  ensuing 
till  subsequently.  In  convulsions,  the  whole  uterus  contracts  closely 
round  the  child;  in  retention  of  the  placenta,  the  contraction  is  entirely 
local  and  confined  to  the  fundus.  It  is  probable  that  movements  take 
place  at  the  time  of  menstruation  and  in  the  act  of  congress,  but  the 
fact  has  not  been  ascertained.  In  the  latter  case,  an  opening  of  the  os 
uteri,  and  a  dilatation  of  the  canal  of  the  cervix,  are  commonly  supposed 
to  take  place.  If  this  is  to  be  regarded  as  a  spontaneous  action  of  the 
cervix,  it  would  be  justifiable,  with  Kiwisch  (1.  c.  p.  103),  to  refuse  assent 
to  the  supposition,  for  the  radiating  fibres  described  by  Kasper,  which 
alone  could  effect  anything  of  the  kind,  do  not  exist ;  the  fact,  neverthe- 
less, is  conceivable,  if  we  assume  a  relaxation  of  the  muscular  element 
in  the  cervix  and  os,  together  with  a  contraction,  especially  of  the  lon- 
gitudinal fibres  in  the  fundus  and  body.  In  comparing  the  uterus,  as 
respects  the  disposition  of  its  muscular  element  and  its  movements,  with 
other  organs,  none  affords  so  apt  a  comparison  as  the  bladder,  in  which 
the  muscular  tissue  is  arranged  essentially  in  the  same  way,  and  a  phy- 
siological antagonism  exists  between  the  superior  and  inferior  portions. 
The  sensibility  of  the  uterus,  and  of  the  internal  parts  of  the  female 
genital  organs  in  general,  is  very  slight ;  careful  sounding  of  the  uterine 
cavity  causes  no  sensation  ;  in  like  manner,  contact  with  the  vaginal  por- 
tion is,  frequently,  scarcely  felt,  whilst  these  parts  give  pain  upon  more 
powerful  pressure  or  traction,  and  when  in  a  state  of  inflammation.  The 
sensibility  of  the  vagina  increases  towards  the  inferior  portion ;  and  as 
regards  the  external  organs,  the  clitoris  is  rendered  especially  susceptible 
of  sensation,  by  its  abundant  supply  of  nerves,  as  is  also  the  entrance 
to  the  vagina,  particularly  at  the  orifices  of  the  glands  of  Bartholini  or 
Duverney. 

The  secretions  of  the  female  genital  organs,  except  those  of  the  ova- 


THE    SEXUAL    ORGANS.  659 

rium,  are :  1,  a  whitish  mucus  in  the  uterus  and  vagina,  which,  in  the 
former  situation,  is  derived  chiefly  from  the  uterine  glands,  and  probably 
differs  in  some  respects  from  the  other ;  2,  a  transparent  viscous  mucus 
in  the  cervix  uteri  (vide  supra) ;  3,  the  clear  viscid  secretion  of  the  Bar- 
tholinian  glands,  which  is  poured  out  in  large  quantity  in  copulation ; 
and  upon  excitation,  as  was  noticed  by  Huguier  and  Scanzoni,  it  even 
frequently  escapes  in  jets,  which  may  be  ascribed  to  the  muscles  of  the 
excretory  ducts ;  4,  the  secretions  of  the  minute  subaceous  and  mucous 
follicles  of  the  external  organs. 

Investigation  of  the  female  organs. — The  Graafian  follicles  should  be 
examined  as  fresh  as  possible,  when  the  membrana  granulosa  and  ova 
will  be  seen  in  their  natural  relations.  In  ovisacs  that  have  been  longer 
kept,  the  former  floats  about  in  flocculi  in  the  liquor  folliculi,  and  the 
"germinal  eminence"  is  also  for  the  most  part  destroyed.  In  order  to 
make  sure  of  obtaining  the  ovulum,  the  position  of  which  is  readily  per- 
ceived even  in  the  still  closed  follicle,  in  certain  animals,  as  in  the  Bitch, 
for  example,  a  large  carefully  extracted  follicle  is  opened  under  water, 
and  the  larger  flocculi  which  escape  are  examined  with  a  low  magnifying 
power ;  it  is  also  readily  found  when  the  contents  of  a  follicle  are  care- 
fully transferred  to  an  Abject-bearer.  In  rough  sections,  or  when  the 
structure  of  the  ovaries  is  teased  out,  ova  are  also  always  readily  found, 
although  this  is  not  exactly  the  mode  of  seeking  for  them  to  be  recom- 
mended. The  muscular  elements  of  the  oviducts,  uterus,  vagina,  &c., 
are  investigated  by  means  of  careful  dissection,  as  also  in  fine  sections 
of  parts  that  have  been  hardened.  Kasper  especially  recommends  that 
the  uterus  should  be  boiled  for  10  minutes  in  water,  and  then  placed  for 
24  hours  in  the  most  concentrated  solution  of  carbonate  of  potassa,  or 
that  it  should  be  treated  with  pyroligneous  acid,  and  the  sections  moist- 
ened with  dilute  acetic  acid;  whilst  Schwartz,  according  to  Reichert, 
dries  the  uterus  hardened  in  alcohol,  and  renders  the  muscular  fibres  dis- 
tinct by  acting  upon  them  for  a  short  time  with  nitric  acid  of  20§.  The 
method,  also,  employed  by  Wittich  (p.  486),  should  be  used,  according 
to  Gerlach.  The  contractile  fibre-cells  are  nowhere  more  beautifully 
displayed  than  in  the  gravid  uterus.  The  uterine  glands  are  be'st  shown 
at  the  menstrual  period  and  in  the  first  months  after  conception.  The 
ciliated  epithelium  is  only  to  be  seen  in  perfectly  fresh  subjects,  and 
best  in  the  Fallopian  tubes ;  the  non-ciliated  cells,  on  the  other  hand, 
are  readily  seen.  The  preparation  of  the  external  parts  presents  no 
difficulty,  and  the  directions  already  given  are  applicable  to  the  glands, 
nerves,  papilla?,  and  epithelium. 

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epist.,"  Lips.  1827,  and  "  Commentarius,"  in  German,  in  Heusinger's 
"  Zeitsch.,"  II. ;  Coste,  "  Recherches  sur  la  ge'ne'ration  des  mammi- 


660  SPECIAL    HISTOLOGY. 

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Mandt,  *4  Zur  Anatomic  der  weiblichen  Scheide,"  in  "  Zeitschr.  fiir  rat. 
Med.,"  VII.  p.  1;  Huguier,  "  Sur  les  appareils  secrets  des  organes 
gfcrit.  de  la  femme,"  in  "Annal.  d.  Sc.  Nat.,"  1850,  p.  239.  [Dalton 
"  On  the  Corpus  Luteuni  of  Menstruation  and  Pregnancy,"  Philadelphia, 
1851 ;  Bischoff,  "  Die  Physiologic  der  Menstruation  und  Conception,"  in 
"Zeitschr.  fur.  rat.  Med."  Bd.  IV.  1.  1853.— DaC.] 

C.     OF  THE  LACTEAL  GLANDS. 

§  210.  The  lacteal  glands  (glandula  lactiferce)  are  a  pair  of  com- 
pound racemose  glands,  which,  in  the  male,  are  only  rudimentary,  but 
in  the  female  fully  developed,  and,  after  parturition,  secrete  the  milk. 


THE     LACTEAL    GLANDS. 


661 


Fig.  272. 


With  respect  to  their  structure,  the  lacteal  glands,  in  all  essential 
particulars,  completely  correspond  with  the  larger  racemose  glands,  for 
instance  the  parotid  and  the  pancreas.  Each  gland  consists  of  15-24 
or  more,  irregular,  flattened  lobes,  %  to  1  inch  wide,  with  a  rounded, 
angular  outline,  which,  although  their  cavities  are  quite  distinct  from 
each  other,  cannot  externally  always  be  definitely  separated.  Each  is 
composed  of  a  certain  number  of  smaller  and  smallest  lobules,  and 
these,  lastly,  of  (/land-vesicles.  The  latter  are  rounded,  or  pyriform, 
0-05-0-07  in  size,  with  a  distinct  constriction  between  them  ;  and  the 
smallest  excretory  ducts,  as  for  instance,  in  the  small  mucous  glands, 
and  as  everywhere  else,  are  formed  of  a  structureless  membrane  and 
tessellated  epithelium,  which,  at  the  time  of  lactation,  undergoes  pecu- 
liar metamorphoses.  All  these  glandular  elements  are  surrounded  by 
dense,  white  connective  tissue,  particularly  abundant  between  the  gland- 
vesicles  and  smaller  lobules,  and 
are  united  into  a  compact,  large 
glandular  mass,  which  is  ultimate- 
ly covered  by  a  quantity  of  adi- 
pose tissue,  and  in  part  by  the 
skin.  The  lacteal  glands  are, 
properly  speaking,  not  simple 
glands,  but  like  the  lachrymal, 
aggregations  of  these.  From  each 
glandular  lobe,  by  the  coalescence 
of  the  excretory  ducts  of  the  smal- 
ler and  larger  lobules,  there  ulti- 
mately proceeds  a  shorter  or 
longer  duct,  1-2  lines  in  diameter, 
the  lacteal  duct  or  canal  (ductus 
lactiferus  s.  galactophorus),  which 
running  towards  the  nipple,  dilates 
beneath  the  areola,  into  an  elon- 
gated sacculus,  2-4  lines  wide,  the  lacteal  sac  or  receptacle  (sacculus  s. 
sinus  lactiferus) ;  afterwards  contracting  to  1  or  J  a  line,  it  bends  round 
into  the  nipple,  and  ultimately  opens,  at  its  apex,  in  an  independent 
orifice,  not  more  than  1-3-1-5  of  a  line  in  diameter,  between  the  papillae 
which  exist  in  that  situation.  All  these  excretory  ducts,  besides  an 
epithelium,  which  in  the  largest  of  them  presents  cylindrical  cells, 
0-006-0-01  of  a  line  long,  and  in  the  finer  ramifications,  rounded  poly- 
gonal smaller  cells,  and  a  homogeneous  layer  beneath  them,  als6  possess 
a  white  dense  fibrous  membrane,  longitudinally  plicated  in  the  larger 
canals,  in  which  I  have  hitherto  been  unable  to  detect  any  indubitable 

FIG.  272. — A  few  of  the  smallest  lobules  of  the  lacteal  gland  of  a  puerperal  female,  with 
their  ducts,  magnified  70  diameters.     After  Langer. 


662  SPECIAL    HISTOLOGY. 

muscular  fibres,  and  nothing  but  a  nucleated,  longitudinally  fibrous, 
connective  tissue  with  fine  elastic  fibres.  Henle,  however,  more 
recently,  thinks  that  he  has  noticed  longitudinal  muscles  in  the  lacteal 
ducts,  not  those  of  the  nipple,  but  more  deeply  within  the  gland. 

The  nipple  (mamilla)  and  the  areola,  present  numerous  smooth  mus- 
cles, to  which  the  contractility  of  those  parts  is  owing  (vid.  §  34) ;  a 
delicate  cuticle,  the  horny  layer  of  which,  in  the  female,  is  not  more  than 
0-006  of  a  line  thick,  whilst  the  Malpighian  layer  has  a  thickness  of  0-04 
of  a  line  and  is  colored  in  the  deeper  portion  ;  and  compound  papilla? 
1-10—1-33  of  a  line  long.  On  the  breast  itself,  the  papillae  are  small 
(1-60-1-80  of  a  line)  and  simple,  and  the  epidermis  still  finer  (0-032- 
0-04  of  a  line),  although  with  a  thicker  horny  layer  of  0-02-0-024  of  a 
line.  In  the  areola,  especially  at  its  borders,  but  not  on  the  nipple 
itself,  there  are  large  sudoriparous  glands,  often  writh  peculiar  contents, 
and  large  sebaceous  follicles  with  fine  hairs,  which  frequently  form 
little  papilla?,  visible  on  the  exterior  (vid.  §§  68  and  73).  In  the  male, 
I  have  seen  sebaceous  glands  without  hairs,  also  on  the  nipple. 

The  bloodvessels  of  the  lacteal  glands  are  numerous,  and  surround  the 
gland-vesicles  with  a  rather  close  plexus  of  capillaries.  The  veins  in 
the  areola  constitute  a  circle,  which  is  not  always  quite  complete  (circu- 
lus  venosus  Halleri).  The  lymphatics  are  equally  abundant  in  the  skin 
covering  the  gland,  whilst  in  the  gland  itself  they  have  not  yet  been 
demonstrated.  The  nerves  of  the  skin  covering  the  mamma  are  derived 
from  the  supraclavicular  nerves,  and  the  cutaneous  branches  of  the 
second,  third,  and  fourth  intercostals.  In  the  interior  of  the  gland,  no 
other  nerves  can  be  traced  than  a  few  fine  twigs  accompanying  the 
vessels,  whose  termination  is  unknown. 

At  the  time  of  lactation  the  gland  enlarges  very  considerably.  Its 
tissue  is  no  longer  uniform,  whitish,  and  firm,  but  softer,  granular,  and 
lobate,  with  a  yellowish-red,  glandular  parenchyma,  distinctly  bounded 
by  the  whitish,  spongy  interstitial  tissue.  The  gland-vesicles  and  lacti- 
ferous ducts  are  wider,  filled  with  milk,  and  the  vessels  excessively 
multiplied.  In  the  external  parts,  the  enlargement  of  the  areola  and 
of  the  nipple  is  especially  worthy  of  remark  ;  the  cause  of  which  appears 
to  depend  upon  a  growth  of  these  parts,  with  all  their  elements,  includ- 
ing the  muscular  fibres  and  minute  glands ;  arid  not  in  a  simple  exten- 
sion of  the  color  over  a  larger  surface.  In  the  male,  the  lacteal  gland 
is  quite  rudimentary  j~2  inches  broad,  and  1-3  lines  thick,  not  lobed, 
and  firm.  The  lacteal  ducts  have  no  sinuses,  and  are  never  so  far  de- 
veloped as  in  the  female,  inasmuch  as  they  either  correspond  in  form 
with  those  met  with  in  the  new-born  child,  or,  in  larger  glands,  are 
more  branched,  and  furnished  with  a  certain  number  of  terminal  vesi- 
cles, which,  on  account  of  their  considerable  size  (they  are  three  times 
as  large  as  the  gland-vesicles  in  the  female),  are  not  to  be  regarded  as 


THE    LACTEAL    GLANDS. 


663 


true  gland-vesicles.  In  rare,  but  well-established  instances,  the  glands, 
even  in  the  male,  have  become  so  much  developed  as  to  be  capable  of 
secreting  milk. 

§  211.  Physiological  remarks. — The  lacteal  gland,  in  its  develop- 
ment,  follows  the  same  course  as  the  other  cutaneous  glands,  and  is, 
as  I  find  ("Mittheil.  d.  Ziircher  nat.  Gesells.,"  1850,  No.  41)  in  ac- 
cordance with  Langer  (1.  c.),  originally  (injthe  fourth  to  the  fifth 
month)  nothing  but  a  solid  papillary  projection  of  the  mucous  layer  of 
the  epidermis,  which  is  invested  by  a  layer  of  denser  dermal  tissue 
(Fig.  273,  x).  In  the  sixth  to  the  seventh 
month,  it  throws  out  a  certain  number  of 
buds,  and  in  this  way  arise  the  first  rudi- 
ments of  the  subsequent  lobes  (Fig.  273,  2). 
These  are,  at  first,  nothing  but  minute  pyri- 
form-  or  flask-shaped  processes  of  the  com- 
mon rudiment  of  the  gland,  which  do  not 
separate  from  each  other  until  towards  the 
end  of  foetal  life,  at  which  time  they  open 
externally;  whilst,  at  the  same  time,  rounded 
or  elongated  solid  buds  begin  to  appear  at 
their  ends,  which  at. this  time  are  also  solid. 
At  the  period  of  birth,  the  gland  measures 
from  1J— 4  lines,  and  already  distinctly  ex- 
hibits a  certain  number  (12-15)  divisions,  of 

which  the  internal  still  approximate  the  rudimentary  papillce,  in  fact 
have  either  simple  flask-like  ends,  or  terminate  in  two  or  three  sinuosi- 
ties ;  whilst  the  others  are  in  connection  with  a  greater  number.  The  ex- 
cretory duct  of  each  of  these  rudimentary  lobules,  which  is  either  simple 
or  possesses  two  or  three  branches,  is  composed  of  a  fibrous  membrane 
of  immature,  nucleated  connective  tissue,  and  an  epithelium  of  small 
cylindrical  cells,  and  is  manifestly  hollow;  whilst  the  dilated  ends, 
which  cannot  in  this  case,  any  more  than  in  other  glands  in  the  process 
of  development,  at  this  time  be  termed  terminal  vesicles,  are  still  solid; 
being  wholly  composed,  besides  the  fibrous  tunic  continued  upon  them 
from  the  ducts,  of  minute  nucleated  cells.  From  this  very  simple  form, 
the  latter  one  is  thus  developed  :  by  the  long-continued  gemmation  of 
the  primary  and  subsequently  formed,  clavate  ends,  and  their  simulta- 
neous excavation,  a  much-branched  duct,  beset  in  its  offsets  with  whole 
groups  of  hollow  gland-vesicles,  is  at  last  formed.  These  processes, 

FIG.  273. — Development  of  the  lacteal  gland.  1,  rudiment  of  the  gland  in^a  male  embryo, 
at  five  months ;  a,  horny  layer  ;  6,  mucous  layer  of  the  epidermis  •  c,  process  of  the  latter  or 
rudiment  of  the  gland ;  d,  fibrous  membrane  around  the  same.  2,  lacteal  gland  of  a  female 
foetus,  at  seven  months,  seen  from  above:  a,  central  substance  of  the  gland,  with  larger  (6) 
and  smaller  (c)  solid  outgrowths,  the  rudiments  of  the  large  gland-lobes. 


664  SPECIAL    HISTOLOGY. 

however,  go  on  more  slowly  in  the  lacteal  gland  than  in  any  other  secre- 
tory organs.  According  to  Langer,  to  whom  we  are  indebted  for  care- 
ful researches  upon  this  subject,  true  terminal  vesicles  are  never  met 
with  in  childhood,  before  menstruation  is  established,  but,  universally, 
only  undeveloped  ducts  with  clavate  ends.  On  the  occurrence  of  puberty, 
true  gland-vesicles  are  formed,  but  at  first  only  at  the  borders  of  the 
gland,  until,  ultimately,  in  the  first  pregnancy,  the  entire  gland  is  fully 
developed.  After  the  ^rst  lactation,  it  is  true,  the  gland  again  dimi- 
nishes in  size,  but  all  its  constituent  parts  remain,  and  again  enlarge  in 
the  succeeding  occasions  of  conception,  without  the  addition  of  any  new 
parts.  At  the  period  of  involution — probably  also,  if  after  a  pregnancy, 
too  long  a  time  has  elapsed  without  the  functions  of  the  gland  being 
called  into  play — it  undergoes  a  retrograde  metamorphosis,  until  finally, 
in  old  age,  all  the  gland-vesicles  have  disappeared,  and  nothing  but  the 
more  or  less  persistent  lactiferous  ducts,  with  their  epithelium  in  a  state 
of  fatty  degeneration,  are  to  be  found  in  the  adipose  cushion  which  sup- 
plies the  place  of  the  glandular  tissue. 

The  milk,  the  secretion  of  the  mammary  glands,  consists  of  a  fluid, 
the  milk-plasma,  and  innumerable  spherical,  opaque  corpuscles,  with  the 
brilliant  aspect  of  fat-drops,  suspended  in  it.  These  corpuscles — the 
milk-globules — vary  in  size,  from  immeasurable  minuteness  up  to  O'OOl- 
0*002  of  a  line  and  more,  and  most  probably  do  not  consist  of  the  fatty 
part  of  the  milk  alone,  but  have  also  a  delicate  investment  of  casein, 

and  it  is  to  them  that  the  whiteness  of  the 
rig<274-     g  milk  is   owing.     With  respect   to   the  for- 

mation of  the  milk,  it  is  to  be  remarked 
that,  except  at  the  periods  of  lactation  and 
pregnancy,  the  glands  contain  nothing  but 
a  small  quantity  of  a  yellowish  viscid 
mucus,  with  a  certain  number  of  epithelial 

cells,  and  are  lined  up  to  their  extremities  by  an  epithelium,  which  in 
that  situation  is  tessellated,  but  externally  is  more  cylindrical.  With 
conception,  this  state  of  things  is  altered.  The  cells  of  the  gland-vesi- 
cles begin  to  develop,  at  first  a  little,  and  subsequently  more  and  more 
fatty  matter  within  them,  and  to  enlarge,  so  as  entirely  to  fill  the  ter- 
minal vesicles.  To  this  is  added,  before  the  end  of  pregnancy,  a  new 
formation  of  fat-containing  cells  in  them,  by  which  the  older  cells  are 
forced  into  the  lactiferous  ducts,  which  they  gradually  fill.  Thus  it 
happens,  that  although  a  true  secretion  is  not  at  that  time  set  up,  still 
in  the  latter  half  of  pregnancy  a  few  drops  of  fluid  may  be  expressed 
from  the  gland,  which,  as  is  shown  by  its  yellow  color,  is  not  milk,  but 
nevertheless  contains  a  certain  tfumber  of  fat-globules  from  the  more  or 

FIG.  274. — Elementary  forms  in  milk,  magnified  350  diameters  :  a,  milk-globules  ;  6,  colos- 
trum corpuscles;  c,  rf,  cells  with  fat-globules  from  the  colostrum,  one  (cf)  with  a  nucleus. 


THE    LACTEAL    GLANDS.  665 

less  disintegrated  fatty  cells,  exactly  resembling  the  subsequent  milk- 
globules,  and  also  contains  such  cells  either  with  or  without  a  tunic — 
the  so-termed  colostrum  corpuscles.  On  the  commencement  of  lactation 
after  parturition,  the  cell-formation  in  the  gland-vesicles  proceeds  with 
excessive  energy,  in  consequence  of  which  the  secretion  collected  in  the 
lactiferous  ducts  and  gland-vesicles  is  evacuated,  as  the  colostrum  or 
immature  milk,  the  true  milk  taking  its  place. 

The  latter,  in  the  extremities  of  the  gland,  consists  only  of  some 
fluid  and  cells  entirely  filled  with  fat-globules,  which  sometimes  occupy 
the  gland-vesicles  alone,  sometimes  associated  with  pale  epithelial  cells, 
which,  however,  always  contain  more  or  less  fat,  and  originate  either  in 
a  free  cell-formation  or  from  epithelial  cells,  in  a  way  analogous  to  that 
in  which  the  cutaneous  sebaceous  matter  is  formed  (vide  §  73),  by  their 
continued  multiplication.  These  cells,  which  I  would  designate  milk- 
cells,  break  up,  so  soon  as  they  reach  the  lactiferous  ducts  into  their 
elements,  the  milk-globules ;  the  membrane,  and  for  the  most  part  also, 
the  nucleus,  disappearing,  without  a  vestige  being  left,  so  that  the 
milk,  when  secreted,  usually  presents  no  indication  of  its  mode  of 
origin.  At  most,  there  occur  in  it  a  very  few  larger  or  smaller  aggre- 
gations of  milk-globules,  which,  from  their  similarity  to  those  met  with 
in  the  colostrum,  may  likewise  be  termed  colostrum-corpuscles.  The 
secretion  of  the  milk,  therefore,  depends  essentially  upon  a  formation 
of  fluid  and  fat-containing  cells  in  the  gland-vesicles,  and  consequently 
falls  into  the  category  of  those  secretions  into  the  composition  of 
which  morphological  elements  enter ;  above  all  to  the  fatty  secretions, 
such  as  the  cutaneous  sebaceous  matter,  in  which  cells  of  precisely 
similar  kind  occur  to  those  met  with  in  the  gland-vesicles  of  the  lacteal 
glands,  and  in  the  colostrum. 

In  the  new-born  child,  the  mammary  gland  very  frequently  contains 
a  small  quantity  of  a  fluid  presenting  the  external  and  microscopical 
characters  of  milk,  the  origin  of  which  is  probably  related  to  the 
formation  of  the  glandular  ducts. 

With  respect  to  the  colostrum-corpuscles  and  fat-globules  of  the 
colostrum,  Reinhardt  was  the  first  to  prove,  -  that  the  supposition 
broached  by  Nasse  and  Henle,  that  these  bodies  are  related  to  a  forma- 
tion of  fat-containing  cells  in  the  mammary  glands,  and  that  the  former 
in  their  more  usual  form  are  nothing  but  membraneless  cells,  and  the 
latter  oil-drops  liberated  from  cells,  is  in  every  respect  well  founded, 
although  he  is  inclined  to  distinguish  the  formation  of  the  colostrum 
from  the  secretion  of  milk,  and  to  regard  the  former  as  a  pathological 
process,  as  a  fatty  metamorphosis,  by  which  the  old  epithelial  cells  of 
the  gland,  previously  to  the  formation  of  true  milk,  are  evacuated 
externally,  and  particularly  because,  in  the  true  milk-formation,  he 


666  SPECIAL    HISTOLOGY. 

was  unable  to  perceive  any  fat-containing  cells.  But  since  Y.  Bueren, 
especially,  has  found  such  cells,  and  consequently  the  formation  of  the 
milk  and  of  the  colostrum,  seem  to  be  morphologically  quite  identical, 
such  a  separation  of  the  two  processes  can  no  longer  be  defended ;  and, 
in  cases  of  repeated  parturition,  the  formation  of  colostrum  can  scarcely 
be  viewed  in  any  other  light  than  as  the  introduction  to  that  of  the 
milk.  On  the  other  hand,  I  am  quite  of  opinion,  that  the  production 
of  the  first  colostrum  is  connected  with  the  excessive  development  of 
the  lacteal  gland  coincident  with  the  first  pregnancy  ;  and  that  it  is 
in  part  derived  from  the  internal  cells  of  the  originally  solid  rudiments 
which  are  removed,  during  the  formation  of  the  ultimate  terminations 
of  the  gland.  I  explain,  in  a  similar  way,  the  formation  of  milk  in 
the  new-born  child;  in  which  case,  surely,  no  true  secretion  can  be 
thought  of. 

Donne,  the  discoverer  of  the  colostrum-corpuscles,  states,  that  in 
inflammations  and  tumefactions  of  the  breast  of  nursing  women,  the 
milk  acquires  the  nature  of  colostrum  ;  which  is,  however,  denied  by 
D'Outrepont  and  Miinz  ("  Neue  Zeitschrift  f  iir  Greburtskunde,"  Bd. 
10);  in  the  same  wray,  according  to  Lehmann  ("Phys.  Chemie,"  II., 
327,  [transl.  II.,  p.  334])  it  would  appear,  that,  in  acute  diseases 
generally,  and  also  in  menstruation  (Donne,  d'Outrepont),  the  milk 
exhibits  colostrum-corpuscles,  which,  when  they  exist  in  larger  quan- 
tity, are  regarded  by  Donne*  as  indicative  of  bad  milk.  In  hoof-mur- 
rain" ("  Klauenseuche"),  Herberger  and  Donne  found  the  milk  to 
contain  a  good  deal  of  colostrum.  In  sour  milk  the  casein  coagulates 
into  granules,  and  the  milk-globules  gradually  run  together  into  larger 
drops.  Blue  and  yellow  milk,  according  to  Fuchs  (vide  Scherer,  art. 
"Milk,"  in  "  Handw.  d.  Phys.,"  II.,  p.  470)  contains  colorless  infuso- 
ria, which  he  terms  vibrio  cyanogenus  and  xanthogenus,  which,  when 
transferred  to  healthy  milk,  also  color  it ;  a  fact  which,  as  regards  blue 
milk,  is  confirmed  by  Lehman  (1.  c.,  p.  335,  Eng.  transl.) ;  according 
to  Bailleul  ("  Comptes  rend.,"  t.  17,  p.  1138),  however,  arid  Lehmann 
[once  only],  a  filamentary  fungus  is  also  found  in  that  sort  of  milk. 
Red  milk  has  also  been  noticed  by  C.  Nageli,  and  vegetable  protococcus- 
like  growths  found  in  it. 

For  the  investigation  of  the  mammary  glands,  those  of  pregnant  or 
nursing  women,  or  of  women  who  have  borne  children,  should  be  pre- 
ferably selected,  because  it  is  only  in  such  that  the  gland-vesicles  are 
well  developed.  When  the  smallest  lobules  are  teased  out,  their  ele- 
ments come  readily  into  view;  but  if  it  be  desired  to  examine  into  their 
arrangement,  fine  sections  of  glands  boiled  in  acetic  acid  and  dried  are 
above  all  to  be  recommended,  as  well  as  injected  preparations,  which  it 
is  not  difficult  to  make  from  the  lacteal  sinuses.  For  the  study  of  the 
development  of  the  gland,  besides  recent  specimens,  preparations  made 


THE    HEART.  667 

with  acetic  acid  are  'necessary.  The  smooth  muscles  of  the  areola  are 
found  by  mere  dissection,  although  not  always  very  easily,  as,  except 
during  pregnancy,  they  are  frequently  very  delicate. 

Literature. — Rudolphi  "  Bemerk.  tiber  den  Bau  der  Bruste,"  in  the 
"Abh.  der  Berliner  Akademie,"  1831,  p.  337;  Astley  Cooper,  "  The 
Anatomy  of  the  Breast,"  London,  1839,  4to ;  C.  Langer,  "  Ueber  den 
Bau  und  die  Entwicklung  der  Milchdriisen,  mit  3  Taf.,"  from  the 
"Derikschr.  d.  Wiener  Akad.,"  Bd.  III.,  Wien,  1851 ;  A.  Donn^,  "Du 
lait  et  en  particulier  du  lait  des  nourrices,"  Paris,  1837;  "Ueber  die 
mikroskopischen  Korperchen  im  Colostrum"  Muller's  "Arch.,"  1839, 
p.  182;  "Cours  de  Microscopic,"  Paris,  1844;  Fr.  Simon,  "Die 
Frauenmilch,  nach  ihrem  chemischen  u.  physiol.  Verhalten  dargestellt," 
Berlin,  1838  ;  "  Ueber  die"  Corps  granuleux  "von  Donnd,"  in  Muller's 
"Arch.,"  1839,  pp.  10  and  187;  J.  Henle,  "Ueber  die  mikr.  Bestand- 
theile  der  Milch,"  in  Fror.  "Notizen,"  1839,  No.  223;  H.  Nasse, 
"Ueber  die  mikr.  Bestandt.  d.  Milch,"  Muller's  "Archiv,"  1840,  p. 
259;  Reinhardt,  in  "Arch.  f.  path.  Anat.,"  Bd.  L,  pp.  52-64;  Lam- 
merts  van  Bueren,  "  Onderzoekingen  over  de  Melkbolletjes,"  in  the 
"  Nederl.  Lancet,"  2d  ser.,  4,  Jaarg.,  p.  722,  or  "  Observat.  microscop. 
de  lacte,"  Traject.  ad  Rhenum,  1849,  Diss.  ;  "  De  Ontwikkeling  van 
de  Vormbestanddeelen  der  Melk,"  in  the  "Nederl.  Lancet,"  2d  ser., 
5,  Jaarg,  p.  1;  Fr.  Will,  "Ueber  die  Milchabsonderung,"  Erlangen, 
1850,  Programm.  Besides  which  should  be  consulted  the  "  General 
Anatomy"  of  Henle,  J.  Muller's  work  on  the  Glands,  and  the  Atlases 
of  Berres,  Donne',  and  Mandl.  [  Vid.  also,  "  Observations  on  the 
muscular  tissue  of  the  Skin,"  by  Joseph  Lister,  M.B.,  "  Quart.  Journ. 
Micros.  Sc.,"  vol.  I.,  p.  262,  1853.— TRS.] 


OF    THE    VASCULAR    SYSTEM. 

§  212.  The  vascular  system,  consisting  of  the  heart,  with  the  blood 
and  lymphatic  vessels,  contains  in  its  interior  the  blood  and  the  lymph 
(chylus),  with  innumerable  morphological  particles.  The  lymphatic  vas- 
cular system  presents  special  organs — the  lymphatic  glands. 

1.— OF  THE  HEART. 

§  213.  The  heart  is  a  thick,  hollow,  muscular  organ,  divided  into  four 
compartments,  invested  externally  by  a  serous  membrane — the  pericar- 
dium,— and  lined  internally  by  the  endocardium,  a  continuation  of  the 
walls  of  the  great  vessels,  particularly  of  the  tunica  intima. 

The  pericardium  does  not  differ  in  structure  from  other  serous  mem- 
branes, as,  for  instance,  the  peritoneum.  The  outer  lamella  is  consi- 


668  SPECIAL    HISTOLOGY. 

derably  the  thicker;  it  is  more  fibrous  towards  the  exterior,  presenting, 
towards  the  interior,  numerous  fine,  elastic  networks,  which  are  imme- 
diately covered  with  one  or  two  layers  of  tessellated  epithelium.  Very 
numerous  elastic  networks  of  the  same  kind  are  found  also  in  the  inner 
thin  lamella,  which  is,  partly,  very  intimately  united  with  the  muscular 
substance,  and  partly,  especially  in  the  sulci,  separated  from  it  by  com- 
mon adipose  tissue,  which,  moreover,  not  unfrequeritly  forms  a  subserous 
fatty  layer,  extending  almost  over  the  entire  heart.  The  vessels  present 
the  same  conditions  as  elsewhere ;  and  with  respect  to  the  nerves,  twigs 
from  the  phrenic  and  recurrent  branch  of  the  right  vagus  have  been 
demonstrated  in  the  outer  lamella  of  the  pericardium  (Luschka). 

The  muscular  fibres  of  the  heart  are  red  and  transversely  striated, 
but  differ  in  many  respects  from  those  of  the  voluntary  muscles.  The 
individual  fibres  themselves  are,  on  the  average,  about  Jd  more  slender 
(0-004-0-01  of  a  line),  frequently  more  distinctly  striated  in  the  longi- 
tudinal than  in  the  transverse  direction,  and  pretty  readily  divisible 
into  fibrils  and  minute  particles  ("  sarcous  elements,"  Bowman);  their 
sarcolemma  is  very  delicate,  or  even  wholly  inappreciable ;  and  in  the 
fibres,  there  almost  uniformly  occur  minute  fatty  granules,  which,  with 
the  nucleus,  are  frequently  disposed  in  a  series  in  the  axis  of  the  fibre, 
and,  where  the  muscular  tissue  is  degenerated,  appear  most  usually  to 
be  excessively  multiplied,  and  also  colored.  Much  more,  however,  than 
by  these  characters,  is  the  muscular  tissue  of  the  heart  distinguished  by 
the  intimate  union  of  its  elements,  which,  except  on  the  internal  surface 
of  the  organ,  not  only  never  form  manifestly  distinct  bundles,  being 
everywhere  in  close  apposition  with  each  other,  and  separated  only  by 
a  scanty  connective  tissue,  but,  as  was  discovered  by  Leeuwenhoek,* 
Fi  275  and  I  also  have  found  (vid.  p.  108),  are  directly  united 
together  in  their  elements.  These  anastomoses  of  the 
muscular  fibres,  which  are  a  universal  attribute  of  the 
cardiac  muscular  tissue,  are  effected  in  the  human  and 
mammalian  heart  generally,  chiefly,  by  short,  oblique, 
or  transverse,  usually  small  fasciculi,  and  are  extremely 
numerous,  so  that,  in  many  places  in  the  ventricles  and 
auricles  (whether  universally  I  know  not),  numerous  in- 
stances of  them  are  presented  in  every  minute  portion. 
Besides  these,  there  also  exist  true  divisions  or  fibres,  by 
which  the  thickness  of  separate  portions  of  muscle  may 
be  rendered  more  considerable  than  it  was  originally. 

The  course  of  the  muscular  fibres  of  the  heart  is  extremely  complex, 
and  a  general  outline  only  of  it  can  here  be  given.  The  muscular  struc- 
tures of  the  ventricles  and  of  the  auricles  are  completely  distinct  from 

FIG.  275. — Anastomosing  primitive  fasciculus  from  the  human  heart. 
*  [See  note,  p.  108 .— TRS.] 


THE    HEART. 

each  other ;  both,  however,  have  as  their  chief  point  of  origin  the  ostia 
venosa  of  the  ventricles,  where  tough,  tendinous  tracts — the  so-called 
annuli  fibro-cartilaginei — are  situated,  two  anterior,  on  the  right  and 
left  of  the  aortal  opening,  and  one  posterior,  which  runs  backwards 
also  from  the  aorta  to  the  border  of  the  auriculo-ventricular  septum, 
where  it  splits  into  two  slender  crura.  In  the  auricles  are  found : 
1,  fibres,  which  are  common  to  both,  in  the  form  of  transverse,  flattened 
bundles,  which  proceed  chiefly  anteriorly,  but  afterwards  also  superiorly 
and  posteriorly,  from  one  auricle  to  the  other,  and  are  continued  in 
them  as  transverse  fibres.  2,  special  fibres.  These  constitute,  in  the 
first  place,  complete  rings  at  the  origins  of  the  great  veins,  and  at  the 
points  of  the  appendices  ;  and,  in  the  second  place,  a  longitudinal  layer 
of  some  thickness  beneath  the  endocardium,  which  springs  from  the 
auriculo-ventricular  openings,  and  is  especially  developed  in  the  right 
auricle  (musculi pectinati}.  Besides  these,  there  exist  between  the  latter 
muscles,  and  also  in  the  auricles,  numerous  other  small  fasciculi,  which, 
on  account  of  their  irregularity,  cannot  be  more  particularly  described. 
The  septum  is  to  some  extent  common  to  both  auricles.  Its  muscles 
arise  from  the  most  anterior  part  of  the  upper  border  of  the  septum  of 
the  ventricles,  immediately  behind  the  aorta,  from  the  posterior  fibro- 
cartilage  and  arch  to  the  right,  around  the  fossa  ovalis,  in  which  only 
slender  fibres  exist,  in  a  superior  and  posterior  direction,  in  order  to 
terminate,  partly  at  the  vena  cava  inferior,  partly  by  forming  a  com- 
plete ring ;  whilst  on  the  left,  they  surround  the  fossa  ovalis  in  the 
opposite  direction. 

The  muscular  structure  of  the  ventricles  is  disposed  so  that  on  the 
external  and  internal  surfaces  the  fibres  everywhere  decussate;  and  in  the 
intermediate  portion,  every  stage  of  transition  from  the  one  direction  to 
the  other  is  presented.  The  muscular  fibres  arise  at  the  ostia  venosa 
and  at  the  arterial  openings,  in  part  immediately,  and  partly  with  the 
intervention  of  short  tendons,  run  more  or  less  obliquely  (and  some 
longitudinally  or  even  transversely),  and  after  they  have  surrounded  a 
portion  of  the  ventricle  in  the  longitudinal  or  transverse  direction,  curve 
back  again,  and  then  terminate,  some  in  the  musculi  papillares,  and 
chordce  tendinece,  whilst  others  are  again  inserted  in  the  points  of  origin 
above  indicated,  so  that  without  being  interrupted  by  tendons,  they 
describe  large  involved  loops,  or  figure-of-8  turns  of  large  size,  and 
running  in  very  numerous  and  diverse  directions. 

The  endocardium  is  a  whitish  membrane,  investing  all  the  elevations 
and  depressions  of  the  internal  surface  of  the  heart,  as  well  as  the  papil- 
lary muscles  and  their  tendons,  and  the  valves.  It  is  most  developed  in 
the  left  auricle  (as  much  as  J  of  a  line),  and  thinnest  in  the  ventricles, 
so  that  the  muscular  substance  there  presents  its  natural  color.  As 
regards  its  structure,  it  consists  of  three  layers ;  an  epithelium,  an 


670  SPECIAL     HISTOLOGY. 

elastic  layer,  upon  which  the  varying  thickness  of  the  endocardium  in 
different  situations  depends,  and  a  thin  layer  of  connective  tissue.  The 
first  is  a  single,  or,  according  to  Luschka,  perhaps  a  double  layer  of 
polygonal,  usually  elongated,  clear,  flattened,  nucleated  cells,  0-007  to 
0.012  of  a  line  long,  resting  immediately  upon  the  most  superficial  layer 
of  the  elastic  membrane,  which  may  be  said  to  consist  of  nothing  but 
very  fine,  longitudinal,  elastic  fibres.  The  remainder  of  this  middle 
layer  is  constituted  of  a  matrix  of  common  connective  tissue  with  scat- 
tered nuclei,  through  which  the  very  abundant  finer  and  coarser  elastic 
networks  penetrate.  This  elastic  element  is  so  abundant,  in  fact,  in  the 
auricles,  and  even  mixed  with  true  fenestrated  membranes  (vid.  §  23)  that 
the  endocardium  of  those  cavities  is  rendered  almost  entirely  a  yellow, 
elastic  membrane,  consisting  of  several  laminae.  Most  externally,  there 
succeeds  to  this  elastic  layer,  a  stratum  of  connective  tissue,  of  great 
tenuity  indeed,  but  which,  nevertheless,  both  in  the  ventricles  and  in 
the  auricles,  may  easily  be  raised  as  an  entire  membrane.  In  the  por- 
tion bordering  upon  the  elastic  tissue  this  layer  contains  fine  elastic 
elements.  It  represents,  in  fact,  a  somewhat  loose  layer,  like  a  sub- 
serous  connective  tissue,  uniting  the  muscles  and  the  true  endocardium. 

The  auriculo-ventricular  valves  are  lamina?  springing  from  the  fibrous 
rings  of  the  ostia  venosa,  in  the  thicker  parts  of  which,  a  middle  layer 
of  connective  tissue  with  numerous  elastic  networks,  and  two  lamella?  of 
the  endocardium  united  with  it,  may  be  clearly  distinguished.  Towards 
the  free  border,  these  three  layers  are  conjoined  so  as  to  form  a  single 
one,  composed  of  connective  tissue  and  fine  elastic  networks,  over  which 
again  the  epithelium  is  continued.  The  semilunar  valves  present  the 
same  conditions  as  the  free  border  of  the  others,  and  with  respect  to  the 
chordce  tendinece,  they  are  constituted  of  common  tendinous  tissue, 
covered  by  a  very  thin  layer  of  endocardium — consisting,  indeed,  merely 
of  epithelium  and  a  fine  elastic  lamella. 

The  bloodvessels  of  the  muscular  substance  of  the  heart  are  very 
numerous,  but  differ  in  no  respect  from  those  of  transversely  striped 
muscle  (§  77),  except  that  the  capillaries,  owing  to  the  slenderness  of 
the  muscular  fibre,  often  encompass  several  of  them  in  common.  The 
endocardium  is  tolerably  well  supplied  with  vessels  in  its  layer  of  con- 
nective tissue,  whilst  they  are  more  scanty  in  the  proper  endocardium. 
In  the  auriculo-ventricular  valves  a  few  vessels  are  readpy  seen,  not 
only  in  animals  but  also  in  Man  (vid.  Luschka,  1.  c.,  p.  182,  Fig.  1), 
some  of  which  enter  them  from  the  papillary  muscles,  but  chiefly  from 
the  basis  of  the  valves,  and  are  also  distributed  in  part,  though  sparingly, 
in  their  proper  endocardial  investment.  The  semilunar  valves  possess 
no  vessels.  Only  a  few  lymphatics  are  found  in  the  external  lamella  of 
the  pericardium^  whilst  they  occur  in  greater  abundance  on  the  inner 
lamella  on  the  muscular  substance,  and  may  there  be  demonstrated 


THE     HEART.  671 

readily  enough,  if  the  heart  be  placed  for  a  few  days  in  water,  as  Cruik- 
shank  correctly  observes.  Their  trunks  collect  in  the  sulci,  accompany- 
ing the  bloodvessels,  and  terminate  in  the  glands,  behind  and  below  the 
arch  of  the  aorta,  on  the  bifurcation  of  the  trachea,  to  which  the  pulmo- 
nary lymphatics  also  proceed.  Whether  the  substance  of  the  heart  and 
the  endocardium  are  also  furnished  with  lymphatics,  as  is  asserted  by 
some,  is  not  yet  determined.  The  nerves  of  the  heart  are  numerous  and 
proceed  principally  from  the  cardiac  plexus  formed  by  the  vagus  and 
sympathetic,  beneath  and  behind  the  arch  of  the  aorta.  These  nerves, 
forming  the  more  scanty  plexus  coronarius  dexter,  and  the  richer  p.  c. 
sinister,  accompany  the  vessels  on  the  right  and  left  ventricles  and 
auricles,  run,  in  part  with  the  vessels,  in  part  crossing  them  in  various 
directions,  toward  the  apex  of  the  heart,  and,  whilst  entering  into  nume- 
rous anastomoses  with  each  other,  usually  at  acute  angles,  enter  the 
muscular  substance  at  various  points,  some  even  in  the  coronary  sulcus, 
in  order  to  terminate,  partly  in  the  muscular  substance,  and  partly  to 
reach  the  layer  of  connective  tissue  of  the  endocardium.  The  cardiac 
nerves,  in  Man,  are  gray,  and,  except  the  largest,  contain  only  fine  and 
very  pale  fibres ;  the  latter,  however,  in  the  greater  number,  and  inter- 
mixed with  not  very  numerous  nucleated  fibres.  Although  the  nerves, 
even  in  the  endocardium,  retain  their  dark  borders  and  are  tolerably 
numerous,  it  has  not  hitherto  been  possible  to  discover  their  terminations 
in  that  situation,  any  more  than  in  the  muscular  substance.  Ganglia 
exist,  not  only  in  the  cardiac  plexus  in  various  situations,  but,  as  Remak 
discovered,  in  the  Calf,  also  in  the  muscular  substance  of  the  auricles 
and  ventricles,  which  is  likewise  true  of  man  and  other  animals.  These 
ganglia  are  best  known  in  the  Frog,  in  which  they  are  situated,  espe- 
cially in  the  septum,  and  at  the  junction  of  the  auricles  with  the  ven- 
tricle, and  contain  apolar  and  unipolar  cells  (Ludwig,  Bidder,  R.  Wagner, 
myself).  The  minute  fusiform  enlargements  on  the  external  nervous 
branches,  especially  noticed  by  Lee,  are  not  ganglia,  being  merely  thick- 
enings of  the  neurilemma. 

With  respect  to  the  particular  direction  of  the  muscular  fibres  of  the 
ventricles,  the  following  remarks  may  be  offered.  On  the  external  sur- 
face of  the  ventricles  there  is  a  layer,  J-l  line  thick,  which,  on  the  left  ven- 
tricle, runs  obliquely  downwards  from  the  pulmonary  artery,  the  anterior 
longitudinal  sulcus  and  the  left  transverse  sulcus,  and  in  the  middle  of 
the  wall  of  the  ventricle,  descends  very  abruptly,  almost  vertically. 
On  the  right  ventricle,  these  fibres  are  oblique  only  on  the  conus  arteri- 
osus,  whilst  on  the  sides  and  posteriorly  they  are  almost  or  quite  trans- 
verse. At  the  longitudinal  sulci,  the  superficial  fibres  are  continued 
from  one  ventricle  upon  the  other,  so  that  a  small  portion  of  those  of  the 
left  ventricle  arise  from  the  anterior  side  of  the  ostium  venosum  dextrum 


672  SPECIAL    HISTOLOGY. 

and  the  greater  part  of  those  belonging  to  the  right  ventricle  from  the 
posterior  portion  of  the  left  ostium  venosum.  If  the  fibres  of  the  left 
ventricle  are  traced,  it  will  be  found,  with  the  exception  of  those  which 
at  the  posterior  longitudinal  sulcus  pass  upon  the  right  ventricle,  that 
they  (Fig.  276  a,  #',  a")  run  towards  the  apex  of  the  heart,  and  there 
form  the  well-known  vortex,  and  then  curve  inwards,  forming  loops  ;  and 
are  continued  as  the  innermost,  for  the  most  part  longitudinal,  fibres  of 
the  cavity  of  the  ventricle,  and  either  ascend  as  high  as  the  venous 
openings,  or  terminate  in  the  posterior  papillary  muscle.  Upon  removal 
of  this  set  of  fibres,  a  thick  layer  comes  into  view,  interposed  between 
its  external  and  internal  portions,  the  fasciculi  in  which,  at  first  sight, 
appear  to  surround  the  cavity  of  the  ventricle  in  an  oblique  and  trans- 
verse direction,  although  they  seem  to  arise,  without  exception,  from  the 
ostia  venosa,  and  again  to  terminate  in  the  same  situation,  and  to  de- 
scribe a  figure-of-8  turn,  still  more  distinctly  than  the  external  muscular 
layer,  as  has  been  clearly  shown  by  Ludwig.  I  find  that  the  bundles  of 
this  layer  (Fig.  276  c,  c  c"  <?"'),  after  their  origin  from  the  left  border 
Fig.  276.  of  the  aorta  and  the  anterior  half  of  the  ostium 

venosum  sinistrum,  extend  obliquely  downwards, 
and  to  the  left  (c),  and  then,  before  reaching  the 
apex  of  the  heart,  curve  towards  the  posterior 
wall  of  the  ventricle  (c'),  whence  they  again  as- 
cend on  the  septum  (c"}  and  the  anterior  wall 
(crfr\  and  are  finally  inserted  in  the  whole  extent 
of  the  venous  opening,  and  also  in  the  upper  bor- 
der of  the  septum  (cffff).  It  is  from  these  fibres 
in  the  free  wall  of  the  ventricle  that  are  derived 
the  deep  layers  which  decussate  with  the  superfi- 
cial, and  on  the  septum  afford  the  fibres  which,  on  the  left  side,  run 
obliquely  from  below  and  behind,  upwards  and  forwards. 

On  the  right  ventricle,  there  are  much  fewer  independent  fibres  than 
on  the  left.  Most  of  the  superficial  fasciculi  are  continued  upon  the 
left  ventricle  ;  both  the  anterior,  which  are  continued  over  the  anterior 
longitudinal  sulcus  and  lost  in  the  vortex,  and  also  many  of  those  which, 
at  the  posterior  longitudinal  sulcus,  stretch  from  the  left  to  the  right 
ventricle.  These  latter  fibres,  consequently,  completely  encircle  the 

FiG.  27G. — Diagram  of  the  left  ventricle,  with  the  septum,  in  order  to  show  the  course  of 
the  muscular  fibres,  a  a'  a",  superficial  fibres :  a,  on  the  anterior  wall ;  a',  the  turning  inwards 
of  them  at  the  vortex;  a",  their  passage  into  the  posterior  papillary  muscle,  b,  bf,  b",  septal 
fibres  of  the  right  side:  b,  their  course,  downwards  and  forwards;  &',  their  passage  into  the 
vortex  and  internal  muscular  layer  of  the  left  ventricle,  as  well  as  their  termination  in  the 
anterior  papillary  muscle,  6".  c — c"",  middle  muscular  layer:  c,  commencement  at  the  right 
side  of  the  ostium  venosum,  and  course  on  the  anterior  wall  obliquely  downwards  and  back- 
wards ;  c7,  curvature  on  the  septum,  and  course  on  it,  c"  ;  c"r,  curvature  on  the  anterior  wall, 
and  deep  course  in  it,  to  the  end  of  the  ostium  venosum,  <!"' '. 


THE     HEART.  673 

right  ventricle,  part  of  them  also  entering  the  vortex,  and  "part,  in  the 
anterior  longitudinal  sulcus,  joining  the  middle  muscular  layers  of  the 
left  ventricle.  Independent,  superficial  fibres  occur  only :  1,  at  the 
conus  arteriosus,  arising  from  the  ostium  venosum  dextrum,  between  the 
right  auricle  and  the  aorta,  surrounding  the  conus  arteriosus,  and  re- 
turning thence,  from  the  left,  back  to  their  point  of  origin  ;  2,  at  the 
apex  of  the  right  ventricle,  where  not  unfrequently  a  distinct,  second 
vortex  exists,  in  which  case  some  of  the  superficial  fibres  arising  from 
the  left  ostium  venosum  also  curve  inwards  in  that  vortex,  as  they  do  in 
that  of  the  left  ventricle,  and  are  continued  into  the  superficial  fibres  of 
the  right  ventricle,  but,  on  account  of  their  intricate  interlacement, 
cannot  be  traced  further.  Besides  these,  other  deeper  fibres  exist  in  the 
right  ventricle,  which  are  disposed  as  follows:  1.  From  the  upper  bor- 
der of  the  septum,  and  the  left  posterior  side  of  the  pulmonary  opening, 
flattened  bundles  commence  and  run  in  the  septum,  downwards  and  for- 
wards, towards  the  apex  of  the  heart  and  the  anterior  longitudinal  sul- 
cus, where  they  join  the  superficial  fibres,  and  are  continued  with  them 
into  the  vortex,  whence  they  may  be  traced  as  far  as  the  anterior  papil- 
lary muscle  of  the  left  ventricle  (Fig.  276  b,  b',  b").  2.  "With  these  fibres 
are  associated  others,  running  obliquely  downwards  and  backwards, 
from  the  right  side  of  the  pulmonary  opening  and  the  right  portion  of 
the  ostium  venosum  dextrum,  beneath  the  superficial  layer  of  fibres  on 
the  free  wall  of  the  ventricle,  as  far  as  the  posterior  longitudinal  sulcus, 
where  they  curve  abruptly  towards  the  septum,  in  which  they  accom- 
pany the  fibres  described  under  (1),  though  more  on  the  inferior  half  of 
the  septum,  to  the  apex  of  the  heart,  and  terminate  in  a  similar  way.  3. 
With  these  fibres  are  also  conjoined,  to  some  extent,  the  elements  of 
the  great  papillary  muscle  of  the  right  ventricle,  whilst  those  of  the  two 
smaller  are  continued  into  the  fibres  of  the  septum  described  under  (1). 
Besides  this,  all  these  muscles  furnish  direct  fibres,  some  of  which  de- 
scend from  the  ostium  venosum  and  return  upon  themselves,  and  some 
proceed  from  the  network  of  the  trafaculce  carnece  and  cannot  be  traced 
further. 

It  would  appear  therefore,  that  the  auricles,  as  regards  their  muscular 
structure,  are  almost  distinct ;  whilst  in  the  ventricles,  the  entire  super- 
ficial, tolerably  thick  muscular  layer  is  continuous  all  round  and  is  dis- 
posed as  if  the  heart  had  only  a  single  cavity.  Properly  speaking,  the 
left  ventricle  alone  in  this  respect,  is  independent,  in  which  there  is  not 
only  beneath  the  superficial  layer  a  very  thick  muscular  mass  arising 
and  ending  in  it,  to  which,  also,  the  greater  part  of  the  septum  belongs, 
but  which  also  receives  nearly  all  the  deeper  muscular  layers  arising  on 
the  right  side,  in  the  free  wall  of  the  ventricle,  and  inserted  into  the 
right  portion  of  the  septum.  The  heart,  consequently,  might  be  de- 
scribed as  composed  of  two  muscular  sacs ;  the  thinner  of  which  is  com- 


674  SPECIAL    HISTOLOGY. 

mon  to  the  whole ;  the  other  and  thicker  belonging  only  to  the  left  di- 
vision, and  to  some  extent  being  interposed  between  the  layers  of  the 
former.  To  the  latter  would  belong  the  entire  septum,  and  the  mid- 
dle muscular  substance  of  the  left  ventricle ;  to  the  former,  the  superfi- 
cial layers  with  their  continuations  in  the  innermost  muscular  strata, 
and  especially  the  whole  of  the  free  portion  of  the  right  ventricle. 

2.— OF  THE  BLOODVESSELS. 

§  214.  As  regards  their  structure,  the  bloodvessels  are  divided  into 
arteries,  capillaries,  and  veins  ;  but  these  three  divisions  are  by  no  means 
separated  by  definite  limits,  inasmuch  as  the  capillaries  are  continuous 
with  the  veins  on  the  one  hand,  as  imperceptibly  as  they  commence  from 
the  arteries  on  the  other.  At  the  same  time  it  is  true  that  both  kinds 
of  larger  vessels,  although  in  their  rudiments  presenting  a  general  con- 
formity of  structure,  are  still  sharply  and  definitely  distinguished  in 
many  respects. 

Concerning  the  tissues  which  enter  into  the  composition  of  the  vessels, 
and  the  mode  of  their  arrangement,  the  following  general  remarks  may 
be  made.  Whilst  the  true  capillaries  possess  only  a  single  perfectly 
structureless  coat,  in  the  larger  vessels,  with  few  exceptions,  the  number 
of  tunics  is  increased  to  three,  which  may  most  suitably  be  described  as 
tunica  intima,  t.  media,  and  t.  externa  s.  adventitia.  In  these  tunics 
there  are  found,  of  the  fibrous  tissues  of  the  body,  in  the  first  place,  the 
elastic  and  smooth  muscular  tissues,  but  the  connective  tissue,  and  even 
the  transversely  striped  muscular  tissue  are  also  represented  in  them ; 
besides  which,  there  exists  epitlielia,  peculiar  homogeneous  membranes, 
vessels,  and  even  nerves  ;  so  that  we  have  presented  in  them  a  com- 
plexity of  structure  which  renders  a  general  description  almost  impossi- 
ble and  which  can  be  made  clear  only  by  an  accurate  examination  of  each 
particular  element ;  and  the  rather  so,  because  the  more  extensively 
distributed  tissues  assume  very  different  forms.  With  respect  to  the 
arrangement  and  subdivision  of  these  tissues,  they  may  be  said  to  exhibit 
a  very  strong  tendency  to  lamination  and,  in  tLe  different  layers,  to  the 
assumption  of  a  constant  direction  in  the  course  of  their  constituent 
elements.  The  former  of  these  dispositions,  however,  rarely  extends  to 
the  actual  isolation  of  the  individual  layers ;  and  to  the  latter,  though 
more  rarely,  there  are  also  exceptions.  The  tunica  intima  is  the 
thinnest  of  the  membranes  of  the  vessels,  and  always  consists  of  a  cel- 
lular layer,  the  epithelium ;  most  usually  also  of  an  elastic  membrane 
in  which  a  longitudinal  direction  of  the  fibres  predominates ;  to  which 
again  may  be  superadded  other  layers  of  one  kind  or  another,  which 
also  almost  invariably  retain  the  longitudinal  direction.  The  t.  media 
is  for  the  most  part  a  thick  layer,  and  is  especially  the  seat  of  the  trans- 


THE    BLOODVESSELS. 


675 


verse  elements  and  of  the  muscles,  although  in  the  veins  it  also  contains 
numerous  longitudinal  fibres,  and  in  all  the  larger  vessels  presents,  in 
addition,  elastic  elements,  and  connective  tissue  in  greater  or  less  quan- 
tity. The  t.  adventitia,  lastly,  again  exhibits  a  preponderating  longi- 
tudinal fibrillation,  is  as  thick  as  or  thicker  than  the  t.  media,  and  con- 
sists, for  the  most  part,  only  of  connective  tissue  and  elastic  net- 
works. 

If  the  separate  tissues  of  the  vascular  tunics  are  investigated  some- 
what more  closely,  it  will  be  seen  that  the  connective  tissue  appears 
almost  universally  fully  developed,  with  fine  and  coarse  bundles  and 
distinct  fibrils.  It  is  only  in  the  smallest  arteries  and  veins  that  it  is 

Fig.  277. 


. 


replaced  by  a  nucleated,  indistinctly  fibrous  tissue,  and  ultimately 
passes  into  a  perfectly  homogeneous,  still  occasionally  nucleated,  delicate 
membrane.  The  elastic  tissue  nowhere  presents  such  manifold  forms  as 
it  does  in  the  vessels.  From  wide-meshed,  lax  networks  of  the  finest, 
middle-sized,  and  thickest  fibres  (Fig.  22,  p.  81),  up  to  the  narrowest, 
closest,  membraniform  interlacements  of  these  fibres,  all  transitionary 
forms  are  here  met  with  ;  and  besides  this,  we  may  notice  every  degree  of 
transformation  of  the  latter,  or  of  the  elastic  reticulated  membranes  into 
true  elastic  membranes,  which  either  betray  their  derivation,  in  an  elastic, 
more  or  less  indistinct,  fibrous  network  pervading  them,  and  distant 
openings,  or  are  transformed,  either  partially  or  entirely,  into  perfectly 
homogeneous  plates,  exhibiting  more  or  fewer  openings  (Fig.  25,  p.  82). 

FIG.  277. — Elastic  membrane  from  the  tunica  media  of  the  popliteal  artery  in  Man,  with 
an  indication  of  fibrous  networks ;  magnified  350  diameters. 

FIG.  278. — Muscular  fibre-cells  from  the  human  arteries,  magnified  350  diameters.  1, 
from  the  popliteal  artery ;  cr,  without,  6,  with  acetic  acid.  2,  from  a  twig,  £  a  line  in 
diameter,  of  the  anterior  tibial  artery :  a,  nuclei  of  the  cells. 


676  SPECIAL    HISTOLOGY. 

In  the  smallest  vessels,  instead  of  the  elastic  elements,  there  occasionally 
occur,  especially  in  the  t.  adventitia,  fusiform  cells,  which  can  only  be 
regarded  as  undeveloped  formative  cells  of  elastic  tissue.  Transversely 
striped  muscle  is  found  only  at  the  openings  of  the  largest  veins  into 
the  heart  ;  whilst,  on  the  contrary,  smooth  muscles  are  extensively  dis- 
tributed, especially  in  vessels  of  a  medium  size,  and  also  to  some  extent 
in  the  larger  vessels.  The  elements  of  these  muscles,  or  the  contractile 
fibre-cells,  in>  the  majority  of  the  vessels,  present  nothing  peculiar, 
except  that  their  length  never  exceeds  0*04  of  a  line,  and  that  they  are 
united,  either  directly,  or  with  the  intervention  of  connective  tissue  and 
elastic  fibrils,  into  flattened  bundles  and  muscular  membranes,  more 
rarely  into  reticulated  muscular  tissue.  In  the  larger  arteries,  in  place  of 
these  elements,  we  find  shorter  plates  resembling  epithelium  cells,  always 
with  elongated  nuclei;  and  in  the  smallest  arteries  and  veins,  slightly 
elongated,  or  even  roundish  cells  ;  both  which  forms  may  be  regarded 
as  being  in  a  less  developed  condition. 

A  peculiar  fibrous  tissue  is  contained  in  the  t.  intima  of  the  larger 
vessels,  which,  since  Henle,  has  generally  been  regarded  as  a  meta- 
,    morphosed  epithelium.     It  consists  of  pale,  usually  striped,  or  it  may 
;   be,   homogeneous  lamella?,   with   elongated  (long-oval)  nuclei  disposed 
\  parallel  to  the  long  axis  of  the  vessel,  and  which  may  not  unfrequently 
be  broken  up  into  slender  nucleated  fusiform  fibres,  similar  to  certain 
epithelial  cells,  or  at  all  events,  into  fibres  ;  but  at  other  times  are  more 
homogeneous  and  without  nuclei,  or  else  appear  to  be  transformed  into 
extremely  delicate  fibrous  membranes,  like  the  closest  and  finest  elastic 
networks.     The  similarity   of   these   layers,   which  I   shall   term   the 
striped  lamella?  of  the  t.  intima,  or  rather  of  the  fibrous  cells  of  which 
constituted,  to  the  epithelium  of  the  vessels,  is 


nevertheless  insufficient  to  justify  the  supposition  of  their  being  derived 
from  the  latter,  since  there  are  no  facts  to  show  that  the  true  epithelial 
cells  and  the  striped  lamella?  stand  in  any  genetic  connection  of  such  a 
kind,  as  that  the  latter  were  at  one  time  a  true  epithelium  and  the 
innermost  layer  in  the  vessel,  being  afterwards  successively  pushed 
back,  and  their  elements  made  to  coalesce  ;  on  the  contrary,  it  seems 
to  be  allowable  to  regard  the  epithelial  cells  and  the  formative  cells  of 
these  layers  as  originally  equivalent,  and  that  in  the  course  of  develop- 
ment, the  one  set  are  transformed  in  one  direction,  and  the  other  in 
another,  and,  in  this  way,  ultimately  become  tissues  of  more  or  less 
different  kinds. 

The  epithelium  of  the  vessels  (Fig.  14,  p.  76)  presents  two  forms  : 
firstly,  especially  in  the  great  veins,  it  appears  under  that  of  a  tessel- 
lated epithelium,  with  polygonal,  mostly  somewhat  elongated  cells  ;  and 
secondly,  as  in  most  of  the  arteries,  as  a  fusiform  epithelium,  with 
acuminated,  slender  cells,  O01-0-02  of  a  line  long.  Normally,  it 


THE     BLOODVESSELS.  677 

exists  in  all  vessels,  may  almost  always  be  pretty  readily  broken  up 
into  its  elements,  and  like  other  simple  epithelia,  is  not  subject  to  any 
constant  detachment  and  restoration.  With  JjUmak,  we  might  describe 
the  epithelium  as  the  cellular  membrane  of  the  vessels,  since  it  differs 
from  other  epitlielia  in  this  respect,  that  in  the  large  vessels,  it  is  often 
continuous  with  the  striped  lamella,  without  any  line  of  demarcation, 
so  that  frequently  it  cannot  be  said  where  the  one  ceases  and  the  others 
commence ;  but  I  should  myself  rather  be  inclined  to  retain  the  old 
name,  both  because  the  innermost  cellular  layer  of  the  vessels  presents 
in  all  respects  the  relations  of  a  simple  epithelium,  and  is,  in  many 
situations  (heart,  smaller  vessels)  abruptly  defined  from  the  deeper 
tissues.  Even  the  circumstance  particularly  adduced  by  Remak,  that 
the  vascular  epithelium  does  not  proceed  from  the  embryonic  epithelial 
membrane,  is  not  with  me  decisive  as  to  the  propriety  of  separating  it 
from  the  other  epithelia,  inasmuch  as  the  investments  of  the  serous 
sacs  and  synovial  capsules,  which  no  one  will  be  disposed  to  separate 
from  the  epithelia,  are  developed  quite  independently. 

All  the  larger  vessels  down  to  those  J-  a  line  in  diameter  and  less, 
possess  nutritive  vessels  as  they  are  termed  (vasa  vasorum  s.  nutrientia), 
derived  from  minute  contiguous  arteries,  and  ramifying  chiefly  in  the 
t.  adventitia,  in  which  they  constitute  a  rich  capillary  plexus  with 
somewhat  rounded  meshes,  from  which  again  the  veins  accompanying 
the  arteries  arise,  and  which,  in  the  case  of  the  venous  vasa  vasorum, 
pour  their  blood  directly  into  the  vein  to  which  they  belong.  The  if. 
media  of  the  larger  arteries  and  veins,  according  to  the  Concurrent 
testimony  of  many  authors,  also  contains  vessels,  although  in  very 
small  number,  and  only  in  the  outer  layers ;  whilst  the  internal  layers 
and  the  t.  intima  have  always  appeared  to  me  to  contain  none  at  all; 
but  even  in  these  situations  some  observers  would  seem  to  have  noticed 
vessels  (in  the  Ox,  the  vena  cava  inferior  is  richly  provided  with  vessels 
up  to  the  t.  intima).  Nerves  derived  from  the  sympathetic  and  spinal 
nerves  may  readily  be  seen  going  to  many  arteries,  but  frequently 
appear  merely  to  accompany  them.  Where  they  enter  the  coats  of  a 
vessel  they  run  only  within  the  t.  adventitia,  and  in  favorable  instances, 
in  animals,  divisions  and  free  terminations  of  their  fine  fibres  may  be 
perceived  (vide  "Mikros.  Anat.,"  II.,  1,  p.  532-33).  Many  arteries  are 
wholly  without  nerves,  as  those  of  the  cerebral  and  spinal  substance,  of 
the  t.  chorioidea,  the  placenta,  as  well  as  many  arteries  of  muscles, 
glands,  and  membranes,  whence  it  is  obvious,  that  nerves  are  not  as 
requisite  for  them  as  we  have  usually  been  inclined  to  believe.  This 
may  be  said  more  decisively  with  respect  to  the  veins,  as  it  is  only  in 
the  larger  ones  that  a  few  fine  nerves  can  be  demonstrated.  Such  have 
been  observed  by  Luschka  in  the  sinuses  of  the  dura  mater,  the  veins  of 


678  SPECIAL    HISTOLOGY. 

the  vertebral  canal,  the  vence  cavce,  the  jugular,  iliac,  and  crural  veins, 
and  in  those  of  the  liver  by  myself.  They  are  derived  both  from  the 
sympathetic  and  the  spinal  nerves,  and  with  regard  to  their  termina- 
tions have  not  yet  been  investigated.  According  to  Luschka,  they 
would  appear  to  extend  to  the  innermost  vascular  tunic ;  but  this  I  have 
not  as  yet  been  successful  in  observing. 

§  215.  For  more  easy  description,  the  arteries^  may  be  divided,  ac- 
cording as  the  middle  tunic  is  purely  muscular,  or  composed  of  muscu- 
lar and  elastic  fibres  intermixed,  or  else  chiefly  elastic,  into  small,, 
medium  sized  and  large  arteries  ;  and  the  more  properly  so,  because, 
concomitantly  with  the  variations  in  the  structure  of  the  middle  tunic, 
the  external  and  internal  coats  present  a  different  conformation,  at  all 
events,  in  many  respects.  A  general  characteristic  of  the  arteries  is 
presented  in  the  circumstance,  that  the  middle  tunic  is  very  strong,  and 
consists  of  numerous,  regularly  disposed  laminae,  the  elements  of  which 
observe  a  transverse  direction.  In  the  largest  arteries  the  t.  media  is 
yellow,  highly  elastic,  and  of  great  thickness ;  towards  the  periphery  of 
the  body  it  gradually  diminishes  in  thickness,  and  becomes  redder  and 
more  contractile,  until,  just  before  the  capillaries  are  reached,  it  appears 
quite  thin  and  subsequently  inapparent.  The  whitish  t.  intima  is 
always  much  thinner,  and  varies  in  thickness  within  narrower  limits, 
but  this  is  also  regulated  by  the  size  of  the  vessel ;  whilst,  on  the  con- 
trary, the  t.  adventitia  of  the  largest  arteries  is  absolutely  considerably 
thinner  than  in  those  of  a  medium  calibre,  in  which  it  often  equals  the 
t.  media  in  thickness,  or  may  even  exceed  it.  In  a  special  exposition 
of  these  points,  it  is  best  to  begin  with  the  smallest  arteries  as  the 
simplest  in  structure  ;  with  these  the  others  may  be  afterwards  readily 
compared. 

Arteries  under  4-5  or  1  line  in  diameter,  with  few  exceptions,  present, 
until  close  to  the  capillaries,  the  following  structure  (Fig.  279).  The  t. 
intima  consists  of  only  two  lamince,  ws\  epithelium,  and  a  peculiar,  glis- 
tening, less  transparent  membrane,  which  I  shall  term  the  elasticjnter- 
nal  tunic.  The  former  contains  well-marked,  fusiform,  pale  cells  with 
long-oval  nuclei,  which  are  readily  separated  in  connection,  in  entire 
fragments,  or  even  in  the  form  of  perfect  tubes ;  but  may  also  be  iso- 
lated, and  then  present  no  small  resemblance,  on  the  one  hand,  with  the 
fusiform  cells  of  pathologists  (also  with  the  formative  cells  of  the  elastic 
fibres  and  of  connective  tissue),  and  on  the  other  with  contractile  fibre- 
cells  ;  from  the  former,  however,  they  are  distinguished  by  the  less  atte- 
nuation of  their  extremities  and  their  paleness ;  and  from  the  latter  by 
their  rigidity,  by  the  nuclei  never  having  the  rod-like  form,  and  by  their 
chemical  reactions.  The  elastic  tunic  is,  on  the  mean  0-001  of  a  line 


THE    BLOODVESSELS. 


679 


thick,  and  in  the  living  subject  is  smoothly  stretched  beneath  the  epithe- 
lium, whilst  in  empty  arteries  it  almost  always  presents  a  greater  or  less 
number  of  usually  strong  folds,  and  frequently  also,  numerous,  fine  trans- 
verJS.e.rwgwBy, which  give  it,  although  perfectly  homogeneous,  a  peculiar  lon- 
gitudinally striated  aspect ;  in  addition,  it  appears  almost  always  as  &fenes- 
trated  membrane,  as  it  is  termed,  with  various  sized,  distinctly  marked  reti- 

Fig.  279. 


culated  fibres,  and  usually  minute  elongated  openings;  more  rarely  as  a 
true  but  very  close  network,  of  chiefly  longitudinal  elastic  fibres,  with  nar- 
row, elongated  fissures, — and  completely  corresponds  in  aspect,  in  its 
great  elasticity,  and  its  chemical  reactions,  with  the  elastic  lamellce  of  the 
t.  media  of  the  larger  arteries.  The \  middle fojw£gof  the  small  arteries  is 
purely  muscular,  without  the  sligntest  admixture  of  connective  tissue  i 
and  elastic  elements,  and  is  stronger  or  weaker  according  to  the  size  of 
the  vessel  (down  to  0-03  of  a  line).  In  vessels  of  1-10  of  a  line  in  dia- 
meter, the  fibre-cells,  which  are  united  into  lamellce^  may  be  pretty 
readily  isolated  by  dissection,  and  in  still  smaller  ones  by  boiling  and 
maceration  in  nitric  acid  of  20  per  cent.,  when  they  appear  as  delicate 
fibre-cells-0-02-0-03  of  a  line  long,  arid  0-002-0-0025  of  a  line  broad. 
The  t.^adventitia  consists  of  connective  tissue  and  fine  elastic  fibres,  and 
is  usuaHyliJTnick  as  the  t.  media  or  even  a  little  thicker. 

FIG.  279. — An  artery,  a,  0-002,  and  vein,  6,  0-007  of  a  line  in  diameter;  from  the  mesen- 
tery of  a  child  ;  treated  with  acetic  acid,  and  magnified  350  diameters:  a,  tunica  advenlitia, 
with  elongated  nuclei;  $,  nuclei  of  the  contractile  fibre-cells  of  the  t.  media,  viewed  in  part 
on  the  flat  surface,  in  part  in  apparent  transverse  section ;  ^,  nuclei  of  the  epithelial  cells ;  «f, 
elastic  longitudinal  fibrous  membrane. 


680 


SPECIAL    HISTOLOGY. 


The  above  description  of  the  structure  holds  good  of  arteries  down  to 
1-8  of  a  line  in  size,  but  nearer  the  capillaries  the  structure  changes 
more  and  more  (Fig.  280).  Even  in  arteries  1-10  of  a  line  in  diameter, 
the  t.  adventitia  contains  no  elastic  tissue,  being  composed  only  of  con- 
nective tissue  with  elongated  nuclei,  which  at  first  still  retains  its  fibrous 
character,  but  afterwards,  though  always  nucleated,  appears  more  homo- 
geneous, and  ultimately  represents  a  thin,  truly  structureless  membrane, 
which,  in  vessels  under  0-007  of  a  line  disappears  altogether.  The  annu- 
lar fibrous  coat  in  arteries  less  than  1-10  of  a 
line,  down  to  those  having  a  diameter  of  1-25 
of  a  line,  still  presents  2-3  layers  of  muscles 
and  a  thickness  of  0-005-0-008  of  a  line; 
in  smaller  vessels  it  has  but  one  layer,  the 
elements  of  which  at  the  same  time  become 
shorter  and  shorter;  and  finally,  in  vessels 
between  0-03-0-007  of  a  line,  appear  only  in 
the  form  of  short,  elongated  or  elliptical  cells 
of  0-015-0-006  of  a  line  with  shorter  nuclei. 
In  vessels  of  0-012  of  a  line  in  diameter, 
these  more  embryonic  forms  of  contractile 
fibre-cells  still  constitute  a  connected  lamina, 
but  after  that,  they  are  gradually  separated 
from  each  other  (Fig.  280)  and  become  wholly 
lost.  The  t.  intima,  in  vessels  more  than 


0-028-0-03  of  a  line  in  size,  has  an  elastic  inner  membrane,  which,  how- 
ever, in  its  earliest  form,  is  very  delicate,  and  does  not  appear  to  attain 
its  full  development  in  arteries  less  than  0-06-0-08  of  a  line  in  diameter. 
On  the  other  hand,  the  epithelium  may  be  traced  in  vessels  of  not  more 
than  0-01  or  even  of  0-07  of  a  line ;  and  it  may  at  the  same  time  be 
remarked,  that  its  cells  can  no  longer  be  isolated,  and  its  presence  only 
be  recognized  from  the  closely  placed  elliptical  nuclei. 

Medium-sized  arteries  above  4-5  or  1  line,  up  to  those  of  2  and  3  lines 
in  diameter,  at  first,  present  no  great  alterations  in  the  external  and  in- 
ternal tunics,  whilst  the  t.  media  is  not^onjj,  always  increased  in  thick- 
ness in  proportion  to  the  size  of  the  vessel  (from  0'05-0'12  of  a  line),  but 
is  also  changed  in  structure.  For  now,  in  addition  to  muscular  layers,  the 
number  of  which  constantly  increases,  but  the  elements  of  which  are  pre- 
cisely the  same  as  before,  we  observe  fine  elastic  fibres ,  which,  united  into 
wide-meshed  networks,  run,  at  first  singly  and  with  little  regularity 
among  the  muscular  elements ;  but  in  larger  vessels  of  this  category 

FIG.  280. — An  artery,  a,  of  O'Ol,  and  a  vein,  6,  of  0'015  of  a  line,  from  the  mesentery  of 
a  child,  magnified  350  diameters,  treated  with  acetic  acid.  The  letters  as  in  Fig.  279:  «,  t. 
media  of  the  vein,  composed  of  nucleated  connective  tissue. 


THE    BLOODVESSELS.  681 

are  accompanied  by  a  certain  amount  of  connective  tissue,  and  here  and 
there  exhibit  a  disposition  to  form 
special  layers  alternating  with  the 
muscular,  though  not  presenting  the 
characters  of  a  continuous  network 
throughout  the  t.  media.  Thus,  al- 
though the  t.  media  is  deprived  of 
its  eminently  contractile  structure, 
it  must  be  allowed  that  the  mus- 
cular fibres  here  also  still  retain  a  considerable  preponderance.  The 
f.  intima  in  the  medium-sized  arteries  has,  not  unfrequently,  between 
the  elastic  inner  membrane  and  the  epithelium,  several  other  layers, 
among  which  the  above  described  striped  lamettce  are  the  most  remark- 

^teMHpflBHMMPMMMiMMHbw 

able.  These  lamella*,  composecTof  fine  elastic  networks,  wider  towards 
the  exterior,  and  lying  in  a  homogeneous,  granular  or  fibrillated  con- 
nective substance,  constitute  the  middle  lamina  of  the  t.  intima,  the 
elements  of  which  also  all  run  longitudinally,  and  are  for  that  reason 
readily  distinguishable  from  the  muscular  layers  of  the  t.^  media,  to 
which  in  some  respects  they  bear  a  resemblance.  The  t.  adventitia, 
lastly,  in  almost  all  these  arteries,  exceeds  the  t.  media  in  thickness,  at- 
taining 0*05— 0*16  of  a  line.  Its  elastic  fibres  at  the  same  time  become 
stronger  and  stronger,  and  even  in  the  vessels  1  line  in  diameter,  a 
considerable  aggregation  of  them,  where  it  adjoins  the  t.  media,  may  be 
perceived,  the  line  of  demarcation  between  the  two  tunics  being  in  all 
these  arteries  extremely  well  defined.  This  elastic  membrane  of  the 
adventitia  is  extremely  well  marked  in  the  largest  of  the  vessels  belong- 
ing to  the  class  now  under  consideration,  as  in  the  external  and  internal 
carotids,  the  crural,  brachial,  prof  undo,  femoris,  mesenteric,  and  creliac, 
in  which  it  measures  from  0-013  to  as  much  as  0-04  of  a  line,  and  more, 
and  is  to  some  extent  very  distinctly  laminated,  the  structure  of  the 
lamella*  very  often  closely  approaching  that  of  the  true  elastic  mem- 
branes. Besides  this,  the  external  layers  of  the  t.  adventitia  also  con- 
tain elastic  networks,  only  that  the  elements  of  the  latter  are  some- 
what finer  and  constitute  minute  lamella?,  but  are  conjoined  with  less 
regularity.  The  largest  of  the  medium-sized  arteries  exhibit  an  approach 
to  the  largest  arteries,  inasmuch  as,  in  their  t.  media  certain  portions 
of  the  elastic  networks  constitute  somewhat  stronger  elastic  lamella?, 
which,  however,  are  continuous  through  the  entire  thickness  of  the 
tunic,  and  also,  more  rarely,  form  true  elastic  membranes,  by  which 
they  are  distinguished  from  the  elastic  plates  of  the  annular  fibrous 

Fia.  281. — Transverse  section  of  the  art.  profunda  femoris  of  Man,  magnified  30  diameters: 
a,  t.  intima,  with  the  elastic  layer  (the  epithelium  is  not  perceptible)  ;  6,  t.  media,  without 
elastic  lamella,  but  with  fine  elastic  fibres ;  c,  t.  adventitia,  with  elastic  networks  and  con- 
nective tissue. 


682 


SPECIAL    HISTOLOGY. 


coat  of  the  largest  arteries,  yet  to  be  described.  Lamellae  of  the  former 
character  are  found  in  the  inner  layers  of  the  t.  media  of  the  aa.  cru- 
ralis,  mesenterica  superior,  cceliaca,  iliaca  externa^bracJiialis,  and  in 
the  external  and  internal  carotids ;  whilst  they  occur  in  a  remarkable 
manner  in  the  commencement  of  the  tibialis  antica  and  postiea,  and  in 
the  popliteal  artery  throughout  the  entire  middle  tunic ;  they  are  par- 
ticularly well  developed  in  the  last-named  vessel,  which  has  also  usually 
somewhat  thicker  walls  than  the  crural. 

From  the  conditions  of  the  t.  media  above  stated,  and  in  other  re- 
spects also,  the  transition  from  the  medium-sized  to  the  largest  arteries 
is  rendered  extremely  gradual.  With  respect  to  the  t.  intima,  its  epi- 
thelial cells  in  the  latter  are  usually  no  longer  so  much  elongated  as  in 
the  smaller  vessels,  though  still  retaining  their  fusiform  figure  and  a 
length  of  0-006-0*01  of  a  line.  The  rest  of  this  tissue  does  not  neces- 
sarily increase  in  amount  with  the  size  of  the  vessel,  although  it  exhibits, 
especially  in  the  aorta,  a  great  proneness  to  become  thickened,  so  that 
it  is  often  difficult  to  determine  its  normal  thickness.  As  regards  its 


structure,  it  consists  chiefly  of  lamella;  of  a  clear,  sometimes  homogeneous, 
sometimes  striated,  or  even  distinctly  fibrillated  substance,  presenting, 
for  the  most  part,  the  characters  of  connective  tissue  (Eulenberg  ob- 
tained some  gelatin  from  the  t.  intima),  and  is  pervaded  by  finer  and 
coarser  longitudinal  elastic  networks.  Usually  these  networks  become 
more  and  more  close  from  within  to  without,  and  their  elements  stronger, 
and  on  the  side  towards  the  t.  media  the  inner  membrane  ceases,  either 
with  an  elastic  close  network  or  a  true  fenestrated  more  or  less  fibrous 
membrane,  obviously  corresponding  with  the  elastic  inner  membrane  of 
the  small  arteries.  Immediately  beneath  the  epithelium  the  elastic  net- 
works are  either  very  fine,  or  are  replaced  by  one  or  several  clear  layers 

FIG.  282. — Transverse  section  of  the  aorta  below  the  superior  mesenteric  artery.  1,  t. 
intima  :  2,  t.  media  ;  3.  t.  adventitia  :  a,  epithelium ;  />,  striped  lamellce  ;  c,  elastic  membrane 
of  the  intima;  d,  elastic  lamellae  of  the  t.  media;  e,  its  muscles  and  connective  tissue; 
/,  elastic  networks  of  the  t.  adventitia.  From  Man. — Magnified  30  diameters,  treated  with 
acetic  acid. 


THE    BLOODVESSELS.  683 

lamella, — which,  when  nucleated,  often  appear  to  consist 
of  coalesced  epithelial  cells  ;  and  when  homogeneous  and  without  nuclei, 
to  approach  pale  elastic  membranes.  In  the  annular  fibrous  layer,  the 
largest  arteries  present,  as  a  new  element,  peculiar  elastic  membranes 
or  plates,  which,  except  in  the  transverse  disposition  of  their  fibres,  are 
constituted  in  all  essential  respects  in  the  same  way  as  the  elastic  inner 
membrane,  particularly  of  the  smaller  arteries,  and  sometimes  appear 
as  very  thick  networks  of  strong  elastic  fibres,  sometimes  as  true  fenes- 
trated  membranes  with  a  less  evident  fibrous  structure.  These  mem- 
branes 0-001-0-0012f'of  a  line  thick,  and  the  number  of  which  may 
amount  to  from  50  to  60,  regularly  alternate,  at  distances  of  0-003- 
0-008  of  a  line,  with  transverse  layers  of  smooth  muscle,  which  are  per- 
vaded by  connective  tissue  and  networks  of  medium-sized  elastic  fibres ; 
nevertheless,  they  are  not  to  be  regarded  merely  as  tubes  inserted  regu- 
larly one  within  the  other  and  having  the  interspaces  occupied  by  muscles  ; 
for,  in  the  first  place,  they  are  connected  with  each  other  and  with 
thejiner  elastic  network  pervading  the  muscular  tissue,  sometimes  more 
frequently,  sometimes  more  sparingly ;  and, 
in  the  second  place,  they  are  not  frequently 
interrupted  in  spots,  or  replaced  by  com- 
mon elastic  networks.  The  plates  are  seen 
most  distinctly  and  most  regularly  disposed 
in  the  abdominal  aorta,  the  a.  innominata, 
the  common  carotid,  and  the  smallest  of 
their  immediate  branches,  although  these 
conditions  vary  considerably  in  different 
individuals,  so  that  in  the  want  of  very 
extended  researches  no  general  statement  with  respect  to  them  can -be 
propounded. 

Another  characteristic  of  the  t.  media  is  the  slight  development  of  its 
muscular  element.  Contractile  fibre-cells,  it  is  true,  may  be  found  also 
in  the  largest  arteries  throughout  all  the  layers  of  the  middle  tunic ; 
but,  in  the  first  place,  compared  with  its  other  elements,  the  elastic 
plates,  the  connective  tissue,  and  the  finer  elastic  networks,  they  con- 
stitute only  a  very  inconsiderable  part  of  that  membrane  (J-J) ;  and, 
secondly,  are  so  undeveloped  in  their  elements,  that  it  appears  very 
doubtful  whether  they  possess  any  notable  contractile  power.  For  in 
the  aorta  and  the  trunk  of  the  pulmonary  artery,  the  fibre^cells  in  the 
inner  layers  of  the  t.  media  are  often  not  longer  than  0-01,  and  0-004- 
0-006  of  a  line  broad,  and  quite  flat,  so  that  they  are  not  unlike  certain 
epithelial  cells ;  at  the  same  time  their  figure  is  irregular,  rectangular, 
fusiform  or  clavate,  though  they  still  contain  the  well-known,  rod-like 

Fia.  283. — Muscular  fibre-cells  from  the  innermost  layer  of  the  axillary  artery  in  Man  ; 
magnified  350  diameters :  a,  without ;  6,  with,  acetic  acid ;  a,  nucleus  of  the  fibres. 


684  SPECIAL    HISTOLOGY. 

nuclei.  In  the  outer  layers  the  fibre-cells  are  more  slender  and  more 
elongated,  up  to  0-02  of  a  line,  and  at  the  same  time  more  like  the  well- 
marked  muscular  fibre-cells  of  other  organs,  though  even  there  retaining 
somewhat  of  a  rigid  and  peculiar  aspect.  In  the  carotids,  subclavian, 
axillary  and  iliac  arteries,  the  contractile  elements  have  become  more 
developed,  whence  also  the  t.  media  of  those  arteries  does  not  present 
the  pure  yellow  color  of  that  of  the  largest  vessels,  but  begins  to  assume 
a  reddish  tinge.  The  t.  adventitia  of  the  largest  arteries  is,  relatively 
and  absolutely,  thinner  than  in  the  smaller,  amounting  to  0-04-0-02  of  a 
line.  Its  structure,  upon  the  whole,  is  the  same  as  in  other  vessels, 
although  the  elastic  inner  layer  is  less  developed,  and  also  very  indis- 
tinctly defined  from  the  thick  elastic  elements  of  the  t.  media. 

The  t.  intima  of  certain  arteries  also  contains  smooth  muscles,  as  I 
have  found  in  the  axillary  and  popliteal  arteries  uuMan,  and  as  has 
been  lately  demonstrated,  particularly  in  the  visceral  arteries  of  the 
Mammalia.  In  the  largest  arteries  in  Man  this  tunic  is  very  frequently 
thickened,  in  which  condition  a  vast  increase  of  the  striped  lamellae  in 
particular  takes  place.  In  the  t.  media  of  no  artery  is  the  muscular 
element  wholly  wanting,  and  Henle  erroneously  adduces  the  arteries  of 
the  retina  in  opposition  to  this,  for  it  occurs  in  those  arteries  even  in 
branches  of  0*08,  and  is  not  absent  in  any  above  0'02  of  a  line.  In.. 
Animals  the  t.  adventitia  of  the  large  arteries  contains  muscles,  but 
not  in  Man. 

§  216.  Veins. —  The  veins  also  admit  of  being  divided  into  three 
groups,  small,  medium-sized,  and  large,  which,  however,  are  not  so 
abruptly  defined  as  is  the  case  with  the  arteries.  The  veins,  without 
exception,  have  thinner  walls  than  the  arteries,  which  depends  just  as 
much  upon  their  containing  a  less  considerable  quantity  of  contractile, 
as  upon  a  more  sparing  development  of  the  elastic  elements ;  whence 
also  the  venous  walls  collapse  more  readily,  and  are  less  contractile. 
The  t.  intima,  in  the  larger  veins  is  frequently  not  thicker  than  it  is 
in  those  of  medium  size ;  it  is  less  developed  than  in  the  arteries,  but 
in  other  respects,  of  the  same  structure.  The  t.  media,  which  is  never 
yellow,  but  usually  grayish-red,  contains  far  more  connective  tissue, 
fewer  elastic  fibres  and  muscles,  and,  what  chiefly  characterizes  it, 
always  presents  together  with  the  transverse,  longitudinal  layers  also. 
It  is  in  general  thin,  but  absolutely  stronger  in  the  medium-sized  veins 
than  in  the  larger,  and  in  these  also  the  muscular  element  is  most 
vigorously  developed.  The  t.  adventitia,  lastly,  is  usually  the  thickest 
of  the  three  coats,  its  relative  and  absolute  thickness  usually  increasing 
with  the  size  of  the  vessels.  In  constitution  it  precisely  resembles  that 


THE    BLOODVESSELS.  685 

of  the  arteries,  except  that  in  many  veins,  especially  of  the  abdomen, 
longitudinal  muscles,  occasionally  very  well  developed,  appear  in  it, 
and  give  the  entire  venous  wall  a  peculiar  character. 

The  smallest  veins  (Fig.  280  b),  may  be  said  to  consist  solely  of  a 
nucleated,  indistinctly  fibrous,  or  homogeneous  connective  tissue  and  an 
epithelium.  The  elements  of  the  latter  are  elliptical  or  round,  with 
oval  or  even  rounded  nuclei,  whilst  the  former  constitutes  a  proportion- 
ately strong  t.  adventitia,  and  besides  that,  a  thinner  layer,  which  sup- 
plies the  place  of  the  t.  media  (Fig.  280  e),  both  having  a  longitudinal, 
fibrous  arrangement.  Below  the  size  of  0*01  of  a  line  the  veins  gradu- 
ally lose  the  external  connective  tissue  and  the  epithelium,  the  t.  media 
appearing  to  pass  into  the  structureless  wall  of  the  capillaries.  A 
muscular  membrane,  and  in  general,  a  layer  of  annular  fibres  are  first 
seen  in  veins  more  than  0§02  of  a  line  in  size,  in  the  form,  at  first,  of 
widely  separated,  transversely  oval  cells,  with  short-oval,  sometimes 
even  almost  rounded,  transverse  nuclei.  By  degrees  these  cells  become 
more  elongated,  and  more  numerous,  and  ultimately,  in  vessels  of  0-06- 
0-08  of  a  line  constitute  a  continuous  layer  (Fig.  279  ft),  but  which  is 
always  less  developed  than  the  corresponding  arterial  tissue.  This 
continues  to  be  the  structure  of  veins  up  to  the  size  of  0-1  of  a  line ; 
when  elastic  networks,  at  first  fine,  begin  gradually  to  make  their  ap- 
pearance externally  to  the  epithelium  in  the  t.t.  musculosa  and  adven- 
titia,  whilst  at  the  same  time  the  muscular  layers  multiply,  and  even 
admit  connective  tissue  and  fine  elastic  fibres  among  their  elements. 

Veins  of  the  medium  diameter  of  1-3-4  lines,  such  as  the  cutaneous 
veins,  and  deeper  veins  of  the  extremities  up  to  the  brachial  and  popli- 
teal, the  veins  of  the  head  and  viscera,  except  the  main  trunks,  are 
characterized  (particularly  those  of  the  lower  extremity)  by  the  not  in- 
considerable development  of  their  annular  fibrous  membrane,  which,  as 
in  the  arteries,  is  of  a  yellowish-red  color,  and  striped  transversely. 
But  even  where  thickest,  it  is  far  from  equalling 
that  of  the  corresponding  arterial  vessels  ;  and 
in  thickness  never  exceeds  0-06  to  0-07  of  a 
line.  It  consists  not  only  of  transverse  but  also 
of  longitudinal  layers,  and  in  this  respect  like- 
wise differs  from  that  of  the  arteries.  The 
transverse  layers  are  composed  of  common,  undu- 
lating connective  tissue,  with  fine,  loosely  ar- 
ranged, or  rather  isolated  elastic  fibres  (nucleated  fibres,  as  they  are 

FIG.  284. — Transverse  section  of  the  vena  saphena  magna,  at  the  mallclus,  magnified  30 
diameters:  a,  striped  lamella  and  epithelium  of  the  t.  intima  ;  6,  its  elastic  membrane;  c,  longi- 
tudinal, internal  connective-tissue  layer  of  the  t.  media,  with  elastic  fibres;  d,  transverse 
muscles,  and  c,  longitudinal  elastic  networks,  disposed  in  a  laminated  manner  ;/,  t.  adventitia. 


686 


SPECIAL    HISTOLOGY. 


.  285. 


termed),  and  a  large  quantity  of  smooth  muscles,  the  fusiform  elements 

of  which,  0-02-0-04  of  a  line  long, 
and  0-004-0-007  broad,  present  the 
usual  characters  of  contractile  fibre- 
cells,  whilst  the  longitudinal  lamince 
consist  of  true,  thick,  and  very  thick, 
reticulated  elastic  fibres.  With  respect 
to  the  mutual  relations  as  lamince 
of  these  tissues,  it  should  be  remark- 
ed that  in  certain  veins  (popliteal, 
profunda  femoris,  saphena  major  and 
minor),  the  t.  intima  is  succeeded  by 
a  layer,  formed  solely  of  connective 
tissue  and  finer  elastic  networks,  and 
having  a  longitudinal  fibrillation — the 
longitudinal  lamina  of  the  t.  media — 
whilst  in  other  veins  the  muscular  ele- 
ments extend  also  into  the  innermost 
lamina.  In  this  case,  immediately 
external  to  the  t.  intima,  there  is  a 
transverse  layer  of  muscles,  with  con- 
nective tissue  and  elastic  fibrils,  which  three  tissues,  in  these  veins, 
always  accompany  each  other ;  to  this  succeeds  a  regular  alternation  of 
longitudinal,  elastic,  reticulated  membranes,  always  in  a  single  layer, 
and  transverse  muscles  with  connective  tissue,  so  that  the  t.  media  of 
these  veins  presents  a  laminated  aspect,  somewhat  resembling  that  of 
the  largest  arteries.  It  should,  however,  be  remarked,  that  the  elastic, 
reticulated  membranes,  although  frequently  very  closely  interwoven, 
nevertheless  never  form  homogeneous,  elastic  membranes ;  moreover, 
that  they  are  occasionally  interrupted,  and,  as  longitudinal  sections 
manifestly  show,  are  invariably  continuous  with  one  another  through 
the  whole  t.  media.  The  number  of  these  elastic  lamella?  fluctuates 
between  five  and  ten,  and  their  interspaces  vary  in  width  from  0-004- 
0-01  of  a  line.  The  t.  intima  of  the  medium-sized  veins  is  0-01-0-04  of 
a  line  thick,  and  consists,  where  it  is  thinner,  only  of  an  epithelium  with 
shorter,  though  elongated  cells,  a  striated,  nucleated  lamella,  and  an 
elastic  longitudinal  membrane,  corresponding  to  the  elastic  inner  mem- 
brane of  the  arteries,  but  which  scarcely  ever  appears  as  a  truly  homo- 
geneous, fenestrated  membrane,  but  most  usually  as  an  extremely  close, 
areolated  network  of  finer  and  coarser  elastic  fibrils.  Where  the  t. 
intima  is  thicker,  the  striated  lamella?  are  multiplied,  and,  above  all,  one 
or  even  several  additional  networks  of  elastic,  fine  fibres  make  their  ap- 

FiG.  285. — Muscular  fibre-cells  from  the  renal  vein  of  Man ;  a,  without ;  6,  with  acetic 
acid;  a,  nucleus  of  the  latter. — Magnified  350  diameters. 


THE    BLOODVESSELS.  687 

pearance  on  the  inner  aspect  of  the  above-described  elastic  membrane, 
which  forms  the  limitary  portion  of  the  t.  intima.  I  have  also  seen 
smooth  muscles  of  the  t.  intima,  in  the  veins  of  the  gravid  uterus,  as 
well  as  in  the  saphena  major  and  popliteal  vein  ;  and  Remak  has  con- 
firmed their  existence  in  the  visceral  veins  of  certain  Mammalia.  The 
t.  adventitia  of  these  veins  is  almost  invariably  thicker  than  the  t.  media, 
often  twice  as  thick,  rarely  of  equal  strength.  Usually  it  contains  only 
longitudinal,  much  interwoven,  often  very  well-marked  elastic  networks 
with  thick  fibres,  and  common  connective  tissue,  but  in  the  case  of  those 
visceral  veins,  the  trunks  of  which  have  longitudinal  muscles  in  the  t. 
adventitia,  similar  muscular  elements  also  extend  for  a  certain  distance 
into  the  branches  (vid.  seq.) 

The  largest  veins  are  distinguished  from  those  of  the  medium  diameter 
chiefly  by  the  sparing  development  of  the  t.  media,  and  especially  of 
its  muscular  elements  ;  a  deficiency,  however,  it  is  true,  often  counter- 
balanced by  the  presence  of  contractile  elements  in  the  t.  adventitia. 
The  thickness  of  the  t.  intima  is  usually  O'Ol  of  a  line,  when  it  presents 
the  same  conditions  as  in  the  medium-sized  veins.  More  rarely,  as  oc- 
casionally in  the  vena  cava  inferior,  in  the  trunks  of  the  hepatic  veins, 
and  in  the  vena  innominata,  it  amounts  to  0-02  and  0-03  of  a  line, 
which  increase  of  thickness  is  due  to  striped  lamellce  with  nuclei,  and 
fine,  elastic,  longitudinal  networks,  never  to  those  composed  of  muscles. 
The  t.  media,  on  the  average,  presents  a  thickness  of  0-02-0-04  of  a 
line,  but  may  occasionally,  as  at  the  commencement  of  the  trunk  of  the 
vena  portai,  in  the  uppermost  part  of  the  abdominal  portion  of  the  v. 
cava  inferior,  and  at  the  orifices  of  the  hepatic  veins,  measure  0-05-0-12 
or  be  wholly  wanting,  as  in  the  greater  part  of  the  v.  cava  inferior  in 
the  liver,  and  in  the  further  course  of  the  largest  hepatic  veins.  Its 
structure,  in  all  essential  particulars,  is  the  same  as  in  the  previous  class 
of  vessels,  except  that  the  longitudinal  elastic  networks  are  intricately 
connected  together,  and  less  distinctly,  or  not  at  all,  laminated;  the 
transverse  muscles,  also,  are  scanty  and  indistinct,  even  where  the  t. 
m,edia  possesses  the  considerable  thickness  above  stated,  and  are  more 
abundantly  intermixed  with  bundles  of  connective  tissue.  I  have  noticed 
the  muscles  to  be  most  developed  in  the  splenic  vein  and  v.  portce ;  they 
appeared  to  me  to  be  wholly  wanting  in  the  abdominal  portion  of  the 
inferior  vena  cava  below  the  liver,  in  certain  spots,  and  also  in  the  sub- 
clavian  vein,  and  in  the  terminal  portions  of  the  superior  and  inferior 
vence  cavce.  The  t.  adventitia  of  the  largest  veins,  is  almost  invariably 
nearly  twice  as  thick  as  the  middle  tunic,  or  even  as  much  as  five  times 
as  thick,  and  exhibits,  in  its  structure,  the  important  difference,  at  least 
in  certain  veins,  as  Remak  correctly  states,  that  it  contains  a  consider- 
able quantity  of  longitudinal  muscles.  These  are  very  distinct,  as  was 
pointed  out  by  Bernard  ("  Gaz.  Med.  de  Paris,"  1849,  17,  331),  in  the 


SPECIAL    HISTOLOGY. 

hepatic  portion  of  the  inferior  vena  cava,  where  their  fasciculi,  0*01— 
0-04  of  a  line  thick,  constitute  a  network  pervading  the  inner  half  or 
two  inner  thirds  of  the  external  membrane,  which,  where  the  t.  media  is 
absent,  rests  immediately  upon  the  t.  intima,  and  may  attain  a  thickness 
of  as  much  as  0*22  of  a  line.  Besides  this,  I  have  found,  as  Remak  has 
also  done,  these  contractile,  longitudinal  bundles  (which  never  contain 


connective  tissue,  though  probably  a  certain  number  of  elastic  fibres), 
still  very  well  developed,  in  the  trunks  of  the  hepatic  veins,  in  that  of 
the  vena  portce,  and  in  the  remaining  portion  of  the  inferior  vena  cava, 
and  have  traced  them  as  far  as  the  splenic,  superior  rnesenteric,  exter- 
nal iliac,  and  renal  veins.  Some  were  also  to  be  found  in  the  vena 
azygos,  whilst  they  were  altogether  absent  in  the  superior  veins.  These 
muscles  extended  through  the  entire  thickness  of  the  t.  adventitia,  only 
in  the  renal  vein  and  vena  portce,  whilst  in  the  other  veins  above  enume- 
rated, a  greater  or  less  portion  of  it,  contained  no  muscular  element, 
and  consisted  as  usual,  of  longitudinal  connective  tissue,  and  elastic 
networks  composed  of  strong  fibres.  The  muscular  layer  of  the  t.  ad- 
ventitia therefore  appears  to  be  a  special  membrane  of  the  vessels,  and 
occasion  would  be  afforded  to  confound  it  with  the  undeveloped,  or,  as 
has  been  stated,  even  absent  t.  media;  an  error,  however,  which  might 
be  readily  avoided  by  tracing  the  conditions  of  the  smaller  veins.  The 
muscular  layer  of  the  t.  adventitia,  besides  the  contractile  elements, 
having  a  length  of  0*02-0-04  of  a  line,  which  present  the  common  cha- 
racter, and  numerous  elastic  longitudinal  networks,  invariably  contains 
a  certain  amount  of  connective  tissue,  which,  as  it  seems,  is  always 
arranged  transversely,  so  that  the  transverse  elements,  even  in  these 
large  veins,  are  compensated  for  though  not  exactly,  by  muscle.  All 
the  large  veins,  which  open  into  the  heart,  are  furnished,  for  a  short 
distance,  with  an  external  annular  layer  of  muscles  similar  to  those  of 
the  heart  itself,  and  which  also  present  anastomoses  of  the  primitive 

FIG.  286. — Longitudinal  section  of  the  inferior  vena  cava,  in  the  liver,  magnified  30 
diameters:  cr,  t.  intima  •  6,  t.  media,  without  muscles,  containing  only  connective  tissue  and 
elastic  fibres ;  c,  inner  layer  of  the  t.  adventitia;  a,  its  longitudinal  muscles;  @,  transverse 
connective  tissue  of  the  same  layer  ;  d,  external  portion  of  the  t.  adventitia,  without  muscles. 


THE    BLOODVESSELS.  689 

fasciculi.  According  to  Rliuschel,  these  muscles,  in  the  region  of  the 
superior  vena  cava,  extend  as  far  as  to  the  subclavian  vein,  and  may  be 
found  also  in  the  main  branches  of  the  pulmonary  veins ;  and  even,  ac- 
cording to  Schrant,  in  the  former  case,  more  in  the  interior  of  the  wall 
of  the  vessels,  and  disposed  longitudinally. 

The  veins  in  which  the  muscular  element  is  excessively  developed  de- 
mand special  notice,  and  also  those  in  which  that  element  is  wholly 
wanting.  To  the  former  class  belong  the  veins  of  the  gravid  uterus,  in 
which  besides  the  t.  media,  the  tt.  intima  and  adventitia  also  present 
muscular  layers,  longitudinal  in  the  two  latter,  the  elements  of  which  in 
the  5th  and  6th  month  exhibit  the  same  colossal  development  as  those 
of  the  uterus  itself.  The  muscular  element  is  wanting  :  1,  in  the  veins 
of  the  maternal  portion  of  the  placenta,  in  whose  walls,  externally  to 
the  epithelium,  large  cells  and  fibres,  which  I  regard  as  undeveloped 
connective  tissue,  occur;  2,  in  most  of  the  veins  of  the  cerebral  sub- 
stance, and  of  the  pia,  mater.  These  veins  consist  of  a  roundish  epithe- 
lium in  a  single  layer,  a  thin  longitudinal  connective  layer,  with  solitary 
elongated  nuclei,  which  supplies  the  place  of  the  t.  media,  and.  in  the 
smaller  vessels  of  a  more  homogeneous,  and  in  the  larger,  of  a  fibrillated 
and  nucleated  t.  adventitia.  It  is  but  rarely  that  a  faint  indication  of 
muscles  in  the  t.  media  is  seen  in  the  largest  of  these  veins,  as  shown  in 
Fig.  279;  3,  in  the  sinuses  of  the  dura  mater  and  the  veins  of  Breschet 
in  the  bones,  which  are  furnished  with  a  layer  of  connective  tissue,  occa- 
sionally containing  fine  elastic  fibres,  external  to  a  tessellated  epithe- 
lium, and  which  layer  is  continuous  with  that  of  the  dura  mater  and  of 
the  interna].  periosteum.  4,  in  the  venous  sinuses  of  the  corpora  cavernosa 
(vid.  sup.],  and  of  the  spleen  of  certain  Mammalia  (vid.  §  169).  5,  in 
the  veins  of  the  retina. 

The  valves  of  the  veins  consist  chiefly  of  distinct  connective  tissue, 
which,  at  their  free  border,  runs  transversely,  containing  numerous 
elongated  nuclei,  and  also  isolated,  undulating,  usually  fine,  in  part 
strong,  elastic  fibres.  Their  surface  is  covered  either  with  nothing  but 
an  epithelium,  with  short  cells,  or  in  addition,  there  is  beneath  it,  a  very 
fine  elastic  network,  the  prevailing  direction  of  which  is  longitudinal. 
The  valves  may,  therefore,  be  regarded  as  continuations  of  the  middle 
and  internal  tunics,  although  muscular  fibres,  so  far  as  I  have  seen,  are 
wanting  in  them  (Wahlgren  states  that  he  has  found  such  fibres  in  the 
larger  valves). 

§  217.  Capillaries  (vasa  capillaria}. — With  the  solitary  exception  of 
the  corpora  cavernosa  of  the  sexual  organs,  and  of  the  uterine  placenta, 
the  arteries  and  veins,  in  Man,  are  universally  connected  by  the  inter- 
vention of  a  rich  plexus  of  microscopically  fine  vessels,  which,  on  account 
of  their  slender  dimensions,  have  been  designated  under  the  above  name. 

44 


690  SPECIAL    HISTOLOGY. 

They  are  everywhere  composed  of  a  single,  structureless  membrane, 
with  coil-nuclei,  and  are  thus  very  essentially  distinguished  from  the 
larger  vessels,  although  the  transition  from  the  one  to  the  other  is  wholly 
imperceptible ;  so  that  at  a  certain  point  in  the  course  of  the  vessels  it 
is  quite  impossible  to  detect  the  characters  of  either  of  the  classes  into 
which  Histology  has  been  accustomed  to  divide  them.  Vessels  of  this 
kind  may  be  best  described  as  venous  and  arterial  transitionary  vessels, 
according  as  they  lie  on  the  one  side  or  the  other,  and  without  any 
further  alteration  of  the  common  classification,  may  be  referred  to  the 
capillaries. 

The  true  capillaries,  when  more  closely  examined,  exhibit  the  follow- 
ing conditions:  Their  structureless  membrane  is  perfectly  clear  and 
transparent,  sometimes  delicate  and  presenting  a  simple  contour,  some- 
times thicker  (0-0008-0-001  of  a  line),  and  bordered  by  a  double  line.  In 
its  microscopical  reactions,  it  corresponds  entirely  with  older  cell  mem- 
branes and  the  sarcolemma  of  the  transversely  striped  muscles  (vid.  §  85), 
and  as  regards  its  other  properties,  it  is  perfectly  smooth  on  both 
aspects,  and  notwithstanding  its  tenuity,  tolerably  resistant  and  elastic, 
although  very  probably  not  contractile.  It  invariably  presents  a  certain 
number  of  elongated  cell-nuclei,  0-003-0-004  of  a  line  in  size,  which  are 
disposed  with  wide  interspaces,  usually  alternately  on  opposite  sides  of 
the  vessel,  sometimes  more  approximated,  or  in  close  contiguity,  though 
rarely  in  actual  contact ;  and,  when  the  capillary  tunic  is  thin,  are 
situated  on  its  inner  side,  when  thicker,  within  its  substance,  in  such  a 
way,  however,  as  not  unfrequently  to  cause  projections  of  it  on  the  outer 
surface.  The  diameter  of  the  capillaries,  in  Man,  varies  from  0-002  to 
0-006  of  a  line;  and,  for  the  sake  of  description,  they  may  be  again 
subdivided  into  finer,  of  0-002-0-003  of  a  line,  with  few  nuclei  and 
thinner  walls ;  and  coarser,  of  0-004-0-006  of  a  line,  with  a  thicker 
membrane  and  numerous  nuclei;  although  in  so  doing  it  is  not  intended 
to  draw  any  distinct  limitation  between  them. 

The  capillaries,  by  their  union,  constitute  the  capillary  plexuses, 
retia  capillaria,  which  have  already  been  described  in  detail,  in  speak- 
ing of  the  individual  organs  and  tissues,  and,  consequently,  here, 
will  be  referred  to  only  in  brief  and  general  terms.  The  forms  pre- 
sented in  these  plexuses,  which,  notwithstanding  considerable  diver- 
sities, are  constant  in  the  different  organs,  and  according  to  their  simi- 
larity or  diversity,  more  or  less  characteristic,  depend  to  some  ex- 
tent upon  the  disposition  of  the  elementary  parts,  and  are  also  in 
some  degree  dependent  upon  the  energy  of  the  functions.  With 
respect  to  the  former,  there  are  in  many  organs  certain  tissues,  into 
which  vessels  never  penetrate, — as  the  transversely  striped  muscu- 
lar fibres,  the  bundles  of  connective  tissue,  nerve-fibres,  cells  of  all 
kinds,  gland-vesicles,  and  which,  therefore,  according  to  their  form, 


THE    BLOODVESSELS. 


691 


Fisr.  287 


trace  out  definite  courses  for  the  capillaries,  so  that  they  sometimes 
present  elongated  meshes,  sometimes  rounded,  narrower  or  wider  reticu- 
lations. The  physiological  energy  is  still  more  influential,  and  it  is  a 
general  rule,  that  the  greater  the  activity  of  an  organ,  whether  as 
regards  contractions  or  sensations,  excretion  or  absorption,  so  much  the 
closer  is  the  capillary  network,  and 
so  much  the  more  abundant  the 
supply  of  blood.  The  capillary 
plexuses  are  closest  in  the  secernent 
and  absorbent  organs,  as  in  the 
glands,  above  all  in  the  lungs,  liver, 
and  kidneys ;  next  in  the  integu- 
ments and  mucous  membranes ;  much 
wider  in  the  organs  which  receive 
blood  only  for  the  purpose  of  their 
own  nutrition,  as  the  muscles,  nerves, 
organs  of  sense,  serous  membranes, 
tendons,  and  bones  ;  although  among 
these  organs  differences  exist,  as, 
for  instance,  the  muscles,  and  the 
gray  nerve-substance,  are  more  abun-  </ 
dantly  supplied  than  the  other  parts 
above  enumerated.  The  diameter 
of  the  capillaries  themselves  is  al- 
most directly  in  an  inverse  rela- 
tion, and  they  have  the  thinnest 
walls  and  are  smallest  (0-002-0-003 
of  a  line)  in  the  nerves,  muscles,  retina,  and  the  Peyerian  patches ;  in 
the  external  integument  and  mucous  membranes  they  attain  the  size  of 
0-003-0-005,  in  the  glands  and  bones,  lastly,  one  of  0-004-0-006  of 
a  line,  and  in  the  compact  substance  of  the  latter,  although  no 
longer  having,  in  all  respects,  the  structure  of  capillaries,  even  the 
diameter  of  0-008—0*01  of  a  line.  Physiology  is  not  as  yet  in  a  con- 
dition to  explain  these  differences  in  all  particulars,  inasmuch  as  infor- 
mation is  wanting  with  respect  to  the  laws  of  diffusion  in  the  various 
capillary  membranes ;  and  also  because  the  more  minute  conditions  of 
the  sanguineous  circulation,  in  the  separate  organs,  are  wholly  un- 
known. 

The  mode  in  which  the  capillaries  pass  into  the  larger  vessels  is  diffi- 
cult of  investigation.  On  the  arterial  side  it  is  found  that  the  capil- 

FIG.  287. — Finest  vessels  on  the  arterial  side  of  the  capillaries.  1,  an  artery  of  the 
smallest  size  ;  2,  transitional  vessel;  3,  coarser  capillary;  4,  finer  capillary  :  a,  structureless 
coat,  with  a  few  nuclei,  representing  the  t.  adventitia  ;  6,  nuclei  of  the  muscular  fibre-cells : 
c,  nuclei  within  the  minute  artery,  probably  still  belonging  to  an  epithelium;  d,  nuclei  of  the 
capillaries  and  transitional  vessels.  From  the  human  brain ;  magnified  300  diameters. 


692  SPECIAL    HISTOLOGY. 

•laries,  as  they  become  wider,  present  more  closely  placed  nuclei,  and 
are  then  invested  externally  with  a  structureless  t.  adventitia,  and  soli- 
tary muscle-cells,  whence,  when  they  have  reached  the  diameter  of 
O'OOT  of  a  line,  they  already  exhibit  the  aspect  of  the  finest  arteries 
(Fig.  287,  1).  Afterwards,  the  nuclei  seem  to  be  replaced  by  efrithe- 
lium  cells,  whilst  the  capillary  membrane  either  ceases,  or  is  continuous 
with  the  elastic  inner  membrane.  The  venous  transitionary  vessels  are 
less  characteristic  for  a  greater  length.  The  first  thing  that  is  super- 
added,  on  this  side,  to  the  capillary  membrane,  is  an  external,  homo- 
geneous, nucleated  layer,  which  may  be  regarded  as  a  sort  of  connec- 
tive tissue,  and  whilst  the  nuclei  of  the  capillary  vessels  become  more 
closely  approximated,  gradually  coalesces  with  their  membranes.  In 
vessels  of  O'Ol  of  a  line,  the  internal  nuclei  have  become  so  numerous, 
as  clearly  to  represent  the  epithelium,  and  as  at  this  time  also,  the 
external  layer  has  likewise  received  the  addition  of  a  nucleated  lamina 
— the  t.  adventitia — the  now7  distinctly  laminated  vessel  (Fig.  280)  may 
be  termed  a  vein.  It  wrould  consequently  appear  that  the  capillaries 
are  transformed  into  the  larger  vessels  by  the  addition  of  layers  on  the 
exterior  and  interior,  whilst  their  proper  membrane  coalesces  with  these 
layers,  and  is  probably  continuous  with  the  fibrous  layer  of  the  t. 

intima. 

i 

Besides  the  finest  capillaries,  which,  however,  always  admit  of  the 
passage  of  the  very  flexible  blood-corpuscles,  the  older  anatomists  have 
admitted  the  existence  of  still  finer  vessels — the  so-termed  vasa  serosa 
— which  no  longer  allow  of  the  passage  of  blood,  but  only  of  its  plasma, — 
a  notion  which  has  been  abandoned  by  most  modern  authors.  Hyrtl 
alone  thinks,  that  it  is  necessary  to  admit  of  the  existence  of  vessels  of 
this  kind  in  the  cornea,  because  the  vessels  at  its  border  escape  the  sight 
without  passing  into  veins,  and  are  too  small  (in  Man,  when  injected, 
0-0009  of  a  line)  to  be  capable  of  conveying  blood-corpuscles.  He  thinks, 
that  still  further  on  they  are  continued  into  vasa  serosa,  and  probably 
are  connected  with  the,  as  yet  undemonstrated,  lymphatics.  In  oppo- 
sition to  this,  Brucke  and  Gerlach  remark,  that  the  corneal  vessels  ter- 
minate in  true  loops,  and  that  it  would  thence  appear  that  Hyrtl's  state- 
ments are  based  upon  incomplete  injections.  I  am  able,  however,  to 
state  that  something  corresponding  with  the  vasa  serosa  of  authors  does 
actually  exist  in  the  cornea,  having  noticed  that,  in  the  Dog,  fine  and 
the  finest  filaments  are  continued  still  further  inwards,  from  the  terminal 
loops  previous  to  the  blood-corpuscles,  which  occur  in  that  animal,  as  in 
all  others,  at  the  margin  of  the  cornea;  which  filamentary  prolongations 
were  connected  in  a  reticular  manner,  and  were  usually  slightly  dilated 
at  the  points  of  junction.  Whether  these  filaments  were  hollow,  and 
had  any  contents,  and  directly  communicated  with  the  canals  of  the  true 


THE    LYMPHATICS. 


693 


capillaries,  could  not  be  determined,  and  I  should  not,  therefore,  at  pre- 
sent definitely  declare  them  to  be  pervious  parts  of  the  vascular  system ; 
whilst  I  have  not  the  least  hesitation,  nevertheless,  in  referring  them  to 
that  system,  for  although  they  may  have  no  canal,  they  scarcely  admit 
of  any  other  possible  interpretation,  than  as  being  derived  from  the  vas- 
cular plexus,  which  covers  almost  the  entire  cornea  in  the  child  at  birth, 
and  as  being  obliterated  capillaries.  Should  these  corneal  elements  not 
turn  out  to  be  vasa  serosa,  I  am  acquainted,  in  the  adult,  with  no  situa- 
tion in  which  such  vessels  exist,  whilst  vessels  conveying  plasma  are 
everywhere  present  during  the  development  of  the  capillaries,  as  a  pre- 
liminary phenomenon  (vid.  infra),  and  it  is  therefore  intelligible  that, 
even  at  a  subsequent  period,  scattered  vessels  of  the  kind  should  occa- 
sionally be  met  with,  as  in  the  brain  of  the  Calf,  according  to  Henle ; 
or  may  perhaps  exist  in  great  quantity,  just  as  in  the  distribution  of  the 
nerves,  the  terminations  often  retain  the  embryonic  character. 

3.— OF  THE  LYMPHATICS. 

§  218.  The  lymphatics,  except  in  their  contents,  correspond  so  closely 
with  the  veins,  that  a  short  exposition  of  their  structure  will  suffice. 

Fig.  288. 


FIG.  288. — Capillary  lymphatic  from  the  tail  of  the  Tadpole,  magnified  350  diameters:  a, 
membrane;  6,  processes  formed  by  it;  c,  remains  of  the  contents  of  the  cells  forming  these 
vessels,  in  which  nuclei  are  concealed;  e,  ca?cal  terminations  of  the  vessels;  /,  one  of  these 
terminations,  still  pretty  distinctly  recognizable  as  a  formative  cell ;  g,  isolated  formative  cells 
about  to  join  with  the  actual  vessels. 


694  SPECIAL    HISTOLOGY. 

The  capillary  lymphatics,  which,  in  the  three  situations  in  which  they 
have  hitherto  been  seen  with  certainty — in  the  small  intestine,  the  tail 
of  the  Tadpole,  and  the  mucous  membrane  of  the  trachea — commence 
partly  with  free  prolongations,  in  part  in  networks.  I  have,  in  a  single 
instance  in  the  tracheal  mucous  membrane  in  Man,  had  an  opportunity 
of  investigation,  and  they  were  found  to  consist  of  a  delicate  structure- 
less wall,  without  distinct  nuclei  after  the  addition  of  soda,  and  having  a 
diameter  of  0-003-0-005-0-01  of  a  line  (Fig.  235).  The  same  structure  is 
presented  in  the  simple  lacteals  of  the  intestinal  villi  in  Mammalia,  ex- 
cept that  these  measure  0-012-0-026  of  a  line,  and  have  a  somewhat 
thicker  wall.  The  lymphatics  discovered  by  me  in  the  tail  of  the  Tad- 
pole (Fig.  288),  on  the  contrary,  correspond  entirely  with  the  blood-capil- 
laries, in  the  occurrence  of  nuclei  on  the  inner  side  of  the  very  delicate, 
structureless  membrane,  whilst  they  differ  from  them  in  being  furnished 
with  short,  jagged  processes  with  prolongations.  The  diameter  of  the 
lymphatic  capillaries  in  this  situation  is  0-002-0-015  of  a  line,  and  the 
two  main  trunks  of  the  tail,  like  those  of  the  blood-vascular  system  itself, 
have  a  perfect  capillary  structure. 

In  what  way  these  capillary  lymphatics  are  changed  into  the  larger 
lymphatic  canals  has  not  been  seen  by  any  one,  or  at  all  events  has  not 
been  investigated.  The  finest  vessels,  which  have  elsewhere  come  under 
my  observation,  had  a  diameter  of  JQ-\-^  of  a  line,  and  these,  except 
in  the  thickness  of  the  individual  layers,  corresponded  in  all  respects 
with  the  larger  vessels  of  1-1J  lines.  The  latter,  the  medium-sized 
lymphatics,  present  three  tunics.  The  t.  intima  consists  of  an  epithe- 
lium, of  elongated,  although  rather  short  cells,  and  of  a  single,  rarely 
double  elastic  reticulated  membrane,  longitudinally  fibrillated,  which, 
as  regards  the  thickness  of  its  fibres,  and  the  narrowness  of  the  meshes, 
exhibits  manifold  diversities ;  but  it  never  has  thick  fibres,  nor  does  it 
ever  constitute  a  true  elastic  membrane  (according  to  Weyrich,  this 
membrane  is  wanting  in  the  lymphatics  of  the  mesentery,  whilst  I  have 
always  found  it  in  those  of  the  lumbar  plexus,  and  in  those  of  the  ex- 
tremities). This  is  succeeded  by  a  stronger,  t.  media,  composed  of 
transverse  smooth  muscles,  with  fine,  also  transverse  elastic  fibres  ;  and 
lastly,  there  is  a  t.  adventitia,  with  longitudinal  smooth-muscular  fasci- 
culi. The  latter  I  have  found,  in  the  extremities,  upon  vessels  of  not 
more  than  l-10th  of  a  line,  and  I  consider  them  a  good  distinctive  cha- 
racter between  lymphatics  and  small  veins  (vid.  "  Mikrosk.  Anat.,"  II. 
p.  236). 

The  thoracic  duct  differs  in  some  respects  from  the  smaller  lympha- 
tics. The  similarly  constituted  epithelium  is  succeeded  by  some  striped 
lamellcc,  and  these  by  an  elastic  reticular  membrane,  longitudinally 
fibrillated,  although  the  entire  t.  intima  scarcely  measures  0-006-0-01 
of  a  line.  The  t.  media,  0-025  of  a  line  thick,  commences  with  an 


THE    LYMPHATICS.  695 

extremely  thin  layer  of  longitudinal  connective  tissue,  with  fine  elastic 
fibres,  and  consists,  besides,  of  a  transverse  muscular  layer,  with 
fine  elastic  fibres.  The  t.  adventitia  lastly,  contains  Fig  289 

longitudinal  connective  tissue,  together  with  elastic 
fibrils,  and  a  few  reticularly  connected  bundles  of  lon- 
gitudinal muscles.  The  valves  of  this  duct,  and  of 
the  lymphatics  in  general,  correspond  completely  with 
those  of  the  veins. 

The  bloodvessels  of  the  lymphatics  present  the  same 
conditions  in  the  thoracic  duct  as  in  the  veins.     No  nerves  have  been 
found  in  them. 

§  219.  Lymphatic  glands. — These  glands  (glandular  lympliaticce)  differ 
very  considerably  from  the  rest  of  the  blood-vascular  glands  with  which 
they  are  usually  classed,  and  approach  nearest  to  the  Peyerian  patches 
of  the  intestine,  although  they  do  not  wholly  correspond  with  them. 
Every  normal  lymphatic  gland,  within  a  thin  but  tough  sheath,  com- 
posed of  nucleated  connective  tissue  and  fine  elastic  fibrils,  presents  a 
soft,  whitish-red  parenchyma,  in  which  three  elements,  viz.  a  fibrous 
tissue,  a  soft,  pultaceous  pulp,  and  bloodvessels,  are  manifest.  The 
fibrous  tissue,  formed  partly  of  fibrous,  and  in  part  of  more  homoge- 
neous connective  tissue,  with  scattered  fine  elastic  fibres,  when  the 
gland  is  well  developed,  as  is  not  always  the  case  in  Man,  but  almost 
invariably  in  the  Cat,  Dog,  Rabbit,  Rat,  &c.,  presents  a  large  number 
of  thin  (0-004-0-005  of  a  line  and  more)  lamella?  arising  from  the 
sheath,  which  are  so  regularly  connected  together  as  to  constitute  an 
elegant  areolated  structure  pervading  the  entire  gland,  all  of  whose 
roundish  spaces,  J— J-  of  a  line  wide,  openly  communicate,  it  is  true, 
with  each  other,  but  much  less  freely  than  is  the  case  with  the  cells  of 
the  corpora  cavernosa,  for  instance.  Now,  since  all  these  spaces  are 
occupied  by  the  grayish-white  pulp,  the  entire  gland  exhibits  externally, 
and,  in  some  degree,  also  in  a  transverse  section,  a  coarsely  granular, 
vesicular  aspect,  which  was  known  even  to  the  older  anatomists,  almost 
like  that  of  the  Peyerian  patches,  since  there  may  be  distinguished  in 
it  a  great  number  of  clear  round  bodies,  like  follicles,  surrounded  by 
narrow,  somewhat  darker  borders.  But  upon  proceeding  to  isolate 
these  bodies  we  shall  fail  in  the  attempt,  arid  the  septa  by  which  they 
are  parted  will  be  found  to  be  always  common  to  several,  something 
like  the  walls  of  the  alveoli  in  the  adult  lung.  Consequently,  notwith- 
standing the  similarity  in  outward  appearance,  and  as  we  shall  find,  in 
contents  also,  there  is  a  very  essential  difference  between  the  follicles  of 

FIG.  289. — Transverse  section  of  the  thoracic  duct  in  Man,  magnified  30  diameters : 
a,  epithelium,  striped  lamella,  and  elastic  inner  membrane ;  6,  longitudinal  connective  tissue 
of  the  t.  media;  c,  transverse  muscles  of  the  same  tunic;  rf,  t.  adventitia,  with  e,  the  longitu- 
dinal muscles. 


696  SPECIAL    IIISTOLOGY. 

the  Peyerian  patches,  as  well  as  of  the  spleen,  and  of  the  tonsils,  and 
the  alveolar  spaces  in  the  lymphatic  glands,  on  which  account  I  shall 
describe  the  latter  as  "alveoli." 

The  grayish-white  alkaline  pulp  which  fills  the  spaces  in  question, 
agrees  in  nearly  all  respects  with  that  contained  in  the  Peyerian  folli- 
cles, and  consists  of  a  certain  proportion  of  fluid,  and  of  very  many 
morphological  elements.  The  latter  are,  in  part  free  nuclei,  of  0-002- 
0-003  of  a  line,  usually  without  distinct  nucleoli,  with  homogeneous 
contents,  which  are  nevertheless  rendered  turbid  by  water ;  in  part 
true,  pale,  uninuclear,  round  cells,  most  of  which  measure  from  0-003- 
0*004  of  a  line,  with  nuclei  similar  to  those  found  in  the  free  condition, 
a  certain  number  of  larger  size  (0-005-0-007  of  a  line)  with  larger, 
often  distinctly  vesicular  nuclei  and  nucleoli,  and  occasionally  a  few  fat 
granules.  These  morphological  elements  also,  to  some  extent,  corre- 
spond entirely  with  the  cells  of  the  lymph  and  chyle;  a  circumstance  in 
itself  of  no  great  significance,  since  no  specific  character  can  be  as- 
signed to  either  of  them.  The  similarity  of  the  contents  of  the  alveoli  of 
the  lymphatic  glands,  with  those  of  the  follicles  of  the  Peyerian  patches, 
is  still  further  increased  by  the  circumstance,  that  they  are  also 
penetrated  by  a  fine  vascular  network,  as  I  at  least  have  observed,  and 
have  already  stated  in  another  place  ("Mikr.  Anat.,"  II.  2,  p.  192).  For 
the  numerous  bloodvessels  of  the  lymphatic  glands,  which  frequently 
penetrate  into  the  interior  at  a  depressed  hilus-Yike  spot,  are  not  dis- 
tributed merely  in  the  septa  of  connective  tissue,  as  has  hitherto  been 
generally  asserted,  but,  as  I  have  seen  in  Man,  also  enter  the  pulp  fitting 
the  alveoli,  where  they  run  freely  among  the  elements,  and  form  a  very 
fine  capillary  plexus,  bearing  the  closest  resemblance  to  that  of  the 
Peyerian  follicles,  except  that  in  general  it  is  rather  wider,  and  fre- 
quently also  varicose. 

The  most  difficult  part  of  the  anatomy  of  these  glands  is  the  ascer- 
taining of  their  connection  with  the  lymphatic  vessels.  After  the  ma- 
jority of  the  most  recent  authors  had  agreed  in  the  assumption,  that 
the  vasa  inferentia  and  efferentia  were  connected  by  numerous  anasto- 
moses of  convoluted  and  looped  vessels,  the  proper  parenchyma  of  the 
glands  being  thus  frequently  left  in  the  background  or  altogether  for- 
gotten, the  number  of  those  has  latterly  been  much  increased,  who 
advocate  the  view  originally  propounded  by  Malpighi,  viz.  that  the  lym- 
phatic glands  consist  of  an  aggregation  of  anastomosing  cells,  into 
which  the  vasa  afferentia  open,  and  from  which  the  vasa  efferentia  pro- 
ceed ;  and,  in  particular,  Ludwig  and  Noll  have  declared  themselves 
most  decidedly  in  favor  of  this  view.  As  for  myself,  it  will  be  appa- 
rent from  the  preceding  account,  that  I  am  one  of  those  who  admit  of 
the  existence  ofc  a  special  glandular  element  in  the  lymphatic  glands, 
and  I  consequently  deny,  in  the  most  explicit  terms,  that  they  are  com- 


THE    LYMPHATICS.  697 

posed  merely  of  a  plexus  of  lymphatic  vessels.  As  regards  the  relation 
of  the  lymphatics  to  the  glandular  part  or  alveoli,  together  with  their 
contents,  I  formerly  felt  compelled  to  express  myself  in  opposition  to 
the  notion  propounded  by  Ludwig  and  Noll,  although  without  having 
entered  deeply  into  the  subject,  principally  because,  whilst  it  seemed  to 
me  improbable,  that  the  alveoli  of  the  glands  in  question  should  contain 
bloodvessels,  and  at  the  same  time  communicate  with  the  lymphatics ; 
and,  in  the  second  place,  because  in  cases  where  the  vasa  afferentia  and 
efferentia  were  full  of  milk-white  chyle,  I  was  never  able  to  perceive 
similarly  colored  contents  in  the  alveoli.  These  facts,  indeed,  still  retain 
all  their  weight  with  me  ;  but  they  are  now  more  than  outweighed  by 
further  experience,  so  that  it  appears  very  doubtful  whether  they  justify 
the  conclusions  which  I  formerly  thought  might  be  deduced  from  them. 
For  I  find,  like  Ludwig,  in  a  considerable  number  of  injections  in  the 
human  subject,  Dog  (cervical  glands),  and  Ox  (lumbar  glands),  that  it 
is  impossible  to  fill  lymphatic  vessels  in  the  interior  of  the  glands,  and 
that  the  injection  either  colors  only  the  ramifications  of  the  vasa  infe- 
rentia  upon  the  gland,  or  when  it  runs  further,  as  it  may  be  more  easily 
made  to  do  in  animals  than  in  Man,  it  enters  the  alveoli,  which  it  fills 
according  to  their  position  in  the  series,  and  escapes  through  the  vasa 
efferentia.  Induced  by  the  result  of  these  experiments,  I  should  now, 
without  being  desirous  of  giving  a  definitive  opinion,  be  inclined  to  side 
with  Ludwig,  and  to  deny  the  existence  of  any  direct  connection  between 
the  afferent  and  efferent  lymphatics,  or  rather  to  view  the  alveoli  of  the 
glands  as  a  specially  modified  part  of  them.*  In  accordance  with  this 
notion,  the  lymph  would  be  poured  out  into  the  alveoli,  and  flow  through 
them  in  fine  divided  streams  among  the  elements  of  which  their  con- 
tents are  composed  ;  and,  to  this  circumstance,  it  is  probably  owing  that 
it  never  -has  a  milk-white  color.  In  this  process  it  is  possible  that  some 
of  the  cells  of  these  contents,  which  so  closely  resemble  the  lymph- 
corpuscles,  may  be  detached  and  become  disintegrated,  whence  the 
chyle  of  the  vasa  efferentia  abounds  more  in  morphological  elements, 
than  the  fluid  conveyed  by  the  vasa  efferentia.  At  the  same  time,  I  am 
decidedly  opposed  to  the  view  which  would  regard  the  morphological 
contents  of  the  alveoli  as  directly  appertaining  to  the  lymph,  as  lymph- 
cells — which  are  there  formed,  and  subsequently  conveyed  away  from 
the  gland.  I  consider  them  rather  as  an  independent,  stationary, 
glandular  element,  standing,  indeed,  in  the  closest  relation  with  the 
chyle,  but  not  necessarily  forming  a  part  of  it,  or  passing  into  the 

*  [In  a  paper  since  published,  Prof.  Kolliker  states,  that  he  is  now  entirely  satisfied 
of  the  correctness  of  the  views  of  Ludwig  and  Noll.  He  considers,  however,  that 
the  lymphatics  regain  their  coats  in  the  medullary  substance,  where  they  form  a  minute 
plexus,  from  which  the  vasa  efferentia  proceed  (Vid.  Kolliker,  "  Ueber  den  feineren  Bau  u. 
die  Functionen  der  Lymphdrusen,"  in  "  Verhand.  d.  Phys.  Med.  Ges.,"  in  Wurzb.  IV.  2,  1854.) 
— DaC.] 


698  SPECIAL    HISTOLOGY. 

blood.  If  we  ascribe  to  the  alveoli  of  the  lymphatic  glands  the  function 
of  inducing  a  metamorphosis  and  changes  in  the  lymphatic  fluid  flowing 
through  them,  under  the  influence  of  the  cells  of  its  pulp,  which  are 
manifestly  in  a  continual  process  of  development,  of  such  a  kind  pro- 
bably, that  its  elements  are  rendered  more  capable  of  development,  or 
new  matters,  such  as  fibrin,  are  mixed  with  it,  the  reason  is  at  once 
evident,  why  the  lymphatic  fluid  should  form  more  cells  after  its  pas- 
sage through  the  glands  than  previously.  The  well-known  cases  also 
of  "white  blood,"  in  which,  together  with  an  enormous  increase  in  size 
of  the  lymphatic  glands,  a  vast  multiplication  of  the  colorless  blood- 
cells  takes  place  (Virchow),  may  be  explained  in  accordance  with  the 
above  view ;  although,  for  the  present,  I  am  not  disinclined  to  assume, 
that  although  no  constant  and  total  passage  of  the  pulp  of  the  lym- 
phatic glands  into  the  lymph  takes  place,  which  from  the  anatomical 
conditions  is  utterly  impossible  (considering  the  bloodvessels  in  the 
alveoli),  nevertheless  a  sort  of  commixture  of  it  from  the  alveoli  con- 
tiguous to  the  vasa  efferentia  occurs,  so  that  the  lymphatic  glands,  after 
all,  at  least  to  some  extent,  appear  to  afford  a  site  for  the  formation  of 
lymph-corpuscles. 

The  lymphatics  of  the  lymphatic  glands  retain  all  their  tunics  up  to 
the  gland.  But  as  they  ramify  in  an  arborescent  manner  on  the  gland 
and  become  smaller,  they  lose  the  muscular  membrane,  and  enter  the 
alveoli,  possessing  only  a  layer  of  connective  tissue  with  fine  elastic 
fibres,  and  an  epithelium.  The  glands,  at  all  events  the  larger  ones, 
always  have  some  delicate  nervous  filaments  composed  of  fine  fibres, 
which  enter  in  company  with  the  bloodvessels,  and  are  lost  to  sight  in 
the  interior.  The  ganglia  in  the  lymphatic  glands,  mentioned  by 
Schaifner  ("  Zeitsch.  f.  rat.  Med.,"  VII.  177),  I  have  not  been  able  to 
find,  nor  is  that  author's  description  of  the  kind  to  command  much 
confidence. 

The  above-described  structure  of  the  lymphatic  glands  does  not  apply 
to  all  cases.  In  Man,  and  in  other  animals,  there  are  small  and  smallest 
glands,  of  3-2-1,  or  even  J-  a  line,  in  which  the  interior  does  not  dis- 
tinctly exhibit  the  alveolar  structure,  appearing,  on  the  contrary,  to 
be  more  continuous  throughout,  and  homogeneous,  notwithstanding  a 
good  many  traces  of  fibrous  structure,  which  always  exist  in  them.  In 
the  larger  glands  also,  especially  in  certain  animals,  a  similar  condition 
of  the  contents  is  not  urifrequently  presented,  which  of  course  does  not 
materially  affect  the  above  exposition  of  the  structure  of  the  lymphatic 
glands,  since,  in  such  cases,  we  simply  see  a  less  developed  condition 
of  the  septa,  and  a  more  intimate  union  of  the  individual  parts  of  the 
pulp. 

0.  Heyfelder  has  lately  described  (1.  c.),  in  the  lymphatic-glands  of 


THE    BLOOD    AND     THE    LYMPH.  699 

the  Mouse,  the  Rat,  and,  to  some  extent,  of  the  Rabbit,  a  complete 
muscular  layer.  In  the  Bat  also,  the  Dog,  Sheep,  Ox,  Goose,  and 
Fowl,  smooth  muscles  are  said  to  occur  sparingly,  and  to  be  fewest  in 
Man.  Heyfelder  also  says  that  they  pass  into  the  internal  .septa,  and 
that  in  the  Rabbit  he  has  noticed  contractions  of  the  glands  upon 
electrical  excitement,  an  experiment  which  has  not  yet  succeeded 
with  me. 

The  lymphatic  glands  are  subject  to  numerous  degenerations.  The 
most  frequent  are  extravasations  of  blood  in  the  alveoli,  and  in  conse- 
quence of  these  effusions,  depositions  of  pigmentary  matter,  which  may 
proceed  to  such  an  extent  as  to  render  the  glands  brownish-red,  or  even 
black  (bronchial  glands) ;  we  also  find  thickenings  of  the  sheath,  and 
of  the  internal  septa  ;  fatty  deposits  in  the  bloodvessels  ;  hypertrophies, 
with  a  uniform  increase  of  all  their  parts  ;  tuberculosis  and  cancer.* 

4.— OF  THE  BLOOD  AND  THE  LYMPH. 

§  220.  Every  part  of  the  vascular  system  contains  in  its  interior  a  special 
liquid,  consisting  of  a  fluid  and  numerous  morphological  particles,  and 
which,  according  to  its  color,  its  occurrence  in  one  or  other  division  of 
the  system,  and  its  other  properties,  is  distinguishable  on  the  one  side 
into  white  and  red  blood,  and  lymph  or  chyle  ;  and  on  the  other,  into 
blood  in  the  more  strict  sense  of  the  term.  Histology  is  concerned  only 
with  the  description  of  the  morphological  elements  existing  in  these 

*  [Professor  Brttcke,  in  a  valuable  communication  read  before  the  Vienna  Academy, 
March  31,  1853  ("  Ueber'die  Cbylus-gefasse  und  die  Fortbewegung  der  Chylus"),  confirms 
the  account  given  by  Ludwig  and  Noll  of  the  structure  of  the  lymphatic  glands,  and  states 
that  the  vasa  inferentia  break  up  into  the  porous,  glandular  tissue,  out  of  which  the  vasa 
efferentia  arise  anew.  In  the  glands  themselves,  a  distinction  must  be  drawn  between  the 
cortical  substance,  composed  of  round  or  ovate  bodies,  like  the  separate  glandular  bodies  of 
Peyer's  patches,  and  the  medullary  substance.  The  framework  of  the  latter  is  formed  by  the 
large  bloodvessels,  with  their  tunica  adventitia.  One  portion  of  their  branches  divides  into 
capillaries  in  the  medullary  substance,  the  rest  enter  the  cortical  substance.  The  accom- 
panying connective  tissue  becomes  looser,  the  finer  the  branches.  The  fully  developed 
connective  fibres  disappear  more  and  more,  and  in  their  place  cytoblasts  appear,  with  closely 
investing^cell-membranes,  which  run  out  into  two  or  three  pointed,  sometimes  flat,  usually 
filiform  processes,  fitted  together  into  a  soft  tissue,  in  which  the  capillaries  of  the  medullary 
substance  lie.  Round  cells  in  different  stages  of  development  follow  them,  resembling  the 
lymph-corpuscles,  and  forming  the  immediate  limit  of  the  fine,  irregular,  frequently  anasto- 
mosing canals,  which  render  the  medullary  substance  as  porous  as  a  sponge.  The  whole 
gland  is  enclosed  in  a  membrane,  which,  as  Heyfelder  observed,  is  composed  of  connective 
tissue  and  smooth  fibre-cells,  and  sends  sheaths  in  towards  the  medullary  substance,  whereby 
imperfect  compartments  are  formed,  in  which  the  glandular  elements  lie.  The  chyle  of  the 
vasa  inferentia  traverses  the  glandular  elements,  enters  the  pores  of  the  medullary  substance, 
and  passes  thence  on  the  opposite  side,  between  the  glandular  elements  to  the  vasa  inferentia. 
"  I  have  never,"  (says  Briicke)  "observed  the  fat-drops  of  the  chyle  enter  into  the  interior  of 
the  glandular  elements,  which  appear  to  be  merely  bathed  with  the  fluid  part  of  it.  On  the 
other  hand,  the  cells  which  are  formed  in  the  glandular  elements  pass  as  lymph-corpuscles 
into  the  chyle." — TRS.] 


700  SPECIAL    HISTOLOGY. 

fluids,  among  which  the  blood-  and  lymph-corpuscles  are  by  far  the 
most  important,  leaving  the  description  of  their  other  conditions  to  phy- 
siology. 

§  221.  The  lympli  and  the  chyle,  like  the  blood,  consist  of  &  plasma, 
which  coagulates  out  of  the  vessels;  and  of  morphological  elements,  in- 
cluding elementary  granules,  nuclei,  colorless  cells,  and  red  blood-corpus- 
cles, which,  however,  are  not  found  in  all  parts  of  this  vascular  system, 
nor  everywhere  in  equal  quantity.  The  elementary  granules  are  im- 
measurably minute  granules,  which,  as  has  been  shown  by  H.  Miiller, 
consist  of  fat  and  a  protein-envelop,  and  are  contained  in  vast  numbers 
in  milky  chyle,  whose  color  is  owing  to  them  alone,  whilst,  in  the  more 
colorless  lymph  they  are  either  wholly  wanting,  or  are  rare  and  scat- 
tered. Free  nuclei,  0*001— 0*002  of  a  line  in  size,  and  of  a  more  homo- 
geneous aspect,  becoming  vesicular  and  granular  on  the  addition  of  water, 

I  have  hitherto  noticed  only  in  the  commence- 
ments of  the  lacteals  in  the  mesentery,  and  in 
the  vasa  efferentia  of  the  mesenteric  glands, 
though  even  there  scantily,  and  never  in  the 
thoracic  duct ;  whilst  the  colorless  cells,  which 
are  identical  in  the  chyle  and  in  the  lymph — 
the  chyle-  or  lymph-corpuscles  of  authors — 
are  found  almost  everywhere  in  the  lymphatic 
vascular  system  in  considerable  quantity. 
These  are  rounded,  pale  cells,  0-0025-0-0055  of  a  line  in  diameter, 
which,  when  examined  in  their  native  fluid,  appear  homogeneous  or 
finely  granular,  and  contain  a  usually  indistinctly  transparent,  homo- 
geneous, slightly  glistening,  round  nucleus;  but  on  the  addition  of 
water,  the  nucleus  and  contents  are  rendered  turbid  by  a  granular  de- 
posit, a.nd  on  that  of  acetic  acid,  becomes  transparent  and  pale,  exhibit- 
ing the  strongly  granulated  contracted  nuclei  with  extreme  distinctness, 
bursting  at  the  same  time,  and  allowing  the  contents  to  escape  ;  a  change 
that  also  frequently  takes  place,  especially  in  the  smaller  cells,  on  the 
addition  of  water,  preceded  by  the  appearance  of  clear  albuminous  drops. 
Otherwise  dilute  solutions,  when  the  lymph-cells  are  already  spherical, 
induce  no  very  remarkable  changes  of  form,  whilst,  in  consequence  of 
the  evaporation  of  the  fluid,  and  by  concentrated  liquids,  a  considerable 
contraction,  and  frequently  also,  a  jagged  outline,  is  caused  in  them 
(Fig.  290  a). 

In  size,  quantity,  and  shape,  the  lymph-corpuscles  present  diversities, 
according  to  situation.  In  the  commencement  of  the  lacteals,  which 

FIG.  290. — Elements  of  the  chyle:  a,  lymph-corpuscles  become  stellate  by  the  escape  of 
their  contents  ;  b,  free  nuclei ;  c,  one  such,  surrounded  by  a  few  granules ;  d,  e,  minute  lymph- 
cells,  some  with  a  distinct  nucleus  ;  /,  g,  larger  cells,  one  with  a  visible  nucleus;  h,  one  such, 
after  the  addition  of  a  little  water ;  i,  with  the  addition  of  acetic  acid. 


THE    BLOOD     AND     THE    LYMPH.  701 

are  eminently  adapted  for  such  investigations,  in  the  mesentery,  and 
before  it  reaches  the  lymphatic  glands,  the  chyle  contains  but  few,  and 
in  the  smallest  mesenteric  vessels  -which  allow  of  being  examined,  fre- 
quently even  no  chyle-corpuscles  at  all.  Where  they  do  exist,  which 
is  always  the  case  in  the  larger  trunks,  they  usually  appear  small 
(0-002-0-003  of  a  line),  closely  investing  the  minute  nucleus,  and  often 
even,  as  it  were,  in  process  of  formation  by  the  apposition  of  granules. 
As  the  chyle  traverses  the  mesenteric  glands,  the  cells  become  more 
and  more  numerous  and  larger,  so  that  in  the  lacteals  at  the  root  of 
the  mesentery  (and  also  in  the  larger  lymphatic  trunks),  together  with 
the  small  cells  which  are  still  present,  we  find  numerous  larger  ones,  up 
to  0-0055  of  a  line  in  size.  At  the  same  time,  at  any  rate  in  the  Dog, 
Cat,  and  Rabbit,  a  multiplication  of  the  lymph-corpuscles  by  division 
takes  place  more  or  less  actively ;  in  this  process  the  larger  cells  elon- 
gate till  they  attain  a  length  of  0-006-0-008  of  a  line,  and  when  the 
nucleus  has  divided,  are  separated  into  two  by  a  median,  circular  con- 
striction. This  proceeding  does  not  usually  occur  at  all  in  the  thoracic 
duct,  and  consequently  the  larger  cell-forms,  of  0*004-0-0055  of  a  line 
are  here  rare.  In  Animals,  at  all  events,  the  majority  of  the  cells  in 
this  situation  are  larger  than  the  blood-corpuscles,  that  is  to  say,  they 
are  0-0025-0-0035  of  a  line,  whilst  in  Man,  at  least  as  observed  by 
Virchow  and  myself  in  an  executed  criminal,  they  were  invariably 
smaller  (from  0*002  of  a  line  on  the  average).  The  nuclei  of  these 
lymph-corpuscles,  which  are  imperceptible  without  the  addition  of  acetic 
acid,  were  for  the  most  part  single  and  round,  occasionally,  also,  horse- 
shoe shaped,  or  constricted  in  t.he  middle,  very  rarely  truly  multiple. 
In  other  Mammalia,  cells  having  nuclei  disintegrated  by  acetic  acid,  or 
naturally  constricted  and  multiple  (3-5  fold)  are  very  rare,  omitting 
those  in  process  of  division ;  although  occasionally  such  occur  even  in 
considerable  quantity. 

Red  blood-corpuscles  I  have  not  as  yet  noticed  in  the  human  chyle, 
when  it  has  been  carefully  taken,  and  under  normal  conditions ;  whilst 
in  animals  these  corpuscles  almost  always  occur  in  the  thoracic  duct  in 
small  quantity,  and  also  frequently  in  the  lymph  of  certain  organs,  as 
of  the  spleen.  As  they  do  not  exhibit  the  slightest  trace  of  a  develop- 
ment within  the  lymphatics,  I  regard  them  as  elements  escaped  from 
the  bloodvessels,  and  indeed,  am  of  opinion,  so.  long  as  direct  connec- 
tions between  the  two  sets  of  vessels  in  the  peripheral  parts  are  not 
shown  to  exist,  that  this  passage  is  an  accidental  occurrence,  from  the 
rupture  of  finer  vessels,  which,  owing  to  the  peculiar  structure  of  cer- 
tain organs,  as  the  spleen  and  lymphatic  glands,  may  be  very  readily 
conceived ;  and,  indeed,  as  I  have  shown  in  the  Tadpole,  may  be 
directly  observed.  I  would,  however,  remark,  that  I  have  not  unfre- 
quently  met  with  brown,  round  granule  cells,  0-004-0-005  of  a  line  in 


702  SPECIAL    HISTOLOGY. 

diameter,  completely  corresponding  with  those  mentioned   as  found  in 
the  blood,  and  which  are  probably  derived  from  the  lymphatic  glands. 

From  the  above  facts,  it  would  seem  not  to  admit  of  doubt  that  the 
lymph-corpuscles  are  formed,  like  cells,  by  the  development  of  mem- 
branes around  free  nuclei,  a  process  which  is  effected,  in  the  first  place, 
in  the  commencements  of  the  lymphatic  vessels,  but  also,  and  chiefly, 
in  the  vasa  efferentia  of  the  lymphatic  glands.  To  this  is  superadded 
the  multiplication  of  cells  by  division,  which  does  not  always  take  place. 
The  total  quantity  of  the  corpuscles,  contained  in  the  lymph,  compared 
with  that  of  the  blood-corpuscles,  is  very  inconsiderable,  not  only  in 
the  middle-sized  and  smaller  trunks  especially,  of  the  lymphatics,  but 
even  in  the  thoracic  duct  itself  is  very  far  from  being  in  an  equal  pro- 
portion ;  and  even  there  all  the  elements  of  the  fluid  may  readily  be 
perceived,  without  any  dilution.  More  precise  enumerations  have  not 
yet  been  instituted,  and  it  can  only  be  added  that  considerable  diversi- 
ties exist,  and  that  a  milk-white  chyle  is  not  always  also  rich  in  cor- 
puscles.* 

*  [Professor  Kclliker  appears  not  to  be  thoroughly  acquainted  with  the  very  accurate  and 
extensive  researches  of  Mr.  Wharton  Jones,  embodied  in  his  memoir  on  "The  Blood-cor- 
puscle, considered  in  its  different  phases  of  development  in  the  Animal  Series,"  "Philoso- 
phical Transactions,"  1S4G;  the  publication  of  which  will,  we  believe,  be  considered  here- 
after to  constitute  an  epoch  in  our  knowledge  of  the  blood.  It  is  shown  in  this  Memoir  that 
"  the  lymph-corpuscle  of  the  Vertebrata  is  identical  with  the  corpuscle  of  their  blood.  In 
the  oviparous  Vertebrata  it  occurs,  like  the  corpuscle  of  their  blood,  in  the  two  phases  of 
granule-cell  and  nucleated  cell ;  whilst  in  man  and  Mammifera  it  occurs  like  the  corpuscle 
of  their  blood  in  the  three  phases,  of  granule-cell,  nucleated  cell,  and  free  celloiform  nucleus. 
"  The  only  difference  that  exists  between  the  corpuscle  of  the  lymph  and  the  corpuscle  in 
the  blood  is,  as  regards  the  oviparous  Vertebrata,  the  little  degree  of  coloration  which  the 
colored  stage  of  the  nucleated  cell  as  yet  presents,  and,  as  regards  the  Mainmifera,  the  small 
degree  of  coloration  which  the  colored  stage  of  the  free  celkeform  nucleus  has  yet  attained" 
(p.  82). 

Mr.  Wharton  Jones  first  pointed  out  in  this  Memoir  the  true  nature  of  the  process  which 
is  described  and  figured  in  the  text  as  the  "bursting,"  &c.,  of  the  lymph-corpuscles.  These 
changes  of  form,  in  fact,  are  not  in  general  produced  by  any  such  cause,  but  they  arise  from 
the  amoeba-like  motions  of  the  corpuscles,  observed  by  Mr.  Jones  in  the  Skate,  Frog,  and  many 
Invertebrata,  and  which  may  be  readily  enough  seen  on  a  smaller  scale  in  the  colorless  cor- 
puscle of  the  human  blood. 

The  subjoined  description  of  the  phenomena  presented  by  the  colorless  corpuscle  (granule- 
cell,  Jones)  of  the  Skate  will  serve  for  all : — 

"  My  attention  was  first  attracted  to  the  phenomenon,  by  observing  a  granule-cell  with  the 
granules  apparently  escaping  from  it,  as  if  burst  (Fig.  3).  But  the  cell  soon  appearing  again 
with  all  the  granules  collected  together,  I  was  led  to  watch,  and  soon  perceived  that  the  ap- 
pearance of  granules  escaping  as  if  from  a  burst  cell,  was  owing  to  this :  The  transparent 
and  colorless  cell-wall  bulged  out  on  one  side,  leaving  the  granules  still  agglomerated  and 
holding  together,  but  this  only  for  a  short  time ;  for  soon,  single  granules  were  seen  to  sepa- 
rate and  burst  out  from  the  rest,  and  to  enter  the  hitherto  empty  compartment  produced  by 
the  bulging  out  of  the  cell-wall.  The  regular  manner  in  which  this  sometimes  took  place 
was  remarkable.  I  have  actually  seen  the  granules  enter  the  compartment  by  one  side, 
and  circulate  along  the  bulging  cell-wall  to  the  other  side,  until  the  whole  compartment  be- 
came filled  with  granules.  This  having  occurred,  the  bulging  began  to  subside,  but  was 
succeeded  by  the  bulging  of  another  part  of  the  cell-wall,  into  which  again  a  flow  of  gra- 
nules took  place,  and  so  on  all  round  the  cell." 


THE    BLOOD    AND    THE    LYMPH.  703 

§  222.  Of  the  Blood. — The  blood,  so  long  as  it  is  circulating  in  the 
vessels,  is  a  slightly  glutinous  fluid,  in  which  only  two  elements,  the 
blood-corpuscles,  -globules,  -cells  (corpuscula  s.  globuli  s.  cellulce  sangui- 
nis),  the  majority  of  which  are  of  a  red  color  while  some  are  white,  and 
the  colorless  blood-plasma  (liquor  s.  plasma  sanguinis),  are  to  be  distin- 
guished ;  when  excluded  from  the  circulation,  it  usually  coagulates  en- 
tirely, by  the  solidification  of  the  fibrin  in  solution  in  the  plasma,  and 
afterwards  by  the  contraction  of  the  coagulated  constituent,  divides  into 
the  "  crassamentum"  and  "serum."  The  former  is  of  a  deep  red  color 
containing,  together  with  the  fibrin,  almost  all  the  colored,  and  most 
of  the  colorless  blood-corpuscles,  with  a  portion  of  the  still  dissolved 
parts  of  the  plasma,  whilst  the  remainder  of  the  latter,  together  with 
some  of  the  colorless  blood-corpuscles,  constitutes  the  serum.  In  cer- 
tain cases  in  Man,  especially  in  disease,  before  the  coagulation  of  the 
blood  has  taken  place,  the  colored  corpuscles  subside  more  or  less  deeply 
below  the  surface  of  the  fluid,  when  the  crassamentum  presents  a  super- 
ficial colorless,  or  whitish  stratum  (inflammatory  crust),  consisting  only 
of  the  coagulated  fibrin  and  colorless  blood-cells,  together  with  the  fluid 
with  which  they  are  imbued. 

The  colored  or  red  blood-globules,  or  simply  blood-globules,  in  which 
alone  the  coloring  matter  of  the  blood  resides,  are  minute  non-nucleated 
cells  of  a  flattened,  lenticular  form,  which  are 
contained  in  the  blood  in  such  vast  quantity,  that 
unless  it  be  diluted  with  serum,  they  do  not 
readily  admit  of  exact  investigation,*  appearing 
of  themselves  to  constitute  the  blood.  However 
important  it  would  be  to  know  accurately  the 
proportion  of  the  blood  globules  to  the  plasma, 

their  number  and  their  volume,  all  researches  hitherto  have  failed,  owing 
to  the  difficulty  of  the  subject ;  and  even  the  very  recent  statements  of 
Schmidt,  according  to  which  47-54  parts  of  moist  blood-globules  exist 
in  100  parts  of  human  blood,  can  only  be  described  as  approximative. 
One  method  only  can  be  successful,  consisting  in  the  direct  enumeration 

FIG.  291. — Blood-globules  of  Man :  a,  viewed  on  the  flat  surface ;  6,  on  the  edge ;  c,  united 
into  rouleaux;  d,  rendered  spherical  by  the  addition  of  water;  e,  rendered  colorless  by  the 
same  agent ;  /,  blood-globules  shrunken  by  the  drying  up  of  the  fluid. 


We  have  already  pointed  out  the  occurrence  of  similar  amaba-like  movements  in  the  young 
cells  of  mucous  membranes  detached  during  slight  inflammation,  and  in  the  cells  of  the 
gelatinous  tissue  of  medusae;  and  we  think  that,  very  probably,  it  will  eventually  be  found 
to  be  a  property  of  all  young  periplastic  substance. 

MM.  Guerin-Meneville  (1849-51),  Davaine  (1850),  and  Robin  (1853),  appear  also  to  have 
observed  these  amceba-like  movements,  without  being  acquainted  with  Mr.  W.  Jones's  essay. 
(See  the  "  Histoire  nat.  des  Vegetaux  parasites,"  by  M.  Robin,  p.  507). — TRS.] 

*  [We  must  caution  the  reader  against  being  guided  by  this  statement.  Nothing  is  easier 
than  the  examination  of  the  blood  as  it  is, — nothing  more  likely  to  mislead  than  the  practice 
of  diluting  it  with  any  fluid  whatsoever. — TRS.] 


704  SPECIAL    HISTOLOGY. 

of  the  globules  in  accurately  determined  quantities  of  blood,  and  as  pre- 
cise a  determination  as  possible  of  the  volume  of  the  individual  corpus- 
cles (Vierordt)  ;  but  this  method,  if  applied  in  such  a  way  as  to  insure 
correct  results,  demands  so  much  time  and  trouble,  that  it  cannot  be 
expected  to  obtain  general  application,  and  we  must  be  contented  with 
an  accurate  investigation  of  the  total  quantity  of  blood- globules  in  a 
single  or  in  some  few  instances,  an  undertaking  in  which  Vierordt  is  now 
engaged.* 

The  red  blood-globules,  more  minutely  examined,  present  the  follow- 
ing characters :  Their  form  is  usually  that  of  a  biconcave  or  plane, 
orbicular  disk,  with  rounded  borders,  and  consequently  they  present  a 
different  aspect  to  the  observer,  according  as  the  surfaces  or  borders  are 
turned  towards  him.  In  the  former  case  they  are  pale  yellow,  orbicular 
corpuscles,  in  which,  according  to  the  focussing  of  the  microscope,  the 
slight  central  depression  which  almost  always  exists,  is  indicated,  some- 
times by  a  clear,  sometimes  by  an  opaque  spot  in  the  centre,  the  latter 
appearance  admitting  of  being  confounded  with  a  nucleus.  Viewed  on 
the  edge,  on  the  other  hand,  they  present  the  form  of  an  elongated, 
narrow  ellipse,  or  of  an  ellipse  constricted  in  the  middle.  The  blood- 
corpuscle  is  constituted  of  a  very  delicate,  but  nevertheless  tolerably 
firm,  and  at  the  same  time,  elastic,  colorless  cell-membrane,  composed 
of  a  protein  substance  closely  allied  to  fibrin,  and  of  colored  viscid  con- 
tents formed  of  globulin  and  licematin,  which  in  the  adult  present  no 
trace  of  morphological  particles,  of  granules,  or  of  a  cell-nucleus  ;  they 

*  [Vierordt's  method,  as  lately  published  by  him  ("Schmidt's  Jahrb.:'  4,  1852)  consists 
in  an  actual  enumeration  of  the  blood-corpuscles,  when  mixed  with  fluids  of  a  certain  den- 
sity. His  mode  of  procedure  is  to  take  up  a  small  quantity  of  blood  by  a  capillary  tube  of 
uniform  size.  The  length  of  the  blood-column  in  the  tube  is  measured  under  a  low  mag- 
nifying power,  and  multiplied  by  the  diameter  of  the  tube;  and  thus  the  total  volume  of  the 
blood-column  is  obtained.  The  blood  is  then  allowed  to  run  from  the  tube  on  to  a  glass  slide, 
is  there  spread  out  in  narrow  streaks,  and  intimately  mixed  with  a  solution  of  gum,  or 
albumen.  The  blood-streaks  are  successively  brought  under  the  divisions  of  an  ocular 
micrometer,  and  the  number  of  corpuscles  in  each  accurately  counted.  This  process  will 
enable  us  to  determine,  with  tolerable  accuracy,  the  number  of  corpuscles  in  a  certain  quan- 
tity of  blood.  It  is,  however,  extremely  laborious,  since  Vierordt  himself  states,  that  in 
order  to  complete  a  single  enumeration,  nearly  one  week  is  required. 

A  mode  of  procedure  by  which  the  number  of  the  blood-corpuscles  may  be  more  readily 
ascertained,  is  the  one  proposed  by  Welcker  (Archiv.  des  Vereins.  fur.  Gem.  Arb.  B.  1,  H.  2, 
1853).  This  observer  employs  a  stage  micrometer,  divided  into  a  known  number  of  paral- 
lelograms. On  this,  the  blood,  mixed  with  a  solution  of  albumen,  is  spread,  and  the  corpus- 
cles in  each  division  counted,  with  the  aid  of  an  ocular  micrometer.  For  practical  purposes, 
Welcker  states  that  the  number  of  the  blood-corpuscles  maybe  ascertained  by  a  yet  simpler 
method.  A  measured  quantity  of  blood  is  diluted  with  a  certain  quantity  of  fluid,  the  color 
of  the  diluted  blood  is  then  compared  with  a  color  scale  determined  upon  by  previous  ex- 
periment, and  by  the  degree  of  color,  the  number  of  the  blood-corpuscles  may  be  approxi- 
mately estimated.  By  employing  both  these  methods,  Welcker  was  able  to  ascertain  that 
healthy  blood  (his  own)  contained  about  4,000,000  corpuscles  in  a  cubic  millimetre,  whilst 
in  a  case  of  hysteria  he  found  but  3,800,000,  and  in  a  patient  in  the  last  stage  of  consump- 
tion, but  2,400,000  corpuscles.— DaC.] 


THE    BLOOD    AND    THE     LYMPH.  705 

are  consequently  vesicles,  whence  the  name  "  blood-cells"  is  to  be  pre- 
ferred. The  elasticity,  softness,  and  flexibility  of  the  membrane  is  so 
considerable,  that  the  corpuscles  are  rendered  capable  of  passing  through 
vessels  of  less  diameter  than  themselves,  and  when  by  pressure  under 
the  microscope  they  have  become  elongated,  flattened,  or  otherwise 
altered  in  shape,  of  reassuming  their  original  form.  The  blood-globules 
are  the  better  adapted  for  the  former  process,  since  their  surface  is  per- 
fectly smooth  and  slippery,  so  that  they  easily  glide  over  the  walls  even 
of  the  smallest  capillaries,  which  present  the  same  conditions. 

The  size  of  the  blood-globules  may  differ  in  different  individuals ;  but 
these  diversities,  owing  to  the  minuteness  of  the  bodies  concerned,  are 
not  altogether  inconsiderable.  As  a  general  mean  size,  the  most  recent 
inquiries  of  Harting  ("  Rech.  micrometr.")  from  measurements  of  recent 
blood-corpuscles,  give  a  width  of  0-0033  (1-300)  and  a  thickness  of 
0*00062  of  a  line  ;  and  of  Schmidt,  from  the  estimation  of  dried  blood- 
globules,  a  width  of  0-0035  of  a  line,  whilst,  according  to  the  former, 
the  mean  width  in  various  individuals  amounts  to  from  0-0028  to 
0-0036,  and  according  to  Schmidt  to  0-0032-0-0035  of  a  line,  with 
which  numbers  those  given  by  other  good  observers  essentially  corre- 
spond. The  differences  in  the  same  individual,  found  by  Harting  to  exist 
between  the  two  extremes,  amount,  as  regards  the  width,  to  0*0010— 
0-0017,  and  for  the  thickness  to  0-00009-0-0005  of  a  line;  the  ex- 
tremes observed  in  general  were  0-0020-0-0040  and  0-0005-0-0009 
of  a  line ;  and  Schmidt  states,  that  in  100  blood-corpuscles  95-98  are 
of  equal  size.  With  respect  to  the  size  of  the  blood-globules  in  one  and 
the  same  individual,  it  may  be  stated  in  general,  that  it  necessarily 
differs  at  different  times,  and  especially  that  it  necessarily  increases  or 
diminishes  according  to  the  varying  degrees  of  concentration  of  the 
blood-plasma ;  but  on  this  subject  we  have  scarcely  any  accurate  re- 
searches. Harting  only  says,  that  the  blood-corpuscles  of  the  same  in- 
dividual, measured  after  an  interval  of  three  years,  presented  the  same 
mean  size,  whilst  in  the  same  individual  after  a  copious  meal,  somewhat 
less  average  dimensions  were  exhibited  (by  about  0-00013  of  a  line),  and 
more  considerable  extremes.  It  has  been  remarked  that  determinate 
data  are  wholly  wanting  as  to  the  number  of  the  blood-globules,  and  we 
must  await  the  results  of  Vierordt's  researches.  But,  at  all  events,  from 
what  has  been  ascertained  with  respect  to  the  amount  of  solid  constitu- 
ents in  the  blood-globules,  this  much  in  general  may  be  concluded,  that 
they  are  more  numerous  in  the  male  than  in  the  female  sex ;  moreover, 
that  after  repeated  venesection,  during  pregnancy  and  after  prolonged 
deprivation  of  food,  they  diminish  in  number;  and  in  certain  diseases, 
as  chlorosis  and  anaemia,  are  also  found  to  be  much  more  scanty  than 
usual.  At  the  same  time,  however,  it  is  certain,  that  all  the  possible 
variations  are  not  as  yet  by  any  means  exhausted,  and  it  can  scarely  be 

45 


706  SPECIAL    HISTOLOGY. 

doubted,  that  in  every  individual  the  number  of  blood-cells  is  subject  to 
numerous,  even  daily  changes,  according  to  the  conditions  of  supply  and 
waste,  with  which  we  have  still  to  be  made  accurately  acquainted.  The 
volume  of  the  blood-cells  is  estimated  by  Harting,  regarding  them  as 
short  cylinders,  as  that  of  a  cell  of  0-0763  cubic  millimeters;  and  the 
iveight,  taking  their  specific  gravity  as  equal  to  that  of  water,  and  ab- 
stracting their  central  depression,  at  1-13,114,000  milligramme.  If,  with 
Schmidt,  the  blood  is  taken  to  contain  50  per  cent,  of  corpuscles,  and 
the  whole  quantity  of  blood  be  estimated  at  10  kilogrammes,  we  have  a 
total  of  65  billions  570,000  millions.  According  to  Schmidt,  the  spe- 
cific gravity  of  the  blood-corpuscles  in  men,  is  1*0885-1*0889,  and  in 
women  1*0880-1*0886 — numbers  which  must  stand  and  fall  with  his 
statements  respecting  the  quantity  of  blood-corpuscles.  Compared  with 
the  other  constituents  of  the  blood,  the  corpuscles  are  heavier  than  the 
serum  and  the  plasma.  In  the  former,  and  in  defibrinated  blood,  they 
form,  upon  standing,  a  red  sediment,  whilst  in  the  plasma,  owing  to  its 
rapid  coagulation,  they  do  not  usually  subside  below  the  level  of  the 
fluid.  This  subsidence  of  the  blood-cells,  which,  according  to  their  own 
density  and  that  of  the  fluid  in  which  they  are  suspended,  may  be  slow 
or  rapid,  is  favored  by  their  mutual  cohesion,  which  is  observed  especially 
in  inflammatory  blood,  in  which,  from  the  rapid  subsidence  of  the  blood- 
cells,  part  of  the  blood  coagulates  into  a  colorless  mass  ;  but  it  also  takes 
place  in  perfectly  healthy  blood,  and,  in  fact,  constantly  in  little  drops 
obtained  by  trifling  injuries  of  the  skin,  and  frequently  also  in  the  blood 
taken  by  venesection.  The  blood-globules  in  these  instances  apply 
themselves  to  each  other  by  their  flat  surfaces,  and  form,  as  it  were, 
columns  or  rouleaux,  to  the  sides  of  which  others  may  be  again  applied, 
so  that  very  complicated  branched  figures,  and  even  networks  are  in  this 
way  produced,  covering  the  entire  field  of  view  (Fig.  291,  c). 

Besides  the  colored,  the  blood  also  contains  a  certain  number  of 
colorless  elements,  of  two  kinds — elementary  granules  of  a  fatty  nature, 
and  true  cells.  The  former,  which  correspond  entirely  with  those  of  the 
chyle  (vide  §  221),  occur  in  very  varying  number,  sometimes  very  scantily 
or  not  at  all,  sometimes  in  greater  or  even  in  vast  numbers,  so  as  to 
give  the  serum  a  whitish  or  even  milk-white  color.  From  all  that  we 
know,  these  must  exist  when  fat  is  introduced  into  the  blood  through 
the  chyle ;  thus  also  in  common  alimentation,  3-6  hours  and  longer 
after  the  taking  of  food,  although  in  many  cases  they  seem  to  disap- 
pear in  the  course  of  the  pulmonary  circulation  ;  at  all  events  Nasse 
(vide  Nasse,  "  Wagn.  Handw.  d.  Phys.,"  I.,  p.  126)  and  others  have 
never  found  them  in  the  systemic  blood  of  healthy  persons,  a  fact  which 
I  can  confirm  as  regards  my  own  blood.  In  herbivorous  Animals,  on 
the  contrary,  in  the  Goose,  and  in  sucking  Animals,  the  occurrence  of 
these  molecules  appears  to  be  constant ;  in  pregnant  women,  also,  and 
after  the  free  use  of  milk  or  alcoholic  drinks,  and  also  in  famishing 


THE    BLOOD     AND    THE     LYMPH.  707 

persons  (in  consequence  of  an  absorption  of  the  fat  of  the  body),  it 
seems  to  be,  at  all  events,  very  frequent.  The  colorless  cells  of  the 
white  blood-corpuscles  are  derived  from  the  chyle ;  and  may,  conse- 
quently, be  termed  the  chyle-  or  lymph- corpuscles  of  the  blood.  Some 
of  them  are  uninuclear,  and  correspond  in  all  respects  with  the  small 
cellular  elements  of  the  chyle  (vide  §  221) ;  some  multinuclear,  having 
an  average  size  of  0-005  of  a  line,  in  which  case 
they  so  closely  resemble  pus-corpuscles,  that  it 
is  quite  impossible  to  distinguish  the  one  from 
the  other.  The  larger  corpuscles  are  rarely  as 
granular  as  the  smaller,  usually  tolerably  homo- 
geneous, often  with  clear  contents,  so  that  their 
two  or  three,  rounded,  minute  nuclei  are  at  once 
apparent.*  Should  this  not  be  the  case,  acetic  acid  or  water  brings 
the  nuclei  distinctly  into  view  by  rendering  the  contents  clear,  of  which 
occasionally  a  drop  escapes  from  the  ruptured  cell;  at  the  same  time, 

FIG.  292. — Colorless  blood-corpuscles,  or  lymph-corpuscles  of  the  blood  :  a,  6,  smaller 
cells,  such  as  are  found  in  the  thoracic  duct,  viewed  on  the  side  (a),  and  on  the  edge  (ft)  ; 
c,  c,  the  same  with  visible  nucleus;  rf,  rf,  larger  cells  with  nuclei  multiple  ab  origine  •  e,e,  e,  the 
same  after  having  been  acted  upon  by  acetic  acid,  the  nuclei  disintegrated  or  becoming  so. 

*  [With  regard  to  the  appearances  presented  by  the  "  nucleus"  of  the  colorless  corpus- 
cle, Mr.  Wharton  Jones  (1.  c.  p.  07  for  the  Frog,  p.  72  for  Man,  the  Horse,  and  the  Ele- 
phant) shows  very  clearly  that  the  singleness  or  multiplicity  of  this  body  depends  entirely 
upon  the  strength  of  the  acetic  acid  used  to  bring  it  out,  and  we  can  fully  confirm  his  state- 
ment so  far  as  our  own  observations  have  gone.  If  the  blood  of  Man,  in  fact,  be  diluted 
first  with  water,  and  then  only  very  dilute  acetic  acid  be  added,  the  "nuclei"  of  the  color- 
less corpuscles  will  all,  or  almost  all,  be  circular,  with  even  edges.  If,  on  the  other  hand, 
strong  acetic  acid  be  added  at  once,  every  variety  of  form,  from  mere  notching,  to  apparent 
division  into  two,  three,  or  four  smaller  ones,  will  be  found.  "•  I  am  satisfied,  however,  that 
this  is,  in  both  cases  (granule-cell  and  nucleated  cell)  merely  an  appearance  produced  by 
the  shrivelling  together  of  the  walls  of  the  single  cellscform  nucleus,  in  consequence  of  the 
action  of  the  acetic  acid. 

"  It  is  proper  to  observe,  that  I  have  come  to  this  conclusion,  only  after  having  particu- 
larly tested  the  point  by  repeated,  careful,  prolonged,  and  varied  observations.  Nor  is  the 
determination  of  the  point  of  small  moment,  as  on  the  appearance  of  a  multiple  nucleus, 
which  I  have  thus  shown  to  be  artificially  produced,  and  on  a  similar,  but  I  believe  equally 
artificially  produced  appearance  of  a  multiple  nucleus  in  the  pus-corpuscle,  a  particular 
view  has  been  founded  as  to  the  first  formation  of  the  nucleus,  and,  indeed,  as  to  cell- 
development  generally."  (Wharton  Jones,  1.  c.,  pp.  67-S.) 

It  will  be  observed  that  in  the  text  Professor  Kdlliker  admits  that  the  multiple  "  nuclei" 
may  be  still  further  broken  up  by  the  action  of  reagents. 

The  existence  of  any  difference  of  specific  gravity  between  the  colorless  and  the  red 
corpuscles  of  the  blood  may  be  doubted ;  their  relative  positions  in  masses  of  blood,  to 
which  reference  is  made  above,  being  fully  accounted  for  by  the  aggregation  of  the  red 
corpijscles  into  rolls. 

With  regard  to  the  blood-corpuscles  of  the  Invertebrata,  Mr.  Wharton  Jones's  Memoir, 
above  cited,  should  be  consulted,  as  it  contains  the  only  complete  account  of  them  extant. 
The  statement  in  the  text,  that  Jlmphioxus  has  no  blood-corpuscles,  is  incorrect.  It  is,  how- 
ever, altogether  exceptional  among  the  Vertebrata,  as  its  corpuscles  are  entirely  of  the 
colorless  kind. — Tns.] 


708  SPECIAL    HISTOLOGY. 

at  all  events  under  the  former  reagent,  the  nuclei  not  unfrequently  are 
farther  disintegrated,  and  fall  into  irregular,  jagged,  and  constricted 
corpuscles,  or  are  even  resolved  into  a  greater  number,  4,  5,  6,  and 
more,  of  smaller  granules,  assuming,  at  the  same  time,  a  yellow  color, 
whilst  the  cell-membranes  gradually  disappear.  The  other  reactions  of 
these  colorless  blood-corpuscles  are  those  of  the  common  indifferent 
cells,  and  as  regards  their  number,  it  is,  compared  with  that  of  the 
blood-corpuscles,  very  small,  though  not  always  the  same,  being  depen- 
dent upon  the  energy  with  which  nutrition  is  going  on,  and  therefore 
more  considerable  when  a  large  quantity  of  chyle  has  entered  the 
blood  after  a  full  meal.  It  is  impossible  to  give  any  definite  statement 
as  to  their  number,  without  perfectly  accurate  enumeration  ;  but  this 
much  is  certain,  that  the  usual  statement,  that  there  is  one  colorless  to 
every  ten  colored  blood-corpuscles,  is  quite  incorrect.  I  find,  with 
Henle  and  Donders,  that  they  are  much  less  numerous  than  this,  and  am 
of  opinion,  that  when  the  latter,  with  Moleschott,  reckons  5*1  colorless 
to  2000  colored  corpuscles,  he  is  not  far  wrong.  After  meals,  these 
authors  found  the  number  of  the  latter  augmented  to  6'2,  whilst  in 
fasting  animals,  as  was  also  noticed  by  Heumann  in  Pigeons,  they 
diminished  in  number ;  and  after  long  fasting,  at  least  in  Frogs,  they 
saw  them  disappear  altogether.*  Their  increase  after  venesections,  not 
only  relatively  but  even  absolutely,  is  a  very  remarkable  circumstance; 
and  this,  as  in  the  Horse,  a'fter  very  copious  abstraction  of  blood  (as 
much  as  50  Ibs.)  may  proceed  to  such  an  extent,  that  the  colored  and 
colorless  corpuscles  appear  to  exist  in  equal  numbers.  The  white  cor- 
puscles are  lighter  than  the  colored,  and  they  are  consequently  more 
numerous  in  the  upper  strata  of  the  crassamentum.  When  the  latter 
presents  a  buffy  coat,  it  always  contains  a  great  number  of  these  cor- 
puscles, and  especially  if  their  number  has  been  augmented  by  previous 
venesections,  so  as  in  such  cases  to  constitute  even  half  of  the  buffy 
coat  (Remak,  Donders).  Their  less  tendency  to  subside  is,  moreover, 
increased  by  the  circumstance,  that  although  they  have  an  uneven  sur- 

*  [Moleschott  has  recently  continued  his  researches  on  the  relative  number  of  the  white 
and  the  red  corpuscles,  and  has  arrived  at  some  interesting  results.  In  boys  from  2£  to  12 
years  of  age,  he  found  as  the  mean  in  seven  enumerations  of  the  corpuscles,  4- 5  colorless  to 
1000  colored;  in  adults  from  21  to  49  years,  2'9  colorless  to  1000  colored  ;  in  old  men  from 
62  to  78  years,  2'G  colorless  to  1000  colored.  In  women  from  14  to  38  years  the  average 
was  only  2*6  colorless  to  1000  colored  corpuscles,  whilst  in  the  blood  of  the  same  women 
while  menstruating,  he  counted  4  colorless  to  1000  colored.  An  increase  of  the  proportion 
of  the  colorless  corpuscles  was  also  observed  in  pregnant  women  (3'6  colorless  to  1000 
colored),  and  in  the  blood  of  persons  after  meals  which  were  rich  in  albuminous  sub- 
stances. After  having  partaken  freely  of  the  latter,  he  noticed  in  his  own  case  3'5  color- 
less to  1000  colored  corpuscles,  whilst  a  few  hours  after  a  breakfast  on  non-albuminous 
substances,  he  counted  only  2'1  colorless  to  1000  colored  corpuscles.  These  observations 
of  Moleschott  are  important,  and  must  be  borne  in  mind  in  determining  the  number  of  the 
colorless  corpuscles  in  suspected  cases  of  leucocythemia. — DaC.] 


fk 

THE    BLOOD    AND    THE     LYMPH.  709 

face,  and  a  disposition  to   cohere,  they  usually  do  not  form   any  large 
aggregations,  and  never  constitute  rouleaux. 

Condition  of  the  blood-corpuscles  in  various  kinds  of  blood. — However 
sensitive  the  blood-cells,  out  of  the  body,  are  towards  various  reagents, 
they  appear,  within  it,  to  be  so  constant,  at  all  events  as  regards  their 
shape,  that  not  only  within  the  bounds  of  the  physiological  condition, 
are  no  notable  and  uniform  differences  to  be  observed  in  them,  in  the 
arterial  and  venous  blood  and  the  blood  of  the  different  organs,  but, 
even  in  the  most  various  diseases,  no  visible  alterations  are  presented. 
And  yet  it  cannot  be  doubted  that,  as  the  color  and  chemical  composi- 
tion of  the  blood-cells  vary,  so  also  are  their  forms  subject  to  certain 
diversities  and  changes,  according  as  the  blood  is  more  concentrated 
or  diluted,  and  abounds  more  or  less  with  one  saline  constituent  or  ano- 
ther, or  with  other  substances;  but  these  changes  of  form  are  so  incon- 
siderable, that  it  cannot  be  wondered  at,  that  we  have  not  yet  been  in 
a  condition  to  recognize  them  with  certainty.  At  all  events,  with 
Henle,  I  must  most  expressly  declare,  that  all  these  forms — the  jagged 
blood-corpuscle  on  the  one  side,  and  the  diminutive,  spherical,  colored 
or  pale — are  never  met  with  in  the  circulating  blood.  Slight  degrees 
of  flattening  and  distension  may  probably  be  noticed ;  but  in  such  re- 
searches it  should  never  be  forgotten  how  quickly  the  blood-corpuscles 
change  their  form,  and  care  must  be  taken  not  to  view  a  condition  set 
up  out  of  the  organism,  as  a  natural  one.-  The  relations  of  the  blood- 
cells,  as  to  their  number,  appear  to  vary  more  than  their  forms.  As 
respects  the  colored,  they  are  more  numerous  in  the  venous  than  in  the 
arterial  blood.  In  speaking  of  the  venous  blood,  that  of  the  hepatic 
veins  stands  pre-eminent,  containing,  according  to  Lehmann,  far  more 
blood-cells  than  that  of  the  portal  vein,  and  even  exceeding  in  that 
respect  the  somewhat  rich  blood  of  the  jugular  vein.  The  colorless 
blood-tells,  as  I  and  Funke  have  found,  exist  in  very  great  number  in 
the  splenic  blood,  and  indeed  sometimes  more  in  the  form  of  uninuclear 
cells?  sometimes  as  multinuclear ;  and  also  in  the  blood  of  the  hepatic 
veins,  according  to  Lehmann,  in  which  they  are  characterized  by  their 
very  various  size  (vid.  §  223) ;  I  have  noticed  this,  in  many  cases, 
though  by  no  means  invariably,  but  am  unable  to  regard  it  as  an  ex- 
clusive character  of  the  blood  in  the  hepatic  veins,  because  I  have  also 
found  the  same  multitude  of  colorless  cells  in  perfectly  healthy  animals, 
in  the  portal  blood,  as  Lehmann  has  done  in  one  case,  as  well  as  in  the 
blood  of  the  pulmonary  veins.  Otherwise,  however,  the  colorless  cells 
are  more  abundant  in  the  venous,  than  in  the  arterial  blood  (Remak). 
In  the  vena  cava  superior,  and  iliac  vein  of  the  Dog,  Zimrnermann 
noticed  uninuclear  cells,  and,  in  the  v.  cava  inferior,  multinuclear  ones. 

Many  experiments  have  already  been  made  as  to  the  influence  of 
various  reagents  on  the  blood-globules,  although  the  results  obtained 


I 

710  SPECIAL    HISTOLOGY. 

have  in  some  measure  been  of  very  trifling  importance ;  and  I,  there- 
fore, here  adduce,  chiefly  from  my  own  researches  on  the  suhject  of  the 
human  blood-corpuscles,  only  what  may  serve  to  illustrate  their  anato- 
mical and  physiological  relations.  Water  at  first  renders  the  blood- 
globules  spherical,  and,  owing  to  the  diminution  of  the  broad  diameter, 
consequent  upon  the  increased  thickness,  smaller  (from  0*002-0-0024 
of  a  line),  which  may  be  best  seen  in  corpuscles  arranged  in  columns. 
The  size  then  usually  remains  without  further  change,  and  the  coloring 
matter  and  remainder  of  the  contents  slowly  (sometimes  suddenly,  and 
by  fits  and  starts)  escape,  so  that  the  fluid  becomes  dark-red,  the  cor- 
puscles at  the  same  time  losing  their  color,  and  acquiring  the  aspect  of 
colorless  vesicles  or  rings,  so  faint,  that  it  is  often  difficult  to  perceive 
them.  But  by  the  addition  of  tincture  of  iodine,  which  colors  them 
yellow,  or  of  salts  (common  salt,  nitre,  &c.),  of  gallic  or  chromic  acid, 
which  cause  them  to  shrink,  and  to  present  a  more  defined  outline,  they 
may  be  readily  brought  into  view  ;  and  it  is  thus  satisfactorily  shown 
that  water,  by  no  means  dissolves,  or  destroys  them.  Some  blood- 
globules  always  withstand  the  influence  of  the  water  for  a  longer  time, 
and  are  still  colored  when  all  the  rest  have  lost  their  coloring  matter ; 
but  it  is  not  yet-  ascertained,  whether  these  are  to  be  regarded  as  of 
younger  formation,  as  is  commonly  supposed,  or  of  older.  The  latter 
notion  seems  to  be  favored  by  the  circumstance  that  older  cells  usually 
have  firmer  membranes  than  younger  ones,  and  also  that  blood-corpus- 
cles, left  to  their  fate  out  of  the  circulation — for  instance  in  extra- 
vasated  blood — always,  in  time,  become  more  resistant;  but  it  must  be 
allowed  that,  at  present,  no  decisive  opinion  can  be  given  either  way. 
Many  other  substances  act  in  the  same  manner  as  water,  only  more 
powerfully  and  even  destructively,  particularly  acids  and  alkalies; 
although  not  all  with  equal  energy.  Gallic  and  pyroligneous  acids, 
aqueous  solutions  of  chlorine  and  iodine,  sulphuric  ether  and  chloro- 
form, act  very  much  in  the  same  way  as  water.  In  the  first  three  the 
blood-globules  remain  as  distinct,  pale  rings,  whilst  in  sulphuric  ether 
they  are  instantaneously  transformed  into  the  most  delicate  and  exces- 
sively faint  rings,  j~-J  the  original  size,  and  which  it  is  very  difficult  to 
perceive  in  the  finely  granular  coagulum  that  is  formed  at  the  same 
time,  although  they  are  rendered  more  distinct  by  the  addition  of  salts 
(nitre  for  instance).  I  have  seen  no  evidence  of  an  actual  solution  of 
the  cells.  Chloroform  acts  in  the  same  manner,  only  more  slowly,  and 
the  corpuscles  first  become  considerably  smaller,  and  of  a  glistening 
yellow  color.  Acetic  acid,  of  10 J,  at  once  renders  the  corpuscles  ex- 
tremely faint,  so  as  to  be  scarcely  perceptible,  but  they  are  by  no  means 
dissolved,  being  visible,  even  at  the  end  of  several  hours,  in  the  form  of 
delicate  rings.  A  solution,  containing  20  per  cent,  of  acid,  acts  more 
energetically,  and  in  glacial  acetic  acid,  the  cells  are  completely  dis- 
solved in  the  space  of  two  hours,  in  the  slimy  brown  blood.  Concentrated 


THE    BLOOD    AND    THE    LYMPH.  711 

sulphuric  acid  renders  the  blood  black-brown.  The  corpuscles  become 
pale,  and  although  still  retaining  some  color,  are  scarcely  recognizable, 
their  contours  running  mutually  together.  On  the  addition  of  nitre  or 
water,  which  latter  throws  down  a  white  precipitate,  they  again  become 
distinct  as  minute,  dull-yellow,  round  corpuscles.  After  some  hours' 
action  of  the  acid  all  is  dissolved.  Concentrated  hydrochloric  acid, 
which  colors  the  blood  brown,  and  produces  a  white  precipitate,  con- 
tracts most  of  the  cells,  which  are  gradually  dissolved,  and  renders 
many  of  them  granular  internally,  also  producing  rents  in  some  of  them, 
so  that  the  contents  escape,  in  the  form  of  a  pale  streak,  appearing  like 
a  stalk  to  the  corpuscle  ;  subsequently  they  become  so  faint  in  color  as 
to  be  scarcely  perceptible,  without  the  aid  of  some  saline  solution. 
After  some  hours  many  are  dissolved,  though  a  few  offer  a  longer  re- 
sistance. Nitric  acid,  when  concentrated,  renders  the  blood  olive-brown, 
and  the  corpuscles  greenish.  The  latter  are  corrugated,  but  are  not 
rendered  smaller,  and  are  partly  enclosed  in  the  coagulum,  which  is 
formed  at  the  same  time,  in  part  free,  and  lying  above  it.  After  several 
hours  there  is  still  no  indication  of  a  solution  going  on,  but  this  takes 
place  at  the  end  of  a  day.  Of  the  alkalies,  potassa  acts  the  most  pow- 
erfully. A  solution  containing  10  per  cent,  makes  the  blood  black,  and 
at  once  dissolves  all  the  blood-cells,  first  rendering  them  spherical  and 
smaller.  The  same  thing  takes  place  with  a  solution  containing  20  per 
cent,  of  the  alkali,  except  that  some  of  the  cells  remain  for  a  time  as 
pale  rings,  whilst  a  concentrated  solution  of  two  parts  potassa  arid  one 
part  water  does  not  attack  the  corpuscles,  beyond  making  them  very 
small  ;  at  the  same  time  they  remain  spherical,  orjagged  and  folded.  The 
whole  blood  is  coagulated  by  this  solution,  and  acquires,  at  first,  a  brick- 
red,  and  afterwards,  a  bright  brown  color.  On  the  subsequent  addition 
of  water,  the  blood-corpuscles  enlarge,  as  in  no  other  reagent,  to  a  size 
of  0-006  of  a  line,  remaining  for  the  most  part  flat,  and  are  then  dis- 
solved as  in  a  dilute  solution.  Caustic  soda,  and  caustic  ammonia,  in 
solutions  containing  about  10  per  cent.,  act  like  the  corresponding 
potassa-solution,  only  that  the  action  is  a  little  weaker,  whilst  concen- 
trated caustic  soda  (1J  part  to  1  part  water)  acts  precisely  like  caustic 
potassa.  The  same  phenomenon  of  a  diminution  of  the  blood-cells,  as 
that  caused  by  some  of  the  reagents  above  noticed,  is  manifested  also 
in  many  other  instances,  and  may  be  referred  to  the  abstraction  of  ma- 
terials, chiefly  water,  from  the  cells,  as  it  is  always  concentrated  solu- 
tions which  so  act.  In  these  cases,  also,  since  the  blood-globules  reflect 
the  light  from  more  numerous  points,  the  color  of  the  blood  becomes 
brighter,  usually  of  a  brick-red.  Even  the  mere  concentration  of  the 
blood-plasma,  by  evaporation,  causes  the  cells  to  shrink  more  or  less,  in 
consequence  of  which  they  become  either  round,  dark,  brilliant  globules, 
0-001-0-002  of  a  line  in  size,  or  jagged,  stellate  bodies,  or,  lastly. 


712  SPECIAL    HISTOLOGY. 

diversely  bent  and  plicated  discs.  All  concentrated  solutions  of  metallic 
and  other  salts,  act  in  the  same  way,  unless,  like  nitrate  of  silver,  they 
exert  an  immediately  destructive  influence.  Bonders  and  Moleschott 
have  carefully  investigated  the  reactions,  especially  of  such  soluble 
salts  as  exist  in  the  blood,  and  have  found  that  a  concentrated  solution 
(1  part  salt,  7  parts  water)  added  to  an  equal  volume  of  blood,  dimi- 
nishes all  the  cells,  and  reddens  the  blood.  The  cells  are  least  affected 
by  the  hydrochlorates  of  soda  and  potassa,  much  more  by  the  phosphate 
and  carbonate  of  soda,  and  nitrate  of  potassa,  most  of  all  by  the  sul- 
phates of  soda  and  potassa.  When  diluted  (1  part  salt,  17  parts  water), 
all  these  salts  color  the  blood  a  dark  wine-red,  and  produce  a  distension 
of  the  cells,  rendering  them  pale,  and  completely  dissolving  them  at  the 
end  of  four  or  five  hours;  in  this  regard  the  soda-compounds,  except 
common  salt,  which  exerts  no  destructive  action,  prove  more  energetic 
than  those  of  potassa.  I  find  changes  similar  to  those  caused  by  the 
salts,  to  take  place  on  the  addition  of  alcohol,  tincture  of  iodine,  chromic 
acid,  and  creasote,  the  first  two  of  which  merely  render  the  blood-globules 
smaller  and  corrugated,  the  latter  also  causing  them  to  become  granular 
internally.  In  this  respect  the  action  of  creasote  is  the  most  remark- 
able, which  transforms  the  blood-corpuscles  partly  into  perfectly  opaque, 
even  fat-like  glistening  granular  and  homogeneous  granules  and  globules, 
and  partly  into  very  beautiful  clear  vesicles,  which  may  even  be  ren- 
dered polygonal  by  their  mutual  pressure.  Lastly,  it  is  very  important 
to  notice  the  influence  of  oxygen  and  of  carbonic  acid  on  the  blood, 
which  by  their  reception  into  the  interior  of  the  cells,  both  in  the  body 
(in  the  pulmonary  and  systemic  capillaries)  as  well  as  externally  to  it, 
as  proved  by  experiment,  produce  sometimes  a  brighter,  sometimes  a 
darker  color  in  it.  This  takes  place  without  any  change  of  form  in  the 
blood-corpuscles  (J.  Miiller,  and  Todd  and  Bowman,  in  opposition  to 
Nasse  and  Harless),  and  the  experiment  may  be  alternately  made  several 
times  in  succession  with  the  same  blood  without  any  alteration  of  the 
corpuscles  (Magnus,  Bischoif,  Del'Espinasse,  and  Renemann,  in  opposi- 
tion to  Harless).  Those  gases  also  act  upon  the  coloring  matter  of  the 
blood,  when  isolated,  in  the  same  way  as  upon  the  corpuscles  (Magnus, 
Marchand),  and  it  is  probable  that  the  change  of  color  is  not  connected 
with  any  chemical  change  in  the  hcematin,  but  is  a  physical  action  of  a 
peculiar  kind,  analogous  to  similar  changes  of  color  in  other  fluids 
caused  by  the  absorption  of  gases. 

Blood-corpuscles  of  other  animals. — The  non-nucleated  blood-corpus- 
cles of  the  Mammalia  do  not  differ  in  form  from  those  of  Man,  except 
that  in  the  Camel  and  Llama  (Auchenia  Paco,  A.  Crlama,  A.  Vicugna) 
they  are  oval,  and  0-0088  of  a  line  long ;  they  are  mostly  smaller  than 
in  Man,  as  in  the  Dog,  0-0031,  Rabbit,  Rat,  0-0028,  Swine,  0-0027, 
Horse  and  Ox,  0-0025,  Cat,  0-0024,  Sheep,  0-0022  of  a  line,  the  small- 


THE    BLOOD    AND    THE    LYMPH.  713 

lest  (0-00094)  in  the  Musk  Deer  ;  seldom  larger  (0-005  of  a  line)  as 
in  the  Elephant.  All  the  lower  Yertebrata  have,  almost  without 
exception,  oval,  nucleated  blood-corpuscles,  of  the  shape'  of  a  melon 
seed.  Those  of  Birds  are  from  0-004  to  0-008  of  a  line  long,  and  con- 
tain roundish  nuclei ;  those  of  the  Amphibia  measure  between  0-008- 
0-025  of  a  line  in  length,  have  round  and  oval  nuclei,  and  are  largest 
in  the  naked  Amphibia  (Frog,  0-011-0-013  of  a  line  long,  0-007-0-008 
of  a  line  broad ;  Proteus,  0-025  of  a  line  long,  0-016  of  a  line  broad, 
/Salamander,  0-02  of  a  line  long);  those  of  Fishes,  lastly,  are  mostly 
0-005-0-007  of  a  line  long,  except  that  in  the  Plagiostomes  they  mea- 
sure 0-01-0-015  of  a  line  ;  in  the  Lepidosiren  they  are  0-020  of  a  line 
long,  and  0-012  of  a  line  broad.  In  Myxine  and  Petromyzon  they  are 
0-005  of  a  line  in  diameter,  round  and  slightly  biconcave.  In  Amphi- 
oxus  the  blood-corpuscles  are  absent.*  The  blood-  Fig. 293. 

corpuscles  of  the  Invertebrata  resemble  the  colorless 
cells  of  the  blood  in  the  higher  animals,  and  are  almost 
always  uncolored. 

The  following  should  here  be  also  noticed  as  extraor- 
dinary constituents  of  the  blood :  1,  cells  enclosing 
blood-corpuscles,  noticed  by  Ecker  and  myself  in  the 
blood  of  the  spleen  and  hepatic  vessels,  and  elsewhere  also  in  the  blood 
(vid.  Mikroskop.  Anat.,  II.  3,  p.  369,  et  seq.)  2,  pigmented  and  color- 
less granule- cells,  observed  by  myself,  Ecker,  Meckel,  Virchow,  and 
Funke,  particularly  in  cases  of  intermittent  fever  and  diseases  of  the 
spleen  (1.  c.)  3,  pale,  fine-granular,  roundish  aggregations,  in  the  blood 
of  the  splenic  vein  (Funke).  4,  peculiar  concentric  bodies,  three  to 
four  times  larger  than  the  white  blood-cells,  similar  to  those  of  the 
tliymus  (vid.  Henle,  "  Zeitsch.  f.  rat.  Pathol.,"  Bd.  VII.  p.  44),  found 
by  Hassall  in  fibrinous  clots  in  the  heart.  5,  cells  resembling  pus-cor- 
puscles, in  tumors  of  the  spleen  and  leukaemia  (Virchow) ;  these  bodies 
are  found  in  vast  quantities,  but,  in  their  form,  cannot  in  any  way  be 
distinguished  from  the  colorless  blood-corpuscles.  6,  caudate,  pale  or 
pigvnented  cells  (Virchow,  "Arch.,"  II.)  Besides  these,  should  be  no- 
ticed, the  morphological  elements  which  are  formed  in  the  blood  without 
the  body  or  in  cases  where  the  circulation  has  been  obstructed — the 
fibrinous  coagula  and  crystals.  The  former  are  seen  in  coagulated 
blood,  usually  in  the  form  of  fine,  extremely  closely  interwoven  fibrils, 
disposed  irregularly ;  occasionally  as  stronger,  straiter  fibres,  having  a 
uniform  width  of  0-001-0-003  of  a  line  ;  not  unfrequently  also  in  the 
shape  of  plates  resembling  epidermis  scales  (fibrinous  flakes,  Nasse).  I 
noticed  crystals  of  a  red  color  in  normal  blood  in  the  year  1849 

FIG.  293. — 1,  blood  cells  of  the  Frog:  a,  viewed  on  the  side ;  6,  on  the  edge ;  f,  rendered 
colorless  by  water.     2,  Blood-cells  of  the  Pigeon  :  a,  viewed  on  the  side ;  b,  on  the  edge. 

*  [Vid.  Note,  p.  707.— Tus.] 


714  SPECIAL     HISTOLOGY. 

("Zeitsch.  fur  wissen.  Zool.,"  I.  p.  266,  Todd's  "Cyclop,  of  Anat." 
Art.  "  Spleen,"  p.  792,  and  Mikros.  Anat.,  II.  p.  280),  in  the  blood  of 
the  Dog,  of  Fishes,  and  of  a  Python ;  sometimes  within  the  blood- 
globules,  sometimes  free  in  the  blood,  particularly  of  the  liver  and 
spleen.  Their  occurrence  in  the  former  situation  especially,  appeared 
to  me  to  prove  that  they  exist  in  the  blood  during  life,  and  consist  of 
a  substance  allied  to  hematin  and  hematoidin  (Virchow) ;  but  I  also 
showed  that  they  were  soluble  in  acetic  and  nitric  acids,  and  in  caustic 
alkalies,  and  consequently  that  they  are  not  identical  with  hematoidin. 
Quite  recently,  Funke,  without  being  acquainted  with  my  observations, 
has  independently  noticed  these  crystals  in  the  blood  of  the  Horse, 
Dog,  Man,  and  Fishes,  and  instituted  very  careful  researches  with  re- 
spect to  them  ("  De  sanguine  vense  lienalis,"  Lips.,  1851;  also  in 
Henle's  "  Zeitsch.  N.  Folge,"  Bd.  I.  p.  172,  and  "  Neue  Beob.  ub.  d. 
Krystalle  d.  Milzvenen-  u.  Fischblutes,"  ibid.,  II.  p.  199),  by  which  it 
is  rendered  certain  that  these  crystals  arise  out  of  the  body.  For  more 
particulars  concerning  them  reference  may  be  made  to  the  works  cited,* 
and  I  will  here  only  further  notice  that  the  crystals  arc  most  readily 
formed,  if  a  drop  of  blood  covered  with  a  piece  of  glass  be  allowed  nearly 
to  dry,  and  a  small  quantity  of  water  be  added  ;  moreover,  that  the 
crystals  are  formed  not  only  in  the  blood  of  the  splenic  vein,  as  it  at 
first  seemed,  but  in  other  kinds  of  blood  also,  in  Man  (I  can  obtain 
crystals  in  my  own  venous  blood)  and  other  animals.  They  assume  the 
form  of  red  or  pale  needles,  columns,  and  plates,  probably  belonging  to 
the  rhombic  system  (Funke),  and  also  tetrahedral  (in  the  Guinea  Pig, 
Lehmann,  Funke),  arid  are  characterized  by  their  little  permanency, 
since  they  perish  in  the  air,  are  very  soluble  in  water,  and  also  in  acetic 
acid,  alkalies,  and  nitric  acid.  Those  found  by  me  in  the  blood  of  the 
Dog  resisted  the  action  of  water,  but  I  do  not  think  that  they  were  of 
a  different  nature,  and  I  should  be  inclined  to  refer  this  difference  to 
the  greater  resistance  of  the  blood-globules  themselves.  Funke  believes 
that  they  consist  of  the  albuminous  contents  of  the  blood-cells  in  com- 
bination with  hematin,  relying,  for  support  to  this  opinion,  especially 
upon  their  numbers,  their  occurrence  in  blood-cells,  their  formation,  as 
observed  by  him,  from  aggregations  of  blood-cells,  and  their  absence 
from  the  serum  of  the  blood ;  but  I  cannot  regard  this  hypothesis  as  at 

*  [Also  to  Funke  in  "  Schmidt's  Jahrbiicher"  No.  IX.  p.  1,  and  in  his  Atlas  of  Patholo- 
gical Chemistry,  Leipsic,  1853;  Robin  and  Verdeil  "  Traite  de  Chemie  Anatomique,"  torn. 
III.  p.  430  ;  Kunde  "  Ueber  Krystall-bilding  in  Blute"'  in  "  Henleu.  Pfeufer's  Zeitschrifr,''  II.  p. 
271,  1852,  and  in  Memoires  de  la  Societe  de  Biologie,"  IV.  1852;  Parker  '•  Med.  Times  and 
Gazette,"  1852;  Lehmanii  "  Bericht  d.  Konigl.  sach.  Gesellschaft  der  Wiss,"  Leipzig,  1853, 
and  in  2d  Ed.  of  his  "  Physiologische  Chemie,"  Bd.  II.  p.  151  ;  L.  Teichmann,  "  Ueber  die 
Krystallization  der  organischen  Bestandtheile  des  Bluts,"  in  Zeitschrift  fur.  rat.  Med.  Bd. 
III.  H.  3.  This  last-named  writer  describes  crystals  procured  from  dried  blood,  differing 
in  form  from  the  ordinary  blood-crystals,  and  for  which  he  proposes  the  name  of  "hamin 
crystals."— DaC.] 


THE    BLOOD     AND    THE    LYMPH.  715 

present  fully  established,  and  it  appears  to  me  that  further  proof  is  re- 
quired before  we  should  admit  the  existence  of  crystals  from  the  sub- 
stances in  question,  and  the  more  so,  because  colorless  crystals  are  also 
formed  in  the  blood,  quite  independently  of  the  blood-cells.  Robin 
and  Yerdeil,  moreover,  assert  that  they  have  also  obtained  crystals 
from  the  serum  of  the  blood  ;  and  the  quantity  of  the  crystals  is  by  no 
means  opposed  to  the  notion  that  they  are  derived  from  a  salt  of  the 
blood  merely  tinged  with  hcematin,  since,  in  the  case  of  fibrin  we  see 
that  not  much  of  a  substance  is  required  to  occupy  a  large  space. 

§223.  Physiological  remarks. —  The  development  of  the  bloodvessels 
takes  place,  essentially  on  the  same  type,  in  the  heart,  arteries,  and 
veins.  The  rudiments  of  all  these  vessels,  and  even  of  the  heart,  are 
solid  tracts  of  cells  of  greater  or  less  thickness,  which,  by  the  liquefac- 
tion of  their  interior  substance,  and  the  metamorphosis  of  the  central 
cells  into  blood-globules,  become  cavities,  which  shortly  coalesce,  and 
constitute  a  continuous  passage  for  the  blood.  The  heart  and  vessels 
having  remained  for  some  time  in  this  condition  of  cellular  tubes,  in 
which  state  the  former,  moreover,  exhibits  contractions,  the  cells  com- 
posing the  walls,  with  the  exception  of  the  innermost,  begin  to  elongate 
into  fibres,  and  to  represent  the  divers  fibrous  tissues  and  tunics.  At 
the  same  time  the  vessels  become  thicker  and  increase  in  circumference, 
which  at  first  is  still  to  be  referred  to  an  increase  in  the  number  of  the 
cells,  but  subsequently,  is  brought  about  chiefly,  or  even  solely,  by  the 
growth  of  their  elements  in  length  and  thickness.  In  the  fifth  month 
of  foetal  life,  all  the  larger  and  medium-sized  vessels  are  formed,  with 
their  tunics  and  tissues,  and  it  is  impossible  to  perceive  any  vestige  of 
formative  cells.  The  tissues,  however,  appear  to  be  still  far  from  com- 
pletion, the  muscular  fibres  being  short  and  delicate,  and  instead  of  the 
strong  elastic  fibrous  networks,  we  perceive  only  finer  and  the  finest 

*  [Reichert  was  the  first  to  draw  attention  to  the  occurrence  and  nature  of  crystallized 
albuminous  matters  colored  with  ha?matin,  in  his  "  Beobachtungen  iiber  eine  eivveissartige, 
Substanz  in  Krystallform,"  Mailer's  "  Archiv,"  1849.  These  were  tetrahedrons  of  as  much 
in  some  cases  as  1-15  of  a  line  long,  and  occurred  upon  the  placenta  and  fostal  membranes 
in  a  Guinea  Pig.  Their  albuminous  nature  was  confirmed  by  Schmidt  and  Buchheim ;  subse- 
quently, "  Bericht,''  Mailer's  "  Archiv,"  1852,  Reichert  states  that  he  has  again  found  the 
crystals  in  the  same  locality,  and  that  he  has  convinced  himself,  by  further  experiments, 
that  the  difference  observed  between  his  crystals  and  those  described  by  Kunde  and  Leh- 
iTiaiin,  arose  entirely  from  the  action  of  the  spirit  in  which  his  first  specimens  had  been 
preserved.  Reichert  observed  the  development  of  crystals  of  the  same  kind,  though 
smaller,  in  fresh  blood  taken  from  the  heart  of  the  Guinea  Pig. 

In  connection  with  this  subject,  Dr.  Ayres  has  recorded  a  very  interesting  observation 
with  regard  to  the  occurrence  of  prismatic,  more  or  less  red  crystals,  in  a  band  of  olive- 
green,  almost  black  matter,  having  the  appearance  of  coagulated  blood  at  the  margin  of  the 
placenta  of  the  Bitch  ("  Quarterly  Journal  of  Mic.  Science/'  vol.  i.  p.  299,  with  figures). 
See  also  the  papers  of  Dr.  Parkes  ("  Med.  Times  and  Gazette,"  1852),  and  of  Dr.  Sieve- 
king  ("  Brit,  and  For.  Med.  Chir.  Rev.,'3  1853)  on  this  subject. — TRS.] 


716  SPECIAL    HISTOLOGY. 

fibrils,  and  in  the  place  of  the  elastic  membranes  themselves,  only  layers 
of  more  or  less  coalescent,  fusiform  cells.  The  internal  longitudinal 
fibrous  membrane  alone,  in  many  vessels,  is  at  this  time  demonstrable 
as  a  homogeneous  elastic  tunic  immediately  under  the  epithelium,  but  in 
the  smaller  vessels  this  is  wanting,  and  is  replaced  by  a  layer  of  elon- 
gated cells,  out  of  which  it  appears  to  be  developed.  It  is  thought  that 
similar  cells  are  occasionally  to  be  seen  also  in  the  adult,  in  which  the 
elastic  inner  membrane  is  likewise  merged.  The  muscular  fibres  of  the 
heart  arise,  as  in  other  situations,  from  the  union  of  cells,  but  I  have 
not  yet  seen  how  their  anastomoses  are  formed,  whether  from  a  branch- 
ing of  certain  formative  cells,  or  by  the  lateral  apposition  of  small  rows 
of  cells — probably  in  both  ways. 

The  mode  in  which  the  development  of  the  capillaries  is  effected,  dif- 
fers in  toto  from  that  observed  in  the  larger  vessels.  The  former,  as 
Schwann  and  I  have  shown,  proceed  from  the  coalescence  of  single  cells. 
At  the  primary  origin  of  these  vessels,  tubules  of  some  size  are 
formed,  at  first  by  the  successive  apposition  in  a  straight  line  and  the 
coalescence  of  rounded-angular  cells,  and  the  subsequent  absorption 
of  the  septa -and  of  the  contents,  but  not  of  the  nuclei,  which  remain 
attached  to  the  former  cell-membrane,  now  become  the  capillary  tunic. 
Delicate  pointed  processes  .then  project  from  the  walls  of  these  little 
vessels,  which  rapidly  elongate,  and  meeting  similar  pointed  processes 
of  stellate  cells  dispersed  in  the  surrounding  tissue,  coalesce  with  them. 
At  the  same  time,  the  other  processes  of  these  cells  join,  so  that  there 
is  soon  produced  a  network  of  stellate  cells,  continuous  with  the  already 
formed  capillary  tube  or  tubes.  This  net,  however,  is  never  spread,  for 
the  prolongations,  given  off  from  already  formed  and  pervious  capil- 
laries, and  the  neighboring  cells  connected  with  them  are  constantly  and 
rapidly  transformed  into  fresh  capillaries,  by  the  continual  increase  in 
size  of  the  coalescing  processes  from  their  point  of  origin  onwards,  and 
their  becoming  hollow.  In  this  way  are  produced  vessels  which  are  at 
first  extremely  fine,  and  admit  only  blood-plasma — true  vasa  plasmatica 
s.  serosa;  but  they  rapidly  enlarge,  until  at  last  the  blood-globules  are 
transmitted  through  them,  and  the  capillaries  are  perfected.  Owing  to 
the  circumstances,  that  while  these  processes  of  the  stellate  formative 
cells  thus  enlarge,  the  bodies  of  the  cells  do  not  expand  in  a  correspond- 
ing  manner,  but  appear  as  simple  nodular  points  in  the  vessels,  all  ves- 
tige of  the  original  cellular  network  is  gradually  lost,  and  subsequently 
the  situation  of  the  bodies  of  the  cells  can  only  be  determined  by  the  posi- 
tion of  the  persistent  nuclei.  When  finer  tubules  have  once  been  formed 
from  the  previous  larger  capillaries,  the  facilities  for  the  passage  of  the 
blood  are  continually  undergoing  augmentation,  inasmuch  as  new  stel- 
late cells  are  constantly  enlarging  into  vessels,  whilst,  at  the  same  time, 
fresh  vascular  material  is  as  constantly  furnished  by  the  apposition  of 


THE  BLOOD  AND  THE  LYMPH. 


717 


-A 


new  cells.  New  connections  are  also  frequently  formed  between  capil- 
laries which  are  already  pervious,  partly  by  the  direct  meeting  of  pro- 
longations from  them,  partly  also  by  the  mutual  connection  of  formative 
cells  lodged  in  their  interstices,  whence,  of  course,  the  original  net  is 
rendered  closer.  This  mode  of  development,  so  far  as  I  have  seen,  ob- 
tains in  all  animals,  without  exception,  in  which  capillaries  exist,  and 
the  various  objections  offered  to  the  exposition  given  by  Schwann  and 
myself,  have  chiefly  arisen  in  the  notion,  that  every  network  connecting 
the  arteries  and  veins  in  embryos,  is  a  capillary  plexus.  This,  however, 
is  by  no  means  the  case,  and  consequently  the  circumstance,  that  the 
wrongly  termed  capillaries  of  the  germinal  area  arise  after  the  type  of 
the  larger  vessels,  is  not  an  objection  of  the  least  weight  in  opposition 
to  us. 

The  capillaries  of  the  lymphatic  system,  which  may  be  readily  traced 
in  the  tail  of  batrachian  larvce  (Fig. 
228),  exhibit,  essentially,  precisely 
the  same  mode  of  development  as 
those  of  the  blood-vascular  system 
(Fig.  294),  except  that  anastomoses 
are  rare  in  them,  and  its  course  is 
more  limited  to  the  mutual  apposition 
of  fusiform  cells,  or  of  cells  furnished 
with  three  principal  processes.  Ob- 
servations are  wanting  with  respect 
to  the  larger  trunks  of  this  system, 
although  it  cannot  be  doubted,  that 
they  follow  exactly  the  same  course 
as  the  bloodvessels.  Engel  (1.  c.)  has 
lately  treated  of  the  lymphatic  glands, 
and  states,  that  they  proceed  from 
lymphatic  vessels  which  throw  out 
buds  and  are  much  convoluted. 

The  development  of  the  blood-cor- 
puscles is  pretty  accurately  known,  in 
the  embryo,  as  concerns  its  principal 
stages.  The  first  blood-corpuscles,  in 
the  Mammalia  and  other  Vertebrata 
in  general,  are  nucleated,  colorless 
cells,  with  granular  contents ;  they 
are  perfectly  identical  with  the  for- 

FIG.  294.— Capillaries  from  the  tail  of  a  Tadpole :  a,  completed  capillaries;  b,  cell-«wcki, 
and  remains  of  the  contents  of  the  original  formative  cells;  c,  ceecal  process  of  a  vessel; 
d,  stellate  formative  cell,  connected  by  three  prolongations,  with  three  processes  of  pervious 
capillaries;  e,  blood-globules,  still  retaining  some  granular  contents. — Magnified  350  dia- 
meters. 


718  SPECIAL    HISTOLOGY. 

mative  cells  of  every  part  of  the  young  embryo,  and  arise  in  the  origi- 
nally solid  rudiments  of  the  heart  and  great  vessels,  in  some  situations 
very  early,  in  others  somewhat  later,  by  the  separation  of  the  central 
cells  contained  in  the  rudiments,  in  consequence  of  the  development  of 
a  fluid  (the  first  blood-plasma)  between  them.  The  first  perfect  blood- 
corpuscles  arise  from  these  colorless  cells,  which  lose  their  granules, 
and,  except  the  nucleus,  become  filled  with  hematin.  These  colorless, 
nucleated,  primary  blood-cells  are  spherical,  of  a  deeper  color  than  the 
blood-corpuscles  of  the  adult,  and  larger  (in  a  foetal  Lamb,  3J  lines 
long,  most  of  them  were  0-005-0-0065,  the  minority  0-0025-0-0035 
of  a  line ;  in  a  human  embryo,  4  lines  long,  according  to  Paget, 
0-004-0-007  of  a  line),  but  in  all  other  respects  present  the  same  condi- 
tions, and,  with  their  colorless  formative  cells,  at  first  constitute  the 
sole  elements  of  the  blood.  But  many  of  them  soon  begin  to  multiply 
by  division  ;  to  this  end  they  grow  into  elliptical,  or  even  flattened 
cells,  0-009  of  a  line  long,  0-004-0-006  of  a  line  broad,  bearing  a  decep- 
tive resemblance  to  the  blood-corpuscles  of  the  Amphibia;  produce  2, 
Fig.  295.  rarely  3  or  4,  rounded  nuclei,  and  afterwards 

t*         ^ik  *    divide  by  one  or  several  annular  constrictions, 

(|||i      nft    into  2,  3,  or  4  new  cells.     When  the  liver  begins 
f.jfH      ^*&r     to  be  formed,  this  multiplication  of  the  blood- 
cells  in  the  entire  mass  of  the  blood  ceases,  and 

XV, 

in  a  short  time  (in  the  foetal  Lamb,  11  lines 
long)  all  trace  even  of  their  development  out  of 
colorless  formative  cells  is  lost ;  whilst  at  the 
same  time,  as  Reichert  supposed  and  I  have  directly  proved,  a  very 
active  formation  of  blood-cells  is  set  up  in  the  liver y  a  reason  for  which 
may  be  found  in  the  circumstance  that,  at  this  time,  all  the  blood  from 
the  umbilical  vein,  which  supplies  the  embryo  with  new  organizable 
materials,  first  flows  into  the  liver,  instead  of  entering  the  general  cir- 
culation as  before.  In  proportion  to  the  extent  in  which  this  cell- 
formation  in  the  hepatic  vessels  is  carried  on,  does  the  self-multiplication 
of  the  blood-corpuscles  become  less  and  less  considerable ;  and  instead 
of  it,  a  new  formation  of  free  colorless  nucleated  cells,  having  a  mean 
size  of  0-003-0-004,  and  an  extreme  diameter  of  0-0015-0-006  of  a 
line,  is  observed  to  take  place  in  the  blood  and  immediately  around 
nuclei,  which  also  occur  in  the  free  condition ;  and  which  cells  after- 
wards, still  for  the  most  part  in  the  liver,  are  transformed,  by  the  de- 
velopment of  coloring  matter  in  their  contents,  into  colored,  nucleated 
blood-cells,  either  immediately  or  after  they  have  multiplied  in  a  similar 
way  to  that  which  the  colored  corpuscles  had  previously  followed.  This 

FIG.  295.— Blood-corpuscles  of  a  foetal  Lamb,  3^  lines  long:  a,  bi-  and  tri-nucleated,  large, 
colored  blood-globules,  in  various  stages  of  division;  6,  larger  spherical,  colored  blood-cells, 
one  with  a  nucleus  undergoing  spontaneous  division ;  c,  a  smaller  one  of  the  same  kind. — 
Magnified  300  diameters. 


THE    BLOOD    AND    THE     LYMPH.  719 

new  formation  of  blood-corpuscles  in  the  liver,  with  which  the  consider- 
able size  of,  and  the  abundant  supply  of  blood  to,  the  embryonic  liver, 
is  perfectly  in  accord,  continues  probably  throughout  the  foetal  life  ;  at 
all  events,  I  have  found  it  in  quite  old  embryos  in  Mammalia,  and  also 
in  newly-born  children,  although  it  probably  diminishes,  pari  passu,  in 
connection  with  the  appearance  of  the  ductus  venosus  (which,  according 
to  Rathke,  is  a  secondary  formation)  and  its  enlargement,  because, 
through  it,  a  considerable  portion  of  the  blood  from  the  umbilical  vein 
enters  the  circulation  directly,  and  is  diverted  from  the  liver. 

The  further  development  of  the   nucleated,  spherical  blood-cells  of 
the  embryo,  which  have  originated  in   either  way,  takes  place  in  this 
manner  :  the  cells  gradually,  and  either  directly,  or  after  they  have 
multiplied  in  the  mode  above  described,  become  more  and   more  flat- 
tened, and  even  present  slight  excavations,  whilst  their  nuclei  mani- 
festly diminish,  and   on  the  application  of  acetic  acid,  exhibit  a  great 
tendency    to    disintegration.      Ultimately,   the   nuclei  disappear   alto- 
gether,  and   the  blood-cells  become  non-nucleated,   like  those   of  the 
adult,  of  which  they  all  soon  assume  the  form,  being  at  first  somewhat 
irregular.     With  respect  to  the  period  at  which  these  non-nucleated 
colored  cells  make  their   appearance,  it  must  be  remarked  that   in   a 
foetal  Lamb,  3J  lines  long,  I  could  perceive  none  of  them,  nor   could 
Paget  in  a  human  embryo,  measuring  4  lines  in  the  fourth  week.     In 
foetal  Lambs,  9  lines  long,  they  were  still  very  scanty,  whilst  in  those 
13  lines  in  length,  they  constituted  by  far  the  majority  of  the  blood- 
cells  ;  and  in  a  human  embryo,  at   three  months,  they  formed,  in  the 
hepatic  blood  J,  and  elsewhere  about  J-J-  of  the  colored  corpuscles.     In 
still  older  embryos,  they  preponderate  greatly,  so  that  in  foetal  Lambs 
of   5-13  lines  in  length,  the  nucleated  colored  cells  in  the  hepatic 
blood  constituted  not  more  than  J  or  f  of  the  blood-cells,  and  in  the 
rest  of  the  blood,  in  the  larger  embryos,  did  not  occur  more  abundantly 
than  the  lymph-globules  in  the  blood  of  the  adult  animal.     At  what 
time,  in  the  human  embryo,  the  nucleated  colored  cells  become  more 
rare  and  disappear,  is   not  yet   ascertained,  although   Paget  saw  them 
still  tolerably  numerous  in  one  instance  in  an  embryo  of  five  months. 
The  blood  of  the  larger  Mammalian  embryos  contains,  not  only  in  the 
liver,  but  also  elsewhere,  besides  the  colored  blood-globules,  other  color- 
less cells  in  great  number,  and  often  as  numerous  as  the  colored,  which 
cells,  there  can  perhaps  be  no  doubt,  are  derived  mainly  from  the  liver, 
in  which,  even  in  foetal  Lambs  13  lines  long,  the  colorless  and  slightly 
colored,    nucleated  blood-cells    constitute,   perhaps,    one-third  of   the 
-whole  blood-corpuscles  ;  and  in   the  latter  periods  of  foetal  life,  are 
probably  also  derived  from  the  lymph.     Whether  these  cells  are  meta- 
morphosed into  colored   ones,   is  by  no  means   determined,  this  much 
only  having  been  ascertained,  that  the  transitionary  forms  between  the 


720  SPECIAL    HISTOLOGY. 

two,  so  numerous  in  the  hepatic  blood,  are  wholly  wanting  in  the  rest 
of  that  fluid. 

The  origination  of  the  blood-globules  after  birth  and  in  the  adult, 
notwithstanding  the  great  pains  specially  devoted  to  this  point,  still 
remains  one  of  the  most  obscure  parts  in  the  history  of  the  blood-cells ; 
in  my  opinion,  however,  the  notion  which  assumes  that  the  red  blood- 
cells  proceed  from  the  smaller  chyle-corpuscles,  which  lose  their  nuclei, 
become  flattened,  and  have  hematin  produced  in  them,  is  the  one  most 
deserving  of  credit.  These  cells  are  about  of  the  same  size  as  the 
blood-globules,  or  even  rather  smaller,  have  the  same  kind  of  membrane 
as  the  latter,  are  flattened,  and  not  unfrequently  of  a  faint  yellow 
color,  and  consequently  may,  as  we  see  in  the  colorless  blood-cells  of 
the  embryo,  pass  without  any  considerable  change  into  colored  cells. 
Where  and  how  this  takes  place,  no  one  has  seen ;  and  notwithstanding 
all  the  trouble  and  care  that  I  have  devoted  to  the  subject,  I  have 
never  noticed  a  nucleated  colored  blood-cell  in  the  adult.  The  only 
thing  of  the  sort  that  I  have  met  with,  has  been  this,  that  in  the  pul- 
monary veins,  and  occasionally  also  in  other  blood,  the  smaller  lymph- 
corpuscles  were  in  many  instances  pretty  distinctly  colored,  much  more 
so  than  in  the  thoracic  duct,  so  that,  except  from  their  faintly  granular 
aspect,  they  were  scarcely  distinguishable  from  the  true  blood-cells 
lying  on  their  flat  side ;  and  the  more  so,  because  they  contained  some- 
what smaller  nuclei  than  elsewhere ;  but  even  this  circumstance  is 
insufficient  to  decide  the  question.  The  following  points,  however,  may 
be  adduced  as  presenting  very  important  analogies  :  1,  that  in  all  the 
lower  Vertebrata,  very  distinctly,  for  instance,  in  the  Amphibia,  even  in 
adult  animals,  the  origination  of  nucleated  blood-cells  from  the  lymph- 
corpuscles  may  be  observed ;  and,  2,  that,  in  the  human  embryo,  also, 
the  formation  of  the  colored  blood-globules  from  colorless  cells,  very 
closely  resembling  the  lymph-corpuscles,  has  been  demonstrated  by  me 
in  the  most  decisive  way.  If  to  this  it  be  added,  that  there  is  not  the 
slightest  evidence  of  an  independent,  or  other  kind  of  origination  of 
blood-cells,  it  may  perhaps  be  considered  quite  justifiable  if  I  maintain 
their  origination  from  the  lymph-corpuscles  ;  and,  in  order  to  explain  the 
reason  why  the  transition  itself  has  not  yet  been  observed,  if  I  broach 
the  supposition  that  it  may  take  place  too  rapidly  to  be  in  any  way 
obvious  with  our  means  of  observation. 

Although  in  what  has  been  said,  I  express  myself  in  favor  of  the  for- 
mation of  the  red  blood-cells  from  the  elements  of  the  lymph  and  of  the 
chyle,  I  would  by  no  means  assert  that  all  the  elements  of  those  fluids 
become  blood-cells  at  every  period  of  post-embryonic  life.  The  micro- 
scopical investigation  of  the  blood  would  rather  show,  that  they  invari- 
ably contain  a  certain  number  of  larger  pale  cells  with  several  nuclei, 
or  a  single  nucleus  disintegrated  by  acetic  acid,  of  which,  although  they 
are  certainly  derived  from  the  chyle,  or  are  metamorphosed  elements  of 


THE     BLOOD    AND    THE    LYMPH.  721 

it,  it  is  perhaps  impossible  to  suppose  that  they  ever  become  blood-cells. 
This  being  established,  it  is  a  question  whether  the  change  of  the  blood- 
cells,  their  formation  and  their  dissolution,  is  not  perhaps  muoh  slower 
than  is  commonly  assumed,  and  whether  they  are  not  elementary  parts 
of  a  more  stable  nature  than  is  supposed.  I  am  unable  to  throw  any 
decided  light  upon  this  point,  and  will  merely  remark  that  in  any  case, 
so  long  as  the  growth  of  the  body  goes  on,  and  the  quantity  of  blood  is 
augmented,  an  energetic  formation  of  blood-cells  must  take  place;  in 
opposition  to  which  it  is  quite  unascertained  whether,  in  this  period  of 
life,  blood-cells  are  dissolved  ;  on  which  account,  also,  it  cannot  be 
stated  how  many  of  the  elements  of  the  chyle  undergo  the  metamor- 
phosis into  blood-corpuscles.  In  the  adult,  only  this  much  should  be 
regarded  as  certain,  that  when  from  any  cause  the  quantity  of  blood 
has  become  diminished,  it  may  be  replaced  together  with  the  red  blood- 
cells  ;  whilst  it  is  altogether  unascertained  whether,  under  the  usual 
conditions,  anything  like  an  energetic  solution  and  re-development 
of  those  cells  takes  place.  As  their  formation  cannot  be  definitely  ob- 
served, nothing  remains  by  which  the  question  can  be  decided  but 
observations  respecting  the  dissolution  of  the  blood-globules;  these  ob- 
servations, however,  have  by  no  means  tended  to  demonstrate  the  occur- 
rence of  a  constant  change  of  the  elements  of  the  blood,  taking  place  at 
short  intervals  ;  for  although  in  the  spleen  of  many  animals  a  vast 
quantity  of  blood-globules  undergoing  disintegration  is  met  with,  the 
frequent  and  regular  recurrence  of  a  dissolution  of  those  bodies  in  that 
organ  has  not  yet  been  proved.  Taking  everything  into  consideration, 
I  am  therefore  of  opinion,  that  the  question  as  to  when,  and  to  what 
extent,  blood-corpuscles  perish  and  are  again  formed  in  the  adult,  can- 
not be  definitely  decided  from  the  facts  at  present  in  our.  possession, 
although  I  am  inclined  to  think  that  the  elements  of  the  blood  are  not 
altogether  such  perishable  structures  as  is  commonly  believed. 

I  have  still  to  mention,  that,  quite  recently,  the  view  that  the  blood- 
globules  are  formed  independently  in  the  blood,  out  of  colorless  cells,  is 
advocated  by  various  authorities.  Lehmann  and  Funke  rely,  the  for- 
mer on  the  large  amount  of  colorless  cells  in  the  blood  in  the  hepatic 
veins,  the  latter  on  the  similar  condition  of  the  blood  in  the  splenic  vein, 
and  they  both  consider  it  probable,  that  a  new  formation  of  red  blood- 
cells  takes  place  within  the  bloodvessels  of  the  liver  and  spleen.  It 
appears  to  me,  that  this  question  must  be  approached  with  very  great 
care,  so  long  as  the  transition  of  the  colorless  cells  into  blood-corpus- 
cles has  not  been  directly  observed,  which  in  this  case  has  by  no  means 
been  done.  At  present  we  are  far  too  little  acquainted  with  the  vital 
relations  of  the  colorless  cells  in  the  blood  to  conclude,  merely  from 
their  existence,  upon  a  formation  of  red  blood-cells,  and  especially  when 
we  remember  the  facts  stated;  since,  as  I  have  elsewhere  shown  ("Mikros. 

46 


722  SPECIAL    HISTOLOGY. 

Anat.,"  II.  2,  p.  292),  it  is  very  possible  that  the  colorless  cells  in  ques- 
tion, in  the  splenic  and  hepatic  veins,  are  derived  from  the  parenchyma 
of  the  spleen,  are  only  accidental  constituents  of  the  blood,  and  as  their 
frequently  multiple  nuclei  seem  to  indicate,  undergo  no  further  develop- 
ments, but  are  in  a  state  of  gradual  removal. 

The  view  propounded  by  Gerlach  and  others,  that  the  cells  contain- 
ing blood-corpuscles,  which  are  met  with  frequently  in  the  spleen  and 
occasionally  in  the  blood,  have  a  relation  to  the  formation  of  blood-cells, 
must  decidedly  be  rejected,  since  the  blood-corpuscles  of  all  these  cells 
are  in  a  state  of  dissolution.* 

*  [It  is  somewhat  surprising  that  Professor  Kolliker  should  not  have  thought  it  necessary 
to  consider  the  doctrine  advocated  by  Wharton  Jones  (1.  c.),  the  truth  of  which  the  latter 
writer  may,  we  think,  be  almost  said  to  have  demonstrated,  viz.  that  the  colored  corpuscle 
of  the  blood  of  Mammalia  is  the  homologue  of  the  "  nucleus"  of  the  colorless  corpuscle  of 
the  same  blood,  and  of  the  "  nucleus"  of  the  corpuscle  of  the  blood  of  oviparous  Vertebrata 
and  of  Jnvertebrata. 

If  we  consider  that  it  is  admitted  on  all  sides:  I,  that  the  colorless  corpuscle  of  Mamma- 
lian blood  and  the  lymph-corpuscle  are  identical.  2,  that  these  are  identical  with  the  color- 
less and  lymph-corpuscles  of  other  Vertebrata.  3,  that  in  the  latter,  the  colored  blood-corpuscle 
proceeds  from  the  colorless  corpuscle  : — only  three  hypotheses  can  well  remain  with  regard 
to  the  relation  of  the  blood-  and  colorless  corpuscles  of  Mammalia — viz.:  that  in  the  text; 
that  which  supposes  that  they  have  an  independent  origin ;  and  that  advocated  by  Wharton 
Jones.  The  two  former  of  these  hypotheses  are  deficient  in  all  positive  basis,  and  the  first 
appears  to  us  extremely  improbable.  On  the  other  hand,  the  third  theory  appears  to  be  in 
harmony  with  all  the  known  facts,  arid  opposed  to  none.  It  is,  shortly,  that  in  Vertebrate 
animals,  the  blood-corpuscle  is  found  in  three  successive  phases  of  development :  that  of 
a  cell  with  granular  contents — the  granules  being  either  fine  or  coarse  ;  that  of  a  cell  with- 
out any  contents  except  the  "  nucleus'' — the  cell  being  either  colorless  or  colored  ;  and, 
finally,  in  that  of  a  free  celloeform  "  nucleus,"  which  is  either  colorless  or  colored.  We 
have  thus  three  phases,  each  of  which  has  two  stages.  The  phases  of  granule-cell  and  nu- 
cleated-cell  are  met  with  in  all  Vertebrata ;  Amphioxus  alone  going  no  further  than  the 
colorless  stage  of  the  second  phase.  In  the  oviparous  Vertebrata  the  blood-corpuscle  pre- 
sents the  first  two  phases  in  both  their  stages.  In  the  Mammalian  cell,  the  phases  exist  in 
all  their  stages ;  but  two  of  the  latter,  that  of  the  colored  nucleated  cell  and  that  of  the 
colorless  free  cellseform  nucleus,  occur  but  rarely  and* scantily.  That  the  red  corpuscle  of 
Mammals  is  the  cella?form  "  nucleus"  of  the  nucleated-cell  stage,  set  free  by  the  bursting  of 
this  cell  itself,  and  become  filled  and  red  by  the  secretion  of  globulin  and  coloring  matter 
into  its  interior,  is  strongly  evidenced  by  the  correspondence  in  size  between  the  "  nucleus" 
and  the  red  corpuscle,  as  the  latter  varies  in  different  animals.  In  the  Elephant  the  red 
corpuscle  is  very  large,  and  in  the  Goat  it  is  very  small;  the  "nucleus"  of  the  colorless  cor- 
puscle varies  correspondingly.  There  is  a  similar  correspondence  in  form  ;  and  it  is  remark- 
able that  in  the  Paco,  whose  red  corpuscles  are,  when  fully  formed,  elliptical,  while  the 
nuclei  of  the  colorless  corpuscles  are  for  the  most  part  circular,  younger  less-colored  red 
corpuscles  are  met  with,  which  are  circular  and  correspond  in  all  respects  with  the  "  nuclei" 
of  the  colorless  corpuscles.  In  dealing  with  objections  which  might  be  raised  from  the 
chemical  and  physical  differences  between  the  red  corpuscles  and  the  "  nuclei,"  Wharton 
Jones  shows  that  these  almost  disappear  if  we  select  the  youngest  state  of  the  red  corpuscle 
as  one  term  of  the  comparison. 

It  is  rare  to  meet  with  the  transition  stage  between  the  phase  of  nucleated  cell  and  that 
of  "  free  cellseform  nucleus"  in  the  blood  of  Man.  We  have,  however,  recently  recorded 
an  observation  of  the  kind  in  unaltered  blood  ("  Quarterly  Journal  of  Micr.  Science,"  vol.  i. 
p.  145),  where  a  well-marked  red  corpuscle  was  observed  within  what  would  otherwise 
have  been  regarded  as  a  colorless  corpuscle,  and  occupying  the  place  of  its  "  nucleus;"  and 


THE    BLOOD    AND    THE    LYMPH.  723 

The  investigation  of  the  heart,  as  regards  the  muscular  fibres  them- 
selves, is  easy,  and  their  anastomoses  will  be  found  without  difficulty  in 
every  carefully  made  preparation.  But  great  difficulties  attend  the 
tracing  of  the  course  of  the  fibres  in  that  organ.  Hearts  that  have 
been  macerated  in  weak  spirit  are  best  adapted  to  this  purpose ;  the 
boiling  in  water,  also,  of  the  recent  heart,  or  of  hearts  that  have  been 
previously  in  salt  for  some  weeks,  has  been  long  recommended,  a  method, 
instead  of  which  Purkinje  and  Palicki  advise  the  boiling  in  a  solution  of 
common  salt,  or  still  better  of  sulphide  of  lime ;  whilst  Ludwig,  after 
removing  the  pericardium,  lays  the  heart  in  water,  and  repeats  this 
maceration  each  time  after  the  removal  of  a  layer  of  the  muscular  sub- 
stance, using  at  the  same  time  slight  pressure.  For  the  bloodvessels, 
the  tearing  of  them  into  lamellae  with  the  forceps  and  scalpel,  which 
alone  was  formerly  employed,  is  not  sufficient ;  the  examination  of 
transverse  and  longitudinal  sections  of  the  entire  wall,  being,  in  addition, 
indispensably  requisite.  The  best  mode  of  proceeding  is  to  dry  portions 
of  the  vessel  stretched  out  upon  paper,  in  which  condition  sections  may 
be  made  even  of  very  small  vessels,  which  are  to  be  again  moistened 
with  water,  and  if  it  be  wished  to  study  the  muscular  structure,  treated 
with  acetic  or  nitric  acid  of  20  per  cent.  (Weyrich),  or  else  with  caustic 
soda,  by  which  reagents  the  elastic  tissue  is  also  very  beautifully  dis- 
played. For  the  speedy,  isolated  demonstration  of  the  epithelium,  the 
elastic  inner  membrane,  and  the  muscular  tunic,  the  larger  vessels  at 
the  base  of  the  brain  have  appeared  to  me  to  be  the  best  adapted;  the 
elastic  membranes  of  the  t.  media  are  readily  isolated  by  maceration  in 
strong  acetic  acid.  Its  muscular  fibres  are  always  to  be  seen  upon  simple 
teasing  out ;  or 'else  readily,  upon  the  addition  of  nitric  acid.  For  the 
study  of  the  capillaries,  the  brain,  the  retina,  the  Tadpole  and  embryos 
are  above  all  to  be  recommended;  for  their  development,  the  Tadpole, 
the  allantois  of  embryos,  and  the  vascular  capsule  of  the  lens.  The 
blood  should  be  examined,  when  it  is  possible,  in  the  serum  itself,  after- 
wards with  the  various  reagents  above  noticed ;  and  regard  must  be 
paid  to  the  great  tendency  to  change  possessed  by  its  elements.  I  inject 
lymphatic  glands  with  carmine  and  size,  or  with  sealing-wax  and  resin 
dissolved  in  alcohol ;  I  also  recommend  sections  of  preparations  hard- 
ened in  alcohol. 

Literature. — J.  C.  Fr.  Wolff,  in  the  "  Memoirs  of  the  Petersburg 
Academy,"  for  the  years  1780-92;  J.  Reid,  Art.  "Heart,"  and  B. 
Searle,  •" Fibres  of  the  Heart,"  in  "Cyclop,  of  Anat.,"  II.;  Par- 

we  may  add  that  the  same  subject  has  recently  afforded,  in  blood  taken  from  the  finger  one 
or  two  hours  after  breakfast,  a  very  considerable  proportion  of  such  corpuscles  with  red 
"nuclei,"  affording  every  transitional  stage  between  the  ordinary  colorless  corpuscle  and 
the  free  red  cellaeform  nucleus.  For  these  observations,  however,  water  and  very  dilute 
acetic  acid  were  added  to  the  blood. — TRS.] 


724:  SPECIAL    HISTOLOGY. 

chappe,  "  Da  Coeur,  de  sa  structure  et  cle  ses  mouvements,"  Paris, 
1844;  C.  Ludwig,  "  Bau  der  Herzventrikel,"  in  "  Zeits.  fur  rat. 
Med.,"  Bd.  VII.,  p.  189,  and  "Ueber  die  Herznerven  der  Frosche," 
in  MUller's  "Archiv,"  1848,  p.  139;  Luschka,  "  Das  Endocardium 
und  die  Endocarditis,"  in  Virchow's  "Archiv,"  IV.,  p.  171;  Remak, 
"  Ueber  die  Ganglien  des  Herzens,"  in  MUller's  "Archiv,"  1844,  p. 
463,  and  "Ueber  den  Bau  des  Herzens,"  ibid.,  1850,  p.  76;  R.  Lee, 
"  Memoir  on  the  ganglia  and  nerves  of  the  heart,"  London,  1851  [and 
"  On  the  Nerves  which  supply  the  Muscular  Structure  of  the  Heart," 
"Proceed.  Roy.  Soc.,"  Nov.  17,  1853,  vol.  vi.,  No.  99,  p.  337];  Bid- 
der "  Ueber  die  Nervencentra  im  Froschherzen,"  in  MUller's  "Archiv," 
1852,  p.  163;  R.  Wagner,  "  Symp.  Ganglien  des  Herzens,"  in 
"Handw.  d.  Phys.,"  part  XIII.,  p.  360;  F.  Rauschel,  "De  arteriar. 
et  venar.  struct.,"  Vratisl.,  1836,  Diss. ;  Kolliker,  "  Ueber  die  Musku- 
latur  der  Gefasse,"  in  "Mitth.  d.  ZUrch.  naturf.,"  Ges.,  1847,  and 
"Zeits.  f.  wiss.  Zool.,"  I. ;  "  Sur  le  developpement  des  vaisseaux  capil- 
laires  sanguins  et  lymphatiques,"  in  "Ann  d.  Sc.  Nat.,"  1846 ;  C. 
Donders  arid  II.  Jansen,  "  Unters.  Uber  die  krankh.  Verander.  d. 
Arterienwande,"  in  "Archiv.  f.  phys.,"  Heilk.,  VII.,  p.  361,  also  in 
"Nederl.  Lancet,"  I.,  p.  473;  Jaesche,  "  De  telis  epithelialibus  in 
gener.  et  de  iis  vasorum  in  specie,"  Dorp.,  1847;  J.  Engel,  "Beitrage 
zur  Anatomie  der  Gefasse,"  in  "  Zeits.  der  Wiener,"  Aerzte,  1847,  pp. 
152,  315,  428,  1849,  p.  121 ;  R.  Remak,  "  Histologische  Bemerkungen 
Uber  die  Blutgefasswande,"  in  Mull.  "Arch.,"  1850;  J.  M.  Schrant, 
"  Ontleedkundige  Studien  over  de  aderlijke  bloedvaten,"  in  "  Tijdschr. 
d.  Maatsch.  tot  bevord.  d.  geneesk.,"  1850,  p.  2;  M.  Schultze,  "  De 
arteriarurn  structura,"  Gryph.,  1850;  H.  Weyrich,  "  De  textura,  et 
structural  vas  lymphatic.,"  Dorpat,  1851 ;  Fr.  Wahlgren,  "  Vensyste- 
mets  allmanna  Anatomi,"  Lund.,  1851 ;  F.  Noll  (and  Ludwig),  "  Ueber 
den  Lymphstrom  u.  die  Anatomie  der  Lymphdrusen,"  in  Henle's 
"  Zeits.,"  IX.,  p.  52 ;  Remak,  "  Ueber  blutleere  Gefasse  im  Schwanze 
d.  Froschlarven,"  in  Mull.  "Arch.,"  1850,  pp.  79,183;  J.  Engel, 
"Bau  u.  Entwicklung  der  LymphdrUsen,"  in  "Prag.  Vierteljahrschrift," 
1850,  p.  Ill ;  0.  Heyfelder,  "  Ueber  den  Bau  der  LymphdrUsen," 
Bresl.,  1851 ;  H.  Nasse,  Art.  "  Chylus,  Lymphe,  u.  Blut,"  in  Wag- 
ner's "  Handw.  d.  Physiol.,"  Bd.  I.;  H.  MUller,  "Beitrage  z.  Morpho- 
logic des  Chylus  u.  Eiters,"  in  "Zeits.  f.  rat.  Med.,"  1845;  R.  Wag- 
ner, "Beitrage  z.  vergl.  Physiologic  d.  Blutes,"  Leipzig,  1833,  and 
"Nachtrage  zur  vergl.  Physiol.,"  I.,  ibid.,  1838;  J.  C.  Fahrner,  "De 
globulorum  sanguinis  origine,"  Turici,  1845 ;  A.  Kolliker,  "  Ueber  die 
Blutkorperchen  eines  menschl.  Embryo  und  die  Entwickl.  d.  Blutk.  b. 
Saugethieren,"  in  "  Zeitsch.  f.  rat.  Med.,"  Bd.  IV.,  1846,  p.  42  ;  C. 
Donders  u.  J.  Moleschott,  "  Untersuch.  U.  d.  Blutkorperchen,"  in  the 
"Holland.  Beitragen,"  III.,  360;  Donders,  in  "Ned.  Lancet,"  1846; 


THE    EYE.  725 

Wharton  Jones,  "  The  blood-corpuscle  considered  in  its  diff.  phases  of 
development,"  in  the  "  Phil.  Trans.,"  1846,  II.,  p.  82.  Besides  which 
should  be  consulted  the  hand-books  of  E.  H.  Weber  and  Henle,  and 
the  recent  embrjological  works  of  Vogt,  Remak,  Pre'vost,  Lebert,  and 
Courty.  [The  more  recent  publications  on  the  vascular  system  are : 
Von  Hessling  "  Histologische  Mittheilungen,"  in  Siebold  and  Kolli- 
ker's  Zeitschrift,  v.,  p.  189  ;  A.  Kolliker,  "  Ueber  den  feinern  Bau 
u.  die  Functionen  der  Lymphdrlisen,"  in  "Verb,  d.  phys.  med.  Ges.  in 
Wurzb.,"  iv.  2,  1854;  Rokitansky,  "Ueber  einige  der  wichtigsten 
Krankheiten  der  Arterien,"  Wien,  1852;  C.  Wedl,  "Ueber  Blut.  u. 
Blutgefass  Neubildung,"  in  "Schmidt's  Jahrbiicher,"  No.  12,  1853;  J. 
Moleschott,  "  Ueber  das  Verhaltniss  der  farblosen  Blutzellen  zu  den 
farbigen  in  verschiedenen  Zustanden  des  Menschen,"  in  "  Wiener 
Mediz.  Wochenbl."  No.  8,  1854 ;  T.  Williams,  "  On  the  Blood  proper 
and  the  Chylaqueous  Fluid  of  Invertebrate  Animals,"  in  "Phil. 
Trans.,"  part  ii.,  1853,  and  "  The  Blood,  its  Chemistry,  Physiology, 
and  Pathology,"  in  British  and  Foreign  Med.  Chirurg.  Review,  Oct. 
1853,  and  Jan.  1854.— DaC.] 


OF  THE  HIGHER  ORGANS  OF  SENSE. 
I.     OF  THE  ORGAN  OF  VISION. 

§  224.  The  visual  organ  consists  of  the  eyeball,  or  the  proper  sensi- 
tive apparatus,  and  the  accessory  parts,  some  for  its  protection,  some  for 
its  movement :  viz.  the  eyelids,  the  ocular  muscles,  and  the  lachrymal 
organs.  The  eyeball  itself  is  a  very  complex  organ,  into  the  constitu- 
tion of  which  nearly  all  the  tissues  of  the  body  enter.  It  is  composed 
essentially  of  three  tunics  :  a  fibrous — the  sclerotica  and  cornea,  a  vas- 
cular— the  cJwrioidea  and  iris,  and  a  nervous;  and  of  two  internal 
refractive  media — the  vitreous  humor  and  the  crystalline  lens. 

A.    OF  THE  EYEBALL. 

§  225.  Fibrous  tunic  of  the  Eye. — The  external  envelop  of  the  eye- 
ball is  formed  by  a  tough,  fibrous  membrane,  composed  chiefly  of 
connective  tissue,  which,  to  outward  appearance,  is  divisible  into  a 
smaller,  anterior,  transparent  portion — the  cornea;  and  a  larger, 
opaque,  posterior  part — the  sclerotic ;  but,  as  shown  by  its  development 
and  more  intimate  structure,  is  to  be  regarded  as  a  membrane  continu- 
ous throughout. 

The  sclerotica,  also  termed  the  tunica  albuginea,  is  a  white,  very 
tough  and  strong,  fibrous  membrane,  which  gradually  diminishes  in 
thickness  as  it  advances  forwards  from  the  posterior  part  of  the  eye, 


726 


SPECIAL    HISTOLOGY. 


where  it  is  directly  connected  with  the  sheath  of  the  optic  nerve, 
although  it  is  again  strengthened,  in  front,  by  the  expanded  tendons  of 
the  recti  muscles,  with  which  it  is  blended,  afterwards  becoming  con- 
tinuous with  the  cornea.  When  boiled,  it  affords  common  gelatin,  and 
it  consists  of  true  connective  tissue,  the  fibrils  of  which  are  very  dis- 
tinctly manifest  when  the  structure  is  teased  out,  or  transverse  sections 

Fig.  296. 

si 
- 


are  treated  with  acetic  acid.  The  bundles  themselves  are  straighter,  in 
other  respects  as  in  the  tendons,  being  intimately  united  and  conjoined 
into  larger,  thinner  or  thicker,  flattened  bands,  which  are  disposed  in 

FIG.  29G. — Transverse  section  through  the  tunics  of  the  eye,  in  the  region  of  the  ciliary  pro- 
cesses, magnified  12  diameters:  <S>cZ.,  sderotica;  C,  cornea ;  Pr.  «7.,  proccssus  ciliaris  •  C.a,  an- 
terior chamber ;  C.p,  posterior  chamber;  C.v.  corpus  vitreum ;  C.P.  canalis  Petiti  ;  Z,  lens  •  /, 
iris;  a,  conjunctiva  cornece,  epithelium;  6,  homogeneous  lamella  beneath,  continuous  with  the 
conjunctiva  sclcrotica,  x;  c,  fibrous  layer  of  the  cornea;  d,  membr.  Demoursii ;  e,  indication  of 
its  epithelium  ;  y,  termination  of  the  membrana  Dcmoursii,  and  its  transition  into  peculiar 
fibres,  g,  which  are  continued  at  i,  upon  the  iris  constituting  the  lig.  pedinatum  iridis ;  h, 
canalis  Schlcmmii ;  k,  musculus  ciliaris  s.  tensor  chorioideas,  springing  from  its  inner  wall,  I;  m, 
pigment  layer  of  the  ciliary  processes ;  «,  the  iris  ;  o,  fibrous  layer  of  the  iris  ;  p,  indication 
of  its  epithelium;  </,  anterior  wall  of  the  capsule  of  the  lens;  z,  posterior  wall;  s,  indication 
of  the  epithelium  of  the  capsule;  t,  zonula  Zinnii,  or  anterior  thickened  portion  of  the  hyaloid 
membrane ;  «,  its  free  anterior  lamina  (proper  zonula),  inserted  into  the  border  of  the  lens: 
v,  its  posterior  lamina  blended  with  the  posterior  wall  of  the  lenticular  capsule;  w,  colorless 
epithelium  of  the  ciliary  processes ;  it/,  anterior  termination  of  this  epithelium.  In  part 
after  Bowman. 


THE    EYE.  727 

the  transverse  and  longitudinal  directions,  alternating  pretty  regularly 
through  the  entire  thickness  of  the  tunic,  and  consequently  in  vertical 
sections,  producing  a  larnellated  structure.  Truly  independent  lamellce, 
however,  nowhere  exist,  the  various  longitudinal  layers  having  numerous 
points  of  connection,  as  have  also  the  transverse  lamince.  However,  on 
the  external,  but  more  particularly  on  the  internal  surface  of  the  sclerotic 
the  longitudinal  fibres  are  collected  into  somewhat  thicker  plates,  and 
thus  acquire  a  greater  independence. 

Numerous  fine  elastic  elements  pervade  the  connective  tissue  of  the 
sclerotic,  of  the  same  form  as  those  in  the  tendons  and  ligaments  (§  80), 
viz. :  as  a  network  of  the  finer  or  finest  fibres,  in  which  the  sites  of  the 
original  formative  cells  are  indicated  by  enlargements  with  nuclear  rudi- 
ments, so  that  the  whole  often  very  closely  resembles  anastomosing,  fusi- 
form, and  stellate  cells.  During  life,  the  elements  of  this  network  occa- 
sionally appear  still  to  possess  cavities  and  fluid  contents ;  at  any  rate 
in  portions  of  a  dried  sclerotic,  air  is  always  to  be  seen  in  the  bodies  of 
all  the  cells  (these  are  the  cretaceous  corpuscles  of  Huschke),  and  con- 
sequently, in  this  situation  the  opinion  propounded  by  Virchow,  that 
channels  of  this  kind  are  a  sort  of  nutritive  canals,  would  appear  to  be 
completely  justified,  and  the  more  so,  because  the  vessels  of  this  tunic 
are  at  all  events  very  scanty.  They  are  derived  chiefly  from  the  ciliary 
arteries  and  from  those  of  the  muscles  of  the  eyeball,  and  constitute, 
as  I  and  Brlicke  have  found,  a  tolerably  wide-meshed  network  of  capil- 
laries of  the  last  order.  Bochdalek  has  recently  described  nerves  (and 
also  Rahm,  in  the  Rabbit)  in  the  sclerotic,  but  with  Arnold  and  Huschke, 
I  have  hitherto  been  unable  to  satisfy  myself  that  these  are  anything 
more  than  branches,  on  its  inner  side,  running  to  the  ciliary  ligament. 

The  cornea  (Fig.  296  0)  is  perfectly  transparent,  still  more  compact 
and  tough  than  the  sclerotic,  and  is  composed  of  three  special  layers, 
viz. :  1,  of  the  conjunctiva!  membrane  (conjunctiva  cornece) ;  2,  of  the 
proper  cornea  ;  and  3,  of  the  membrane  of  Descemet ;  the  first  and  last 
of  which  are  formed  of  an  epithelium  and  a  subjacent  structureless  mem- 
brane, and  the  middle  one  of  a  fibrous  tissue  of  a  peculiar  kind. 

The  proper  cornea,  or  the  fibrous  layer  (Fig.  296  c),  by  far  the  most 
important  part  of  the  whole  tunic,  consists  <Jf  a  fibrous  substance  closely 
allied  to  connective  tissue,  but  which,  according  to  J.  Mliller,  affords 
when  boiled,  not  gelatin,  but  chondrin.  Its  elements,  pale  bundles, 
0*002-0'004  of  a  line  in  diameter,  in  which,  at  least  when  teased  out, 
finer  fibrils  are  usually  perceptible,  sometimes  more  and  sometimes  less 
distinctly,  are  united  into  flat  bundles.  These  bundles,  which  have  their 
flat  sides  always  parallel  with  the  surface  of  the  cornea,  decussate  in 
various  directions,  and  exhibit,  if  not  complete  lamellce,  yet  a  distinctly 
laminated  structure,  owing  to  which  the  cornea  is  very  readily  torn  and 
penetrated  in  the  direction  of  its  surfaces,  and  with  great  difficulty  in 


728  SPECIAL    HISTOLOGY. 

that  of  its  thickness.  The  correspondence  of  the  corneal  elements  with 
connective  tissue  is  also  shown  by  the  following  circumstances  :  1,  that 
it  is  continuous  at  the  border,  by  its  elements,  which  in  that  situation 
follow  principally  a  radiating  direction,  directly  and  without  interruption 
with  the  similarly  disposed  fibres  of  the  sclerotic,  so  that  there  cannot 
be  the  least  question  as  to  the  non-existence  of  any  natural  demarcation 
between  the  two  tunics  ;  and  2,  as  Virchow  was  the  first  to  show,  that  a 
great  number  of  anastomosing,  fusiform  and  stellate,  nucleated  cells  lie 
among  its  bundles,  just  as  they  do  in  undeveloped  elastic  tissue  (connec- 
tive tissue-corpuscles  of  Virchow),  which  also  exist  in  the  sclerotic, 
though  more  branched.  It  can  perhaps  scarcely  be  doubted,  that  the 
nutritive  fluid,  with  which  the  cornea  is  constantly  imbued  in  conside- 
rable quantity,  and  which,  in  the  large  eyes  of  animals,  may  be  directly 
demonstrated  by  expression,  js  in  great  measure  conveyed  and  distri- 
buted in  the  interior,  by  the  cells  in  question;  a  view  which  is  only 
strengthened  by  the  knowledge  that  these  cells,  in  morbid  conditions  of 
the.  cornea,  very  frequently  contain  oil-drops,  and  occasionally,  accord- 
ing to  Bonders,  even  pigment,  in  their  interior.  The  "  corneal  tubes" 
injected  by  Bowman  in  the  eye  of  the  Ox  and  in  that  of  Man  must  not 
be  confounded  with  this  cellular  network,  and  are  probably  to  be  ex- 
plained as  artificial  dilatations  of  the  minute  interstices  which  normally 
exist  between  the  structural  elements  of  the  cornea,  and  which  it  is 
thought  may  occasionally  be  perceived  on  microscopical  examination. 

The  conjunctival  membrane  of  the  cornea  (Fig.  296  a,  b)  is  composed 
principally  of  a  soft,  laminated  epithelium,  0-023-0-050  of  a  line  thick, 
in  which  the  deeper  layers  of  cells  are  elongated  and  placed  vertically 
upon  the  cornea,  whilst  the  middle  ones  are  more  of  a  rounded  form, 
and  as  they  approach  the  surface,  pass  into  a  layer,  0*008—0*01  of  aline 
thick,  corresponding  to  the  horny  layer  of  the  epidermis,  composed  of 
plates  0*01-0*14  of  a  line  in  size,  though  still  nucleated  and  soft.  Many 
of  these  latter  cells,  as  I  have  shown  ("Zeitsch.  f.  wiss.  Botanik,"  II., 
p.  80),  in  consequence  of  their  mutual  pressure,  present  larger  or  smaller 
pits,  like  certain  cells  in  the  urinary  bladder,  so  as  when  viewed  on  the 
side  often  to  exhibit  a  stellate  figure,  which  induced  Valentin,  who  first 
noticed  this  form,  to  regard  them  as  cells  with  processes.  Beneath  the 
epithelium,  which,  after  death,  is  very  soon  rendered  opaque  by  both 
water  and  acetic  acid,  is  a  structureless  lamella,  first  described  by  Bow- 
man (anterior  elastic  lamella,  of  Bowman),  0*003-0*004  of  a  line  thick, 
which  is  especially  evident  in  vertical  sections  and  in  folds  of  thin  super- 
ficial sections,  upon  the  addition  of  alkalies,  although  it  is  by  no  means 
so  sharply  defined  from  the  true  cornea  as  the  membrane  of  Descemet, 
nor  does  it  seem  to  be  of  the  same  import  as  that  membrane,  but  is  per- 
haps no  more  than  the  remainder  of  the  vascular  layer  of  the  corneal 
conjunctiva,  which  exists  at  an  earlier  period.  Arched  fibres,  like  rigid 


THE    EYE.  729 

bundles  of  connective  tissue  or  elastic  fibres,  are  occasionally  visible, 
given  off  from  it,  and  penetrating  the  cornea  to  a  certain  distance,  where 
they  are  lost. 

The  membrane  of  Descemet  or  Demoiirs,  also  termed  the  membrane 
of  the  aqueous  humor  (memb.  Descemeti,  s.  Demoursii  s.  humoris  aquei) 
(Fig.  296  d),  consists  of  an  elastic  membrane  rather  laxly  attached  to 
the  cornea!  tissue- — the  proper  membrane  of  Descemet  \_posterior  elastic 
lamina  of  the  cornea,  Bowman},  and  of  an  epithelium  on  its  inner  sur- 
face. The  former  is  as  clear  as  glass,  brilliant,  quite  structureless, 
easily  lacerable,  though  tolerably  firm,  and  so  elastic,  that  when  it  is 
raised  from  the  cornea  by  the  scalpel  and  forceps,  by  boiling  in  water, 
or  by  maceration  in  alkalies,  under  which  treatment,  as  under  reagents 
in  general,  it  does  not  lose  its  transparency,  it  always  rolls  up  strongly 
and  towards  the  front.  Towards  the  border  of  the  cornea,  the  mem- 
brane of  Descemet,  which  is  0-006-0-008  of  a  line  thick,  and  in  chemi- 
cal properties  approaches  the  homogeneous  membranes  (§  16),  passes 
into  a  peculiar  system  of  fibres,  first  accurately  described  by  Bowman. 
This  set  of  fibres  commences  at  a  short  distance  from  the  margin  of  the 
cornea  on  the  anterior  surface  of  the  membrane  of  Descemet  (Fig.  296  </), 
as  an  elongated  network  of  fine  fibrils,  like  the  finer  elastic  fibrils,  after- 
wards gradually  increasing  in  thickness,  until  at  the  very  margin  of  the 
cornea,  the  whole  thickness  of  the  membrane  of  Descemet  is  broke*n 
up  into  a  network  of  thicker  fibres  and  trabeculce,  which  turn  over  upon 
the  border  of  the  iris  (Fig.  296  i],  and  are  blended  with  its  anterior 
surface.  Consequently,  the  membrane  of  Descemet  does  not  cease,  as 
is  usually  stated,  with  a  free  border,  but,  on  the  contrary,  is  continued 
(Fig.  296/)  all  round  the  anterior  chamber,  by  numerous  free  processes 
passing  across  it,  upon  the  iris.  The  elements  of  this  ligamentum 
iridis  pectinatum,  as  it  is  termed  by  liuek  \_pillars  of  the  iris,  Bowman], 
and  which,  according  to  Luschka,  is  much  more  distinct  in  the  eyes  of 
certain  animals  (Dog,  for  instance)  than  in  Man,  were  formerly 
("  Zeitsch.  f.  wiss.  Zool.,"  I.,  p.  54)  referred  by  me  to  reticular  connec- 
tive tissue,  at  a  time  when  I  was  acquainted  with  their  form  but  not 
with  their  reactions;  now,  however,  I  should  rather  be  inclined  to 
describe  them  as  an  intermediate  form  between  the  connective  and 
elastic  tissues.  The  bundles  in  question  correspond  with  those  of  con- 
nective tissue,  in  their  width  (0-004-0-012  of  a  line)  and  paleness,  and 
also  in  the  circumstance  that  still  finer  fibrils  are  usually  to  be  distin- 
guished in  them,  whilst  in  their  rigidity  and  chemical  reactions  they 
approach  the  elastic  tissue  and  the  membrane  of  Descemet  itself,  of 
which  latter,  though  probably  differing  from  it  genetically,  they  are,  in 
the  adult  at  any  rate,  an  integral  constituent. 

The  epithelium  of  the  "membrane  of  Demours"  (Fig.  296  e\  which, 
in  Man,  frequently  does  not  retain  the  perfect  condition,  is  a  single 
layer,  0-002-0-003  of  a  line  thick,  of  well-formed,  polygonal  cells, 


730  SPECIAL      HISTOLOGY. 

0'006-0'01  of  a  line  in  size,  with  extremely  fine  and  pale  granular 
contents,  and  round  nuclei  of  0-003-0-005  of  a  line.  Towards  the 
border  of  the  cornea  the  cells  of  which  the  epithelium  is  constituted 
become  smaller,  and  then  ceases  as  a  connected  layer,  whilst  isolated 
indications,  usually  of  elongated,  or  even  fusiform  epithelial  cells,  are 
continued,  over  the  fibrous  network  of  the  lig.  pectinatum,  and  sur- 
rounding its  elements,  upon  the  border  of  the  iris,  where  a  perfect 
epithelium  is  again  met  with.* 

The  cornea  in  the  adult  is  nearly  altogether  non-vascular,  whilst,  as 
J.  Miiller  and  Henle  first  observed  ("  De  membr.  pupilL,"  p.  44),  in 
the  human  embryo  and  foetal  Lamb  a  rich  capillary  plexus  exists  in  the 
conjunctiva  cornea?,  but  which  does  not  appear  to  extend  as  far  as  the 
centre.  Towards  the  end  of  foetal  life  and  after  birth,  this  plexus  dimi- 
nishes in  breadth,  in  animals  to  a  less  extent  than  in  Man,  so  that  in 
the  latter  we  find  bloodvessels  at  the  margin  of  the  cornea,  only  in  a 
zone  of  J-  or  at  most  of  1  line  in  width.  These  vessels  are  for  the  most 
part  the  fine  and  finest  capillaries  of  0-002-0-004  of  a  line,  forming  one 
or  several  rows  of  arches,  and  thus  terminating ;  they  are  lodged  in  the 
substance  of  the  conjunctiva,  which  here  extends,  in  the  form  of  a  dis- 
tinct layer,  for  a  short  distance  upon  the  cornea,  ceasing  in  its  anterior 
structureless  lamella.  In  animals  these  superficial  or  conjunctival  vessels 
aho  exist,  but  are  usually  much  better  displayed,  and  extend  further 
towards  the  centre ;  frequently  over  half  the  radius,  or  even  beyond  it. 
Besides  these,  deeper  capillaries  derived  from  the  sclerotic  also  occur  in 
the  substance  of  the  cornea,  usually  accompanying  the  nervous  trunks, 
in  which  they  either  form  a  single  or  a  few  very  much  elongated  loops, 
or  extend  a  little  beyond^  them ;  they  all  terminate  in  loops,  the  finest 
vessels  constituting  which,  like  the  superficial  capillaries,  measure 
scarcely  more  than  0-002  of  a  line.  I  have  also  noticed,  in  Man,  these 
peculiar  corneal  vessels  accompanying  the  nervous  trunks,  although  not 
constantly  and  never  so  much  developed. 

Nothing  certain  is  known  of  the  lymphatics  of  the  cornea  (vid.  also, 
Arnold,  "Anat."  II.  p.  988),  though  I  have  recently  observed  vessels 
in  the  cornea  of  a  young  Cat  (Fig.  297),  which  I  can  scarcely  regard 
as  anything  else  than  lymphatics.  In  this  instance,  at  the  margin  of 
the  cornea,  together  with  the  very  distinct  capillary  loops  containing 
blood-corpuscles,  there  were  numerous  wider  vessels  (of  0-01-0-02,  or 
even  0-03  of  a  line),  which  either  extended  singly  into  the  cornea  to  the 

*  [This  statement  is  directly  opposed  to  Mr.  Bowman's  observations  (op.  c.,  p.  22).  who 
says,  "  that  it  would  appear  from  what  has  been  said  concerning  the  conversion  of  the  pos- 
terior elastic  lamina  at  its  border  into  fibrous  tissue,  which  in  part  passes  through  the 
aqueous  humor  to  the  iris,  that  this  epithelium  must  cease  with  the  elastic  lamina,  since 
there  is  no  longer  any  stratum  upon  which  it  can  rest."  He  has  been  unable  "  to  discover 
the  smallest  appearance  of  it  upon  the  pillars  of  the  iris,  and  conceives,  therefore,  that  it  is 
limited  to  the  cornea."  And  according  to  the  same  accurate  observer,  the  front  of  the  iris 
has  no  true  epithelial  investment. — Tus.] 


THE     EYE.  731 

same  distance  as  the  bloodvessels,  and  terminated  in  dilated  clavate 
ends,  or  in  acuminate  points,  or  two,  three,  or  more  together,  formed 
simple  loops,  from  which  in  like  manner  other  caecal  processes  were 
given  off.  Notwithstanding  their  capacity  these  vessels  presented  a 
delicate,  structureless  coat,  with  scattered,  appressed  nuclei,  and  con- 
tained a  clear  fluid,  in  which  frequently  a  few,  and  occasionally  even  a 
good  many  clear  spherical  cells,  exactly  like  lymph-corpuscles,  were 
visible.  If  I  had  found  these  vessels  in  other  animals  as  well,  I  should 
at  once  have  declared  them  to  be  the  commencements  of  the  lymphatics 
of  the  conjunctiva,  but  it  appears  to  me,  at  present,  more  prudent  to 
regard  this  explanation  perhaps  as  probable,  but  not  as  certain.  For 


although,  in  this  one  instance  of  the  Cat,  the  vessels  in  question  were 
very  manifest  in  both  cornece,  so  that  I  was  able  to  point  them  out  to 
many  of  my  colleagues,  particularly  to  R.  Yirchow  and  H.  Miiller,  I 
have  since  been  unable  to  perceive  any  decided  indication  of  pale  vessels 
of  the  same  kind,  either  in  the  adult  Cat  or  in  the  newly  born  Kitten, 
or  in  the  Dog,  Ox,  Sheep,  Pig,  and  Rabbit.  But  it  is  now  well  known 
that  the  commencements  of  lymphatics,  for  once  when  they  are  distinct 
(in  the  intestinal  villi  for  instance),  escape  the  sight  perhaps  twenty  or 
thirty  times.  Nevertheless,  in  this  case  there  seems  to  be  every  reason 
for  caution.  Should  the  vessels  in  question  not  be  lymphatics,  they 
might  be  regarded  as  pathological  excavations,  or  as  transformations  of 
earlier  embryonic  corneal  vessels  ;  but  the  manifest  limitary  membrane 
of  the  canals  is  opposed  to  the  former  supposition,  and  the  latter  is 
upset  by  the  circumstance  that  they  occurred  in  the  same  plane  with 
true  vessels,  and  did  not  enter  into  the  least  anastomosis  with  them. 

The  nerves  of  the  cornea  discovered  by  Schlemm,  are  derived  from 
the  nervuli  ciliares,  penetrate  the  sclerotic  at  its  anterior  border  (in  the 

FIG.  297. — Capillaries  and  lymphatics  (?)  at  the  border  of  the  cornea  of  a  Kitten :  a  a, 
trunks  of  the  colorless  vessels;  6,  caecal  clavate  extremity  of  one  of  these  vessels;  c,  pointed 
prolongation;  d,  loops;  e,  blood-capillaries. — Magnified  250  diameters. 


732  SPECIAL    HISTOLOGY. 

Rabbit,  according  to  Rahm,  in  the  posterior  half  of  the  globe),  and 
thence  enter  the  fibrous  layer  of  the  cornea.  In  Man,  they  are  readily 
found  at  the  margin  of  that  tunic,  in  the  form  of  24-36  finer  and 
thicker  twigs,  but  scarcely  exceeding  0*02  of  a  line  in  size.  What 

especially  characterizes  these  nerves, 

Fig.  298.  .  i      .1      •  ^          c    j. 

_! is  not  so  much  their  mode  of  dis- 

tribution, which  takes  place  with 
numerous  bifurcations  and  anasto- 
moses, so  as  to  produce  a  wide  ner- 
vous plexus  extending  throughout 
the  cornea,  as  the  circumstances  that 
they  still  contain  dark-bordered 
though  fine  (0-001-0-002  of  a  line), 
primitive  tubules,  only  at  the  mar- 
gin of  the  cornea,  in  a  zone  not 
always  of  uniform  width,  -J-l  line 
broad,  and  in  their  further  course 
present  nothing  but  non-medullated 
perfectly  clear  and  transparent  fibres,  O'0005-O'OOl  of  aline  at  most  in 
diameter,  so  that  they  offer,  at  any  rate,  no  more  obstacle  to  the  pas- 
sage of  the  rays  of  light  than  the  other  corneal  elements,  as  is  evident 
from  the  difficulty  with  which  they  are  traced  under  the  microscope. 
The  trunks  of  these  nerves  exhibit,  though  rarely,  bifurcations  of  the 
primitive  tubules,  but  divisions  of  this  kind  are  never  presented  in  the 
plexus  formed  by  them,  the  conditions  in  which,  however,  on  account  of 
their  paleness,  scarcely  admit  of  being  quite  certainly  traced.  This 
plexus  is  situated  in  the  proper  cornea,  although  nearer  to  its  anterior 
surface,  and  from  the  absence  of  any  indication  of  free  terminations  to 
the  nerve-fibres,  appears  to  consist  altogether  of  anastomosing  branches 
of  the  finest  sort,  so  that,  though  not  in  the  form  of  loops,  a  mutual 
connection  of  the  nerve-tubes  may  be  assumed  to  exist. 

The  bloodvessels  of  the  conjunctiva  cornece,  in  the  healthy  condition 
of  the  organ,  are  very  scanty,  and  the  figures  given  by  Homer  (Am- 
mon's  "  Zeitsch."  V.  21,  Tab.  I.  Figs,  9,  11),  and  Arnold  ("  Icon.  org. 
sens,"  II.  Fig.  6),  I  regard  as  exceptional  instances  ;  but,  as  is  well 
known,  they  may  become  so  much  developed,  in  inflammations,  as 
almost  to  cover  the  entire  cornea.  The  proper  corneal  vessels  also,  in 
such  cases,  appear  to  be  developed  more  deeply  in  the  interior.  With 
regard  to  the  vasa  serosa  of  the  cornea,  vid.  §  217.  The  statements 
that  have  been  made  respecting  the  bloodvessels  of  the  membrana  De- 
moursii,  in  inflammation  of  the  eye  (vid.  Henle,  "De  memb.  pupill.,"  p. 

FIG.  298. — Coarser  ramifications  of  the  nerves  of  the  cornea  of  the  Rabbit.  Where  the 
trunks  are  represented  as  dark,  they  contain  dark-bordered  primitive  fibres. 


THE    EYE.  733 

53),  appear  still  to  demand  confirmation ;  and  Arnold's  "  serous  ves- 
sels," in  the  normal  condition  of  the  membrane  of  Descemet  ("Anat." 
I.  Tab.  II.  Fig.  5,  II.  p.  1015),  are  nothing  more  than  the  anastomo- 
sing fibres  of  the  ligamentum  pectinatum  of  the  iris.  The  cornea, 
although  vascular  only  at  its  margin,  is  nevertheless  not  unfavorably 
circumstanced  as  regards  its  nutritive  conditions.  Wounds  in  it  rapidly 
unite,  portions  of  the  epithelium  or  even  of  the  fibrous  layer  -when  re- 
moved, are  restored,  and  ulcers  are  filled  up  from  the  bottom  with  new 
corneal  substance.  Fatty  deposits  in  its  tissue,  particularly  in  its  cel- 
lular elements  (especially  above  and  below,  or  even  all  round),  produce 
a  yellow  zone — the  so-termed  arcus  senilis  (gerontoxori).* 

§  226.  The  vascular  tunic  (tunica  vasculosa)  or  uvea. — The  second 
tunic  of  the  eyeball  is  a  highly  vascular  membrane,  containing  a  great 
amount  of  pigmentary  matter,  and  divisible  into  a  larger  posterior  por- 
tion— the  choroid,  and  a  less  extensive  anterior  segment — the  iris. 

The  choroid  is  an  easily  lacerable  membrane,  1-15-1-30  of  a  line 
thick,  extending  from  the  entrance  of  the  optic  nerve,  where  it  is  per- 
forated by  a  rounded  opening,  nearly  to  the  anterior  border  of  the 
sclerotic,  where  it  presents  a  thicker  part — the  corpus  ciliare,  and  is 
then  continuous  with  the  iris.  Its  external  surface  is  attached  not  only 
by  larger  vessels  and  nerves,  but  also  otherwise,  tolerably  intimately,  to 
the  sclerotic,  so  that  in  exposing  the  cJioroid  a  portion  of  the  membrane 
always  remains  more  or  less  adherent  to  the  sclerotic,  in  the  form  of  a 
brown  tissue.  This  is  the  so-termed  lamina  fusca  of  authors,  which 
there  is  no  ground  for  separating  from  the  vascular  tunic  and  regard- 
ing as  a  distinct  membrane,  although  in  many  instances  scattered  pig- 
ment-cells, such  as  exist  in  it,  are  found  to  extend  even  into  the  con- 
nective tissue  of  the  sclerotic.  The  inner  surface  of  the  choroid  is 
smooth  and,  at  the  ora  serrata,  very  closely  connected  with  the  retina, 
elsewhere  more  loosely ;  whilst  anteriorly  to  the  ora  serrata,  and  par- 
ticularly in  the  processus  ciliares,  it  is  very  intimately  united  with  the 
hyaloid  membrane  (zonula  Zinnii),  so  that  the  two  are  never  com- 
pletely separable. 

The  choroid  consists  essentially  of  two  portions,  a  vascular,  external 
thicker  layer — the  proper  choroid,  and  an  inner  distinctly  colored 
lamina — the  pigmentum  nigrum  ;  the  former,  however,  may  be  again 
subdivided  into  three,  but  by  no  means  sharply  defined  layers,  viz.  :  1, 
an  external,  brown,  soft  lamella,  supporting  the  ciliary  nerves  and  long 
ciliary  vessels,  and,  in  front,  containing  the  ciliary  muscle — the  outer 
pigment-layer ;  2,  the  less  deeply  colored,  proper  vascular  layer,  with 
the  larger  arteries  and  veins ;  and  3,  a  colorless,  delicate,  internal  laytr, 

*  [As  shown  by  Mr.  Edwin  Canton'  in  his  "  Observations  on  the  Jlrcus  senilis,  or  fatty 
degeneration  of  the  Cornea.'' — -"Lancet,"  vol.  i.  1850,  p.  5.60. — TRS.] 


734  SPECIAL    HISTOLOGY. 

containing  an  extremely  abundant  capillary  plexus — the  membrana 
choriocapillaris,  which,  however,  does  not  extend  further  in  front  than 
the  ora  serrata.  The  tissue  of  which  the  proper  choroid  is  constituted, 
except  the  vessels  and  nerves,  which  indeed  make  up  a  considerable  part 
of  it,  and  the  ciliary  muscle,  is  of  a  peculiar  kind,  and  cannot  conve- 
niently be  described  under  any  particular  head,  but  like  the  fibres  of 
the  lig.  pectinatum  of  the  iris,  though  in  somewhat  different  respects,  is 
intermediate  between  the  connective  and  elastic  tissues.  In  the  outer 
portions  of  the  tunic,  this  stroma  is  formed  of  fusiform  or  stellate,  very 
irregular,  and  extremely  pale,  or  more  or  less  brown  nucleated  cells, 
0-008-0*02  of  a  line  long,  which  anastomose  frequently  with  each  other 
by  shorter  or  longer,  usually  very  delicate  (0-0005  of  a  line),  but  rather 
rigid  processes,  and  from  their  great  number  represent  a  lax  membra- 
nous tissue.  There  would  be  nothing  very  pecu- 
liar in  this,  and  these  cellular  networks  might 
properly  be  classed  with  other  similar  anasto- 
mosing pigment-cells,  as  for  instance  in  the 
batrachian  larva  (most  characteristic  in  Alytes); 
but  in  the  inner  layers  of  the  choroid,  and  espe- 
cially in  the  membrana  cJioriocapillaris,  they 
gradually  pass  into  homogeneous,  nucleated  tis- 
sue, at  first  containing  a  little  pigment,  but  after- 
wards none  at  all ;  and  which,  although  in  ap- 
pearance very  similar  to  homogeneous  connective 
tissue,  is  distinguished  from  it  by  its  resistance 

to  acids  and  alkalies,  and  approximates  the  elastic  tissue,  from  which, 
however,  it  likewise  differs  in  its  trifling  elasticity  and  paleness ;  whence 
it  is  better,  at  present,  to  regard  it  as  sui  generis. 

The  ciliary  ligament  of  anatomists,  or  the  musculus  ciliaris  s.  tensor 
clwrioidece  (Fig.  296  &),  the  really  muscular  nature  of  which  was  recog- 
nized almost  simultaneously  by  Briicke  and  Bowman,  is  a  tolerably 
thick  layer  of  radiating  smooth  muscular  bundles,  passing  from  the 
most  anterior  border  of  the  sclerotic  upon  the  ciliary  body,  and  ceasing 
in  its  anterior  half,  opposite  the  part  where  the  ciliary  processes  are 
placed,  internally.  More  precisely  described,  the  ciliary  muscle  arises 
where  the  sclerotic  is  grooved  for  the  formation  of  the  venous  sinus  of 
Schlemm,  and,  in  fact,  from  a  special,  dense,  smooth  tract  (Fig.  296  T), 
which,  forming  the  inner  wall  of  the  canal  in  question,  coalesces  with 
the  sclerotic,  and  also  receives  a  portion  of  the  fibrous  network,  into 
which  the  membrana  Demoursii  is  prolonged,  the  fibres  of  which  are 
completely  blended  with  the  elements  of  the  tract  in  question,  and  re- 
seinble  the  others  in  all  respects  except  that  they  are  much  finer, 

FIG.  299. — Cells  from  the  stroma  of  the  choroid :  cr,  pigment-cells ;  6,  uncolored  fusiform 
cells  ;  c,  anastomoses  of  the  former.  Human. — Magnified  350  diameters. 


THE     EYE.  735 

anastomose  more  closely,  and  run  in  a  circular  direction.  The  ciliary 
muscle  terminates  at  the  most  adherent  portion  of  the  ciliary  processes, 
though  not  in  those  processes  themselves,  and  as  regards  the  elements 
of  which  it  is  composed,  they  are  rather  shorter  (0-02  of  aline)  and 
broader  (0'003-0'004  of  a  line)  than  the  common  fibre-cells;  being  at 
the  same  time  finely  granular,  soft,  and  so  perishable,  as,  in  Man,  not 
readily  to  admit  of  being  isolated. 

The  pigmentum  nigrum  (Fig.  296  m)  is  a  continuous,  purely  cellular 
layer,  completely  investing  the  inner  surface  of  the  choroid  and  consist- 
ing, as  far  as  to  the  ora  serrata,  of  a  single  layer  of  well-formed,  almost 
regularly  hexahedral,  contiguous  cells,  O'OOG-O'OOS  of  a  line  in  diame- 
ter, 0'004  of  a  line  thick,  disposed  in  an  elegant  mosaic  manner,  in 
which  the  large  quantity  of  brownish-black  pigment  usually  prevents  the 
nucleus  being  apparent  as  more  than  a  clear  spot  in  the  interior.  On 
the  side  towardsuthe  retina,  however,  a  narrow  clear  border  is  frequently 
left  free  of  color,  showing  that  the  cells  must,  at  one  time,  have  pos- 
sessed contents  or  have  had  a  thickened  mem- 
brane. From  the  ora  serrata  onwards,  the  Fig.  300. 

/L 

pigment-cells  are  disposed  in  several,  at  least 
two,  layers,  become,  rounded,  smaller,  and 
entirely  filled  with  pigment,  so  that  the  nuclei 
even  are  scarcely  visible.  All  the  pigment- 
cells  have  extremely  delicate  walls,  and  are 
very  easily  ruptured  under  pressure ;  the  pig- 
ment is  composed  of  minute,  flattened,  oval  corpuscles,  at  most  0-0007 
of  a  line  long,  and  presenting,  sometimes  even  while  contained  in  the 
cell,  but  still  better  when  liberated,  the  phenomenon  of  molecular  motion 
in  the  most  marked  manner.  The  pigment  of  the  clioroid  is  wanting  in 
the  eyes  of  albinoes,  as  well  as,  at  any  rate  partially,  in  the  region  of 
the  tapetum  in  animals  ;  but  the  cells,  which  would  elsewhere  contain  it, 
exist  in  both  these  instances,  only  perfectly  colorless. 

The  iris  differs  from  the  choroid  in  containing  true  connective  tissue, 
the  delicate,  lax  fasciculi  of  which,  partly  radiating,  in  part  circular, 
especially  at  the  ciliary  border,  and  much  interlaced,  constitute  the  prin- 
cipal bulk  of  the  stroma  of  this  tunic,  and,  towards  its  surface,  form  a 
more  homogeneous  layer.  It  contains  a  large  number  of  elongated 
nuclei,  which,  at  any  rate  in  part,  are  situated  in  fusiform  cells,  similar 
to  those  of  the  choroid,  only  smaller;  and  also  a  few  rigid,  pale  fibres, 
which,  as  prolongations  of  the  ligamentum  pectinatum  of  the  iris,  or  of 
the  "membrane  of  Demours,"  are  continued  over  a  part  of  the  anterior 
surface;  lastly,  the  smootH  muscular  fibres  of  the  iris,  presenting  ex- 
actly the  same  characters  as  those  of  the  choroid  [ciliary  muscle].  In 
Man,  these  fibres  constitute  a  very  distinct  occlusor  muscle  of  the  pupil 

FIG.  300. — Cells  of  the  pigmentum  nigrum  of  Man :  o,  viewed  on  the  surface  ;  6,  on  the 
side ;  c,  pigment-granules. 


736  SPECIAL    HISTOLOGY. 

(sphincter  pupillce)  in  the  form  of  a  smooth  ring,  \  of  a  line  wide,  close 
to  the  pupillary  margin  of  the  iris,  and  somewhat  nearer  to  the  pos- 
terior surface,  which,  in  a  blue  iris,  may  be  readily  recognized  after  the 
removal  of  the  posterior  pigment,  with  and  without  the  application  of 
acetic  acid,  and  may  also  be  torn  up  into  its  elements,  0-02-0-03  of  a 
line  long.  Besides  this  larger  muscular  ring,  I  find,  close  to  the  annu- 
lus  iridis  minor,  another  very  narrow  ring,  nearer  the  anterior  surface 
of  the  iris,  not  more  than  1-40  of  a  line  in  breadth.  Briicke  traces  the 
dilator  pupillce  as  far  as  the  lig  amentum  pectinatum  and  the  border  of 
the  vitreous  lamella  of  the  cornea,  but  I  am  unable  to  do  so ;  and  it 
rather  appears  to  me  to  commence  in  the  substance  of  the  iris  at  the 
ciliary  margin.  From  what  the  difficulty  of  the  investigation  has 
allowed  me  to  see  of  this  muscle,  it  consists  of  numerous  slender  fasci- 
culi, which,  far  from  constituting  a  continuous  membrane,  run  inwards, 
each  separately  between  the  vessels,  and  are  inserted  at  the  border  of 
the  sphincter.* 

The  iris  differs  from  the  clioroid  also,  in  possessing  a  cellular  layer  on 
the  anterior  and  posterior  surfaces.  The  latter,  the  so-termed  uvea  of 
authors,  or  the  pigmentum  nigrum  of  the  iris  (Fig.  295  ri)  is  a  stratum, 
0-0089  of  a  line  thick,  of  minute,  closely  filled  pigment-cells,  like  those 
of  the  ciliary  body,  with  which  they  are  also  uninterruptedly  connected, 
and  which  lines  the  whole  of  the  posterior  surface  of  the  iris,  extending 
as  far  as  the  border  of  the  pupil.  When  the  iris  is  folded,  the  pig- 
mentary stratum,  or  its  free  surface,  appears  to  be  bounded  by  a  deli- 
cate, but  sharply  defined  line,  which  has  been  described  by  several 
authors  as  a  special  membrane  (membrana  pigmenti,  Krause,  m. 
limitans,  Pacini  [?],  Briicke,  M.  Jacobi,  Arnold),  and,  in  fact,  in  eyes 
that  have  been  kept  for  some  time,  and  on  the  addition  of  alkalies,  may 
be  raised  in  places  from  the  pigment.  But  since,  in  such  instances,  the 
pigmentary  layer  is  always  without  any  defined  outline,  and  its  granules 
are  exposed  and  dispersed,  it  appears  to  me  that  this  membrane  is 
nothing  more  than  the  conjoined  outer  cell-walls  of  the  pigment-cells, 
which,  as  is  known  to  be  the  case  elsewhere  (intestinal  villi  for  instance) 
are  raised  in  their  totality,  and  apparently  as  a  special  membrane.  The 
cellular  layer  of  the  anterior  surface  of  the  iris  is  a  simple  epithelium  of 
rounded  and  much  flattened  cells,  which,  when  viewed  in  a  fold  of  the 
iris,  are  seen  to  constitute,  not  a  continuous,  clear  border  of  uniform 
breadth  throughout,  but  on  the  contrary,  only  distinct,  slight  elevations. 
This  layer  is  better  seen  after  the  removal  of  the  posterior  pigment,  in 
a  horizontal  view,  and  also  by  scraping  or  shaving  off  the  anterior  sur- 
face of  the  m's.f  The  color  of  the  iris,  in1  blue  eyes,  depends  simply 
upon  the  posterior  pigment  seen  through  its  substance;  whilst  in 

*  [Compare  Mr.  Lister's  "  Observations  on  the  contractile  tissue  of  the  Iris,"  "  Quarterly 
Journal  of  Micr.  Science,"  vol.  i.  p.  8,  October,  1852. — TRS.] 
t  [Fid.  note,  p.  730.— TBS.] 


THE    EYE. 


737 


Fig.  301. 


brownish-yellow,  brown,  and  black  eyes,  it  is  owing  to  a  special  iris- 
pigment,  which  is  very  unequally  distributed,  and  thus  produces  the 
peculiar  markings  of  the  anterior  surface.  This  pigment  is  seated,  in 
the  first  place,  in  the  stroma  itself,  and  in  fact,  chiefly  in  its  fusiform 
cells,  but  also,  as  it  appears  to  me,  occurs  free  among  the  fibres  and 
vessels,  and  in  the  fibre-cells  of  the  sphincter  pupillce ;  lastly,  in  the 
anterior  epithelial  layer,  it  consists  of  larger  and  smaller  cells,  gold- 
yellow  or  brownish  irregular-sized  granules,  aggregations  of  granules  and 
streaks,  never  of  the  regular  pigment-granules  of  the  true  ocular  pigment. 
The  vessels  of  the  tunica  vasculosa  are  extremely  numerous,  and  are 
variously  disposed  in  its  different  parts.  The  choroid  receives  its  blood 
from  the  short  posterior  ciliary  arteries,  about  twenty  small  vessels, 
penetrating  the  sclerotic,  in  the  posterior  part  of  the  eyeball,  at  a 
greater  or  less  distance  from  the  optic  nerve,  and  which,  dividing  in  a 
dichotomous  manner  in  the  middle  or  vascular  layer  of  the  choroid,  run 
anteriorly,  and  subdivide  into  three  sets  of  branches  :  1,  external,  which, 
having  attained  a  certain  fineness  by  continued  division,  pass  directly 
into  the  vence  vorticosce  ;  2,  internal,  which  pass  into  a  capillary  plexus 
immediately  beneath  the  pigment,  in  the  so-termed  membrana  chorioca- 
pillaris,  or  Ruyschiana  ;  and  3,  anterior,  which  are  continued  into  the 
ciliary  body  and  iris.  The  above-mentioned  capil- 
lary plexus  of  the  innermost  layer  of  the  choroid 
— which  in  animals  having  a  tapetum  lies  upon  its 
internal  aspect,  and  may  easily  be  demonstrated  as 
a  special  membrane,  as  may  also  occasionally  be 
done  in  Man — is  one  of  the  most  elegant  and 
closest  that  exists,  inasmuch  as  its  meshes,  formed 
by  vessels  of  0*004  of  a  line,  do  not  measure  more 
than  0-002-0-005  of  a  line,  the  capillaries  arising 
from  the  larger  vessels,  as  it  were  in  a  stelliform 
manner.  It  extends,  as  has  been  already  said,  only 
as  far  as  the  ora  serrata,  where  it  gives  place  to 
somewhat  coarser  convolutions  of  vessels,  0-004  of 
a  line  in  diameter,  which,  proceeding  from  the  an- 
terior branches  of  the  short  posterior  ciliary  arte- 
ries, constitute  the  ciliary  processes,  and  are  so 
closely  approximated  that,  besides  the  vessels  and 
a  homogeneous  sheath  supporting  the  processes,  the 
latter  seem  to  contain  no  other  tissue.  From  these 
various  points,  and  from  the  ciliary  muscle,  which 

FIG.  301. — Vessels  of  the  choroid  and  iris  of  a  Child,  after  Arnold  ;  viewed  from  within ; 
magnified  10  diameters  :  a,  capillary  plexus  of  the  posterior  segment  of  the  choroid,  terminating 
at  the  ora  serrata,  b  ;  c,  arteries  of  the  corona  ciliaris,  supplying  the  ciliary  processes,  d,  and 
in  part  passing  upon  the  iris,  e ;  f,  capillary  plexus  on  the  inner  surface  of  the  pupillary 
margin  of  the  iris. 

47 


738  SPECIAL    HISTOLOGY. 

likewise  obtains  some  twigs  from  the  same  arteries,  the  blood  is  returned 
principally  through  the  vence  vorticosce,  which,  lying  upon  the  arteries, 
constitute  elegant  vascular  stars  or  vortices,  two  above  and  two  below 
(or  it  may  be  five  or  six);  and  also  at  the  back  of  the  eyeball,  through 
some  minute  vence  ciliares  posticce  breves,  all  of  which  veins  penetrate 
the  sclerotic  in  the  same  way  as  the  arteries. 

The  iris  receives  its  blood  in  the  first  place  from  the  arteries  of  the 
choroid,  and  secondly,  from  the  long  posterior  and  the  anterior  ciliary 
arteries.  The  former,  with  their  anterior  branches,  in  part  immediately 
enter  the  iris,  between  the  ciliary  processes,  and  in  part,  after  supplying 
the  ciliary  processes,  form  small  trunks  at  their  border  and  anterior  ex- 
tremity, which  are  also  continued  upon  the  iris.  The  long  ciliary 
arteries,  two  in  number,  perforate  the  sclerotic  on  the  right  and  left  a 
little  anterior  to  the  short  ciliary  vessels,  run  in  the  external  pigment 
layer  of  the  choroid,  as  far  as  the  tensor  chorioidece,  where,  each 
dividing  into  two  branches  and  joining  the  ciliares  anticce,  which  to  the 
number  of  five  or  six  penetrate  the  sclerotic  in  front,  they  constitute  a 
superficial  irregular  arterial  circle  in  that  muscle — the  circulus  art. 
iridis  major.  From  this  circle,  together  with  small  vessels  passing 
either  from  it,  or  from  the  vessels  forming  it  to  the  tensor  muscle,  very 
many  convoluted  branches,  continued  to  the  iris,  are  given  off;  which, 
with  the  arteries  already  mentioned  from  the  choroid,  divide,  partly 
into  a  few  true  capillaries,  a  layer  of  which  is  found  particularly  at  the 
posterior  surface  of  the  pupillary  margin,  beneath  the  pigment  (Arnold), 
and  partly  run,  continually  dividing,  as  far  as  the  pupillary  margin, 
where,  forming  arched  loops,  they  pass  into  fine,  but  still  not  capillary, 
venous  trunks,  after  they  have  constituted  a  second,  usually  irregular 
circulus  arteriosus  minor  close  to  the  annulus  iridis  minor.  The  veins 
of  the  iris  arise  from  the  arteries  and  capillaries  just  mentioned,  run, 
except  frequent  transverse  anastomosing  branches,  also  in  a  radiating 
manner,  and  open  :  1,  more  from  the  posterior  surface  of  the  iris  into 
the  vasa  vorticosa ;  2,  into  the  vence  ciliares  posticcv  longce  ;  and  3, 
according  to  Arnold  and  Retzius,  also  into  the  "canal  of  Schlemm,"  a 
narrow  annular  channel  situated  between  the  choroid  and  sclerotic 
(Fig.  295  h),  from  which  the  venulce  ciliares  antica?,  passing  through 
the  sclerotic,  afterwards  convey  the  blood  outwardly. 

The  nerves  of  the  tunica  vasculosa  are  also  very  numerous,  but 
destined  solely  for  the  ciliary  muscle  and  the  iris.  They  are  the  ner- 
vuli  ciliares,  which  perforate  the  sclerotic  posteriorly,  then  run  forwards 
in  the  outer  lamella  of  the  choroid,  partly  in  grooves  in  the  sclerotic, 
and,  before  entering  the  ciliary  muscle,  divide  with  repeated  bifurca- 
tions. Within  the  muscle  they  break  up  into  a  rich  and  close  plexus, 
numerous  filaments  from  which  proceed  to  the  muscle  and  to  the  cornea, 
while  others  constitute  the  proper  nerves  of  the  iris.  The  latter  ac- 


THE     EYE.  739 

company  the  vessels,  dividing  repeatedly,  and  with  frequent  anasto- 
moses, especially  in  the  annulus  minor,  to  the  pupillary  margin,  where 
their  mode  of  termination  is  at  present  unknown.  The  elements  of  all 
these  nerves  are,  in  the  trunks,  of  the  medium  and  fine  kinds,  from 
0-002-0-004,  and  in  the  iris  of  not  more  than  0-001-0-002  of  a  line. 
I  have  never  noticed  ganglion-cells  in  them,  nor  in  the  ciliary  muscle, 
where  Bochdalek  describes  them  as  existing. 

Some  authors,  and  among  them,  recently,  Bochdalek,  believe  that 
they  have  seen  scattered  nerves  in  the  choroid — a  circumstance  that  I 
am  unable  to  confirm  from  my  own  observations.  Quite  recently, 
Rainey  ("Philos.  Magaz.,"  May,  1851,  p.  420)  describes  a  transversely 
striped  choroideal  muscle,  occupying  the  posterior  part  of  the  choroid 
and  extending  through  its  entire  thickness  in  the  form  of  variously  de- 
cussating layers,  which  he  says  may  be  most  easily  demonstrated  in  the 
eye  of  the  Sheep.  I  agree  with  Henle  in  thinking  that  these  state- 
ments rest  upon  deceptive  grounds  ;  at  all  events,  in  the  situation  in 
question,  either  in  animals  or  in  Man,  I  can  discover  nothing  like  mus- 
cular fibres. 

§  227.  Nervous  membrane  (retina). — The  retina  is  the  innermost  of 
the  five  tunics  of  the  eyeball,  and  is  in  close  apposition  with  the  choroid, 
though  not  coextensive  with  it,  ending  at  the  or  a  serrata  in  an  undula- 
ted margin  (mar go  undulato-dentatus  s.  or  a  serrata  retina?),  which  is 
very  intimately  connected,  on  the  one  side  with  the  choroid,  and  on  the 
other  with  the  hyaloid  membrane.  A  continuation  of  the  retina  on  the 
ciliary  portion  of  the  hyaloid  membrane,  which  is  described  by  many 
anatomists,  does  not  exist. 

The    retina    is    a  delicate    mem-  Fis-  202. 

brane ;  when  recent,  almost  per- 
fectly transparent  and  clear,  and 
after  death  whitish  and  opaque. 
It  commences  at  the  point  of  en- 
trance of  the  optic  nerve,  with  which 
it  is,  in  part,  continuous.  Its  thick- 
ness at  first  is  0-1  of  a  line,  but 
as  it  extends  anteriorly  it  soon 
diminishes  to  0-06,  until  ultimately, 
close  to  the  anterior  border  of  the 

FIG.  302. — Vertical  transverse  section  of  the  retina  of  Man,  from  the  posterior  portion  of 
the  membrane,  magnified  250  diameters:  a,  hyaloid  membrane  with  decumbent  nuclei:  6, 
membrana  limitans ;  c,  clear  globules  (epithelium?} ;  rf,  expansion. of  the  optic  nerve;  e,  layer 
of  gray  nerve-substance;/,  internal  granular  layer;  g,  fine-granular  layer,  in  which  the 
radiating  fibres  are  more  distinct  than  elsewhere;  h,  external  granular  layer;  i,  internal  divi- 
sion of  the  bacillar  layer,  with  the  "cones;"  fc,  external  division,  with  the  prolongations  of 
the  "  cones:'  and  the  true  "  rods." 


740 


SPECIAL    HISTOLOGY. 


Fig.  SOS. 


retina,  it  is  not  more  than  0*04  of  a  line  in  thickness,  and  finally  ter- 
minates quite  abruptly.  Notwithstanding  this  various  thickness,  the  fol- 
lowing layers  from  without  to  within  may  be  evidently  distinguished  in 
all  parts  of  it;  1,  the  layer  of  rods  and  cones  [bacillar  layer];  2,  the 
granular  layer  ;  3,  the  layer  of  gray  nerve-substance  ;  4,  the  expansion 
of  the  optic  nerve  ;  and  5,  the  limitary  membrane.  These  layers,  with 
the  exception  of  the  innermost,  which  is  of  uniform  thickness  through- 
out, in  general  become  thinner  towards  the  front,  in  correspondence  with 
the  diminished  thickness  of  the  whole  retina. 

1.  The  bacillar  layer,  stratum  bacillorum  s.  memb.  Jacobi  (Fig.  802 
i,  &),  presents  a  very  remarkable  structure,  being  composed  of  innume- 
rable rod-like  and  conical  corpuscles,  disposed  with  the  utmost  regularity 
and  reflecting  the  light  very  strongly.  With  the  exception  of  H.  Mul- 
ler  (vid.  infra),  this  structure,  in  animals,  has  been  understood  quite 
erroneously  ;  and  even  in  Man  it  has  been  but  very  superficially  known. 
It  consists  of  two  elements — the  rods,  bacilli  (k),  and  the  cones,  coni  (i), 
which  together  constitute  a  single  layer,  0-036  of  a  line  thick  at  the 
bottom  of  the  eye,  more  anteriorly  0-024,  and  quite  in  front  not  more 
than  0-015  of  a  line  in  thickness.  In  general  these  bodies  are  so 

arranged  that  the  more  nume- 
rous rods  have  their  largest  end 
directed  outwards,  whilst  the 
cones  are  disposed  in  the  re- 
verse direction,  whence  the  lat- 
ter, when  imperfectly  examined, 
appear  to  constitute  an  inner, 
distinct,  thinner  layer,  lying 
between  the  inner  extremities 
of  the  "rods." 

In  Man,  the  rods  (Fig.  303, 
1,  k,  2)  are  cylindrical,  slender, 
elongated  corpuscles,  in  which 
a  larger  external  end,  the  pro- 
per rod,  is  to  be  distinguished 
from  a  more  slender  internal 
portion,  the  prolongation  or 

FIG.  303. — Retinal  elements  of  Man,  magnified  350  diameters,  1,  "  rods"  and  radiating 
fibres:  k,  proper  "  rod  ;"  r,  prolongation  of  its  pointed  inner  extremity;  A,  "  granule"  (cell) 
of  the  outer  granular  layer ;  /,  enlarged  extremity  of  the  radiating  fibres  proceeding  from 
them  to  the  surface  of  the  optic  layer ;  A/,  "  rod"  seated  on  a  ''  cone,"  i;  r',  fibre  proceeding 
from  the  latter,  connected  with  the  "  granule,"/,  of  the  inner  granular  layer,  and  the  terminal 
enlargement,  Z,  on  the  inner  surface  of  the  retina;  n,  one  of  the  fibrous  bundles  in  which  the 
radiating  fibres  frequently  terminate  at  their  innermost  extremity.  2, "  rods"  torn  off  from 
their  fibres,  in  various  states  of  curvature,  &c.  3,  fibres  of  the  optic  nerve :  a,  6,  straight, 
coarser  and  finer  fibres,  with  varicosities ;  c,  without  varicosities.  4,  two  "cones,"  6,  torn  off 
from  their  processes,  d,  with  somewhat  altered  "  rods,"  a,  at  their  outer  ends ;  c,  nucleus  of 
the  "  cones." 


THE    EYE.  741 

filament.  The  former  portion  of  the  rods,  which  alone  almost  has  hitherto 
been  known  to  anatomists,  is  a  cylinder,  0-0075-0-012-0-015  of  a  line 
long,  0-0008  of  a  line  broad,  and  truncated  at  the  outer  end,  whilst  the 
inner  is  produced  into  a  short  point,  0-002-0-003  of  a  line  in  length, 
which  is  often  separated  from  the  rest  of  the  "rod"  by  a  faint  transverse 
line,  and  might  even  perhaps  be  assigned  to  the  "  filament."  The  latter 
is  an  extremely  delicate  process,  not  more  than  0-0002-0-0003  of  a  line  in 
thickness,  of  uniform  width  throughout,  prolonged  immediately  from  the 
point  of  the  "rod, "and,  extending  through  the  inner  half  of  the  bacillar 
layer  ;  it  is  connected  with  the  other  elements  of  the  retina  in  a  manner 
to  be  afterwards  described.  The  filament  is  so  delicate  that  it  is  usually 
torn  off  near  its  origin  on  the  slightest  mechanical  impression  affecting  the 
bacillar  layer;  on  which  account  also  it  has  happened  that  observers  hi- 
therto have  been  acquainted  only  with  the  "  proper  rods,"  and,  though  they 
had  often  seen  the  somewhat  longer  filaments  attached  to  them,  the  latter 
were  regarded  merely  as  artificial  products.  Since  Hannover,  also,  the 
points  of  these  organs  have  been  misplaced  outwardly  by  all  writers, 
which  is  wholly  incorrect.  The  substance  of  the  "rods"  is  clear,  homo- 
geneous with  a  faint  glistening  fatty  aspect,  very  soft  and  flexible,  and 
at  the  same  time  extremely  fragile.  Their  delicacy  is  so  great  that  they 
undergo  the  most  manifold  changes  even  in  water,  often  even  to  their 
being  rendered  unrecognizable,  bending,  as  it  were,  into  a  hook  of  vari- 
ous forms,  curling  and  rolling  up  in  all  ways,  or  breaking  up  into  two  or 
more  pieces,  and  allowing  clear  drops  to  escape,  which  are  often  met 
with  on  the  -external  surface  of  the  retina  in  vast  quantity,  derived  partly 
from  the  "rods,"  partly  from  the  ruptured  pigment-cells  of  the  choroid. 
One  of  the  most  usual  changes  consists  in  this,  that  the  point,  if  it  be 
not  detached,  which  is  very  frequently  the  case,  becomes  distended  in  a 
varicose  manner,  and  assumes  a  lancet-shape,  or  is  even  transformed 
into  a  sphere,  on  which  the  "filament"  of  various  lengths  is  placed,  in 
consequence  of  which,  the  obtuse  end  of  the  "rod"  often  presents  a 
hook-like  curve  or  a  slight  enlargement.  The  "rods"  are  almost  inva- 
riably very  much  altered  by  reagents ;  and,  above  all,  the  proper  "  rods," 
which,  notwithstanding  their  greater  bulk,  yet  offer  less  resistance  than 
the  "filaments."  Ether  and  alcohol  cause  them  to  contract  and  shrivel  up, 
often  rendering  them  unrecognizable,  but  do  not  dissolve  them.  In  acetic 
acid  of  10  per  cent,  they  are  immediately  shortened  very  considerably, 
swelling  out  in  several  places,  and  disintegrating  into  clear  drops,  which 
at  first  offer  some  resistance,  but  afterwards  disappear.  Concentrated 
acetic  acid  dissolves  them  in  a  short  time,  as  do  alkalies  and  mineral 
acids  ;  whilst  diluted  chromic  acid,  although  it  causes  them  to  shrink  a 
little,  is  the  best  preservative  of  them. 

The  "cones"  (Fig.  303  4)  are  "rods"  which  instead  of  a  filament  are 
furnished  at  their  inner  extremity  with  a  conical  or  pyriform  body,  the 


742  SPECIAL    HISTOLOGY. 

length  of  which  equals  half  the  thickness  of  the  bacillar  layer  (from 
0-007-0-015  of  a  line),  and  whose  breadth  is  from  0-0025  to  0-0045 
of  a  line.  Each  of  these  "cones"  consists  of  an  external,  thicker  and 
longer,  finely  granular  extremity,  often  more  or  less  ventricose,  which, 
gradually  diminishing  in  size,  passes  into  a  common  "rod"  without  a 
point,  and  of  a  shorter  inner  portion,  somewhat  constricted  from  the 
other  by  a  slight  incurvation,  in  which  an  elongated  or  pyriform,  more 
opaque  and  brilliant  body,  0-002-0-003  of  a  line  in  length,  is  enclosed. 
On  the  internal  aspect,  these  "  cones,"  in  which  I  can  see  nothing  but  a 
cell  with  a  nucleus,  are,  like  the  "rods,"  continued  into  the  succeeding 
layers  of  the  retina,  where  we  shall  again  have  to  consider  them,  by  fine 
filaments,  0-0004-0-0006  of  a  line  in  size,  similar  to  those  of  the  "  rods." 
The  "rods"  and  "cones"  are  arranged  vertically  upon  the  retina, 
like  palisades,  in  close  apposition,  and  consequently,  one  of  their  ends 
is  directed  towards  the  cJwroid  and  the  other  towards  the  granular 
layer.  Close  to  the  macula  lutea  the  "cones"  form  an  almost  continu- 
ous stratum  (Fig.  304  2),  so  that  the  "rods"  are  placed  only  in  single 
series  between  them,  but  more  anteriorly  they  are  wider  apart,  the  dis- 
tance between  them  at  first  being  about  0-002-0-003  of  a  line,  and  in  the 
anterior  portions  of  the  retina  even  0-0004-0-005  of  a  line  (Fig.  304  3), 
thus  affording  room  for  more  "rods"  in  the  interspaces.  Viewed  from 
without,  the  bacillar  layer,  when  its  outermost  sur- 
face is  brought  into  focus,  exhibits  rounded  spaces, 
placed  at  a  greater  or  less  depth,  filled  with  a  clear 
substance,  which  also  occupies  elsewhere  the  inter- 
stices between  the  elements  of  this  layer.  These 
clear  spaces,  corresponding  to  the  "  cones,"  pre- 
sent an  internal,  dark,  smaller  circle,  the  terminal 
surface  or  apparent  transverse  section  of  the  "  rod" 
which  is  seated  upon  the  "cone,"  and  are  surrounded  by  the  closely 
^crowded  terminal  surfaces  of  the  "proper  rods,"  disposed  in  a  sort  of 
mosaic  manner,  their  outlines  being  indicated  by  the  single,  double,  or 
multiple  series  of  reticulations  (Fig.  304). 

2.  The  granular  layer,  stratum  granulosum  (Fig.  303  h,  /),  is  com- 
posed of  opaque,  granular  corpuscles,  reflecting  the  light  tolerably 
strongly,  of  a  round  or  oval  figure,  and  0-002-0-004  of  a  line  in  size, 
sometimes  looking  like  free  nuclei,  sometimes  like  minute  cells  almost 
entirely  filled  by  large  nuclei,  although,  according  to  my  observations, 
they  should  all  be  referred  to  the  latter  category.  For  I  find,  especially 
in  preparations  made  with  chromic  acid,  that  from  both  sides  of  every 
granule  very  fine  filaments,  0-0002-0-0003  of  a  line  thick,  are  regularly 

FIG.  304. — Bacillar  layer  from  without.  1,  at  the  "yellow  spot"  (only  "  cones");  2,  at 
the  border  of  the  same ;  3,  from  the  middle  of  the  retina :  a,  "  cones,"  or  vacuities  corre- 
sponding with  them  ;  6,  "  rods  "  of  the  "  cones,"  whose  terminal  surface  is  often  placed  rather 
more  deeply  than  that  of  the  proper  "  rods,"  c. — Magnified  350  diameters. 


THE    EYE. 


743 


Fi?.  305. 


given  off,  which  in  many  cases  may  be  distinctly  seen  to  proceed  from 
a  pale  border  surrounding  the  granule,  so  that  the  whole  is  very  like 
a  bipolar  ganglion-cell  in  miniature.  In  Man,  the  granules,  in  the 
greater  part  of  the  retina,  are  disposed  in  two  layers — an  outer,  thicker 
of  0-013-0-016  (A),  and  an  inner,  thinner  (/),  of  0-006-0-008  of  a  line 
— which  are  parted  from  each  other  by  a  clear,  fine-granular,  and,  to 
some  extent,  vertically  striated  layer  (g],  0-006-0-008  of  a  line  thick, 
whilst,  towards  the  ora  serrata,  the  two  constitute  a  single  stratum 
of  not  more  than  0-015  of  a  line  in  thickness.  The  granules  of  the 
inner  layer  are  a  trifle  larger  than  those  of  the  outer,  and  when  they 
are  oval,  as  is  most  usually  the  case,  I  find  that  they  are  placed  with 
the  long  axis  in  the  direction  of  the  thickness  of  the  retina,  so  that  their 
processes,  like  those  of  the  external  layer,  run  directly  outwards  and 
inwards. 

3.  The  layer  of  cineritious  cerebral  substance  (Fig.  302  e)  is  pretty 
sharply  defined  on  the  side  of  the  granular  layer,  and  less  so  towards 
that  of  the  fibres  of  the  optic  nerve, 
between  the  elements  of  which  it  pene- 
trates more  or  less.  It  is  composed  of 
a  finely  granular  matrix,  corresponding 
exactly  with  that  of  the  gray  substance 
on  the  surface  of  the  cerebrum  and  cere- 
bellum, and  of  numerous  nerve-cells  scat- 
tered in  it.  Of  the  latter,  some,  parti- 
cularly in  the  outer  half  of  this  layer, 
which  is  0-008-0-012-0-02  of  a  line 
thick,  are  small  (0-003-0.006  of  a  line), 
inconspicuous,  and  in  fresh  preparations 
recognizable  only  by  their  beautiful  vesi- 
cular nuclei;  whilst  another  portion, 
forming  an  almost  continuous  layer  on 
the  inner  side,  are  of  a  larger  size 
(0-006-0-016  of  a  line).  These  cells 

are  usually  pyriform  or  rounded,  or  occasionally  prolonged  into  3-5 
angles;  and  most  of  them,  perhaps  all,  are  furnished  with  pale  pro- 
cesses like  those  of  the  central  nerve-cells — which  were  first  noticed  by 
Bowman  ("Lectures,"  &c.,  pp.  84  and  125),  and  afterwards  also  de- 
scribed by  Hassall,  Corti,  and  myself.*  The  processes  occur  either 
single  or  in  numbers  varying  from  two  to  six  and  more ;  are  at  first  as 
much  as  0-002  of  a  line  wide,  but  in  their  further  course  continually 
% 

FIG.  305. — Nerve-cells  with  processes  from  the  retina  of  the  Ox,  magnified  350   diameters. 

*  [Pacini  appears  to  have  been  the  first  to  perceive  the  existence  and  true  nature  of 
the  caudate  cells  in  this  layer  of  the  retina.  ("  Sulla  tessitura  int.  dell.  Retina,"  1844,  p. 
32.)— TRS.] 


744  SPECIAL    HISTOLOGY. 

diminish  in  size,  under  repeated  divisions,  till  they  are  reduced  to  fine 
filaments  of  scarcely  0-0004  of  a  line  in  diameter,  which,  in  isolated 
cells,  terminate  in  torn  ends.  In  every  case  in  which  I  have  noticed 
these  nerve-cells  distinctly  in  situ,  their  processes  were  given  off  towards 
the  exterior,  and  afterwards  in  their  further  course,  without  entering 
the  granular  layer,  appeared  to  be  curved,  in  order  to  ramify  in  the 
gray  nervous  layer  itself.  The  nuclei  of  these  nerve-cells,  which  behave 
towards  reagents  like  those  of  the  cerebrum,  measure  0-003—0-005  of  a 
line,  and  usually  present  a  very  distinct  nudeolus. 

4.  On  the  inner  aspect  of  the  layer  in  question  we  find  the  expansion 
of  the  optic  nerve  (d).  This  nerve,  after  quitting  the  chiasma  (concern- 
ing which  vid.  p.  390)  and  till  it  reaches  the  eye,  presents  the  same 
conditions  as  a  common  nerve ;  its  dark-bordered  fibres,  0-0005 — 0-002 
of  a  line  in  diameter,  much  disposed  to  become  varicose,  and  between 
which,  according  to  Hassall,  nerve-cells  would  also  seem  to  occur,  but 
which  I  have  not  yet  noticed,  form  polygonal  bundles,  0-048-0-064  of  a 
line  thick,  surrounded  by  a  nurilemma  of  the  usual  kind.  When  the 
optic  nerve  reached  the  eye,  its  sheath  is  lost  in  the  sclerotic,  which 
tunic  is  perforated  for  the  entrance  of  the  nerve  by  a  funnel-shaped 
opening,  the  narrower  part  being  inward ;  and  the  internal  neurilemma 
also  ceases  on  a  level  with  the  inner  surface  of  the  same  tunic,  where  it 
may  be  artificially  displayed,  as  a  cribriform  lamella  (lamina  cribrosa  of 
authors),  so  that  the  fibres  of  the  optic  nerve  enter  the  eye,  each  inde- 
pendently, without  their  sheaths  of  connective  tissue.  Within  the  canal 
of  the  sclerotic,  and  as  far  as  the  slight  eminence,  the  colliculus  nervi 
optici,  visible  on  the  inner  surface  .of  the  retina  opposite  its  point  of 
entrance,  the  optic  nerve  retains  its  white  color,  and  continues  to  pre- 
sent dark-bordered  tubules ;  but,  from  that  point  onwards,  its  elements, 
in  Man  and  in  many  animals,  become  perfectly  clear,  yellowish  or  gray- 
ish, and  transparent,  like  the  finest  tubules  in  the  central  organs,  mea- 
suring on  the  average  not  more  than  0-0006-0-0008  and  a  good  many 
only  0-0002-0-0004  of  a  line,  whilst  some,  it  is  true,  have  a  size  of 
0-001-0-0015  or  even  of  0-002  of  a  line.  What  chiefly  distinguishes 
these  from  other  pale  nerve-terminations,  is  the  absence  of  nuclei  in 
their  course,  a  somewhat  greater  refractive  power,  and  the  frequent  oc- 
currence of  varicosities,  which  two  latter  particulars  would  seem  to  in- 
dicate, if  not  exactly  a  nerve-medulla  as  in  the  common  nerves,  still  the 
existence  of  partially  semi-fluid  and  perhaps  fatty  contents,  and  assimi- 
late the  nerve-fibres  of  the  retina  to  the  most  delicate  elements  of  the 
cerebrum.  I  have  not  yet  been  able  to  demonstrate  axis-fibres  and 
sheaths  in  the  fibres  of  the  retina,  although  I  would  not  from  that  cir- 
cumstance at  present  conclude  that  they  do  not  exist.*  At  any  rate 

*  [Here  again,  Professor  Kolliker  is  at  variance  with  Mr.  Bowman,  who  gives  as  one  of 
the  peculiar  characteristics  of  the  fibres  of  the  optic  nerve  in  the  retina,  that  they  have  lost 


THE     EYE.  745 

the  retinal  fibres  are  not  composed  solely  of  nerve-medulla,  for,  if  they 
are  treated  never  so  thoroughly  with  ether,  they  always  remain,  smal- 
ler indeed,  but  more  distinct  and  more  opaque  than  previously.  Fibres 
which  have  been  thus  treated  enlarge  again  in  cold  acetic  acid,  and  dis- 
solve in  alkalies,  and  consequently  consist,  perhaps  without  doubt,  chiefly 
of  a  nitrogenous  substance. 

As  respects  the  course  of  the  nerve-fibres  in  the  retina,  this  much  is 
certain,  that  they  radiate  on  all  sides  from  the  colliculus  nervi  optici 
and  constitute  a  continuous  membranous  expansion,  which  extends  as 
far  as  the  ora  serrata  retina?,  and  presents  any  considerable  interrup- 
tion only  in  the  situation  of  the  macula  lutea.  In  this  true  nervous 
membrane  the  fibres  are  associated  into  larger  and  smaller  compressed 
bundles,  usually  0*01-0-012  of  a  line  wide,  which  either  mutually  anas- 
tomose at  very  acute  angles,  or  run  for  considerable  distances  parallel 
with  each  other.  Notwithstanding  all  that  has  been  stated  by  various 
authors,  it  may  be  boldly  asserted  that  the  terminations  of  these  nerves 
are  as  yet  wholly  unknown ;  and,  as  more  will  be  said  upon  this  subject 
afterwards,  I  shall  here  merely  remark  that,  in  any  case,  they  exist  not 
only  in  front,  but  in  every  part  of  the  retina,  because  the  layer  of  nerve- 
fibres  becomes  visibly  thicker  from  before  to  behind.  I  have  estimated 
its  thickness,  in  Man,  at  the  bottom  of  the  eye  at  0*036,  two  lines 
beyond  the  yellow  spot  at  0-006-0-008,  and  near  the  ora  serrata  at 
0-002  of  a  line. 

5.  The  limitary  membrane,  membrana  limitans*  (b),  is  a  delicate 
membrane,  0-0005  of  a  line  thick,  intimately  united  with  the  rest  of  the 
retina,  which,  when  that  structure  is  teazed  out,  and  on  the  application 
of  reagents,  is  frequently  detached  in  large  shreds,  and  then  appears 
perfectly  structureless.  On  its  inner  aspect,  towards  the  hyaloid  mem- 
brane (a),  when  the  retina  is  folded,  flattened  cell-nuclei  are  occasionally 
perceptible,  which  certainly  cannot  be  referred  to  an  epithelium,  and 
scarcely  to  the  vitreous  body,  as  the  latter  is  always  readily  separable 
from  the  retina.  It  seems  to  be  different  with  regard  to  a  clear,  light 
yellowish  border,  0*002-0-003  of  a  line  wide,  situated  on  the  outer  side 
of  the  membrana  limitans,  which,  in  folds  of  a  perfectly  fresh  retina, 
appears,  as  it  were,  to  be  completely  blended  with  the  limitary  mem- 
brane, but  occasionally  exhibits,  more  or  less  distinctly,  the  contours  of 
excessively  clear  and  transparent  spherical  bodies  (fy,  0-002—0*003  of  a 
line  in  size.  At  a  longer  interval  after  death,  as  well  as  on  the  addi- 
tion of  water,  a  large  number  of  transparent  globules,  like  drops  of 
albumen,  are  afforded  by  the  clear  border  of  the  retina,  which  then  dis- 
appears altogether,  except  the  membrana  limitans,  frequently  also, 

"  the  tendency  to  fall  into  the  varicose  or  beaded  state ;  in  a  word,  that  the  fibres  of  the 
nerve,  in  expanding  into  the  retina,  lose  their  white  substance,  but  retain  the  axis-  or  cen- 
tral fibre."— -TBS.] 

*  [So  named  by  Pacini  (1.  c.,  p.  22).— -TR3.] 


746  SPECIAL    HISTOLOGY. 

together  with  it.  Todd  and  Bowman  describe  the  clear  bodies  above 
noticed  as  cells,  and  also  figure  a  minute  nuclear  corpuscle  in  them; 
and  I  will  not  directly  contradict  this  notion,  although  I  have  not  as 
yet  been  in  any  way  able  to  satisfy  myself  of  the  existence  of  nuclei  and 
true  cells  in  this  layer. 

The  condition  of  the  retinal  elements  at  the  " yelloiv  spot"  is  in  many 
respects  peculiar.  In  the  first  place,  any  continuous  layer  of  optic 
fibres  is  there  wholly  wanting,  and  the  stratum  of  nerve-cells,  which 
are  in  close  mutual  apposition,  lies  immediately  upon  the  membrana 
limitans.  Between  these  cells,  however,  nerve-fibres  run  equally  from 
the  sides  and  the  internal  end  of  the  spot  into  it,  either  isolated  or  in 
very  minute  bundles,  and  terminate  in  a  way  that  cannot  be  accurately 
determined.  In  the  centre  of  the  macula  lutea  there  is  a  thin  unco- 
lored  spot  in  which  the  granular  layer  is  wanting,  from  O'OS-0-1  of  a  line 
in  diameter,  through  which  the  pigment  of  the  choroid  is  visible — the 
so-termed  foramen  centrale.  The  plica  centralis  never  exists  during  life  ; 
but  this  is  not  the  case,  probably,  with  the  yellow  color,  which  depends 
upon  diffused  pigment  pervading  all  the  parts  of  the  retina,  except 
the  "  rods."  The  latter,  in  this  situation,  assume  the  form  of  "  cones" 
exclusively,  inasmuch  as  the  "proper  rods,"  as  Henle  ("  Zeitsch.  f.  rat. 
Path.,"  1852,  II.  p.  807)  correctly  states,  are  wholly  wanting  in  the 
"yellow  spot"  and  its  immediate  neighborhood.  Instead  of  them,  the 
"  cones"  form  a  perfectly  continuous  layer,  are  more  slender  than  else- 
where (not  more  than  0-002-0*0024  of  a  line  in  breadth),  and  support 
at  their  outer  end,  here  as  elsewhere,  not  short  points,  as  Henle  states, 
but  the  usual  "  rods,"  which  in  this  situation  are  not  more  than  0-0006- 
0-0007  of  a  line  broad  (Fig.  304). 

After  this  description  of  the  elements  of  the  various  retinal  layers,  it 
will  be  as  well  to  cast  a  glance  upon  their  mutual  connection.  I  have 
ascertained,  in  the  human  eye,  that  the  fibres  proceeding  from  the 
"rods"  and  "cones"  inwards,  and  from  the  "granules,"  on  both  sides, 
are  connected,  and  simply  constitute  parts  of  a  fibrous  system  of  the 
retina,  as  yet  not  recognized  as  a  connected  whole,  except  by  H.  Mul- 
ler.  This  system,  the  greater  number  of  whose  elements  are  vertical, 
penetrates  the  entire  thickness  of  the  tunic,  and  might  be  termed  the 
radiating  fibre-system  (radial  fibres,  H.  Muller),  in  contradistinction  to 
the  horizontal,  referable  to  the  expansion  of  the  optic  nerve.  Proceed- 
ing from  the  bacillar  layer,  it  is  obvious,  that  the  fine  filaments  arising 
from  the  "rods"  and  "  cones"  are  directly  continuous  with  the  similar 
processes  given  off  from  the  external  side  of  the  "granules,"  in  such  a 
way  that  the  filaments  of  the  "  rods"  (Fig.  303  *,  rr)  are  connected. with 
the  "granules"  of  the  outer  granular  layer,  and  those  of  the  "  cones" 
(Fig.  303  *,  r)  with  the  "  granules"  of  the  inner  layer ;  in  fact,  each 
"cone"  or  "  rod"  is  in  connection  with  a  granule,  the  latter  also  per- 


THE     EYE.  747 

haps  with  several.  The  filaments  which  run  inwards  from  both  kinds 
of  "  granules,"  which  may  be  pretty  readily  traced  in  vertical  sections, 
are  continued  in  a  straight  line,  or  slightly  curved,  through  the  layer  of 
gray  nerve-substance  without  any  connection  with  its  elements,  and 
enter  the  expansion  of  the  optic  nerve,  where,  as  especially  in  the  pos- 
terior part  of  the  eye,  in  which  situation  the  layer  of  nerve-fibres  is 
thick,  it  is  easy  to  perceive  that  they  run  in  the  narrow  interstices  be- 
tween the  nervous  bundles,  in  a  fascicular  manner  towards  the  metnbrana 
limitans.  I  have  taken  much  pains  in  the  investigation  of  their  re- 
lations at  the  surface  of  the  retina,  and  have  arrived  at  the  following 
results.  If  the  inner  surface  of  the  retina  be  examined  under  a  strong 
magnifying  power,  in  its  posterior  half,  where  the  fibrous  bundles  of  the 
optic  nerve  are  still  very  distinct,  a  peculiar  marking  will  be  observed 
between  them,  consisting  of  series  of  points,  of  minute  stelliform 
figures,  or  of  little  streaks,  which  often  (also  in  animals,  as  the  Ox  for 
instance)  regularly  converge  towards  each  other  from  the  bundles  of 
fibres  like  the  rays  of  a  feather.  If  these  structures  are  traced  in  ver- 
tical sections,  it  is  easily  seen  that  they  are  nothing  but  the  extremities 
of  the  radiating  fibres  dipping  down  between  the  nervous  bundles,  and 
presenting  a  somewhat  peculiar  aspect.  For,  whilst  in  the  deeper  part 
of  the  retina  they  are  simple  pale  fibres,  of  at  most  O0008  of  a  line  in 
size,  they  are  here  so  modified  that  some  of  them  simply  expand,  and 
terminate  in  a  triangular  pale'  corpuscle,  0'0015-0'003  of  a  line  in 
length  and  breadth  (Fig.  303  *  Z),  from  the  internal  angles  of  which,  one 
or  two  horizontal  fibres  are  again  given  off;  whilst  the  others,  without 
expanding,  end  in  a  complete  bundle  of  5-9  or  more  fine  fibres  (Fig. 
303  *  n\  which  also  turn  to  the  sides  and  continue  in  the  plane  of  the 
nervous  expansion.  What  further  becomes  of  these  latter,  innermost 
processes  of  the  radiating  fibre-system,  I  have  not  yet  been  fortunate 
enough  to  observe,  however  zealously  I  have  investigated  the  matter, 
and  regret  that  the  decision  of  this  very  important  point  in  the  ana- 
tomy of  the  retina  must  still  be  left  in  abeyance.  The  radiating  fibres 
either  actually  terminate  in  the  filaments  observed  by  me  on  the  surface 
of  the  expansion  of  the  optic  nerve,  or  they  are  continuous  with  the 
true  fibres  of  that  nerve,  or  at  any  rate  are  in  connection  with  them.  In 
a  physiological  point  of  view  the  latter  supposition  would,  in  any  case, 
be  the  most  plausible ;  and  in  support  of  it,  it  may  be  stated,  that  in 
the  true  fibrous  bundles  of  the  retina,  together  with  the  varicose  nerve- 
tubules  (Fig.  303 3  «,  6),  there  are  fibres  of  another  sort  (Fig.  303 3  <?), 
which,  although  of  equal  size,  agree  in  all  respects  with  the  radiating 
fibres  in  the  absence  of  varicosities,  and  in  their  less  straight  or  more 
serpentine  and  irregular  course.  It  may  be  that  these  fibres  are  the 
direct  continuations  of  the  horizontal  terminal  processes  of  the  radia- 
ting fibres,  which  subsequently,  in  their  .further  progress  towards  the 


748  SPECIAL    HISTOLOGY. 

optic  nerve,  acquire  more  and  more  of  the  character  of  common  nerve- 
tubules,  and  follow  a  more  direct  course.  However  interesting  this 
notion  may  be,  according  to  which  the  "rods"  would  be  the  termina- 
tions of  the  optic  fibres,  the  considerable  difficulties  attending  it  must 
not  be  concealed  ;  among  which  not  the  least  is  the  circumstance,  that, 
although  the  "  rods"  and  "  cones"  are  certainly  fifty  times  more 
numerous  than  the  fibres  of  the  optic  nerve,  yet  the  radiating  fibres 
arising  from  the  former,  on  their  passage  into  the  optic  fibres,  subdivide, 
and,  as  it  must  probably  be  assumed,  are  continuous  with  several  of 
them — a  difficulty,  which  might  indeed  be  removed  on  the  hypothesis, 
that  a  single  optic  fibre  receives  or  gives  off  numerous  radiating  fibres, 
but  is  nevertheless  of  such  a  kind  that  I  do  not  consider  it  advisable  to 
proceed  any  further  upon  a  basis  unsupported  by  facts. 

In  spite  of  the  obscurity  which,  from  what  precedes,  still  hangs  over 
a  very  important  point  in  the  anatomy  of  the  retina,  physiology  may 
nevertheless  even  at  present  draw  some  useful  conclusions  from  the  facts 
in  our  possession.  In  the  first  place,  since  the  demonstration  by  H. 
Miiller  and  myself  of  its  connection  with  the  radiating  fibre-system  and 
the  "granules,"  the  bacillar  layer  appears  in  quite  a  different  light  from 
that  in  which  it  was  previously  held,  and  it  is  now  obviously  impossible 
to  regard  it,  with  Briicke,  as  a  catoptric,  reflecting  apparatus.  I  look 
upon  the  "rods"  and  "  cones,"  which  may  also  be  said  to  correspond  in 
all  chemical  characters  with  the  nerve-fibres  of  the  retina,  and  the,wThole 
of  the  radiating  fibre-system  of  the  retina,  as  true  nervous  elements ; 
and  venture  at  the  same  time  to  broach  the  bold  supposition,  founded 
upon  a  less  established  basis,  which  has  been  already  thrown  out,  that 
the  "rods"  and  "cones"  are  the  true  percipients  of  light,  and  that  they 
communicate  their  condition  to  the  fibres  of  the  optic  nerve,  by  means 
of  the  direct  or  indirect  connection  of  their  fibrous  processes  with  the 
former,  through  which  again  the  impressions  are  conveyed  to  the  senso- 
rium.  That  the  optic-fibres  in  the  nervous  expansion  of  the  retina,  do 
not  perceive  light,  appears  to  me  to  be  proved  by  the  circumstance :  1, 
that  the  point  of  the  retina,  where  those  fibres  alone,  and  no  other  ele- 
ments of  the  retina,  are  found,  viz.  at  the  entrance  of  the  optic  nerve, 
is  not  sensitive  to  light ;  2,  that  the  optic  fibres  are  superimposed  upon 
each  other  in  such  numbers,  in  almost  every  part  of  the  retina,  and 
above  all  in  the  neighborhood  of  the  macula  lutea,  that  it  is  impossible 
they  should  perceive  light,  inasmuch  as  each  luminous  impression,  owing 
to  the  transparency  of  the  fibres,  must  in  any  case  always  affect  many 
of  them,  and  consequently  would  of  necessity  give  rise  to  confused  sen- 
sations ;  and  3,  because  the  part  of  the  retina  in  which  there  is  no  con- 
tinuous layer  of  nerve-fibres  on  the  inner  surface,  that  is  to  say,  the 
"yellow  spot,"  is  the  most  sensitive  to  luminous  impressions.  Under 
this  notion,  the  import  of  the  "rods,"  and  their  remarkable  arrange- 


THE    EYE.  749 

ment,  would  be  intelligible,  and  the  almost  inexplicable  correspondence 
in  the  size  of  the  images  of  the  smallest  distinguishable  interspaces  be- 
tween two  objects,  with  the  diameter  of  the  "rods"  and  "  cones,"  be 
placed  in  its  true  light.  I  consider  it  impossible  to  say  anything  with 
respect  to  the  import  of  the  other  elements  of  the  retina,  for  although 
the  "  granules"  may  be  compared  to  minute  bipolar  ganglion-corpuscles, 
and  their  continuity  with  the  radiating  fibres  is  known,  this  affords  as 
little  ground  for  discussion  as  to  their  function,  as  is  given  by  the  know- 
ledge of  the  fact  that  the  large  nerve-cells  of  the  inner  layers  have  nu- 
merous processes  and  probably  free  terminations. 

The  vessels  of  the  retina  are  derived  from  the  art.  centralis  retince, 
which  enters  the  eye  enclosed  in  the  optic  nerve,  and  begins  to  ramify 
from  the  centre  of  the  colliculus  nervi  oirtici  in  4  or  5  main  branches. 
Lodged  at  first  only  beneath  the  membrana  limitans,  these  vessels  pene- 
trate through  the  layer  of  nerve-fibres  into  that  of  gray  nerve-substance, 
ramify  in  an  elegant  arborescent  manner  as  far  as  the  era  serrata,  and 
pass  by  their  terminal  prolongations  on  all  sides  into  a  rather  wide- 
meshed  network  of  very  fine  capillaries  (0-002-0-003  of  a  line),  which  is 
lodged  chiefly  in  the  gray  layer,  but  partly  also  in  the  expansion  of  the 
optic  nerve.  In  animals,  the  veins  commence  with  a  complete  circle, 
circulus  venosus  retinae,  at  the  ora  serrata,  accompany  the  arteries  in 
single  trunks,  and  converge  to  the  vena  centralis,  which  quits  the  eye 
together  with  the  artery.  No  large  vessels  exist  in  the  "yellow  spot,*' 
where  there  are  only  numerous  capillaries.  I  have  never  yet  met  with 
nerves  on  the  retinal  vessels,  whilst  on  the  outside  of  the  larger  vessels 
I  have  occasionally  noticed  traces  of  an  accompanying  fibrous  tissue,  ap- 
proaching nearest  to  the  embryonic,  reticular  connective  tissue. 

The  radiating  fibre-system  of  the  retina,  though  known  in  its  separate 
parts  to  older  and  more  recent  observers,  had  not  been  comprehended 
in  its  connection,  and  we  are  very  greatly  indebted  to  H.  Muller  for  his 
accurate  investigations  into  this  important  structure  in  animals  of  every 
class.  I  have  repeated  Mailer's  observations  in  the  human  eye,  which 
was  not  investigated  by  him,  and  have  been  enabled  to  confirm  in  it  all 
that  he  has  stated,  and  in  some  respects  to  carry  the  observations  fur- 
ther. The  reason  why  the  radiating  fibre-system  and  the  relation  of 
the  "  rods"  to  it  has  hitherto  remained  unknown,  is  because  no  one  ex- 
cept Bowman,  so  far  as  I  am  aware,  has  engaged  in  the  indispensable 
study  of  vertical  sections  of  the  retina,  and  moreover,  because  no  one 
had  thought  of  applying  chromic  acid  to  that  tunic,  which  has  elsewhere 
in  the  nervous  tissues  been  of  such  important  service,  and  although  I 
had  particularly  shown  that  the  multipolar  retinal  cells  were  well  pre- 
served in  it.  If  parts  still  fresh  be  taken  for  examination,  in  transverse 
sections  and  chromic  acid  preparations,  very  satisfactory  views  of  the 


750  SPECIAL    HISTOLOGY. 

structures  above  described  will  be  obtained,  and  it  will  excite  surprise 
that  such  numerous  fibres  pervading  the  entire  retina  should  have  been 
hitherto  overlooked.  A  wholly  new  investigation  of  the  retina  has  com- 
menced with  what  has  been  made  known  by  Miiller  and  myself,  but  it 
will  still,  demand  much  time  and  pains  before  it  can  be  conducted  to  any 
certain  results.  Future  inquirers  should  take  up  particularly  the  rela- 
tions of  the  radiating  and  optic  fibres  in  the  eye,  also  the  point  whether 
the  latter  subdivide  in  the  retina,  as  is  asserted  by  Hassall  and  Corti, 
and  lastly,  whether  the  nerve-cells  are  directly  connected  with  the 
nerve-fibres  (Corti)  or  not.* 

§  228.  The  crystalline  lens  is  a  perfectly  transparent  body,  in  rela- 
tion by  its  posterior  surface  with  the  vitreous  humor,  and  laterally  with 
the  termination  of  the  hyaloid  membrane,  the  zonula  Zinnii ;  and  in 
which  are  to  be  distinguished  the  lens,  properly  so  termed,  and  its 
capsule. 

The  capsule  of  the  lens  consists  of  two  elements — the  proper  capsule 
and  the  epithelium.  The  former  is  a  perfectly  structureless  and  trans- 
parent, highly  elastic  membrane,  enclosing  the  lens  on  all  sides,  as  if 
moulded  to  it,  and  parting  it  from  the  neighboring  structures.  If  the 
lens  with  its  capsule  be  placed  in  water,  the  latter  becomes  considerably 
distended  by  imbibition,  whence  it  is  apparent,  that  membranes  of  that 
kind,  notwithstanding  their  homogeneous  structure,  are  yet  very  per- 
meable, so  that"  the  nutrition  of  the  non-vascular  lens  is  provided  for 
without  difficulty,  by  means  of  materials  penetrating  from  without.  The 
lenticular  capsule,  measuring  in  its  anterior  wall,  0*005— 0*008  of  a  line, 
and  posteriorly  to  the  attachment  of  the  zonula  Zinnii)  where  it  is 
abruptly  thinned,  not  more  than  0*002-0*003  of  a  line,  may  be  readily 
torn,  punctured,  or  incised,  whilst  it  offers  considerable  resistance  to  a 
blunt  instrument.  If  an  uninjured  capsule  be  punctured,  it  contracts 

*  [Profs.  Kolliker  and  Muller  (vid.  Coraptes.  rend.  torn,  xxxvii..  Sept.  1853)  have  since 
been  able  by  further  researches,  to  confirm  their  views  on  the  structure  of  the  retina.  They 
state  also,  that  they  have  succeeded  in  tracing  in  the  human  retina  the  direct  connection  of 
the  nerve-fibres  with  the  nerve-cells — a  fact  first  noticed  by  Corti  in  the  Ruminants,  and 
to  which  they  attach  extreme  physiological  importance.  The  radial  fibres  proceeding 
from  the  "rods,"  Kdlliker  observed  frequently  to  unite  into  fasciculi,  which  was  not  the  case 
in  those  derived  from  the  "  cones."  At  the  yellow  spot,  he  found  the  nerve-cells  to  consti- 
tute a  thick  layer,  formed  of  from  9  to  12  rows  of  cells ;  but  both  he  and  Muller  deny  most 
strongly  the  presence  of  nerve-fibres  in  this  situation,  although  their  existence  has  been 
quite  lately  again  positively  affirmed  by  Hannover  (Zeitschrift  fur  wiss.  Zool.  B.  V.  H.  1, 
1853). 

The  physiological  conclusions  which  Kolliker  and  Muller  deduce  from  these  more  recent 
anatomical  observations  are,  in  the  main,  the  same  as  those  above  expressed.  They  seem, 
however,  less  inclined  to  view  the  "  rods"  and  "  cones"  as  the  only  percipients  of  light,  but 
regard  them  more  as  conductors  of  the  luminous  impressions  to  the  nerve-cells  of  the  retina. 
These  they  consider  to  form  a  true  ganglion,  capable  of  perceiving  the  light,  the  expansion 
of  the  fibres  of  the  optic  nerve  merely  serving  as  a  means  of  communication  with  the  sen- 
sorium. — DaC.J 


THE    EYE. 


751 


to  such  an  extent,  owing  to  its  elasticity,  that  the  lens  not  unfrequently 
escapes  spontaneously.  In  its  micro-chemical  reactions  the  capsule  of 
the  lens  behaves  exactly  like  other  transparent  membranes,  except  that, 
according  to  Strahl  ("  Archiv  f.  phys.,"  Heilk.,  1852)  it  would  appear 
to  be  dissolved  by  boiling  in  water.  The  epithelium  of  the  capsule  is 
placed,  not  on  the  outer  surface,  as  Briicke  states,  but  on  the  inner, 
towards  the  lens,  lining  the  anterior  half  of  the  capsule  with  a  single 
layer  of  beautifully  clear,  polygonal  cells,  of  0-006-0-01  of  a  line,  with 
round  nuclei.  After  death  its  elements  are  readily  separated,  expand 
into  transparent  spherical  vesicles,  many  of  which  burst,  and  together 
with  a  few  drops  of  aqueous  humor  which  have  penetrated  into  the  in- 
terior, constitute  the  so-termed  aqua  Morgagni,  which  during  life,  when 
the  epithelium  is  accurately  applied  to  the  surface  of  the  lens,  does  not 
exist  at  all. 

The  lens  itself  consists  entirely  of  elongated,  flat,  hexaheclral  ele- 
ments, 0-0025-0-005  of  a  line  broad,  and  0-009-0-0014  of  a  line 
thick,  of  a  perfectly  transparent  aspect,  very  flexible  and  soft,  and 
having  a  considerable  degree  of 
toughness,  which  have  usually 
been  described  as  the  fibres  of  the 
lens,  although  they  are  nothing 
more  than  thin-walled  tubes  with 
clear,  viscous,  albuminous  con- 
tents, which,  when  the  tubes  are 
torn,  escape  from  them  in  the 
form  of  large  irregular  drops,  and 
consequently  might  suitably  be 
described  as  the  tubes  of  the  lens. 
As  concerns  the  microscopic  cha- 
racters of  these  bodies,  they  are 
distinguished  by  the  circumstance 
of  their  becoming  opaque  and 
more  distinct  in  all  reagents  by 
which  albumen  is  coagulated ;  con- 
sequently, reagents  of  that  kind, 
particularly  nitric  acid,  alcohol, 
creasote,  and  chromic  acid,  are  especially  suitable  for  the  investigation 
of  the  lens ;  but  in  caustic  alkalies  they  are  quickly  dissolved,  and 
they  are  also  speedily  attacked  by  acetic  acid.  The  union  of  the  tubes 
which  are  more  solid,  slender,  and  opaque  in  the  more  compact  inner 
layers  of  the  lens — the  so-termed  nucleus — than  in  the  softer  external 
portions,  is  brought  about  simply  by  their  apposition.  They  invariably 

FIG.  300. — Fibres  or  tubes  of  the  lens.     1,  from  the  Ox,  with  slightly  toothed  borders;  2, 
transverse  section  of  the  lenticular  tubes  of  Man. — Magnified  350  diameters. 


752  SPECIAL    HISTOLOGY. 

lie  with  their  sides  parallel  to  the  surface  of  the  lens,  regularly  inter- 
digitating  with  each  other  by  their  acute  borders,  so  that,  as  is  shown 
in  Fig.  306 2,  in  the  interior  of  the  lens,  each  tube  is  surrounded  by  six 
others,  and  their  transverse  section  presents  the  aspect  of  a  wall  built 
up  of  hexagonal  bricks.  As  the  edges  and  corresponding  surfaces  of 
the  tubes  are  usually  somewhat  uneven,  or  even  toothed  (in  animals, 
particularly  Fishes,  beautifully  so)  their  lateral  union  is  rendered  more 
intimate  than  it  is  between  their  border  surfaces,  and  on  this  account 
also  the  structure  is  more  readily  torn  into  lamellse  in  the  direction  of 
the  surfaces,  than  into  vertical  plates  in  that  of  its  thickness.  For  the 
same  reason,  also,  a  lamellar  structure  may  be  assigned  to  the  lens,  as 
is  commonly  done,  seeing  that  it  is  constituted  of  concentric  laminae 
like  an  onion,  only  it  must  not  be  forgotten  that  these  laminae  are  not 
regularly  defined  layers,  and  never  consist  of  a  single  stratum  of  tubes, 
and,  moreover,  what  may  prove  of  great  physiological  importance,  that 
the  elements  of  the  lens  are,  properly,  still  more  regularly  disposed  in 
the  direction  of  its  thickness,  so  that,  throughout  the  lens,  they  cover 
each  other,  and  the  Matter  might  be  regarded  as  consisting  of  very 
numerous  vertical  segments,  the  thickness  of  which  would  correspond 
with  the  width  of  a  single  fibre.  [Bowman,  1.  c.,  p.  69.] 

The  course  of  the  tubes  of  the  lens  in  the  separate  lamellse  is  in 
general  such  that  both  the  superficial  and  the  deeper,  in  the  centre  of 
the  lens,  radiate  towards  the  margins,  and  then  curve  round  upon  the 
other  surface,  anterior  or  posterior,  but  in  such  a  way  that  no  fibre 
extends  through  the  entire  semi-circumference  of  the  lens,  or  reaches, 
for  instance,  from  the  middle  of  the  anterior  surface  to  that  of  the 
posterior.  More  precisely  described,  the  tubes  on  the  anterior  and 
posterior  surfaces  of  the  lens  do  not  proceed  exactly  to  the  middle,  but 
terminate  in  a  stelliform  figure  which  exists  in  that  situation.  In  the 
foetus  and  in  the  new-born  child,  each  of  these  stelliform  figures  of  the 
lens,  which  are  readily  seen  by  the  naked  eye,  presents  three  rays, 
which  usually  meet,  regularly,  at  angles  of  120° ;  in  the  anterior  star, 
two  of  the  rays  are  directed,  the  one  upwards  and  the  other  down- 
wards ;  the  reverse  being  the  case  with  the  posterior  "star,"  which, 
therefore,  as  compared  with  the  anterior,  appears  as  it  were  turned 
round  in  an  arc  of  60°.  Now,  the  tubes  arising  from  the  middle  of  the 
anterior  "  star"  extend,  on  the  posterior  aspect,  only  as  far  as  the 
extremities  of  the  three  rays;  and,  on  the  other  hand,  those  commen- 
cing from  the  posterior  pole  do  not  reach  the  middle  of  the  anterior. 
Similar  conditions  obtain  in  all  the  tubes  situated  between  these  two 
points,  so  that  none  of  them  reach  entirely  round ;  and  all  the  tubes  in 
a  layer  are  of  equal  length.  Now  precisely  the  same  thing  also  exists 
in  the  "nucleus"  of  the  lens  in  the  adult,  whilst  in  the  superficial 
lamella,  and  on  the  surface  itself,  we  observe  a  more  complex  "star," 


THE     EYE.  753 

with  from  nine  to  sixteen  rays  of  various  lengths,  and  rarely  quite 
uniform,  among  which,  however,  three  principal  rays  may  be  distin- 
guished. The  course  of  the  fibres  is  consequently  rendered  more  com- 
plex, and  the  rather  so,  because  fibres  attached  to  the  sides  of  the  rays 
converge  in  an  arched  manner,  so  that  the  latter  appear,  as  it  were, 
feathered,  or  form  whirls  (vortices  lentis);  but,  notwithstanding  this, 
the  course  of  the  fibres  remains  essentially  the  same  in  all  respects  as 
that  above  described,  inasmuch  as  in  this  case  also  the  anterior  and 
posterior  "stars"  do  not  correspond  with  each  other,  and  no  fibre 

Fig.  307. 


extends  from  the  one  pole  to  the  other.  In  the  "  stars,"  the  substance 
of  the  lens  is  not  formed  of  tubes  as  elsewhere,  but  is  in  part  finely 
granular,  in  part  homogeneous ;  and,  consequently,  since  the  "  stars" 
involve  all  the  layers,  three  or  more,  vertical,  non-fibrous  lamellae 
("central  planes,"  Bowman)  exist  in  each  half  of  the  lens.  Moreover, 
the  tubes  themselves  in  the  neighborhood  of  the  "  stars"  become  less 
distinct,  are  gradually  fused  together,  and  ultimately  lost,  without  any 
line  of  demarcation,  in  the  substance  in  question. 

§  229.  The  vitreous  body  or  humor,  occupies  the  entire  space  between 
the  lens  and  the  retina  ;  its  relations  being  such  that  excepting  at  the 
point  of  entrance  of  the  optic  nerve,  where  the  connection  is  rather  more 
intimate,  it  is  only  in  loose  apposition  with  the  retina,  whilst  it  is  very 
closely  united  with  the  corona  ciliaris  and  the  lens  itself.  The  mem- 
brane enclosing  the  vitreous  body,  or  the  hyaloid  membrane,  which 
behind  the  ora  serrata  constitutes  an  extremely  fine  and  delicate,  per- 
fectly transparent  membrane  scarcely  perceptible  under  the  microscope, 
in  front  of  that  part  becomes  rather  firmer  (Fig.  296  t),  and  is  continued 
to  the  border  of  the  lens  as  the  pars  ciliaris  hyaloidece  s.  zonula  Zinnii 
("suspensory  ligament  of  the  lens,"  Bowman  [and  Retzius]),  where  it 

FIG.  307. — Lens  of  the  adult,  after  Arnold,  to  show  the  "  star."     1,  anterior  aspect ;  2, 
posterior. 

48 


754  SPECIAL    HISTOLOGY. 

becomes  blended  with  the  capsule  of  that  body.  In  doing  this  it  splits 
into  two  lamellce,  a  posterior  (v),  which  is  blended  with  the  capsule  of 
the  lens  a  little  behind  its  border,  and  cannot  be  traced  further,  so  that 
beyond  that  point  the  posterior  wall  of  the  lenticular  capsule  and  the 
vitreous  body  are  directly  in  contact ;  and  an  anterior  (u)  connected 
with  the  ciliary  processes, — the  zonula  in  the  more  restricted  sense, — 
which  is  attached  to  the  capsule  of  the  lens  a  little  in  front  of  its  margin. 
Between  the  two  lamellce  and  the  border  of  the  lens,  there  is  left  a  space 
surrounding  the  latter  in  an  annular  manner,  and,  in  a  transverse  sec- 
tion, of  a  triangular  form — the  canal  of  Petit; — which,  though  con- 
taining a  little  clear  watery  fluid,  yet  during  life  is  very  narrow,  inas- 
much as  its  anterior  wall  or  the  zonula  Zinnii  so  long  as  it  is  continuous 
with  the  ciliary  processes,  like  them  presents  the  aspect  of  a  much  pli- 
cated membrane,  and  consequently  is  brought  into  close  approximation 
with  the  posterior  wall,  at  as  many  points  as  there  are  ciliary  processes. 
These  folds,  however,  are  still  visible  where  the  zonula,  quitting  the 
ciliary  processes,  is  continued  independently  upon  the  border  of  the 
lens,  as  a  part  of  the  posterior  wall  of  the  posterior  chamber  of  the  eye  ; 
and  it  is  therefore  attached  to  the  capsule,  not  in  a  straight  but  in  a 
slightly  undulating  line. 

With  respect  to  the  structure  of  the  parts  in  question,  much  pains 
have  recently  been  bestowed  upon  the  elucidation  of  that  of  the  proper 
vitreous  body ;  although  it  cannot  be  asserted  that  at  present  the  truth 
has  been  arrived  at.  Briicke's  view,  according  to  which  the  vitreous 
body,  like  an  onion,  consists  of  concentric  lamellae  parted  by  a  gela- 
tinous fluid,  was  contradicted  by  Bowman,  who  has  shown,  that  the  con- 
centrated solution  of  acetate  of  lead  used  by  Briicke  for  the  exposition  of 
these  lamellce,  produces  the  appearance  of  lamination  not  only  on  the 
superficial  surface  but  also  on  that  of  any  section  whatever,  but  without 
rendering  true  lamellae  manifest.  Hannover's  opinion,  according  to 
which,  after  treatment  of  the  vitreous  body  with  chromic  acid,  numerous 
dissepiments  are  found  in  it,  running  from  the  surface  towards  the  axis, 
so  that  in  a  vertical  section  a  number  of  "  rays"  are  perceptible  pro- 
ceeding from  the  central  point,  and  the  whole  resembles  an  orange  laid 
open,  appears  to  have  more  in  its  favor,  inasmuch  as,  at  any  rate,  the 
vitreous  body  of  the  new-born  child,  according  to  Bowman  (Lectures,  p. 
100,  and  Fig.  5,  p.  97),  when  treated  with  chromic  acid,  very  distinctly 
exhibits  an  areolated  aspect  of  the  kind  described,  but  it  should  be  re- 
marked that  from  the  same  author's  observations,  the  conditions  are 
widely  different  in  the  eye  of  the  adult,  for,  in  this  instance,  in  chromic 
acid  preparations,  a  few  concentric  lamellce  are  found  externally,  to 
which  succeed  very  irregular  radiating  septa,  and  lastly  an  irregular 
central  cavity.  If  to  this  it  be  added  that  these  lamellce  formed  by 
chromic  acid  also  cannot  be  demonstrated  as  true  membranes,  and  that 


THE    EYE.  755 

in  the  fresh  vitreous  body  no  trace  of  them  is  perceptible,  the  appear- 
ances produced  by  this  second  reagent  can  likewise  not  to  be  considered 
as  proving  much. 

A  more  correct  notion  of  the  constitution  of  the  vitreous  body  would 
appear  to  be  derivable  from  the  study  of  its  development.  It  has  been 
long  known  that  the  vitreous  body  in  the  foetus  has  vessels  on  its  sur- 
face and  in  the  interior ;  it  might  thence  have  been  concluded  that  some 
tissue  for  the  support  of  these  vessels  must  also  exist — but  no  one  has, 
till  recently,  sought  farther  information  with  the  aid  of  the  microscope. 
Bowman  was  the  first  (1.  c.,  p.  100  and  p.  97,  Fig.  7)  to  remark,  that 
the  vitreous  body  of  the  new-born  child  exhibited  a  very  distinct  and 
peculiar  fibrous  structure,  consisting  in  fact  of  a  close  network  of  fibres, 
presenting  at  nodular  enlargements  [where  the  fibres  join]  "minute 
nuclear  granules  resembling  oil-particles,  but  not  soluble  in  ether;" 
the  whole  exhibiting  "  a  peculiar  fibrous  texture  not  at  all  unlike  that 
of  the  enamel  pulp"  in  the  foetal  tooth-sac,  that  is  to  say,  to  its  gelati- 
niform  connective  tissue.  This  agrees  pretty  nearly  with  what  Virchow 
has  recently  found.  According  to  the  latter  author,  the  vitreous  body 
of  a  foetal  Pig,  4  lines  long,  consists  of  a  homogeneous  substance,  con- 
taining mucus,  and  faintly  striated  at  distant  spots,  in  which  round 
nucleated  granular  cells  lie,  scattered  at  regular  distances  apart.  This 
substance  is  surrounded  by  a  delicate  membrane,  with  very  elegant  vas- 
cular networks  and  a  fine  fibrous  areolated  mesh-work  containing  nuclei 
at  the  nodular  intersections,  and  also  enclosing  in  its  meshes  a  gela- 
tinous mucus  with  rounded  cells.  Consequently,  and  also  because  he 
found  mucus  in  the  vitreous  body  in  the  adult,  Virchow  believes  that 
the  tissue  of  the  foetal  corpus  vitreum  should  be  ranked  with  what  he 
terms  "mucous  tissue,"  corresponding  with  my  gelatinous  connective 
tissue  (§  24) ;  and  that  it  might  be  assumed  that,  in  the  course  of  de- 
velopment, the  structure  may  so  change  that  the  cells  disappear  and  the 
intercellular  substance  alone  remains.  As  regards  my  own  views,  I  can 
only  partially  agree  with  these  authors.  In  the  vitreous  body  of  the 
human  foetus  and  of  that  of  animals,  I  can  perceive  nothing  but  a  homo- 
geneous matrix  containing  mucus  and  numerous  round  or  elongated 
granular,  nucleated  cells,  O-004-O'Ol  of  a  line  in  size,  dispersed  in  it  at 
pretty  regular  distances  of  0-01-0-02,  or  even  0-03  of  a  line  apart.  It 
is  true  I  have  also  noticed  stelliform  anastomosing  cells  also,  but  only 
on  the  outer  side  of  the  hyaloid  membrane,  and  which  when  the  vessels 
once  began  to  convey  blood,  could  be  easily  shown  to  communicate  with 
them,  and  to  be,  in  fact,  capillaries  in  process  of  development.  Of 
membranes,  such  as  Hannover  describes,  I  have  never  seen  any  certain 
indication  with  the  microscope ;  and  yet  such  membranes,  did  they 
exist,  would  incontestably  be  as  easily  recognized,  where  they  are 
folded,  as  the  excessively  delicate  hyaloid  membrane  itself.  In  the 


756  SPECIAL    HISTOLOGY. 

vitreous  body  of  the  adult,  of  the  previous  conditions  there  was  usually 
nothing  left  but  the  homogeneous  matrix,  the  cells  having  disappeared; 
I  noticed  the  latter,  however,  in  many  instances,  though  rare  and  indis- 
tinct, particularly  in  those  parts  of  the  organ  bordering  upon  the  lens 
and  the  hyaloid  membrane  in  general.  From  these  observations  I  con- 
clude that  the  vitreous  body,  at  an  early  period  probably  presents  a 
sort  of  structure  most  nearly  approximated  to  embryonic  cellular  tissue, 
but  that  subsequently  all  trace  of  such  a  structure  is  normally  lost,  and 
it  consists  merely  of  a  more  or  less  consistent  mucus. 

Zonula  Zinnii. — At  the  ora  serrata,  the  hyaloid  membrane  comes 
into  intimate  contact  with  the  retina,  and  the  latter  again  with  the 
choroid,  so  that  it  is  extremely  difficult  to  display  the  relations  of  the 
above-noticed  zonula  Zinnii.  If  this  part  be  exposed  from  the  outside, 
some  of  the  pigmentum  nigrum  of  the  ciliary  processes  is  almost  always 
left  adherent  at  certain  spots  and  often  over  a  considerable  extent.  If 
the  places  where  this  is  not  the  case  are  examined,  it  is  evident  that 
the  outermost  lamina  of  the  zonula  is  a  grayish  layer,  extending  exactly 
so  far  as  the  processus  ciliares  are  in  connection  with  the  zonula,  and 
ceasing  anteriorly  in  a  slightly  toothed,  irregular  border.  Under  the 
microscope  there  are  always  visible  in  this  layer,  even  when  the  zone 
appears  quite  clear,  and  particularly  towards  the  front,  a  good  many 
rows  of  pale  pigment-cells  belonging  to  the  choroid,  which  are  situated 
principally  in  the  folds  in  which  the  processus  ciliares  were  contained, 
and  give  the  entire  zone  a  striped  aspect.  On  the  inner  side  of  this 
lies  a  single  layer  of  clear,  frequently  very  pale,  polygonal,  nucleated 
cells,  of  0-006-0-012  of  a  line  in  size,  but  which  is  never  entire,  being 
always  partially  removed,  together  with  the  ciliary  processes,  on  which 
Henle  and  others  have  noticed  it.  This  layer  of  cells  does  not  belong 
to  the  retina,  as  most  authors  assume,  and  still  less  to  the  hyaloid 
membrane,  but  to  the  choroid,  and  is  nothing  more  than  a  stratum  of 
cells  not  containing  pigment,  lying  immediately  upon  the  corona  ciliaris, 
internally  to  the  pigment  (Fig.  296  w,  w1} ;  it  does  not,  however,  in 
any  way  appear  to  be  a  distinct  epithelial  layer,  but  only  the  uncolored 
part  of  the  pigmentary  stratum,  to  which  it  would  stand  in  the  same 
relation  as  the  colorless  epidermis-cells  to  the  colored,  in  dark  skins. 
This  colorless  epithelium  of  the  corona  ciliaris,  as  I  shall  term  these 
cells,  is  most  distinctly  shown  on  the  ciliary  processes,  as  a  clear  border 
sharply  defined  on  the  inner  side,  and  often  0-006-0-008  of  a  line  broad, 
whose  large,  frequently  shortly  cylindrical  cells,  may  usually  be  recog- 
nized without  any  trouble,  and  are  always  rendered  distinct  by  acetic 
acid ;  whence  it  is  evident  that  the  boundary  is  composed  only  of  them, 
and  is  not  a  special  membrane.  Posteriorly,  this  cellular  stratum 
reaches  as  far  as  the  ora  serrata,  extending  anteriorly  to  the  termina- 
tion of  the  ciliary  processes  (Fig.  296  w'),  and  on  either  side  it  is  con- 


THE    EYE.  757 

tinuous,  without  any  line  of  demarcation,  with  the  pigmentary  layer, 
the  clear  cells  being  gradually  replaced  by  cells  containing  pigment. 

Excepting  these  cells,  the  zonula  is  a  thin,  transparent  but  tolerably 
firm  membrane,  stretching  from  the  ora  serrata  retince  as  far  as  the 
border  of  the  lens,  and  appearing  to  be  a  continuation  of  the  hyaloid 
membrane.  It  consists  of  peculiar,  pale  fibres,  already  very  well  cha- 
racterized by  Henle,  resembling  certain  forms  of  reticular  connective 
tissue,  except  that  they  are  more  rigid,  usually  present  no  distinct 
fibrils,  and  are  less  swollen  in  acetic  acid.  They  commence,  very  fine, 
a  little  behind  the  ora  serrata  retince  on  the  outer  side  of  the  hyaloid 
membrane,  although  most  intimately  connected  with  it,  in  part  like 
fibrils  of  connective  tissue,  then  run  forwards,  forming  a  layer  at  first 
more  lax,  and  becoming  more  and  more  dense,  and  increasing  in  thick- 
ness (up  to  0-004  or  even  0-01  of  a  line  and  more),  with  numerous  divi- 
sions and  anastomoses,  and  for  the  most  part  parallel  with  each  other, 
until  they  constitute,  at  the  free  portion  of  the  zonula,  a  perfect,  con- 
tinuous layer — though  still  containing  a  few  isolated  bundles,  and  are 
ultimately  blended  with  the  capsule  of  the  lens.  From  the  ora  serrata 
to  the  commencement  of  the  "canal  of  Petit,"  no  hyaloid  membrane 
besides  the  fibres  of  the  zonula,  can  be  any  longer  distinguished,  whilst 
at  the  canal  itself,  where  the  substance  of  the  vitreous  body  is  separated 
from  the  fibrous  layer,  it  is  again  furnished  with  a  limitary  membrane, 
only  thinner  than  before,  which  constitutes  the  posterior  wall  of  the 
"  canal  of  Petit,"  and  extends  no  farther  than  to  the  border  of  the  lens, 
where  it  ceases  as  a  special  membrane,  the  vitreous  body  being  most 
intimately  united  with  the  posterior  lamina  of  the  capsule  of  the  lens. 

M.  Langenbeck,  some  years  ago  described,  in  the  free  portion  of  the 
zonula  Zinnii,  what  he  believes  to  be  a  muscular  ring,  and  terms  the 
musculus  compressor  lentis  s.  accommodatorius  ("  Klinisch.  Beitrage  zur 
Ophthalmol.,"  1849,  p.  66),  of  which  I  have  been  unable  to  perceive  any 
indication.  He  has  probably  confounded  the  zonular  fibres  with  such  a 
structure. 

B.     ACCESSORY  ORGANS. 

§  230.  The  eyelids  are  supported  by  the  so-termed  tar  sal  cartilages 
(tarsi),  thin,  semilunar,  flexible,  but  tolerably  elastic  plates,  attached 
internally  and  externally  by  the  fibrous,  tarsal  ligaments, — and  belong- 
ing, as  far  as  their  structure  is  concerned,  to  the  solid,  fascicular,  con- 
nective tissue,  though  occasionally  containing  a  certain  number  of  minute 
cartilage  cells.  These  plates,  0-3-0-4  of  a  line  thick,  the  fibres  in  which 
chiefly  run  parallel  with  the  borders,  are  covered  externally  by  the  orbi- 
cularis  palpelrarum  and  the  integuments,  and  internally  by  the  con- 


758  SPECIAL    HISTOLOGY. 

junctiva.  The  skin  is  here  very  thin  (1-5-1-8  of  a  line),  with  scanty, 
subcutaneous  connective  tissue  containing  no  fat,  a  delicate  cuticle, 
0-055-0-058  of  a  line  thick,  and  short  papilla  (of  0-060-0-066  of  a  line) ; 
but  it  is  furnished  throughout  with  minute  sudoriparous  glands  (of  1-10— 
1-12  of  a  line)  and  almost  invariably,  with  numerous  minute  hairs  (fre- 
quently, with  contiguous  sebaceous  glands,  but  whether  always  so  pro- 
vided I  do  not  know).  At  the  edges  of  the  palpebrce  these  hairs  are  more 
considerably  developed  and  constitute  the  eyelashes,  which  are  also  fur- 
nished with  sebaceous  follicles.  Agreeing  in  all  respects,  in  structure 
and  secretion,  with  the  sebaceous  glands,  the  Meibomian  glands,  never- 
theless, differ  somewhat  in  form.  They  are  imbedded  in  the  tarsal  car- 
tilages, to  the  number  of  from  twenty  to  forty,  in  the  form  of  elongated, 
white,  delicate,  parallel,  racemose  follicles,  disposed  in  such  a  direction 
that  the  long  axes  of  the  glands,  cut  those  of  the  tarsal  cartilages  at  a 
right  angle.  Each  of  these  glands  which  are  visible  at  once  upon 
inverting  the  eyelid,  and  do  not  occupy  the  entire  width  of  the  tarsi, 
consists  of  a  straight  excretory  duct,  0-04-0*05  of  aline  wide,  which  at  its 
orifice  on  the  inner  edge  of  the  free  palpebral  border,  is  lined  with  com- 
mon epidermis,  including  the  horny  and  the  mucous  layers,  and  more 
internally  presents  the  usual  structure  observed  in  the  sebaceous  glands. 
This  canal,  throughout  its  length,  is  beset  with  round  or  pyriform,  shortly 
pedunculated,  gland-vesicles,  0-04-0-07-0-1  of  a  line  in  diameter,  either 
isolated  or  aggregated  several  together,  in  which,  in  a  mode  similar  to  that 
already  described  in  speaking  of  the  sebaceous  glands  (§  74),  a  constant 
production  of  spherical,  adipose  cells,  0-005-0-01  of  a  line  in  size,  takes 
place ;  the  cells  differing  from  the  sebaceous  cells,  only  in  the  circum- 
stance that  the  oil-drops  contained  in  them  do  not  usually  run  together 
into  a  single  large  drop,  but  remain  separate.  As  these  cells  advance 
towards  the  excretory  duct  they  gradually  break  up  into  a  whitish  pul- 
taceous  substance  composed  of  oil-drops,  and  form  the  so-termed  lema 
s.  sebum  palpebrale.  The  orbicularis  palpebrarum,  constituted  of  trans- 
versely striped,  though  rather  slender  and  pale  muscular  fibres,  lies  im- 
mediately beneath  the  skin,  its  stratum  internum  being  separated  from 
the  tarsi  by  a  layer  of  lax,  and  to  some  extent  adipose  connective  tissue, 
so  that  it  may  be  readily  raised  into  a  fold  together  with  the  integuments. 
It  is  only  towards  the  free  margin  that  this  muscle  is  more  closely 
attached  to  the  tarsi,  and  there  presents  a  bundle  of  fibres  situated  at 
the  very  verge  of  the  eyelid,  which  is  parted  from  the  rest  of  the  muscle 
by  the  follicles  of  the  cilia — the  so-termed  ciliar  muscle  (musculus  cili- 
aris,  Riolan). 

The  conjunctiva  (a  mucous  membrane),  commences  at  the  free  palpe- 
bral margin,  as  an  immediate  continuation  of  the  external  integument, 
lines  the  posterior  surface  of  the  eyelids,  and  is  then  reflected  upon  the 
eyeball,  investing  the  anterior  part  of  the  sclerotic  and  the  entire  cornea. 


THE    EYE.  759 

The  palpebral  conjunctiva  is  a  reddish  membrane,  0-12-0-16  of  a  line 
thick,  very  intimately  connected  with  the  posterior  surface  of  the  tarsi, 
and  consisting  of  a  dense  layer  of  connective  tissue  corresponding  to 
the  cutis,  0-08-0-11  of  a  line  thick,  and  of  a  squamose  epithelium,  0-04 
of  a  line  in  thickness,  containing  deeper  cells  of  an  elongated  form,  and 
more  superficially,  polygonal,  slightly  flattened,  nucleated,  and  (so  far 
as  I  have  seen  in  Man)  non-ciliated  cells.  Papillae  also,  similar  to  those 
of  the  cutis,  are  met  with  in  the  palpebral  conjunctiva,  some  of  which 
are  smaller  and  more  cylindrical,  whilst  others,  particularly  towards  the 
point  of  reflection  of  the  membrane  where  it  is  generally  thicker,  are 
larger  (as  much  as  1-10  of  a  line  long),  more  verrucose  and  fungiform. 
At  the  line  of  reflection  itself,  Krause  describes  minute  racemose  mu- 
cous glands,  1-5-1-26  of  a  line  in  size,  but  which  do  not  always  exist. 
The  conjunctiva  scleroticce,  is  white,  less  dense  and  thinner  than  that  of 
the  lids,  tolerably  rich  in  fine  elastic  fibres,  and  loosely  and  movably 
attached  to  the  sclerotic  by  an  abundant  submucous  connective  tissue, 
containing  more  or  fewer  fat-cells.  Papillce  are  wholly  wanting  in  this 
portion,  except  at  the  line  of  reflection,  as  well  as  glands,  whilst  the  epi- 
thelium is  well  developed,  as  on  the  conjunctiva  cornece,  and  beneath  it 
there  is  not  unfrequently  an  outermost  layer  of  the  proper  mucous  mem- 
brane, in  the  form  of  a  very  distinct  structureless,  narrow  seam.  At 
the  margin  of  the  cornea,  particularly  in  elderly  persons,  the  conjunc- 
tiva scleroticce  forms  a  slight  annular  elevation  J-l  line  broad, — the  an- 
nulus  conjunctivce,  which  encroaches  a  little  upon  the  cornea  at  the  lower, 
and  especially  at  the  upper  border.  The  corneal  conjunctiva  has  been 
already  described,  and  it  only  remains  to  notice  the  plica  semilunaris, 
or  the  third  palpebra  at  the  inner  canthus  of  the  eye.  This  is  a  simple 
duplicature  of  the  sclerotic  conjunctiva,  which  rises  in  front  into  a  coni- 
cal elevation — the  caruncula  lachrymalis, — in  which  are  seated  about  a 
dozen  fine  hairs,  surrounded  by  an  equal  number  of  rosette-like  sebace- 
ous follicles  1-5-1-4  of  a  line  in  size,  encompassed  by  numerous  fat-cells. 
The  lachrymal  apparatus  consists,  in  the  first  place,  of  the  lachrymal 
glands — a  certain  number  of  larger  and  smaller  compound  racemose 
glands,  disposed  in  two  groups — termed  the  superior  and  inferior  lachry- 
mal glands,  and  in  the  structure  of  the  larger  and  smaller  lobules,  as 
well  as  in  the  rounded  gland-vesicles,  0-02-0-04  of  a  line  in  diameter, 
precisely  resembling  the  salivary  and  mucous  glands  (§§  134,  135).  The 
excretory  ducts  of  these  glands,  6-12  in  number,  perforate  the  conjunc- 
tiva in  the  fold  between  the  outer  part  of  the  eyelid  and  the  globe  of 
the  eye ;  they  are  excessively  fine  canaliculi,  composed  of  connective 
tissue,  with  a  few  nuclei  and  elastic  fibrils,  and  of  a  cylindrical  epithe- 
lium. It  is  extremely  difficult  to  display  these  canals  in  man,  whilst  in 
animals  (the  Ox  for  instance)  they  are  easy  of  demonstration.  The  pas- 
sages by  which  the  tears  are  conveyed  away  from  the  eye  are  con- 


760  SPECIAL    HISTOLOGY. 

structed  in  the  same  simple  manner  as  the  excretory  ducts  of  the  lach- 
rymal glands,  consisting  merely  of  a  dense  connective  tissue  with  nu- 
merous networks  of  fine  elastic  fibres,  particularly  abundant  in  the 
lachrymal  canals,  which  appears  to  be  a  continuation  of  the  mucous 
membrane  of  the  nose  and  of  the  conjunctiva,  and  of  an  epithelium 
which,  in  the  lachrymal  canals,  is  of  the  squamous  kind,  and  in  the 
lachrymal  sac  and  nasal  duct  is  furnished  with  vibratile  cilia,  as  in  the 
cavity  of  the  nares.  The  muscles  of  the  globe  of  the  eye  and  of  the 
eyelids,  as  well  as  the  musculus  Horneri,  are  all  composed  of  trans- 
versely striped  muscular  fibres,  and  together  with  their  tendons,  pre- 
sent no  differences  from  those  of  the  trunk  and  extremities.  The  fascia 
lulbi  oculi  s.  Tenoni  is  a  true  fibrous  membrane,  and  the  trochlea  is 
formed  principally  of  dense,  connective  tissue,  in  which  only  a  few 
cartilage  cells  can  be  seen. 

The  vessels  of  the  organs  described  in  this  section  present  little 
worthy  of  remark.  Excepting  those  of  the  muscles  and  skin,  they  are 
most  abundant  in  the  palpebral  conjunctiva,  in  which  they  chiefly  enter 
the  papilla?,  and  in  the  next  place  in  the  lachrymal  glands  and  the 
caruncula  lachrymalis.  The  sclerotic  conjunctiva  also  contains  numerous 
vessels,  and  the  Meibomian  glands  within  the  tarsi  are  also  surrounded 
by  a  few.  Except  in  the  skin  of  the  eyelids,  lymphatics  have  only  been 
demonstrated  by  Arnold  in  the  conjunctiva  scleroticce,  where  they  form, 
at  the  border  of  the  cornea,  a  closer,  and  more  externally  a  looser 
plexus,  passing  outwards  in  several  small  trunks.  The  palpebrce  and 
conjunctiva  are  everywhere  well  supplied  with  nerves,  but  their  rela- 
tions have  been  minutely  examined  only  in  the  conjunctiva.  In  this 
membrane,  in  Man,  I  have  found  terminal  plexuses  as  in  the  external 
integument,  with  numerous  divisions  of  fibres,  0-001-0-006  of  a  line 
thick,  extending  up  to  the  margin  of  the  cornea,  together  with  pretty 
clear  indications  of  loops  and  free  terminations.  Besides  which,  in  one 
instance,  there  were  presented,  towards  the  palpebral  conjunctiva,  pecu- 
liar "nerve-coils,"  0-02-0-028  of  a  line  in  size,  into  which  a  single 
nerve-fibre  usually  entered,  whilst  2-4  were  given  off  from  it  (vid.  "  Mik. 
Anat."  II.  1,  p.  31,  Fig.  13,  A,  3).  The  relations  of  the  nerves  of  the 
lachrymal  apparatus  are  entirely  unknown. 

§  231.  Physiological  remarks. — The  eyeball  is  not  developed  from  a 
single  point  as  a  whole,  but  arises  from  the  conjunction  of  formations, 
proceeding  on  one  side  from  the  central  nervous  system,  on  another  from 
the  skin,  and,  thirdly,  from  the  parts  lying  between  the  two.  In  the 
Chick,  the  primitive  ocular  vesicles  arise  before  the  commencement  of 
the  second  day,  from  the  primitive  cerebral  vesicle  or  the  anterior  cere- 
brum, in  the  form  of  two  protrusions,  at  first  sessile,  but  afterwards 
having  a  hollow  peduncle — the  rudiment  of  the  optic  nerve.  At  the 


THE     EYE.  761 

beginning  of  the  third  day,  the  formation  of  the  lens  commences,  from 
the  skin  of  the  face  covering  these  vesicles,  by  the  thickening  on  the 
inner  aspect,  and  inversion  of  the  epidermis,  in  consequence  of  which 
the  anterior  wall  of  the  primitive  ocular  vesicle  is  also  inverted,  and 
becomes  applied  to  the  posterior  wall,  so  that  the  cavity  of  the  vesicle 
is  wholly  obliterated.  Now,  at  first,  this  secondary  ocular  vesicle 
encompasses  the  lens,  which  in  the  mean  time  has  been  separated  by 
constriction  from  the  epidermis,  and  comes  into  exact  apposition  with  it 
beneath,  like  a  cup  ;  subsequently,  however,  the  vitreous  body  is  developed 
between  the  two,  in  a  special  new  cavity.  How  the  latter  is  formed  has 
not  yet  been  ascertained,  although,  as  Scholer  observes,  it  is  most  pro- 
bable that  it  also  grows  in  from  the  skin, — in  fact,  from  the  region 
below  and  behind  the  lens, — and  participates  with  the  latter  in  the 
inversion  of  the  primitive  ocular  vesicle.  According  to  Remak,  the 
retina  is  formed  from  the  inner,  thicker  wall  of  the  inverted  or  second- 
ary ocular  vesicle,  and  from  the  outer  and  thinner,  the  choroid,  from 
the  anterior  border  of  which  the  iris  is  not  produced  till  afterwards. 
The  sclerotic  and  cornea  are  applied  from  without  upon  the  eyeball 
thus  constituted,  the  former  being  to  some  extent  a  production  of  the 
skin. 

An  interesting  phenomenon  is  presented  in  the  vessels  existing  in  the 
foetal  eye,  even  in  the  transparent  media.  The  vitreous  body,  on  its 
outer  surface,  between  the  hyaloid  membrane  and  the  retina,  presents  a 
tolerably  wide-meshed  vascular  plexus,  which  is  supplied  by  branches 
of  the  arteria  centralis  retina?,  given  off  from  it  at  its  entrance  into  the 
eye,  and  anteriorly,  at  the  border  of  the  lens  on  the  zonula  Zinnii, 
forms  a  vascular  circle,  the  circulus  arteriosus  Mascagnii,  from  which 
again  vessels  are  given  off  to  the  memlrana  capsulo-pupillaris,  pre- 
sently to  be  described.  Besides  this,  a  special  arteria  Jiyaloidea,  also 
derived  from  the  central  artery  of  the  retina,  runs  in  the  so-termed 
canalis  Jiyaloideus,  in  a  straight  line  through  the  vitreous  body,  to  the 
lens,  and  ramifies  in  the  most  elegant  arborescent  manner,  at  very  acute 
angles,  in  a  membrane  closely  applied  to  the  posterior  wall  of  the  len- 
ticular capsule.  This  is  nothing  else  than  a  portion  of  an  external  vas- 
cular capsule,  which  at  first  very  closely  surrounds  the  lens,  and  in  its 
anterior  wall  is  supplied  by  the  continuations  of  the  hyaloid  artery, 
coming  round  the  border  of  the  lens  towards  the  front,  with  which 
branches  of  the  circulus  arteriosus  Mascagnii  and  of  the  anterior 
border  of  the  uvea  are  connected.  Afterwards,  when  the  lens  retreats 
from  the  cornea,  with  which  it  is,  at  first,  in  close  apposition,  and  the 
iris  buds  out  from  the  border  of  the  uvea,  the  anterior  wall  of  the  vas- 
cular lenticular  capsule  is  divided  into  two  portions :  one  central  and 
anterior,  which,  arising  from  the  border  of  the  iris,  and  connected  with 
that  membrane  by  vessels,  closes  the  pupil — the  membrana  pupillaris  ; 


762  SPECIAL    HISTOLOGY. 

and  another,  external  and  posterior,  extending  backwards  from  the 
same  points  upon  the  border  of  the  lens — the  membrana  capsulo-pupil- 
aris.  The  latter  becomes  more  and  more  distinct  as  the  lens  and 
aqueous  chambers  are  developed  and  the  lens  retreats,  until  at  last  it 
represents  a  delicate  membrane  stretching  across  the  posterior  chamber. 
The  venous  blood  from  all  these  parts  is  returned  through  the  veins  of 
the  iris,  and  from  the  outer  surface  of  the  vitreous  body,  also  through 
those  of  the  retina,  and  perhaps  through  a  vena  hyaloidea,  said  to  take 
the  same  course  as  the  artery,  but  of  the  existence  of  which  many 
authors  doubt,  and  which  I  have  never  myself  seen.  With  respect  to 
the  genetic  import  of  the  vascular  capsule,  nothing  has  as  yet  been 
ascertained.  I  find  it  to  be  composed  of  a  homogeneous  tissue,  with  a 
few  scattered  cells,  and  regard  it  as  a  structure  corresponding  to  the 
cutis,  which,  in  the  formation  of  the  lens,  is  detached  from  the  skin, 
together  with  a  portion  of  the  epidermis,  and  remains  in  the  eye.  The 
vitreous  body,  then,  may  be  understood  as  modified  subcutaneous  con- 
nective tissue, — a  supposition  not  at  all  incongruous  with  the  observations 
above  adduced,  and  the  more  so,  because,  as  I  have  shown  (§  24),  all 
the  subcutaneous  connective  tissue  of  the  foetus  is  at  one  time  perfectly 
gelatinous,  and,  like  the  enamel  organ  which  also  belongs  to  the  same 
tissue  in  specie,  strikingly  resembles  the  vitreous  body  in  aspect  and 
consistence. 

Concerning  the  histological  development  of  the  eyes,  the  following 
only  need  be  remarked.  At  an  early  period  they  consist  in  all  their 
parts  of  formative  cells  of  uniform  size,  which,  in  process  of  time,  are 
metamorphosed  into  the  various  tissues.  In  the  fibrous  coat,  in  the 
second  and  third  month,  the  cells  are  developed,  in  the  mode  already 
described  (§  24),  into  connective  tissue,  and  at  the  same  time  the  dis- 
tinction is  set  up  between  the  cornea  and  sclerotic,  which  are  at  first, 
externally,  exactly  alike,  and  constitute  only  a  single  membrane.  In 
the  uvea  the  cells  are  for  the  most  part  employed  in  the  formation  of 
vessels ;  another  portion  goes  to  the  formation  of  the  inner  and  outer 
pigment-layers,  pigment-granules  being  deposited  in  them  at  the  com- 
mencement of  the  third  month,  whilst  another  is  transformed  into 
muscles,  nerves,  the  epithelia  and  connective  tissue  of  these  membranes. 
The  development  of  the  nerve-cells  and  of  the  so-termed  "granules" 
from  embryonic  cells,  may  be  readily  traced.  I  have  observed  the 
same  thing  also  with  respect  to  the  "cones;"  and  I  think  that,  in  the 
Frog,  it  may  be  assumed  with  respect  to  the  "  rods"  likewise,  that  they 
are  nothing  but  elongated  cells ;  whilst  in  the  Mammalia,  the  formation 
of  the  "rods,"  and  of  the  nerve-fibres  themselves,  has  not  yet  been 
traced.  The  lens,  lastly,  is  originally  composed  entirely  of  cells, 
which,  in  course  of  time,  are  transformed  into  the  tubes.  The  precise 
nature  of  the  processes  attending  these  changes  has  not  yet  been 


THE    EYE.  763 

investigated,  although  I  agree  with  H.  Meyer  in  the  conclusion,  that 
since  the  tubes,  both  in  the  foetus  and  child,  present  only  a  single 
nucleus,  each  of  them  is  developed  out  of  a  single  cell.  These  nuclei 
taken  as  a  whole,  constitute  a  thin  layer,  extending  from  the  borders  of 
the  lens,  through  the  middle  of  its  anterior  half,  and  slightly  convex  in 
front  ("  nuclear  zone,"  Meyer) ;  the  nuclei  being  smaller  in  the  interior 
portions,  and  as  it  were  in  progress  of  solution,  whence  it  may  cer- 
tainly be  concluded  that  the  lens  increases  by  the  apposition  of  thin 
layers  from  without.  The  formative  cells  of  the  tubes  of  the  lens  are 
those  which  exist  on  the  anterior  half  of  the  capsule  and  the  starting 
point  of  the  formation  of  the  lenticular  elements,  according  to  my 
observation,  is  the  entire  anterior  surface  and  the  border  of  the  organ. 
Nuclei  are  visible  in  the  tubes  even  in  the  lens  of  the  adult,  as  was 
known  to  Harting,  though  only  at  its  margin. 

With  respect  to  the  vessels  of  the  foetal  eye,  Dr.  Thiersch  has  quite 
recently  communicated  to  me  a  mass  of  interesting  details,  accompanied 
by  beautiful  injections,  to  which  I  shall  refer  in  the  concluding  part  of 
my  "Microscopical  Anatomy." 

Investigation  of  the  visual  organ. — The  fibrous  tunic  of  the  eye 
should  be  examined  in  the  recent  condition,  and  in  moistened  sections 
of  dried  preparations,  which  latter,  especially  of  the  cornea  and  at  its 
point  of  transition  into  the  sclerotica,  afford  very  useful  information. 
If,  after  the  removal  of  the  vitreous  body  and  lens,  the  iris  and  choroid 
are  dried,  their  connection  with  each  other  and  with  the  fibrous  tissue  may 
be  studied.  In  order  to  view  the  nerves  and  vessels  of  the  cornea,  the 
latter  is  removed  by  a  circular  section  in  the  recent  eye,  together  with 
the  margin  of  the  sclerotic,  the  whole  is  divided  into  three  or  four  seg- 
ments, which,  in  order  that  they  may  lie  the  better,  have  little  incisions 
made  into  them  around  the  edge,  are  moistened  with  the  aqueous 
humor,  and  covered  with  a  thin  plate.  The  nervous  trunks,  which  are 
here  usually  opaque,  are  then  sought  for  at  the  border  of  the  cornea,  first 
with  a  low  power,  and  afterwards  traced  under  a  higher.  The  nerves 
are  beautifully  displayed  in  the  eye  of  the  Babbit,  where  I  can  perceive 
their  trunks  with  the  naked  eye,  though  they  may  usually  be  readily 
found  in  other  eyes  also,  but  are  always  traced  with  difficulty  towards 
the  centre.  If  the  epithelium  is  cloudy,  it  must  be  removed  by  caustic 
soda,  which  at  first  does  not  affect  the  nerves.  The  vessels  under  these 
circumstances  are  usually  full  of  blood,  and  consequently  present  no 
difficulties.  The  corneal  epithelium  is  visible  on  the  surface  in  sections 
of  dried  preparations,  and  is  very  well  shown  when  the  surface  is 
scraped.  The  "  membrane  of  Demours"  is  very  distinct  in  sections, 
and  frequently  its  epithelium  also ;  otherwise  the  latter  is  well  seen  on 
the  surface,  and  in  detached  shreds  of  the  membrane.  The  passage  of 
this  membrane  into  the  lig amentum  pectinatum  of  the  iris,  may  be  seen 


764  SPECIAL    HISTOLOGY. 

in  sections,  and  by  careful  dissection.  In  the  latter  case,  the  inner 
wall  of  the  "canal  of  Schlemm"  should  be  carefully  removed,  together 
with  the  iris  and  choroid,  and  an  attempt  made  to  raise  from  it  portions 
of  the  membrana  Demoursiana,  which  is  not  unfrequently  successful. 
The  uvea  offers  no  difficulty.  The  pigment-cells  of  the  stroma,  with 
their  processes,  and  the  inner  pigment  are  readily  seen ;  the  latter  at 
the  margin  of  folds,  and  in  carefully  detached  portions.  For  the  inves- 
tigation of  the  ciliary  muscle,  a  fresh  eye  is  requisite,  as  its  elements 
very  soon  become  unrecognizable.  The  muscles  of  the  iris  should  be 
studied  in  a  blue  eye,  and  best  in  that  of  a  child,  after  removal  of  the 
posterior  pigment ;  and  also  in  the  eye  of  a  white  Rabbit,  in  which  the 
sphincter  pupillse  may  be  readily  seen  without  farther  trouble  on  the 
application  of  acetic  acid.  The  same  preparation  should  be  employed 
in  order  to  examine  the  nerves  of  the  iris,  but  a  perfectly  fresh  eye  and 
a  dilute  solution  of  soda  are  indispensable.  The  retina  should  be 
examined  in  the  recent  state,  on  the  surface,  in  vertical  sections,  and  at 
the  edges  of  folds,  moistened  with  aqueous  humor,  and  without  any 
covering  glass ;  and  also  with  the  aid  of  slight  compression,  and  by  the 
teasing  out  of  the  tissue.  Chromic  acid  preparations  are  very  impor- 
tant in  the  study  of  this  structure.  This  reagent,  it  is  true,  affects  the 
"rods"  to  some  extent,  but  preserves  the  other  parts  so  much  the 
better,  and  without  its  aid  Midler  and  I  should  never  have  arrived  at 
the  results  above  stated,  although  Hannover,  on  account  of  its  influence 
upon  the  "rods,"  erroneously  considered  it  an  unfit  agent  to  employ. 
The  most  advantageous  mode  of  applying  it,  is  to  treat  a  fresh  retina 
at  once  with  chromic  acid,  and  to  trace  all  the  stages  of  its  effect  step 
by  step.  If  the  solution  be  much  diluted,  the  elements  are  very  little 
changed,  and  in  particular  may  be  easily  isolated ;  and  if  more  con- 
centrated, sections  through  the  retina  may  be  prepared,  without  which 
no  complete  view  of  the  structure  of  that  tunic  can  be  arrived  at.  I 
apply  it  by  extending  a  portion  of  the  retina  upon  an  object-bearer, 
with  a  little  chromic  acid,  in  such  a  way  that  it  should  lie  flat  and  not 
float.  Extremely  fine  slices  may  then  be  taken  by  a  sharp  convex 
scalpel  or  razor  from  any  sectional  surface,  by  pressing  downwards, 
which,  with  a  little  pains,  may  be  done  easily  enough.  It  is  as  well, 
however,  to  guide  the  cutting  scalpel  by  the  handle  of  another  held  in 
the  other  hand,  until  the  edge  of  the  former  is  brought  immediately 
over  the  border  of  the  retina.  When  the  nervous  layers,  which  are 
very  well  defined  from  each  other,  have  been  studied  in  sections  of  this 
kind,  which  should  be  taken  especially  from  the  neighborhood  of  the 
macula  lutea,  as  well  as  from  other  situations  in  the  transverse  and 
longitudinal  directions,  and  which  when  useful  necessarily  exhibit  only 
a  few  layers  of  the  elements,  they  may  be  carefully  teased  out  or  ren- 
dered more  transparent  by  soda,  which  last,  however,  is  not  generally 
of  much  use,  since  it  makes  the  elements  pale.  The  hyaloid  membrane 


THE    EYE.  765 

is  posteriorly  always  very  readily  detached  from  the  retina,  together 
with  the  vitreous  body,  and  may  be  recognized  in  every  eye,  in  sections 
from  the  surface  of  that  body,  examined  under  the  microscope,  and,  in 
folds,  occasionally  by  the  naked  eye.  The  zonula  Zinnii,  on  the  other 
hand,  in  the  recent  eye,  is  always  so  covered  by  detached  pigment  and 
the  colorless  epithelium  of  the  ciliary  processes,  and  at  its  posterior 
border  by  the  retina,  that  it  cannot  well  be  recognized  in  that  situation, 
and  almost  only  in  its  free,  most  anterior  portion.  In  such  prepara- 
tions, also,  after  the  removal  to  the  greatest  possible  extent  of  the 
adherent  parts  by  means  of  a  hair  pencil,  pretty  good  views  of  it  may 
be  obtained,  particularly  if,  in  addition  to  the  viewing  of  the  external 
and  internal  surface  of  segments  of  the  zonula  detached  from  the 
vitreous  body,  and  of  preparations  made  by  the  teasing  out  of  the 
structures,  the  borders  of  folds,  especially  of  the  inner  surface,  are 
also  examined,  which,  with  some  care,  may  be  obtained  to  the  whole 
extent  of  the  zonula,  and  of  its  points  of  connection  with  the  retina. 
The  zonula,  in .  connection  with  the  hyaloid  membrane,  is  very  beauti- 
fully and  distinctly  isolated  from  the  retina  and  the  cells  of  the  ciliary 
processes,  in  half-putrid  eyes,  and  in  macerated  preparations  of  the 
vitreous  body ;  and  preparations  of  this  kind  are  especially  adapted  to 
show  that  the  zonula  is  a  part  of  the  hyaloid  membrane,  as  well  as  the 
mode  of  origin  and  course  of  its  fibres.  For  the  study  of  the  zonular 
fibres  I  can  also  particularly  recommend  chromic  acid  preparations,  in 
which  they  become  quite  opaque  and  glistening,  almost  like  elastic 
fibres.  The  capsule  of  the  lens  and  its  epithelium  present  no  difficul- 
ties. The  tubes  of  the  lens,  when  fresh,  are  very  transparent,  but  in 
dilute  chromic  acid  they  are  rendered  quite  distinct.  Sections  of  the 
lens  may  be  easily  procured  from  preparations  made  in  alcohol,  or 
chromic  acid,  or  from  dried  and  hardened  preparations,  which  may  be 
rendered  transparent  again  by  means  of  acetic  acid.  The  accessory 
organs  of  the  eyes  require  no  particular  remark,  unless,  with  respect 
to  the  Meibomian  glands,  it  may  be  stated,  that  they  are  best  seen  in 
tarsi  which  have  been  cleanly  dissected  and  treated  with  acetic  acid  and 
alkalies,  and  in  longitudinal  and  transverse  sections  of  similar  prepara- 
tions, dried. 

Literature. — THE  "EYE"  AS  A  WHOLE:  Valentin,  in  his  "  Report.," 
1836  and  1837,  and  "  Handw.  d.  Physiol.,"  I.  p.  748  ;  S.  Pappenheim, 
"  Gewebelehre  d.  Auges,"  Berlin,  1842  ;  E.  Briicke,  "  Anat.  Beschreib, 
d.  menschlichen  Augapfels,"  Berlin,  1847;  W.  Bowman,  "Lectures  on 
the  parts  concerned  in  the  operations  on  the  eye  and  on  the  structure  of 
the  Retina  and  Vitreous  Humor,"  London,  1849  ;  A.  Hannover,  "  Bidrag 
til  Ojets  Anatomic,  Physiologic  og  Pathologic,"  Copenhagen,  1850.  SCLE- 
ROTICA:  M.  Erdl,  "Disquisit.  anat.  de  oculo,"  I.  "  De  m.  sclerotic^," 


766  SPECIAL    HISTOLOGY. 

Monach.,1839;  Bochdalek,  "Ueber  die  Nerven  der  Sderotica,"  in  "Prag. 
Viertelj.,"  1849,  IV.,  119.  CORNEA:  Kolliker,  "Ueber  die  Nerven 
der  Hornhaut,"  in  "Mitth.  d.  naturf."  Ges.,  in  Zurich,  1848,  No.  19; 
Rahn,  "  Ueber  die  Nerven  der  Hornhaut,"  in  "  Mitth.  d.  naturf.,"  Ges., 
in  Zurich,  1850,  No.  45 ;  Luschka,  "  Die  Nerven  der  durchsichtigen 
Augenhaut,"  in  "  Zeitsch.  f.  rat.  Med.,"  X.,  p.  20,  and  "  Die  Structur 
der  serb'sen  Haute  des  Auges,"  in  "  Str.  d.  serosen  Haute,"  Tubingen, 
1851  ;  Strube,  "Der  normale  Bau  der  Cornea,"  Diss.,  Wurzburg,  1851. 
CHOROID  AND  IRIS  :  C.  Krause,  "  Ueber  die  Pigmenthaut,"  in  Muller's 
"Arch.,"  1837,  p.  33;  E.  Briicke,  "Ueber  den  Muse,  cramptonianus 
u.  d.  Spannrauskel  der  Chorioidea"  in  Mull.  "Archiv.,"  1846;  Boch- 
dalek,  "Beitrage  zur  Anatomie  des  Auges,"  "Prag.  Yiertelj.,"  1850, 
I.  RETINA:  G.  Treviranus,  "Ueber  den  Bau  der  Netzhaut,"  in  his 
"Beitragen,"  Bremen,  1835  and  1837;  C.  M.  Gottsche,  "  Ueber  d. 
Nervenausbreitung  d.  Retina"  in  Pfaff 's  "  Mittheil.  a.  d.  Geb.  d.  Med.," 
1846  [and  "  Ueber  die  Retina  im  Auge  der  Gratenfische,"  in  Mull. 
"Archiv,"  1835,  p.  457];  A.  Michaelis,  in  Muller's  "Archiv,"  1837, 
p.  12,  and  "N.  Acta,"  T.  XIX.,  1842;  B.  Langenbeck,  "-De  retin& 
observat.,"  Gott.,  1836 ;  R.  Remak,  "  Zur  mikrosk.  Anatomie  der  Re- 
tina" in  Mull.  "Archiv,"  1839;  B.  Lersch,  "  De  retinae  struct, 
microsc.,"  Berolini,  1840;  A.  Burow,  "Ueber  den  Bau  der  macula 
lutea"  in  Mull.  "Archiv,"  1840;  E.  Bidder,  "Zur  Anatomie  der 
Retina"  in  Muller's  "Archiv,"  1839  and  1841 ;  R.  Hannover,  "  Ueber 
die  Netzhaut,"  in  Muller's  "Archiv,"  1840  and  1843,  and  "Recherches 
microsc.  sur  le  syst.  nerveux,"  Copenh.,  1844;  E.  Briicke,  "Ueber  die 
physiologische  Bedeutung  der  stabformigen  Korper,"  in  Muller's 
"  Archiv,"  1844,  p.  444,  and  "  Anat.  Untersuchung  liber  die  sog.  leuch- 
tenden  Augen,"  ibid.,  1845,  p.  337;  F.  Pacini,  "  Sulla  "tessitura  intima 
della  retina,"  in  "Nuovi  Annali  delle  scienze  naturali  di  Bologna," 
1845;  H.  Muller,  "Zur  Histologie  des  Netzhaut,"  in  "Zeitsch.  fur 
wissenschaft.  Zool.,"  1851,  p.  234;  Corti,  "  Beitrag  zur  Anatomie  der 
Retina"  in  Muller's  "Archiv,"  1850,  p.  274.  [A.  Kolliker,  "Zur 
Anatomie  und  Physiologie  der  Retina,"  in  "  Verhandl,  d.  Wurzb. 
phys.  med.,  Ges."  Bd.  III.,  p.  216;  H.  Muller,  "Bemerkungen 
liber  den  Bau  n.  die  Funktion  der  Retina,"  ib.,  Bd.  III.,  p.  336,  and 
Bd.  IV.,  p.  96;  also  conjointly  with  Kolliker,  in  "Verhandl.  d. 
Wurzb.  phys.  med.  Ges.,"  p'.  3,  Bands.  III.  and  IV.,  and  in  "  Comptes 
rendus  de  TAcademie  des  Sciences,"  torn.  XXXVII.,  No.  13, 
Sept.  1853;  A.  Hannover,  "Zur.  Anatomie  und  Physiologie  der  Re- 
tina," in  "Zeitsch.  f.  wiss.  Zool.,"  Bd.  X.,  p.  17,  1853.— ED.] 
VITREOUS  BODY  :  E.  Briicke,  "  Ueber  den  innern  Bau  des  Glaskorpers," 
in  Mull.  "Archiv,"  1843,  p.  345,  and  1845,  p.  130  ;  Hannover,  "  Ent- 
deckung  des  Baues  des  Glaskorpers,"  in  Muller's  "Archiv,"  1845,  p. 
467  ;  W.  Bowman  (op.  cit.),  and  in  "  Dublin  Quarterly  Journal,"  Aug. 


THE     EAR.  767 

1845,  p.  102;  Virchow,  "Notiz  Uber  den  Glaskorper,"  in  "Arch.  f. 
path.  Anatomic,"  IV.,  p.  468  [and  V.  2,  p.  298],  and  in  "  Verh.  d. 
Wurzb.  phjs.  med.,"  Gesellsch.,  IL,  p.  317.  LENS:  W.  Werneck, 
"  Mikr.  Betracht.  der  Wasserhaut  u.  des  Linsensystems,"  in  Ammon's 
"  Zeitsch.,"  Bd.  IV.  and  V. ;  R.  Hannover,  "  Beobachtungen  iiber  den 
Bau  der  Linse,"  in  Mull.  "Archiv,"  1845,  p.  478;  Harting,  "  His- 
tolog.  Anteekennigen,"  1846,  pp.  1-7,  and  "  Recherch.  microme'triques." 
DEVELOPMENT  or  THE  EYE  :  H.  Scholer,  "  De  oculi  evolutione,"  Mitav., 
1849,  Diss. ;  Remak,  in  his  large  work,  "  Ueber  Entwicklungsge- 
schichte,"  1850-51 ;  Gray,  "  On  the  development  of  the  retina  and  the 
optic  nerve,"  in  "Phil.  Trans.,"  L,  1850;  Henle,  "De  membr.  pupil- 
lari,"  Bonn.,  1832;  Reich,  "  De  membr.  pupillari,"  Berolini,  1833;  J. 
Muller,  also  Arnold,  and  Henle,  on  the  "M.  capsulo-pupill.,"  in  Am- 
mon's "  Zeitsch.,"  IL,  p.  391,  III.,  p.  37,  IV.,  pp.  23  and  28.  Besides 
which,  see  Arnold,  "  Org.  sensuum." 

IL— OF  THE  ORGAN  OF  HEARING. 

§  232.  The  auditory  organ  consists  of  the  proper  sentient  parts  with 
the  expansion  of  the  acoustic  nerve,  which  are  contained  in  the  osseous 
substance  of  the  labyrinth  ;  and  of  special  accessory  apparatus,  the 
external  and  middle  ear,  intended  chiefly  for  the  reception  and  conduc- 
tion of  the  undulations  of  sound. 

§  233.  External  and  middle  ear. — The  auricle  (pinna)  and  the  car- 
tilaginous external  auditory  canal,  are  supported  by  the  cartilage  of  the 
ear  (cartilago  auris],  J-l  line  thick,  and  while  retaining  the  thick 
pericJiondrium  very  flexible,  but  otherwise  extremely  brittle,  and  the 
form  of  which  is  well  known.  This  cartilage,  in  its  more  intimate  struc- 
ture, approaches  the  yellow  or  reticular  cartilages,  though  it  is  distin- 
guished by  a  considerable  preponderance  of  cartilage-cells,  O'Ol  of  a 
line  in  diameter,  in  the  striated  matrix.  It  is  covered  by  the  external 
integument,  which,  except  in  the  lobule,  contains  no  fat  and  on  the  con- 
cave side  of  the  auricle  is  closely  adherent  to  the  cartilage,  where  it  is 
characterized  by  a  great  abundance  of  glands.  These  are,  in  the  first 
place,  common  sebaceous  follicles,  which  are  most  developed  in  the  concha 
and  fossa  scaphoidea,  where  they  attain  the  diameter  of  J-l  line  ; 
secondly,  minute  sudoriparous  glands  of  1-16  of  a  line  on  the  convex 
side  of  the  pinna  ;  and,  lastly,  the  ceruminous  glands,  already  described 
(§  71,  72),  in  the  cartilaginous,  external  auditory  canal  itself.  In 
the  latter,  the  cutis  measures  1-5-1-8  of  a  line  in  thickness,  without  the 
epidermis,  which  is  1-75-1-50  of  a  line  thick  ;  and  presents,  besides  the 
glandulce  ceruminosce,  hairs  and  sebaceous  follicles  in  a  dense  subcu- 
taneous tissue,  whilst  in  the  osseous  part  of  the  passage  it  is  very  thin, 


768  SPECIAL    HISTOLOGY. 

contains  no  organs  of  any  kind,  and  is  blended  very  intimately  with  the 
periosteum  of  the  canal. 

The  middle  ear,  in  all  its  cavities,  together  with  the  ossicles,  tendons, 
and  nerves  contained  in  it,  is  lined  with  a  delicate  mucous  membrane, 
which,  in  the  mastoid  cells  and  on  the  ossicula  auditus,  where  it  also 
forms  the  memb.  obturator ia  stapedis,  and  on  the  membrana  tympani, 
is  still  more  delicate  than  in  the  accessory  sinuses  of  the  nose,  being 
thickest  in  the  Eustachian  tube.  In  the  latter  situation,  its  epithelium 
is  of  the  squamose,  ciliated  kind,  0-024  of  a  line  thick,  whilst  in  the 
tympanic  cavity  it  is  changed  into  a  thin,  tessellated  epithelium,  com- 
posed of  one  or  two  layers,  extending  as  far  as  the  accessory  cavities. 
The  membrana  tympani,  which,  according  to  Todd  and  Bowman,  is 
furnished  with  a  ciliated  epithelium,  consists  of  a  middle  fibrous  plate, 
which,  at  the  sulcus  tympanicus,  in  connection  with  the  periosteum  of 
the  cavity  of  the  tympanum  and  of  the  osseous  meatus  and  with  the 
cutis  lining  the  latter,  commences  in  a  dense  tract  of  chiefly  annular 
fibres — the  so-termed  annulus  cartilagineus, — and  further  inwards  is 
composed  principally  of  slender  radiating  fasciculi  converging  towards 
the  centre,  where  the  handle  of  the  malleus  is  inserted  into  this  mem- 
brane, and  in  part  reticulated,  with  undeveloped  fine  elastic  fibres 
("  connective  tissue  corpuscles,"  Virchow).  Externally,  this  membrane 
is  covered  by  a  delicate  continuation  of  the  epidermis  of  the  external 
meatus,  and  internally  is  lined  by  a  fine  investment  of  the  mucous  mem- 
brane of  the  tympanum. 

The  ossicula  auditus  are  composed  principally  of  spongy  osseous  sub- 
stance, with  a  thin  compact  cortex;  and  their  articulations  and  liga- 
ments resemble,  in  miniature,  those  of  other  similar  organs  in  all  re- 
spects, even  down  to  the  cartilaginous  layer,  consisting  of  scarcely  more 
than  a  single  stratum.  Their  muscles,  like  those  of  the  external  ear, 
are  transversely  striped.  The  Eustachian  tube  has  in  part,  as  a  foun- 
dation, cartilage  which  in  structure  approaches  the  true  cartilages ; 
usually,  however,  presenting  a  pale,  fibrous  matrix  ;  and  containing,  in 
the  cartilaginous  portion,  especially  towards  the  aperture,  numerous 
racemose  mucous  glands,  of  precisely  the  same  conformation  as  those 
of  the  pharynx,  in  the  mucous  membrane  of  which  organ  that  of  the 
Eustachian  tube  is  imperceptibly  lost.  The  external  ear  is  supplied 
with  vessels  and  nerves,  in  the  same  manner  as  the  external  integuments. 
In  the  middle  ear,  the  mucous  membrane,  especially  of  the  walls  of  the 
tympanum,  is  highly  vascular,  as  is  also  the  Eustachian  tube  and  the 
membrana  tympani,  in  which  latter  the  largest  arteries  and  veins  run 
along  the  manubrium  of  the  malleus  in  the  middle  coat,  constituting 
arterial  and  venous  circles  around  the  periphery  of  the  membrane,  and 
also  ramifying  abundantly  in  the  mucous  membrane.  The  nerves  are 
derived  principally  from  the  ninth  and  fifth  pairs,  and  upon  the  whole 


THE    EAR.  769 

are  scantily  distributed  in  the  mucous  membrane  and  membrana  tympani. 
With  their  terminations  we  are  unacquainted,  whilst  it  is  known  that 
the  tympanic  nerve  contains  numerous  large  ganglion-cells,  either 
isolated  or  aggregated  into  small  ganglia. 

§  234.  The  inner  surface  of  the  vestibule  and  of  the  osseous  semicir- 
cular canals  is  lined  by  an  extremely  thin  periosteum,  consisting  of  a 
rigid,  finely-fibrous  connective  tissue,  without  elastic  fibres,  but  with  nu- 
merous nuclei  and  in  many  respects  resembling  the  forms  of  fibre  met 
with  in  the  inner  wall  of  the  "canal  of  Schlemm"  in  the  eye.  On  the 
surface  of  this  periosteum  rests  a  tessellated  epithelium  in  a  single  layer, 
with  delicate,  polygonal,  nucleated  cells  of  0-007-0-009  of  a  line,  which, 
as  well  as  its  certainly  not  very  numerous  vessels,  stands  in  relation  to 
the  perilympha  s.  aqua  Cotunni,  filling  the  osseous  labyrinth.  By  the 
conjunction  of  the  periosteum  of  the  labyrinth  and  the  lining  of  the 
tympanum,  are  produced  the  membranes  tympani  secundarice,  which, 
like  the  proper  membr.  tympani,  are  composed  of  a  middle  fibrous  layer 
with  vessels  and  scattered  nervous  filaments,  and  two  epithelial  layers. 

The  two  sacculi  and  canals,  contained  in  the  interior  of  the  vestibule 
and  of  the  osseous  semicircular  canals,  all  essentially  present  the  same 
structure.     Their  firm,  transparent,  and  elastic 
walls,  which  are  tolerably  thick  in  proportion  to 
the  minuteness  of  the  parts  (0-012-0-015  of  a 
line  in  the  canals,  and  0-016  in  the  sacculi), 
present,    most    externally,    a    membrane  com- 
posed  of  reticulated,  fine  fibres,    approaching 
very  nearly  to  the  outer  colored  layer  of  the 

choroid  or  the  lamina  fusca,  like  which  it  also  occasionally  contains  irre- 
gular brownish  pigment-cells.  This  is  succeeded,  by  a  transparent, 
glassy  membrane,  sharply  defined,  especially  on  the  inner  aspect,  0-004- 
0-008  of  a  line  thick,  presenting  in  part  a  distinct,  delicate,  longitudinal 
striation,  and  on  the  addition  of  acetic  acid  always  exhibiting  a  multi- 
tude of  elongated  nuclei,  and  which  consequently  cannot  well  be  placed 
in  the  same  class  with  the  membrana?  proprice,  the  capsule  of  the  lens, 
&c.,  although  it  very  nearly  approaches  them  in  its  chemical  reactions. 
The  innermost  layer,  lastly,  is  a  simple,  readily  disintegrated,  tessellated 
epithelium,  0-003  of  a  line,  with  sometimes  larger,  sometimes  smaller 
(0-004-0-008  of  a  line)  polygonal  cells,  lining  all  the  spaces  in  question, 
and  enclosing  the  so-termed  endolymph.  s.  aquula  vitrea  auditiva,  in 
which,  in  Fishes,  Barruel  has  ascertained  the  presence  of  mucus. 

The  vessels  of  the  membranous  labyrinth  are  tolerably  numerous,  and 
are  distributed  in  minute  arteries  and  veins  and  abundant  capillary  net- 

FiG.  308. — Transverse  section  of  a  semicircular  canal,  magnified  250  diameters :  a,  fibrous 
membrane  with  nuclei ;-  6,  homogeneous  membrane ;  c,  epithelium.  From  the  Calf. 

49 


770  SPECIAL    HISTOLOGY. 

works,  on  the  fibrous  membrane  and  vitreous  tunic  of  these  parts,  being 
most  abundant  near  the  terminations  of  the  nerves.  Of  these,  we  are 
acquainted  only  with  that  of  the  acoustic  nerve,  which,  with  the  nervus 
vestibuli,  supplies  the  three  membranous  canals  and  the  elliptic  sac- 
culus, and,  with  a  branch  of  the  cochlear  nerve,  the  round  sacculus. 
In  the  semicircular  canals,  the  nerves  are  distributed  only  on  the  am- 
pullae, and,  indeed,  enter  each,  as  Steifensand  has  shown,  in  an  inversion 
or  duplicature  of  the  wall  situated  on  the  concave  side  of  the  canal, 
which  appears,  viewed  on  the  inside,  as  a  transverse  projection  extend- 
ing through  about  one-third  of  the  circumference.  Within  these  folds, 
the  nerves  divide  at  first  into  two  principal  branches,  which,  diverging 
towards  both  sides,  penetrate  into  the  vitreous  membrane  of  the  ampullae, 
where  each  of  them  breaks  up  into  a  rich  bundle  of  smaller,  frequently 
anastomosing  ramuscules,  which  ultimately  appear  to  terminate  free,  in 
fine  twigs,  composed  of  from  two  to  ten  primitive  fibres,  0-001-0-0015 
of  a  line  thick.  In  the  sacculi,  the  distribution  of  the  nerves  is  the 
same,  except  that  it  occupies  a  larger  space,  and  does  not  occur  in  a  pro- 
jection of  the  wall.  In  this  situation,  also,  I  think  I  have  noticed  free 
prolongations  of  the  attenuated  nerves,  although  it  may  be  very  possible, 
as  Todd  and  Bowman  point  out,  that  they  are  continuous  with  very  pale 
fibres,  in  which  they  ultimately  terminate.  In  the  situation  of  the  ner- 
vous expansion,  we  find,  in  each  of  the  sacculi,  a  sharply  defined  spot, 
as  white  as  chalk,  and  readily  seen  by  the  naked  eye,  which  is  attached 
to  the  inner  wall  of  the  sacculus  by  a  perfectly  clear  membrane,  0-01  of 
a  line  thick,  and  probably  epithelial.  These  are  the  so-termed  otoconia 
of  Breschet,  or  otolithes,  which  are  constituted  of  innumerable  corpus- 
cles, 0-0004-0-005  of  a  line  long,  and  (in  the  largest)  0-001-0-002  of  a 
line  broad,  of  a  rounded  or  elongated  form,  or  distinctly  pointed  at  each 
end,  probably  hexahedral  prisms,  suspended  in  a  homogeneous  substance. 
They  are  composed  of  carbonate  of  lime,  and  are  said  to  leave  a  resi- 
duum of  some  organic  matter;  but  this  I  have  not  succeeded  in  observing. 

§  235.  Cochlea.— The  canal  of  the  cochlea,  filled  by  the  fluid  of  the 
labyrinth,  is  lined  in  both  its  scalce  by  a  periosteum,  here  and  there 
presenting  a  small  quantity  of  pigment,  and  which  is  constituted  pre- 
cisely like  that  of  the  vestibule,  and  also  partially  invests  the  lamina 
spiralis  ossea.  An  epithelium,  0-0005  of  a  line  thick,  with  delicate, 
flattened  polygonal  cells,  0-007-0-009  of  a  line  in  size,  covers  this  liga- 
mentous  membrane,  and  is  also  continued  upon  the  lamina  spiralis 
membranacea,  where  its  nature  is,  to  some  extent,  altered.  The  most 
important  part  of  the  cochlea  is  the  lamina  spiralis,  which,  in  its  osseous 
zone,  contains  narrow-meshed  anastomosing  canals  for  the  reception  of 
the  cochlear  nerves,  which  canals,  towards  the  free  border  of  the  lamina, 
coalesce  so  as  to  form  a  fissure-like  cavity  and  consequently,  in  this 
situation,  the  osseous  spiral  lamina  actually  consists  of  two  plates. 


THE     EAR. 


771 


The  membranous  zone,  having  a  constant  width  of  0-2  of  a  line,  is 


Fig.  310. 


Fig.  309.  subdivided  into  a  zona  denticulata 

and  a  zona  pectinata,  the  former 
of  which  constitutes  about  the 
inner  two-thirds,  and  the  latter 
the  outer  third  of  the  breadth  of 
the  membranous  lamina,  and  are 
both  characterized  by  a  great 
complexity  of  structure,  the  im- 
portance of  which  was  first,  in 
more  recent  times,  pointed  out 
by  Corti  (I  c.)  (vid.  Figs.  309, 
310). 

1.  The  zona  denticulata  (d-v) 
may  be  again  subdivided  into  two 
portions,  an  internal,  the  habe- 
nula  interna  s.  sulcata  (d-g),  and 
an  external,  the  habenula  externa 
s.  denticulata  (h-t).  The  former 
is  developed  at  d,  as  an  immediate 
continuation  of  the  periosteum  of 
the  lamina  spiralis  ossea,  and,  in 
fact,  only  from  that  portion  of  it 
which  looks  towards  the  scala 
vestibuli,  increasing  in  width  and 
thickness  from  the  commence- 
ment to  the  termination  of  the 
cochlear  canal.  In  the  first  and 
second  turns  of  the  cochlea,  its 
under  surface  supplies  the  place 
of  the  periosteum  upon  the  most 
external  portion  of  the  osseous 

Fia.  309. — Vertical  section  of  the  lamina  spiralis,  at  6  lines  from  its  commencement,  mag- 
nified about  225  diameters  (Cat  or  Dog) ;  the  epithelial  layer  investing  its  upper  and  lower 
surfaces  is  removed :  a,  periosteum  of  the  osseous  zone ;  6,  the  two  lamellae  of  the  osseous 
zone  near  its  free  border;  c,  cf,  (?',  termination  of  the  auditory  nerves;  d-w,  lamina  spiralis 
mcmbranacea  •  d-w,  zona  denticulata;  d-df -f,  habenula  sulcata]  d,  place  where  the  periosteum 
is  thickened ;  e,  granules  in  the  groove  of  the  habenula  sulcata  ;  f-g,  "  teeth  of  the  first  series ;" 
g-f-h,  sulcus  s.  semicanalis  spiralis  ;  A,  its  inferior  wall:  k,  epithelial  cells  at  the  entrance  of 
the  sulcus  spiralis  ;  h-iv',  habenula  denticulata  ;  h-m,  apparent  teeth  ;  n-t,  "  teeth  of  the  second 
series;"  n-p,  their  posterior  joint ;  o,  nucleated  enlargement  upon  them;  p-q  and  q-r,  articular 
portions;  r-t,  anterior  joint  of  the  second  row;  s  s  s,  three  cylinder-cells,  placed  upon  them; 
l-v,  membrane  covering  the  habenula  denticulata;  u,  one  of  the  epithelial  cells  underneath; 
7I/-M),  zona  pectinata ;  :r,  periosteum,  attaching  the  lamina  spiralis  (muse,  cochlearis,  Todd  and 
Bowman)  ;  y,  vas  spirale  internum  ;  z,  its  inner  coat.  After  Corti. 

FIG.  310. — Vestibular  surface  of  the  lamina  spiralis  membranacea,  magnified  225  diameters. 
The  letters  are  in  part  the  same  as  in  Fig.  309 :  a  a,  cylindrical  elevations  of  the  habenula 


1 

' 


772  SPECIAL    HISTOLOGY. 

zone,  whilst  in  the  last  half  turn  it  is  bounded  only  by  the  expansion  of  the 
nerve,  so  that  the  habenula  sulcata,  in  the  strict  sense  of  the  word,  properly 
constitutes,  in  this  situation,  only  a  part  of  the  so-termed  membranous 
spiral  lamina.  On  the  upper  surface  of  this  layer,  and  on  the  outer  border 
of  it,  there  is  an  uninterrupted  series  of  clear,  peculiarly  glistening, 
elongated,  slightly  clavate  processes  (#),  the  "  teetJi,"  as  they  are  termed 
"  of  the  first  series,"  which,  in  the  first  spiral  turn  of  the  cochlea,  are 
0-02  of  a  line  long,  0-004-0-005  of  a  line  wide,  and  0-003  of  a  line 
thick,  at  their  origin,  whilst  in  the  last  turn  they  are  not  more  than 
0-015  of  a  line  long  and  0-003  of  a  line  broad.  They  project,  free, 
into  the  scala  vestibuli,  and  arch  over  the  commencement  of  the  habenula 
externa,  so  that  between  the  two  a  tolerably  deep  sulcus,  semicanalis 
spiralis  (Huschke),  opening  externally,  is  left.  Towards  the  axis  of 
the  cochlea  the  so  termed  "teeth"  are  directly  continuous,  with  simi- 
larly constituted,  elongated  ridges  or  costce  (Fig.  309  a  a),  which  are 
occasionally  conjoined  in  pairs,  or  divided  into  two,  and  still  further 
inwards  break  up  into  divisions,  which  become  shorter  and  shorter  and 
smaller  and  smaller,  being  at  first  elongated  and  afterwards  rounded. 
In  the  longitudinal  and  transverse  grooves  between  these  costce  arid 
tubercles  and  the  teeth,  there  usually  exists,  in  single  series,  rounded 
or  elongated,  opaque  glistening  corpuscles  (e),  0-0015-0-002—0*003  of 
a  line  in  size,  which,  on  the  addition  of  acetic  acid,  prove  to  be  nuclei ; 
and  by  the  same  reagent,  nucleiform  strice  occasionally  become  distinct 
in  the  pale  and  somewhat  swollen  "teeth"  and  costce,  which  parts, 
consequently,  as  well  as  those  presently  to  be  described,  I  am  inclined 
to  regard  as  belonging  to  the  connective-tissue  group. 

The  habenula  externa  s.  denticulata  (h-t)  arises  under  the  base  of  the 
"teeth"  of  the  first  series,  directly  from  the  just-described  habenula 
sulcata,  and  constitutes  at  first  the  bottom  of  the  spiral  sulcus  noticed 
above.  In  most  places  its  thickness  does  not  amount  to  more  than 
0-001  of  a  line,  which  is  also  that  of  the  rest  of  the  membranous  spiral 
lamina,  that  is  to  say,  of  the  zona  pectinata,  and  its  width  increases 
towards  the  cupola  in  proportion  to  the  decreasing  breadth  of  the  habe- 
nula sulcata,  so  that  it  measures  at  first,  not  more  than  0*05,  and  ulti- 
mately, 0-1  of  a  line.  With  respect  to  its  structure,  it  presents,  on  the 
side  of  the  scala  vestibuli,  a  considerable  number  of  elevations,  whilst 
towards  the  scala  tympani  it  is  perfectly  smooth  and  even.  These  ele- 
vations, proceeding  from  within  to  without,  are  as  follow  : — first,  come 
the  so-termed  "apparent  teeth"  ("  dents  apparents,"  Corti),  a  crowded 

sulcata:  $,  spot  where  a  "tooth  of  the  first  series"  originates;  y,  spaces  between  the  "ap- 
parent teeth  ;''  <f,  anterior  portion  of  a  "  tooth  of  the  second  series  "  thrown  back  ;  t,  the  same 
in  its  natural  position,  without  its  epithelial  cells;  £,  the  same  with  only  the  lowermost 
epithelial  cells ;  »,  the  same  with  two  of  the  lowermost  cells ;  3-,  streaks  or  slight  elevations 
of  the  zona  pectinata :  *,  periosteum,  by  which  the  lamina  spiralis  is  attached,  with  spaces, 
x,  between  the  bundles.  After  Corti. 


THE    EAR.  773 

series  of  elongated  projections,  0-08  of  a  line  long,  0-002  of  a  line  broad, 
which,  separated  from  each  other  by  shallow  grooves,  are  slightly  raised 
at  the  outer  end,  and  then  suddenly  depressed.  Externally  to  these 
processes  which,  in  the  first  turn  of  the  cochlea,  are  still  situated  on  the 
zona  ossea,  beneath  the  "  teeth  of  the  first  series,"  and  in  that  situation 
present  minute  elongated  hollows  between  their  outer  ends  (Fig.  309,  y), 
but  in  the  second  and  third  turns  are  placed  more  externally  than  the 
"  teeth  of  the  first  series,"  being  bounded  on  the  under  surface  only  by 
the  nerves,  succeed  in  equal  number  the  "teeth  of  the  second  series," 
(Corti)  (n-t),  very  remarkable  structures,  of  which  the  adjoining  figure 
will  afford  a  better  exposition  than  any  description.  Each  of  them 
represents  a  little  rod,  somewhat  compressed  from  above  to  below,  and 
lies  free  and  movable  on  the  membranous  spiral  lamina,  to  which  it  is 
affixed  only  by  the  inner  extremity,  as  a  continuation  of  which,  there- 
fore, these  teeth  must  be  regarded.  Viewed  more  closely,  each  of  them 
presents  three  joints.  The  innermost  (n-p),  an  attached  joint,  resem- 
bles a  cell  of  cylinder  epithelium,  and  contains  in  its  somewhat  dilated 
internal  extremity  (o)  a  round  nucleus,  0-005  of  a  line  in  size  ;  to  this 
succeed  the  middle  joints  (p,  q,  r)  two  equal,  elongated,  quadrangular 
segments,  0-0044  of  a  line  long,  of  the  same  homogeneous  and  glisten- 
ing substance  as  that  of  which  all  these  "  teeth"  in  general  are  com- 
posed (the  coni  articulares  of  Corti),  which  are  connected  with  each 
other  and  with  the  internal  and  external  joints,  so  as  to  allow  the  latter 
a  certain  extent  of  motion  up  and  down.  The  last  joint,  finally  (r-t), 
is  at  first  attenuated,  but  towards  the  extremity  again  becomes  wider 
and  bifurcate,  and  supports  three  nucleated  segments  attached  to  its 
inner  extremity,  resembling  pedunculated  cells  (s,  s,  s),  one  above  the 
other,  the  undermost  being  the  longest,  which  may  be  termed  "  teeth 
of  the  third  series"  ("  cylinder  epithelium-cells,"  Corti).  The  habenula 
denticulata,  as  far  as  to  the  "teeth  of  the  second  series,"  is  covered 
by  round  or  oval  epithelium  cells  (h)  which  also  occupy  the  spiral  sulcus 
below  the  "  teeth  of  the  first  series,"  though  lying  free  and  separate  in 
immediate  contiguity,  and  forming  a  continuous  layer  only  on  the  ha- 
mulus  membranaceus.  Upon  these  cells  and  over  the  entire  habenula 
denticulata,  we  then  find  a  peculiar,  thin,  finely  striated  membrane  (l-v), 
which  externally  projects  a  little  over  the  commencement  of  the  zona 
pectinata,  though  separated  from  it  by  some  large  epithelial  cells  (u), 
and  passing  internally  upon  the  habenula  sulcata,  where  it  is  gradually 
thinned  and  ultimately  lost.  This  membrane,  covered  by  the  epithelium 
of  the  cochlear  canal,  can  hardly  be  viewed  as  anything  but  a  continua- 
tion of  the  habenula  sulcata,  and  may  be  most  suitably  compared  with 
the  zona  pectinata. 

2.  The  zona  pectinata  (Todd  and  Bowman)  (w'  -w),  is  the  outer  por- 
tion of  the  membranous  spiral  lamina,  smooth  on  both  the  upper  and 


774  SPECIAL    HISTOLOGY. 

under  surfaces,  and  affixed  at  the  outer  side,  on  a  projection  of  the 
external  wall  of  the  cochlear  canal.  It  is  a  perfectly  homogeneous 
lamella,  but,  except  at  the  borders,  appears  to  be  very  closely  ribbed, 
and  thence  assumes  a  fibrous  aspect.  At  its  outer  edge  this  lamina, 
which  seems  to  be  opened  out  in  a  narrow  border,  receives  a  peculiar 
fibrous  substance  (x)  arising  from  the  wall  of  the  cochlea,  which  there 
presents  a  minute  osseous  ridge  (the  lamina  spiralis  accessorial 
Huschke  ;  which  Todd  and  Bowman  describe  as  a  cochlear  muscle,  but 
in  which  I  can  perceive  nothing  but  a  form  of  nucleated  connective 
tissue,  whence  I  shall  term  it  the  ligamentum  spirale. 

The  nerves  of  the  cochlea  enter  the  cavities  of  the  osseous  zone  from 
the  canal  of  the  modiolus,  and  there  form  a  close  plexus  of    dark- 
bordered  fibres,  0-0015  of  a  line  in  diameter,  throughout  its  whole 
length,  and  which,  as  discovered  by  Corti,  contains,  at   a  very  definite 
spot  not  far  from  the  border  of  the  zone,  an  aggregation,  at  first,  O'l 
of  a  line  in  width,  of  bipolar,  oval,  minute  (0-011-0-016  of  a  line  long, 
0-0066-0-0097  of  a  line  broad),  and  pale  ganglion-cells,  which  it  is  very 
probable  intercept  all  the  fibres  of  the  cochlear  nerves  in  their  course. 
The  dark-bordered  fibres  proceeding  from  the  external  side  of 
these  cells,  are   again  disposed  in  anastomosing,  and  after- 
wards in  simply  parallel,   flattened  bundles,  which  become 
less  and   less  close  as  they  approach  the  hamulus,  so  that, 
upon  that  process,  the  fibres  may  be  perceived  forming  a  sin- 
gle layer,  and  even  separated  by  interstices.     The   end  of 
these  nerves,  in  all   the  parallel  bundles  and  fibres,  is  always 
in  the  same  line,  but  in  the  first  spiral  turn  will  be  found 
nearer  to  the  outer  wall   of  the  cochlea  than  it  is  higher  up. 
Besides  this,  there  are  terminations,  also   situated  between 
the  two  plates  of  the  osseous  zone,  although  exactly  at  its 
border  ;  in  the  second  turn,  in  an  extent  of  0-02-0-03  of  a 
line,  and  even  outside  it,  on  the  under  surface  of  the  com- 
mencement of  the  habenula  denticulata,  consequently  within 
the  scala  tympani  ;  in  the  third  half  turn,  lastly,  they  appear 
in  the  form  of  a  nervous  border,  0-08-0-09  of  a  line  broad, 
also  on  the  under  surface  of  the  halenula  sulcata.      The 
actual  termination  of  the  nerve-fibres  which  are  reduced  to 
0-001   of  a  line  in  diameter,  appears  to  me,  as  well  as  to 
Corti,  to  take  place  by  their  first  becoming  pale,  and  still  finer,  and 
afterwards   ceasing — and    I   must    here   express  myself  as   decidedly 
opposed  to  the  notion  of  the  existence  of  loops.* 

FIG.  311. — Bipolar  ganglion-globules  from  the  zonula  osseo  of  the  lamina  spiralis  of  the  Pig, 
magnified  350  diameters.  After  Corti. 

*  [More  recent  researches  have  induced  Prof.  Kdlliker  to  alter  materially  his  views  on 
the  termination  of  the  cochlear  nerve,  and  indeed  of  the  structure  of  the  cochlea  itself.  As 
the  result  of  careful  investigations  in  the  Ox,  Cat,  Pig,  Rabbit,  and  in  Man,  he  found  that 


THE    EAR.  775 

The  vessels  of  the  cochlea,  though  fine,  are  yet  very  numerous ;  they 
are  distributed,  in  the  first  place,  to  the  parietal  periosteum  of  the 
cochlear  canal,  and  secondly,  to  the  lamina  spiralis.  In  the  former 
situation,  besides  the  capillary  plexus,  wnich  is  found  throughout,  they 

the  cochlear  nerves  do  not  terminate  in  the  scala  tympani,  but  that  the  fibres  penetrate 
through  openings  in  the  membranous  lamina  spiralis  into  the  scala  vestibuli,  where  they 
become  attached  to  the  "teeth  of  the  second  series."  These  latter  as  well  as  the  peduncu- 
lated  cells  they  support,  he  now  regards  as  a  nervous  apparatus  constituting  the  true  termi- 
nations of  the  cochlear  nerves,  and,  he  adduces  in  proof  of  the  correctness  of  this  opinion 
the  following  histological  observations. 

The  membranous  lamina  spiralis,  is  not  merely  a  continuation  of  the  periosteum  of  the 
vestibular  surface  of  the  osseous  zone,  but  also  of  that  of  its  tympanal  surface.  The  first- 
mentioned  periosteal  lamella  forms  the  habenula  sulcata  with  its  teeth  and  the  commence- 
ment of  the  habenula  denticulata,  and  then  unites  externally  to  the  "  apparent  teeth,!:  and 
the  "  teeth  of  the  second  series''  with  the  other  periosteal  layer.  This  besides  lining  the 
bone,  extends  beyond  the  edge  of  the  osseous  zone  as  a  covering  to  the  nerve-fibres,  which 
are  thus,  even  after  leaving  the  bone,  enclosed  between  two  layers  of  periosteum,  and  hence 
do  not,  as  stated  by  Corti,  lie  free  in  the  scala  tympani.  Now  in  vertical  sections  of  the 
lamina  spiralis,  treated  with  chromic  acid,  the  pale  nerve-fibres  may  be  traced  running 
towards  the  scala  vestibuli,  and  perforating  the  habenula  denticulata  near  the  external 
extremities  of  the  "  apparent  teeth.'  Exactly  over  the  perforated  portion  of  the  habenula 
denticulata  (habenula  perforata)  are  seated  the  teeth  of  the  second  series,  which  may  be 
seen  to  be  connected  with  the  dark-bordered  nerve-fibres,  by  means  of  delicate  pale  pro- 
cesses. 

The  nervous  nature  of  the  "  teeth  of  the  second  series"  Kolliker  states,  becomes  further 
apparent  by  a  micro-chemical  analysis.  Corti  affirms  them  to  be  chemically  similar  to  the 
membranous  lamina  spiralis,  but  this  Kolliker  proves  to  be  incorrect.  He  found  them  on 
the  contrary  to  correspond  most  closely  to  the  dark-bordered  nerve-fibres,  and  the  processes 
of  the  ganglion-cells.  Caustic  soda  and  potassa  destroyed  them  almost  immediately.  The 
addition  of  water  produced  in  them  two  or  three  varicose  enlargements,  containing  a  fila- 
ment precisely  similar  to  an  axis-cylinder.  The  nucleated  swelling  at  their  commencement 
described  by  Corti,  he  regards  as  a  bipolar  ganglion  globule,  one  process  of  which  is  con- 
nected with  the  dark-bordered  nerve-fibres,  whilst  the  other  supports  three  unipolar  nerve- 
cells  ("  three  epithelial  cells"  of  Corti). 

Based  upon  these  histological  data,  Kolliker  advances  some  interesting  and  novel  views 
with  regard  to  the  physiology  of  the  cochlea.  The  existence  of  the  peculiar  nervous  appa- 
ratus at  the  extremity  of  the  cochlear  .nerves,  renders  it,  he  thinks,  highly  probable  that  this 
is  the  only  portion  of  the  nerve  which  possesses  the  power  of  receiving  sonorous  undulations. 
These  undulations  reach  the  cochlea  through  the  fenestra  ovalis,  and  are  not  communi- 
cated, as  most  physiologists  suppose,  by  the  osseous  lamina  to  the  cochlear  nerve,  since  the 
latter  lies  free  in  the  labyrinth  and  is  unconnected  with  the  osseous  zone.  The  isolated  po- 
sition of  the  cochlear  nerve,  its  movability  and  great  softness,  renders  it,  Ktilliker  further  sur- 
mises, specially  applicable  to  receive  the  undulations  transmitted  by  the  fluid  of  the  labyrinth. 
Regarding  the  special  function  of  the  cochlea,  he  is  inclined  to  attribute  to  it  a  greater  phy- 
siological importance,  than  to  any  of  the  other  parts  of  the  labyrinth.  The  free  position  of 
the  expanded  portion  of  the  nerve,  and  the  extent  of  surface  over  which  its  numerous 
terminal  fibres  are  spread,  constitute  it,  he  thinks,  an  organ  of  great  delicacy  of  hearing, 
enabling  us  to  distinguish  several  sounds  at  once,  and  also  to  estimate  accurately  their 
exact  pitch.  The  ganglionic  termination  of  the  cochlear  nerves,  Kolliker  concludes,  esta- 
blishes a  surprising  analogy  between  the  auditory,  and  visual  apparatus,  since  the  sensory 
nerves  of  both  are  possessed  at  their  peripheral  expansion  of  a  ganglion,  which  receives  the 
impressions,  the  nerve-fibres  merely  serving  to  conduct  them  to  the  brain.  (Vid.  Kdlliker, 
"Ueber  die  Endigimgen  des  Nervus  Cochleae  und  die  Functions  der  Schnecke,"  Wiirzburg, 
1854.)— DaC.] 


776  SPECIAL    HISTOLOGY. 

constitute  a  peculiar  vascular  tract  in  the  scala  vestibuU,  immediately 
under  the  ligamentum  spirale, — the  stria  vascularis  of  Corti,  and  which 
though  continuous  with  the  vessels  of  the  periosteum,  still  lies  above  it, 
imbedded,  as  it  were,  in  the  partially  colored  epithelium.  In  the  zona 
spiralis,  we  find  in  the  osseous  portion,  but  also  in  the  nervous  expan- 
sion itself,  a  rich  capillary  plexus,  continuous  with  a  vas  spirale  running 
on  the  under  or  vestibular  surface  of  the  zona  memlranacea,  through 
the  whole  extent  of  the  cochlea.  This  vessel,  which  is  probably  venous, 
lies  immediately  under  the  Jiabenula  denticulata,  sometimes  more 
towards  the  interior,  sometimes  more  externally,  becoming,  in  the  last 
half  turn  of  the  cochlea,  a  capillary  vessel  of  not  more  than  0-004  of 
a  line  in  diameter  ;  but  towards  the  base,  it  gradually  enlarges  to 
0*013  of  a  line,  and  is  distinctly  composed  of  two  coats.  In  rare 
instances,  there  are  two  capillary  vasa  spirala  in  the  situation  above 
indicated,  and  on  two  occasions,  in  Man  and  in  the  Sheep,  Corti 
also  noticed  an  external  vas  spirale,  near  the  ligamentum  spirale  on 
the  zona  pectinata,  which,  however,  did  not  communicate  with  the 
internal  vessels,  so  that,  speaking  generally,  the  zona  pectinata  is 
non-vascular. 

Lastly,  we  have  to  consider  the  acoustic  nerve.  The  fibres  of  its 
trunk,  in  Man,  measure  0-002-0-005  of  a  line,  are  very  readily  de- 
stroyed, and  have  only  a  delicate  neurilemma.  Among  these,  in  the 
trunk  itself  and  in  the  vestibular  and  cochlear  nerves,  there  occur  nu- 
merous bipolar,  apolar,  and  unipolar,  pale  and  colored  ganglion-cells, 
measuring,  in  the  Mammalia  and  in  Man,  0-02-0-07  of  a  line,  of  which 
the  two  latter  forms  are,  as  Stannius  correctly  observes,  probably  only 
truncated  bipolar  cells,  inasmuch  as,  particularly  in  Fishes,  the  acoustic 
nerve  contains  cells  of  this  kind  only  or  nearly  so.  Similar  cells,  but 
smaller,  are  also  met  with,  as  already  mentioned,  in  the  cochlea,  as  well 
as  in  the  nervous  twigs  in  the  vestibule  (Pappenheim,  Corti).  Divisions 
of  the  fibres  of  the  auditory  nerve  were  noticed  by  Czermdk  in  the 
ultimate  ramifications  in  the  ampullae  and  sacculus  of  the  Sturgeon,  by 
myself  and  Harless  in  the  Frog,  and  by  Leydig  in  the  Chimcera. 

Of  the  development  of  the  auditory  organ,  it  need  here  merely  be 
mentioned,  that  according  to  Huschke's  discovery,  confirmed  by  Reiss- 
ner  and  Remak,  the  membranous  portions  of  the  labyrinth  are  formed 
from  the  external  integument,  simply  by  its  inversion,  and  consequently 
in  their  origin  may  be  compared  with  the  lens  and  vitreous  body.  To 
this  inversion,  in  which  the  cellular  layers  corresponding  to  the  epider- 
mis, principally,  but  not  alone,  as  Remak  believes,  take  part,  the  audi- 
tory nerves  are  afterwards  continued  from  the  brain ;  and  from  the 
middle  germinal  layer  are  afforded  the  hard  tissues  and  the  rest  of  the 
soft  parts  in  order  to  complete  the  sentient  organ.  With  respect  to  the 


THE     EAR.  777 

histological  development  of  the  soft  parts  of  the    labyrinth,  nothing  of 
consequence  is  known. 

In  the  description  of  the  cochlea,  I  have  altogether  followed  Corti, 
having  formerly  satisfied  myself  of  the  correctness  of  his  statements, 
when  that  zealous  and  intelligent  observer  pursued  his  investigations  in 
Wurzburg ;  and  having  also,  recently,  confirmed  the  greater  part  of 
them  by  the  examination  of  the  human  cochlea.  At  the  same  time  the 
parts  of  the  habenula  denticulata,  which  are  so  difficult  of  investigation, 
have  always  appeared  to  me  to  demand  further  consideration,  and  par- 
ticularly with  respect  to  the  ascertaining  of  the  kind  and  mode  of  the 
movements  of  its  processes,  the  relations  of  the  epithelium,  and  of  the 
investing,  structureless  membrane.  So  long  as  these  points  are  not  as- 
certained, all  suppositions  respecting  the  function  of  these  delicate 
structures  are  without  any  secure  basis,  and  the  physiology  of  the 
cochlea,  otherwise  so  difficult,  is  rendered  only  still  more  perplexed 
(vid.  Harless,  1.  c.).  As  regards  the  nature  of  the  so-termed  "  teeth," 
they  are  certainly,  as  Corti  assumes,  nothing  more  than  developments 
of  the  periosteum  of  the  cochlear  canal,  and  may,  in  my  opinion, 
although  in  chemical  respects  very  similar  to  the  vitreous  membranes, 
yet  be  regarded  as  belonging  to  the  connective-tissue  group.  Whether 
the  three  so-termed  cylinder  epithelium-cells  (Corti)  on  the  habenula 
denticulata  are  really  epithelial,  as  Corti  supposes,  still  demands  inves- 
tigation. These  bodies,  notwithstanding  their  great  delicacy,  appear 
to  me  rather  to  be  referable  to  the  category  of  the  other  tissues  of  the 
habenula  denticulata;  and  on  that  account  I  have  termed  them  "  teeth 
of  the  third  series."* 

For  the  investigation  of  this  organ,  which,  however,  presents  any 
very  considerable  difficulties  only  in  the  labyrinth,  perfectly  fresh  objects 
are  indispensable,  and  are  best  taken  from  animals  just  killed.  For  the 
moistening  of  them,  serum  or  syrup  should  be  employed,  when  it  is  de- 
sirable to  view  the  parts  in  a  perfectly  normal  condition.  Successful 
results  will  be  obtained,  especially  if  a  certain  amount  of  practice,  in 
the  exposing  and  dissection  of  the  delicate  tissues  with  which  we  have 
to  do,  be  combined  with  great  patience,  seeing  that  it  is  often  a  matter 
of  chance  whether  any  given  relations  are  brought  into  view.  In  order 
to  see  the  nervous  plexus  of  the  osseous  zone  of  the  cochlea,  the  latter 
must  be  deprived  of  its  calcareous  constituents  by  dilute  muriatic  acid; 
whilst  in  the  case  of  the  ganglion-cells  in  that  situation,  the  only  means 
of  attaining  our  object  consists  in  a  careful  breaking  down  of  the  osseous 
zone  in  a  neutral  medium. 

*  [Tid.  Note  p.  775.— DaC.] 


778  SPECIAL    HISTOLOGY. 

Literature.— E.  Huschke,  in  "Fror.  Not.,"  1832,  No.  707;  "Iris," 
1833,  No.  18,  34  ;  K.  Steifensand,  "  Untersuchungen  iiber  die  Ampullen 
des  Gehororgans,"  in  Miiller's  "  Archiv,"  1835;  S.  Pappenheim,  "Die 
specielle  Gewebelehre  des  Gehororgans,"  Breslau,  1840,  and  Froriep's 
"Not.,"  1838,  Nos.  141,  194,  and  195  ;  G.  Breschet,  "  Recherches  sur 
1'organe  de  1'ouie  dans  l'homme  et  les  animaux  verte'bre's,"  2d  ed.  Paris, 
1840  ;  E.  Krieger,  "  De  otolithis,"  Berol.  1840  ;  Wharton  Jones,  "  The 
Organ  of  Hearing,"  in  Todd's  "  Cyclopaedia,"  Vol.  II.  p.  529;  J.  Hyrtl, 
"  Ueber  das  innere  Gehororgan  des  Menschen  und  der  Saugethiere," 
Prag.,  1845  ;  A.  Corti,  "  Recherches  sur  1'organe  de  1'ouie  des  mam- 
miferes,"  in  Zeitsch.,  f.  wiss.  Zool.  III.,  p.  109 ;  Reissner,  "  De  auris 
internee  formatione,"  Dorpat,  1851;  E.  Harless,  Art.  "Horen,"  in 
Wagner's  "Handw.  der  Physiol."  IV.,  p.  311,  and  "  Miinchn.  Gel.  An- 
zeiger,"  1851,  No.  31  and  37;  Stannius,  "Ueber  die  ganglibse  Natur 
des  Nervus  acusticus,"  in  Gott.  Nachr.,  1850,  No.  16 ;  Ib.,  1851,  No. 
17 ;  [A.  Kolliker,  "  Ueber  die  letzten  Endigungen  des  Nervus  Cochleae 
und  die  Function  der  Schnecke,"  Wurzburg,  1854. — DaC.]  Besides 
•which  should  be  consulted  the  general  works  of  Krause,  Huschke,  Ar- 
nold, Todd  and  Bowman,  Reraak  (Entwicklungsgeschichte),  and  the 
"  Icones  org.  sensuum,"  of  Arnold. 

III.—OF  THE  OLFACTORY  ORGAN. 

§  236.  The  olfactory  organ  consists  of  the  two  nasal  cavities,  or  fossce, 
supported  by  bones  and  cartilages,  and  lined  by  a  mucous  membrane, 
and  of  a  certain  number  of-  accessory  cavities,  viz.,  the  frontal,  sphe- 
noidal,  and  ethmoidal  sinuses  and  the  antrum  HigJimori.  Of  all  these 
cavities,  however,  only  the  uppermost  portions  of  the  nasal  fossae,  where 
the  olfactory  nerve  is  distributed,  are  subservient  to  the  sense  of  smell 
itself,  the  others  being  either  simple  conducting  canals,  and  participating 
as  well  in  the  action  of  respiration,  or  at  any  rate  having  no  direct  rela- 
tion to  the  olfactory  sense. 

The  hard  structures,  just  named,  present  nothing  much  worthy  of 
remark ;  and  of  the  bones  it  need  merely  be  mentioned,  that  the  thin- 
nest parts  of  the  ethmoid  consist  only  of  a  fundamental  substance  and 
bone-fibres,  without  any  Haversian  canals.  The  nasal  cartilages  are 
true  cartilages,  and  most  nearly  approach  those  of  the  larynx,  except 
that  the  contents  of  the  cartilage-cells  are  usually  very  pale,  and  with- 
out fat,  the  cell-walls  little  thickened,  and  the  matrix  finely  granular. 
Beneath  the  pericJiondrium  there  is,  also  in  this  situation,  a  layer  of  flat- 
tened cells,  which,  on  the  septum  attains  a  thickness  of  0-024  of  a  line, 
whilst  in  the  interior  the  cells  are  more  rounded,  larger,  and  disposed  in 
rows,  in  the  direction  of  the  thickness  of  the  septum. 

With  respect  to  the  coverings  of  these  parts,  the  integument  of  the 
nose  may  be  first  noticed:  it  is  characterized  by  a  thin  epidermis 


THE    NOSE.  779 

I 

0-024-0-032  of  a  line  thick,  a  dense  cutis  of  1-4  with  minute  unde- 
veloped papillae  of  1-40-1-66  of  a  line,  and  fine  hairs,  as  well  as  by  a 
close  adipose  tissue  1  line  thick,  intimately  united  with  the  cartilage, 
containing  large  sebaceous  follicles,  extending  into  the  latter,  and  minute 
sudoriparous  glands  1-10-1-12  of  a  line  in  diameter.  This  external 
integument,  with  its  sebaceous  follicles,  and  with  stronger  hairs  (vibrissce) 
also  extends  a  short  distance  into  the  nasal  fossce,  but  not  quite  so  far  as 
the  point  where  the  cartilaginous  portion  of  the  nose  terminates,  passing 
imperceptibly  into  the  mucous  membrane  of  the  olfactory  organ,  by 
which  all  the  remaining  cavities  are  lined,  though  it  does  not  everywhere 
present  the  same  conditions.  As  was  discovered  by  Todd  and  Bowman, 
and  I  can  fully  confirm,  this  mucous  membrane  is  subdivided  into  a  cili- 
ated and  a  uou-ciliated  portion,  the  latter  being  limited  to  the  uppermost 
parts  of  the  nasal  fossce,  where  the  olfactory  nerve  is  distributed,  and 
consequently  should  perhaps  be  termed  the  olfactory  mucous  membrane 
in  the  stricter  sense,  whilst  the  other  might  retain  the  old  name  of 
"  Schneiderian  membrane." 

Upon  first  viewing  the  latter,  it  will  be  found  that,  although  the  epi- 
thelium vibrates  throughout,  still  that  its  structure  is  not  everywhere 
the  same,  and  that  we  may  conveniently  distinguish  in  it  the  thicker 
glandular  mucous  membrane  of  the  proper  nasal  fossce  from  the  thinner 
membrane  of  the  accessory  sinuses,  and  of  the  interior  of  the  spongy 
bones.  The  epithelium,  in  both  situations,  is  squamose  and  ciliated,  like 
that  of  the  larynx  (Fig.  8112),  measuring,  in  some  places,  0-018-0-020 
of  a  line  in  thickness,  and  in  others  as  much  as  0'042  of  a  line.  In 
Man  it  presents  pale,  fine-granular  cells,  of  which  the  outermost  ciliated 
ones  attain  a  length  of  0*03  of  a  line,  and  in  animals  produce  a  current 
running  from  before  to  behind.  To  this  succeeds,  a  true  m.  mucosa, 
wholly  without  elastic  elements,  or  at  all  events  very  scantily  supplied 
with  them,  and  composed  chiefly  of  common  connective  tissue.  In  the 
proper  nasal  fossce  there  are  imbedded  in  this  membrane  very  nume- 
rous larger  and  smaller,  racemose  mucous  glands  of  the  usual  kind, 
with  gland  vesicles  of  0-02-0-04  of  a  line,  so  that,  in  places,  especially 
at  the  borders  of  the  septal  cartilage,  and  on  the  inferior  spongy  bones, 
it  presents  a  thickness  of  1—2  lines.  The  thickness  of  the  mucous  mem- 
brane of  these  regions,  however,  does  not  depend  upon  the  glands  alone, 
but  also,  especially  at  the  border  and  posterior  extremity  of  the  inferior 
spongy  bone,  upon  abundant,  almost  cavernous  venous  plexuses  in  its 
interior.  In  the  accessory  cavities,  the  glands  are  almost  wholly  want- 
ing, and  I  have  as  yet  only  occasionally  found  them  in  the  antrum  High- 
mori,  where  their  excretory  ducts  and  gland-vesicles  are  sometimes  dilated 
into  cysts  containing  mucus,  J  a  line  in  diameter.  Except  in  these  places, 
the  mucous  membrane  of  the  accessory  cavities  is  extremely  delicate 
and  inseparable,  as  a  distinct  membrane,  from  the  periosteum  lining  them ; 


P80 


SPECIAL    HISTOLOGY. 


and  the  same  may  be  said  of  it  in  the  nasal  fossos  themselves,  particu- 
larly in  the  glandular  parts,  notwithstanding  the  intimate  connection  of 
the  two.  A  remarkable  appearance  presented  itself  to  me  in  the  body 
of  a  youth  aged  15  (who,  as  I  was  informed  by  Virchow,  also  exhibited 
ossifications  in  the  lungs),  consisting  in  the  deposition — in  the  mucous 
membrane,  in  all  these  accessory  cavities,  as  well  as  in  the  similarly 
constituted  mucous  membrane  on  the  concave  side  of  the  spongy  bones, 
immediately  beneath  the  epithelium — of  calcareous  salts,  to  such  an  ex- 
tent, that  its  uppermost  layer  was  transformed  into  a  peculiar  ossified 
though  still  flexible  membrane,  in  which  there  existed,  in  places,  larger 
and  smaller,  often  very  regularly  disposed  openings,  but  no  evidence  of 
a  special  structure.  Under  this  layer,  which,  where  well  developed,  ap- 
peared perfectly  white,  like  a  membrane  filled  with  air-vesicles,  as  which 
I  at  first  regarded  it,  there  always  occurred  a  looser  connective  tissue 
with  vessels,  of  which  latter,  however,  some  were  also  incrusted ;  and 
in  the  deeper  parts  of  the  epithelial  layer  itself,  there  were  scattered, 
smaller,  simple  or  aggregated  concretions,  like  "  brain-sand"  in  minia- 
ture. 

The  proper  olfactory  mucous  membrane  of  all  the  divisions  of  the 
organ,  occupies  only  the  uppermost  parts  of  the  septum  and  of  the 

walls  of  the  proper  nasal  fossce,  where 
the  superior  spongy  bones  are  situated, 
to  a  distance  of  about  }-l  inch  down- 
wards from  the  lamina  cribrosa.  It  is 
distinguishable,  even  by  the  naked 
eye,  from  the  contiguous  ciliated  mem- 
brane, by  its  greater  thickness  and  its 
color,  which  is  sometimes  yellowish,  as 
in  Man,  the  Sheep,  and  Calf;  some- 
times yellowish-brown  or  brown,  as  in 
the  Rabbit  and  Dog;  and,  when  ex- 
amined microscopically,  it  is  seen  to 
be  bounded  by  a  tolerably  well-defined, 
toothed  or  undulated  border.  The 
differences  of  the  structure  depend 
upon  the  condition  of  the  epithelium, 
the  occurrence  of  numerous  peculiarly 
constructed  glands,  which  I  shall  term 
"  Bowman's  glands,"  and  upon  the  relations  of  the  nerves.  The 

* 

FIG.  312. — From  the  nasal  mucous  membrane  of  the  Sheep;  magnified  150  diameters.  1, 
from  the  regio  olfactoria,  transverse  section  of  the  mucous  membrane  :  a,  epithelium  without 
cilia;  6,  olfactory  nerves,  with  a  dividing,  pale,  nucleated  fasciculus;  c,  one  of  "Bowman's 
glands;"  rf,  its  orifice.  2,  ciliated  epithelium  of  the  Schneiderian  membrane. 


THE    NOSE.  781 

epithelium  is  not  ciliated,  of  which  I  have  most  fully  satisfied  myself, 
not  indeed  in  Man,  in  whom  I  have  never  yet  met  with  the  epithelium 
of  the  true  olfactory  region  in  a  perfect  condition,  although  the  ciliated 
epithelium  occurred  frequently  enough  still  in  a  state  of  vibration,  but 
in  the  animals  just  named.  It  is  also  much  thicker ',  so  that  in  the 
Sheep,  in  which  the  ciliated  epithelium  is  0-03  of  a  line,  it  measures 
0-05,  and  in  the  Rabbit,  the  one  is  0-04,  and  the  other  0-07  of  a  line 
thick.  Notwithstanding  this  thickness,  which  is  considerable  for  a 
mucous  membrane,  it  is  remarkably  delicate  and  soft,  and  is  so  much 
affected  by  almost  all  reagents  as  to  allow  of  its  being  studied  only 
with  considerable  trouble.  According  to  my  observations,  it  should  be 
described  as  a  squamose  cylinder -epithelium  ;  at  all  events,  in  opposi- 
tion to  Todd  and  Bowman,  I  always  find  as  its  outermost  layer,  one  or 
two  strata  of  slender,  vertical  cells,  0-005-0-007  of  a  line  long,  whilst 
it  must  be  allowed  that,  more  deeply,  spherical  elements,  of  0-003- 
0-004  of  a  line,  alone  appear  to  exist.  All  these  cells  have  minute, 
round  nuclei,  usually  pale,  finely  granular  contents  of  a  brownish  hue 
in  the  deepest  layer  only  in  the  Rabbit  and  Dog,  and  such  delicate 
membranes,  that  in  water  they  instantly  burst.  Although  the  ciliated 
cells  of  the  nasal  fossce  are  much  more  readily  affected  by  water  than 
those  of  other  situations,  this  is  true  to  a  much  greater  extent  as 
regards  the  cells  of  the  olfactory  region ;  and  the  destructive  effect  of 
the  filling  of  the  nasal  cavities  with  water  (E.  H.  Weber)  and  other 
fluids  is  thus  easily  accounted  for,  as  well  as,  on  the  other  hand,  is  the 
ready  transition  of  volatile  substances  through  the  epithelium  rendered 
intelligible.  For  the  moistening  and  protection  of  this  epithelium 
throughout  the  region  in  which  it  exists,  it  is  furnished  with  a  great 
number  of  the  "  glands  of  Bowman,"  which  is  the  more  remarkable, 
because  the  immediately  contiguous,  ciliated  mucous  membrane  is  but 
scantily  supplied  with  glands,  or  is  wholly  without  them.  These  glands 
are  simple  cylinders,  either  straight  or  slightly  convoluted  at  the  lower 
end,  and  O'08-O-l  of  a  line  in  length,  or  elongated  pyriform  follicles, 
situated  principally  between  the  larger  branches  of  the  olfactory  nerves, 
in  crowded  rows,  in  part,  however,  more  isolated,  as  at  the  lower 
boundaries  of  the  olfactory  region.  They  most  nearly  approach  cer- 
tain forms  of  the  Lieberkuhnian  glands,  and  the  sudoriparous  glands  of 
the  foetus.  I  have  never  yet  noticed  divisions  of  the  follicles,  although 
it  is  very  possible  that  I  may  have  overlooked  them,  since  these  organs 
are  extremely  delicate,  and  easily  altered.  Their  canals,  0-014-0-025 
of  a  line  wide,  are  lined  by  a  beautiful,  simple  epithelium,  compose^  of 
rounded  polygonal  cells,  0-006-0-008  of  a  line  in  size,  containing  more 
or  fewer  yellowish  or  brownish  pigment-granules,  to  which  is  due  the 
varying  color  of  the  olfactory  mucous  membrane.  Their  excretory 


782 


SPECIAL    HISTOLOGY. 


ducts  are  rather  more  contracted  (0-008-0-012  of  a  line)  than  the 
glandular  canals,  and  ascend,  always  lined  by  rounded  larger  cells, 
straight  through  the  epithelium,  in  order  to  terminate  on  the  surface 
with  rounded  orifices,  0-01  of  a  line  in  diameter,  surrounded  by  a  few 
large  cells.  The  tissue  beyond  these  glands  is,  as  in  other  regions,  soft 
connective  tissue,  without  elastic  elements. 

The  mucous  membrane,  in  the  proper  nasal  cavities,  is  very  richly 
supplied  with  vessels,  and  less  so  in  the  accessory  sinuses.  The  termi- 
nal branches  of  these  vessels  form  loose  plexuses  around  the  glands, 
and  in  the  trunks  and  branches  of  the  olfactory  nerves ;  while  on  the 
surface  of  the  mucous  membrane  itself,  they  constitute  a  more  close 
network  with  numerous  horizontal  loops,  at  first  sight  leading  to  the 
supposition  of  the  presence  of  papillae,  which,  however,  do,  not  exist. 
The  branches,  also,  of  the  arteries  and  veins  enter  into  numerous 
anastomoses,  and  constitute  (the  latter  especially)  on  the  inferior 


Fig.  313. 


spongy  bones,  the  abundant  spongiform  plexus  already  noticed.  Nothing 
is  known  of  the  lymphatics  of  the  nasal  mucous  membrane.  The 
nerves  are,  in  the  first  place,  branches  of  the  fifth  pair  (ethmoidal, 
posterior  nasal,  and  a  branch  of  the  greater  anterior  dental  nerve),  which 
supply  especially  the  ciliated  region  of  the  organ,  presenting  there  the 
same  conditions  as  the  nerves  in  other  sentient  mucous  membranes  (of 
the  pharynx,  for  example),  but  also  extend  to  the  proper  olfactory 
region ;  and,  as  I  noticed  in  one  instance  in  the  Calf,  send  scattered 
dark-bordered  primitive  fibres  in  the  course  of  the  branches  of  the 
olfactory  nerves.  The  olfactory  nerve,  in  its  tract  and  bulb,  contains 
dark-bordered  fibres  and  nerve-cells,  of  which  we  have  already  spoken. 

FIG.  313. — From  the  olfactory  nerve  of  Man;  magnified  350  diameters  :  «/2,  nerve-tubes 
from  the  tractus,  in  water;  U,  in  syrup,  appearing  contracted ;  C,  nerve-cells,  from  the  bulb  ; 
J9,  nerve-fibres,  from  the  branches  in  the  olfactory  organ. 


THE    NOSE.  783 

The  nervi  olfactorii,  on  the  other  hand,  in  Man  and  in  other  Mammalia, 
even  in  the  main  trunks  given  off  from  the  olfactory  bulb,  present  no 
white  medullated  fibres  at  all,  but  are  wholly  constituted  of  pale, 
slightly  granular  flattened  fibres,  0-002-0-003  of  a  line  wide,  with 
elongated  nuclei,  which  are  closely  adherent  and  retained  in  connection 
by  common  sheaths  of  connective  tissue,  which  are  somewhat  thicker 
and  therefore  whiter  in  the  rami  ad  septum.  With  respect  to  the 
origin  of  these  fibres,  which  very  closely  resemble  the  embryonic  nerve- 
elements,  whether  they  are  derived  from  the  olfactory  bulb,  or  from  the 
cerebrum  itself,  has  by  no  means  been  as  yet  ascertained  in  Man,  or  in 
other  Mammalia,  although,  from  the  observations  of  Leydig  in  the 
"Plagiostomata,"  ("Beitrage,"  p.  34,  Tab.  I.,  fig.  6),  it  is  probable 
that  the  former  is  the  case.  The  termination  of  these  nerves  is  yet 
more  doubtful.  This  much  is  readily  seen,  that  the  nervi  olfactorii,  in 
their  course  in  the  mucous  membrane  of  the  olfactory  region,  are  gra- 
dually attenuated  as  they  descend,  in  consequence  of  numerous  divi- 
sions at  acute  angles,  and  form  a  plexus  which  may  also,  in  Mammalia, 
be  traced  almost  throughout  the  olfactory  region ;  but  shortly  before 
reaching  its  border,  these  plexuses  are  always  lost  to  sight,  nor  is  any 
other  indication  of  terminal  branches  presented;  so  that,  as  regards 
the  main  fact,  I  remain  quite  in  the  dark.  At  present  it  appears  to  me 
most  probable  that  the  terminal  distribution  takes  place  throughout  the 
non-ciliated  region,  and  above  all  at  its  border ;  at  any  rate  I  have 
never  yet  been  able  to  detect  the  filaments  of  the  olfactory  nerves  in 
the  ciliated  epithelium,  although  they  can  be  traced  down  to  twigs  of 
the  size  of  0*005-0-01  of  a  line.  I  have  not  seen  the  ganglion-globules 
on  the  inner  surface  of  the  finer  plexus  mentioned  by  Valentin  ("  Ner- 
venlehre,"  p.  303),  and  the  rather  strange-looking  "  glands  of  Bow- 
man," might  have  been  mistaken  for  such  bodies. 


In  the  investigation  of  the  olfactory  organ,  the  chief  difficulty  arises 
from  the  softness  of  the  epithelium,  and  on  this  account  a  solution  of 
albumen,  or  liumor  vitreus,  only  should  be  employed  to  moisten  it. 
Vertical  sections  in  detached  portions  of  the  mucous  membrane,  are 
best  made  with  the  scissors ;  and  the  edges  of  folds  not  unfrequently 
afford  good  sectional  views.  The  mucous  glands,  are  found  in  sections; 
those  of  Bowman  on  teasing  out  the  structure.  Chromic  acid  cannot 
be  recommended  for  the  olfactory  nerves :  teasing  out  the  membrane  is 
the  most  suitable  mode  of  proceeding ;  as  well  as  the  compression  of 
fresh  preparations  or  of  preparations  moistened  with  soda  or  acetic 
acid ;  lastly,  the  examination  of  mucous  membrane  macerated  in  water, 
in  which  the  nerves  are  preserved  for  a  long  time. 


784  SPECIAL    HISTOLOGY. 

Literature. — Todd  and  Bowman  (op.  cit.,  II.)  [Horn,  "  Ueber  die 
Endschlingen  des  Geruchsnerven,"  Miill.  "Archiv,"  1850.  Dr.  Horn 
professes  to  have  discovered  looped  terminations  of  the  olfactory  nerve 
in  the  Frog  (TRS.) ;  0.  Kohlrausch,  "  Ueber  das  Schwellgewebe  an  den 
Muscheln  der  Nasenschleimhaut  in  i  Muller's  Archiv,'  "  1853 ;  A.  Kol- 
liker,  "  Ueber  den  Bau  der  grauen  Nervenfasern  der  Geruchsnerven  in 
4  Yerhand.  d.  phvs.  med.  Ges.'zu  Wurzburg,"  IV.  1,  1853.— DaC.] 


APPENDIX. 

BY    THE    TRANSLATORS, 


§  1.  THE  first  section  of  the  Appendix  should,  according  to  promise, 
have  been  constituted  of  an  exposition  of  the  views  which  we  have  taken 
with  regard  to  the  Cell-theory.  Finding,  however,  that  it  would  be 
inexpedient  to  extend  this  already  somewhat  voluminous  work  by  the 
amount  of  space  and  number  of  illustrations  which  would  be  necessary  for 
a  more  complete  discussion  of  the  subject  than  has  already  appeared 
in  the  pages  of  the  "British  and  Foreign  Medico-Chirurgical  Review" 
(October,  1853),  we  must  refer  the  reader  to  the  article  in  question. 

We  hope,  however,  in  the  course  of  a  short  time,  to  treat  of  the  whole 
subject  at  length  in  another  place. 

Corpuscula  tactus  and  Pacinian  bodies. — In  an  essay  on  this  sub- 
ject, contained  in  the  "  Quarterly  Journal  of  Microscopical  Science," 
for  October,  1853,  we  have  endeavored  to  show  that  papillae  which 
contain  "  corpuscula  "  may  also  possess  a  vascular  loop,  and  that  there 
is,  at  any  rate,  no  inverse  relation  between  nerves  and  vessels  in  the 
papillae,  since  in  the  Frog,  the  terminations  of  the  nerves  in  the  fungi- 
form  papillae  of  the  tongue,  first  described  by  Dr.  Waller  ("Phil.  Trans.," 
1848),  take  place  in  obviously  vascular  papillae.  We  regard  the  "  cor- 
pusculum"  as  no  peculiar  body,  but  simply  as  embryonic  connective 
tissue,  differing  from  that  of  the  rest  of  the  papilla  only  in  the  regular 
arrangement  of  its  elastic  element ;  it  is,  in  fact,  the  dilated  termination 
of  the  neurilemma  of  the  nerve  of  the  papilla. 

With  regard  to  the  mode  of  termination  of  the  nerves,  while  not 
venturing  to  deny  the  existence  of  loops,  we  doubt  it ;  on  the  other 
hand,  repeated  instances  of  the  so-called  free  termination  of  dark-con- 
toured nerve-tubules  on  the  surface  of  the  corpuscula  are  described  and 
figured  (1.  c.,  p.  3,  Fig.  4).  The  termination  is  not  really  "free,"  inas- 
much as  the  tubules  become  continuous,  both  here  and  in  the  Frog's 
tongue,  with  the  imperfect,  reticulated,  elastic  fibrils  of  the  papillae. 

As  respects  the  Pacinian  bodies,  we  stated,  at  that  time  in  opposition 
to  all  authorities,  that  their  central  portion  is  solid  and  not  hollow,  and 
that  in  Birds  and  in  the  human  hand,  the  fluid  supposed  to  exist  be- 

50 


786  APPENDIX. 

tween  the  concentric  laminae  was  equally  hypothetical.  In  structure, 
the  Pacinian  body,  in  fact,  is  identical  with  the  corpusculum  tactus — 
being  a  solid  mass  of  connective  tissue,  whose  apparent  lamination  de- 
pends on  the  regular  disposition  of  its  elastic  elements.  We  stated 
further,  that  the  central  nerve-tubule  gradually  terminates,  passing  into 
the  central  solid  axis  of  the  Pacinian  body.  In  reality,  the  Pacinian 
bodies  are  also  nothing  more  than  thickened  processes  of  the  neurilemma 
of  the  nerve  to  which  they  are  attached,  and  differ  from  the  tactile  cor- 
puscles only  in  the  circumstance  that  in  the  latter  the  thickening  takes 
place  on  one  side  of  the  nerve-fibril,  while  in  the  Pacinian  body  it  takes 
place  on  both  sides. 

In  the  meanwhile,  contemporaneous  observations  on  this  subject  were 
made  by  Leydig  ("  Ueber  die  Vater-Pacinischen  Kbrperchen  der 
Taube")  and  by  Kolliker  ("Einige  Bemerkungen  iiber  die  Pacinischen 
Kbrperchen,")  and  were  published  in  Siebold  and  Kblliker's  "  Zeit- 
schrift,"  B.  V.,  H.  1. 

Leydig  and  Kblliker's  results  are,  in  the  main,  in  accordance  with 
our  own,  especially  as  respects  the  solidity  of  the  Pacinian  body.  The 
"central  cavity"  is  given  up  by  both,  but  Kolliker  still  maintains  the 
existence  of  a  fluid  between  the  outer  layers,  at  least  in  the  Cat.  Ley- 
dig  regards  the  central  solid  axis  of  the  Pacinian  body  in  the  Bird  as 
the  expanded  termination  of  the  nerve  itself. 

Wagner  had  already  drawn  attention  to  the  resemblance  between  the 
corpuscula  tactus  and  the  Pacinian  bodies ;  Leydig  further  shows  that 
the  latter  form  one  series  with  the  Savian  bodies  and  the  so-called  muci- 
parous  canals  of  osseous  and  cartilaginous  Fishes.  We  ventured,  in  the 
paper  in  question,  to  add  the  "tactile  hairs"  or  "vibrissce"  of  Mam- 
malia to  this  series  of  cutaneous  organs,  by  showing  that  they  are  but  a 
further  development  of  the  muciparous  canals — pointing  out,  at  the  same 
time,  that  even  the  highest  organs  of  sense,  the  Eye  and  the  Ear,  are 
constructed  upon  the  same  principle. 

§  2.  Malpighian  bodies  of  the  spleen. — Having  recently  carefully 
investigated  the  structure  of  these  organs,  we  have  arrived  at  the  fol- 
lowing conclusions  (vid.  "  Quarterly  Journal  of  Micr.  Science,"  Jan. 
1854). 

1.  In  the  various  animals  examined  (Man,  Sheep,  Pig,  Rat,  Kitten), 
we  find,  as  Dr.  Sanders  had  already  demonstrated  in  the  Pig,  that  the 
minute  arterial  twigs  supplying  the  Malpighian  bodies  are  not  only  dis- 
tributed over,  but  enter  and  ramify  in  them,  breaking  up  into  their  fine 
penicillate  branches  as  they  pass  out. 

Furthermore,  connecting  these  arterioles,  there  is  a  network  of  fine 
capillaries,  whose  walls  are  hardly  distinguishable,  but  which  are  readily 
detected  by  using  syrup,  which  retains  the  coloring  matter  in  their  con- 
tained blood-corpuscles. 


APPENDIX.  787 

The  pulp  of  the  Malpighian  body  stands,  as  Remak  pointed  out,  in 
the  relation  of  tunica  adventitia  to  the  arterioles  ;  it  is  composed  of  in- 
different tissue,  consisting  of  endoplasts  imbedded  in  a  homogeneous 
periplast,  and  which  may  or  may  not  become  surrounded  by  cell-walls. 

The  Malpighian  body  has  no  wall,  but  passes  insensibly,  as  Wharton 
Jones  had  already  shown,  into  the  fusiform  fibres  of  the  red  pulp. 

We  adduce  evidence  from  Remak  and  Leydig  that  the  Malpighian 
bodies  of  other  Vertebrata  present  similar  relations,  and  that  the  spleen, 
lymphatics,  Peyer's  patches  and  the  glandulce  solitarice,  the  supra-renal 
capsules,  thymus,  and  pituitary  body,  belong  to  the  category  of  the  so- 
called  "vascular"  glands,  all  consisting  essentially  of  masses  of  indif- 
ferent tissue  contained  in  a  vascular  plexus. 

We  proceed  to  show  that  the  follicles  of  the  tonsil  are  not  closed, 
but  traversed  by  capillaries;  and  that  it  is  a  gland  of  the  same  class, 
distinguished  from  a  Peyer's  patch  only  in  the  fact  of  its  elements 
being  aggregated,  not  on  a  plane,  but  round  a  diverticulum  of  mucous 
membrane. 

Finally,  we  suggest  that  the  liver  itself  is  but  a  huge  tonsil — a  vascu- 
lar gland,  with  what  might  be  termed  a  false  duct ;  and  we  indicate  the 
agreement  of  this  doctrine  with  the  view  taken  by  Dr.  H.  Jones  with 
regard  to  this  organ,  and  we  may  add,  with  the  recent  beautiful  re- 
searches of  Bernard. 

§  3.  Corpora  lutea. — Prof.  Kblliker  does  not  appear  to  be  acquainted 
with  the  exact  description  of  the  structure  of  the  corpora  lutea,  given 
by  Mr.  Wharton  Jones  so  long  ago  as  1843-4,  in  his  "  Report  on  the 
Ova  of  Man  and  the  Mammifera  before  and  after  Fecundation,"  "  Brit, 
and  For.  Med.  Review,"  1843,  and  in  a  paper  entitled  "  Microscopical 
Examination  of  an  early  Corpus  Luteum"  in  the  "London  Med.  Ga- 
zette" for  1844.  From  the  latter  we  extract  the  following  passages, 
premising  that  to  the  naked  eye  a  section  of  this  corpus  luteum  pre- 
sented the  appearance  of  a  dark  clot  with  a  central  membranous  shred 
from  which  processes  radiated. 

"  The  body  in  question  (early  corpus  luteum)  is  of  a  lenticular  form, 
about  6-10  inch  in  diameter,  and  about  4-10  inch  thick,  and  projects  on 
the  surface  of  the  ovary  by  somewhat  more  than  half  its  diameter.  The 
prominent  part  being  covered  merely  by  the  indusium  of  the  ovary, 
the  dark  brown  red  color  of  the  body  shines  through.  Examined  micro- 
scopically the  central  membranous  shred  was  found  to  present  the  fol- 
lowing structure : 

"  1.  On  its  free  surface  a  fine  film  of  tessellated  epithelium.  2.  In- 
vested by  this  epithelium  was  a  stratum  of  finely  interwoven  transpa- 
rent fibres,  with  dark  contours,  somewhat  like  elastic  tissue.  3.  Out- 
side all  was  a  layer  identical  in  structure  with  the  stroma  of  the  ovary, 


788  APPENDIX. 

I 

the  same  structure  as  that  composing  the  principal  thickness  of  the  walls 
of  Graafian  follicles. 

"The  membranous  processes  possessed  a  similar  structure,  and  were 
found  to  be  continuous  with  the  stroma  of  the  ovary.  That  part  of  the 
body  next  the  substance  of  the  ovary,  had,  by  its  pressure,  so  condensed 
the  stroma  at  the  place,  that  the  latter  looked  somewhat  like  an 
external  capsule  sending  processes  inwards,  which  met  and  interwove 
with  those  sent  outward  by  the  central  membranous  striae.  But  that 
this  appearance  of  external  capsule  was  the  result  simply  of  the  matting 
of  the  stroma  of  the  ovary  by  pressure,  is  shown  by  the  circumstance 
that  it  was  absent  at  the  peripheral  part  of  the  clot-like  body,  there 
being  there,  as  already  said,  merely  the  indmium. 

"  As  to  the  microscopical  characters  of  the  clot-like  matter  itself, 
this  was  found  to  consist  of  granulous  corpuscles  somewhat  like  so- 
called  compound  inflammation  globules  closely  aggregated,  and  red 
blood-corpuscles  interspersed  amongst  them.  The  latter  had  lost  some 
of  their  coloring  matter,  but  the  granulous  corpuscles  were  tinged  red, 
as  if  they  had  imbibed  it. 

"  The  conclusion  which  is  to  be  drawn  as  to  the  nature  of  the  body 
from  this  investigation  is,  that  it  is  a  true  corpus  luteum  in  an  early 
stage ;  that  the  central  membranous  shred  is  the  wall  of  the  Graafian 
follicle,  from  which  the  ovum  had  escaped  ;  and  that  the  clot-like  mass 
(which  would  by  and  by  have  acquired  the  characteristic  yellow  appear- 
ance of  the  corpus  luteum,  traces  of  which  could  indeed  in  some  deep 
places  be  detected),  together  with  the  membranous  processes  extending 
through  it  from  the  central  shred  to  the  stroma  of  the  ovary,  is  the 
stroma  surrounding  the  Graafian  follicle  infiltrated  with  bloody-looking 
matter." 

With  regard  to  the  important  question  of  the  nature  and  reason  of 
the  differences  between  true  and  false  corpora  lutea,  Mr.  Wharton  Jones 
observes : 

"If  in  the  human  female,  Graafian  follicles  burst  periodically,  inde- 
pendently of  coitus,  why  is  there  no  corpus  luteum  left  ?  The  explana- 
tion which  might  be  given  of  this  is  : 

"  By  a  slow,  natural,  and  regular  process,  a  Graafian  follicle  maturates, 
points,  bursts,  and  is  evacuated  like  a  small  healthy  abscess  or  pimple, 
and  like  this  the  part  quickly  cicatrizes.  A  Graafian  follicle,  at  the 
time  of  coitus,  not  happening  to  be  in  this  fully  matured  state,  its 
bursting  is  hastened  by  the  process  of  congestion,  exudation,  and  extra- 
vasation above-described ;  but  when  burst,  the  lymph  and  blood  in  an 
altered  state  remain  for  a  while  in  the  form  of  a  corpus  luteum,  which 
may  thus  be  compared  to  the  hard  base  of  an  abscess  evacuated  prema- 
turely. Though  true  corpora  lutea,  there  is  reason  to  believe,  are 
formed  only  after  coitus,  impregnation  may  take  place  without  the  for- 


APPENDIX.  789 

mation  of  a  corpus  luteum.  How  is  this  ?  The  explanation  which  might 
be  offered  of  such  rare  cases  is  this :  Coitus  may  have  chanced  to  take 
place  at  the  very  time  when  a  Graafian  follicle,  having  become  mature, 
had  spontaneously  given  way  and  expelled  the  ovum.  No  congestion, 
exudation,  and  extravasation,  would  in  this  case  take  place,  but  the  part 
would  quickly  close  and  cicatrize.  4.  Lastly,  what  explanation  can  be 
given  of  the  origin  of  false  corpora  lutea  ?  To  this  it  might  be  answered, 
that  from  some  circumstance  or  other,  effusion  of  blood  takes  place  into 
the  interior  of  a  Graafian  follicle,  perhaps  on  the  point  of  bursting 
spontaneously.  This  blood  coagulates  and  remains  filling  and  distend- 
ing the  Graafian  follicle,  even  although  its  walls  may  have  subsequently 
given  way.  But  besides  this  effusion  of  blood,  an  exudation  of  lymph 
takes  place  on  the  inner  surface  of  the  walls  of  the  Graafian  follicle,  in 
consequence  of  the  irritation  produced,  which,  becoming  organized,  pre- 
sents the  same  yellow  appearance  as  the  substance  of  the  true  corpus 
luteum  formed  outside  the  walls  of  the  Graafian  follicle. 

"  In  conclusion,  I  would  remark  that,  though  physiologically  one  may 
be  permitted  to  speculate,  as  I  have  done,  on  the  relation  between  the 
occurrence  of  corpora  lutea  in  the  ovaries  and  preceding  coitus,  it  would 
be  rash  and  unwarrantable  in  any  one  to  pronounce  positively  from  the 
occurrence  of  a  corpus  luteum  in  the  ovaries  that  coitus  had  taken  place. 
The  discovery  of  an  ovum  >  in  the  uterus,  in  process  of  development, 
could  alone,  in  the  present  state  of  knowledge,  warrant  such  an  affirma- 
tion in  a  court  of  law.  But,  on  the  other  hand,  the  absence  of  a  corpus 
luteum  could  not  warrant  the  affirmation  that  coitus  had  not  taken  place." 

§  4.  Development  of  the  Teeth. — In  an  Essay  on  this  subject  in  the 
"  Quarterly  Journal  of  Microscopical  Science,"  for  April,  1853,  we  have 
taken  a  very  different  view  from  that  advocated  by  Professor  Kolliker, 
and  which  amounts  to  this,  that  all  the  tunics  of  the  teeth  are  the  result 
of  calcareous  deposition  from  the  pulp,  the  so-called  "  enamel  organ" 
taking  no  direct  share  whatever  in  the  process.  This  view  was  based 
upon  observations  made  upon  the  teeth  of  all  the  principal  orders  of  the 
Vertebrata,  i.  e.,  the  Mackerel,  the  Skate,  the  Frog,  the  Calf,  and  Man; 
and  subsequent  observations  on  these  and  on  other  animals,  have  only 
confirmed  our  belief  in  the  substantial  truth  of  the  matters  of  fact  there 
stated. 

The  keystone  of  the  theory  of  dental  development  there  enunciated 
is  the  fact,  that,  in  all  the  orders  of  the  Vertebrata,  a  membrane  homo- 
logous with  the  so-called  "persistent  capsule,"  discovered,  in  1839,  by 
Mr.  Nasmyth,  and  which  we  have  therefore  denominated  "  Nasmyth's 
membrane"  can  be  demonstrated  covering  the  enamel  of  the  teeth  and 
extending  over  the  dentine,  to  be  continuous  with  the  membrana  prefor- 
mativa  and  basement  membrane  of  the  sac,  in  an  incompletely  formed 


790  APPENDIX. 

tooth ;  or  with  the  surface  of  the  cement,  in  a  fully  developed  one. 
Nasmyth's  membrane,  in  fact,  is  at  first  the  membrana  preformativa 
more  or  less  altered. 

We  hold  this  statement  to  be  incontrovertible,  nor  less  so  the  corre- 
lated doctrine,  that  the  enamel  and  cement,  as  well  as  the  dentine,  are 
developed  beneath  Nasmyth's  membrane;  between  it  and  the  pulp ;  that 
the  enamel  is,  consequently,  during  the  whole  course  of  its  formation, 
separated  from  the  enamel-organ  by  Nasmyth's  membrane ;  and  that, 
therefore,  the  direct  conversion  of  the  long  cylinders  of  the  epithelium 
into  the  fibres  of  the  enamel,  strongly  as  their  mutual  resemblance  may 
suggest  the  notion,  is.  to  say  the  least,  highly  improbable. 

Thirdly,  we  have  met  with  no  facts  in  opposition  to  what  we  have 
stated  with  regard  to  the  mode  of  development  of  dentine  and  the  re- 
lation of  the  latter  to  the  pre-existing  elements  of  the  pulp,  and  we 
believe  that  there  is  every  reason  to  regard  what  we  have  there  called 
the  "  Deposition  theory,"  as  an  established  position.  According  to  this 
theory,  the  dentine  is  not  the  result  of  the  conversion  of  the  elements  of 
the  pulp ;  the  endoplasts  of  the  latter  never  becoming  engaged  in  the 
calcareous  deposit,  as  they  are  in  bone  ;  but  the  young  dentine  is  formed 
by  a  deposit  of  transparent  calcareous  granules  in  a  thin  layer  between 
the  pulp  and  the  membrana  preformativa.  It  must  be  understood,  how- 
ever, that  the  latter  two  structures  are  continuous,  and  that  when  the  den- 
tine is  said  to  be  deposited  between  them  it  is  not  meant  that  any  real 
interval  exists,  but  only  that  the  outer  portion  of  the  periplast  of  the 
pulp,  of  which  the  membrana  preformativa  constitutes  a  part,  increases 
and  receives  a  calcareous  deposit  without  any  corresponding  implication 
of  the  endoplasts  of  the  pulp. 

The  thinnest  and  youngest  layer  of  the  dentine  appears  to  be  struc- 
tureless, which  may,  however,  arise  from  the  small  quantity  of  calcareous 
matter  which  it  contains :  subsequently,  minute  cavities,  irregular  in 
form,  and  l-5000th  of  an  inch  apart,  appear  in  it ;  and  these  corre- 
sponding with  one  another  in  successive  layers  of  the  dentine,  become 
the  dentinal  tubuli.  The  appearance  of  walls,  &c.,  to  these  tubuli,  we 
consider  to  be  the  result  of  a  subsequent  differentiation  in  the  dentine. 

A  careful  study  of  the  mode  in  which  the  dentine-like  tegumentary 
organs  of  many  of  the  lower  animals  (Fishes,  Articulata,  Mollusca)  are 
formed,  has  afforded  the  fullest  confirmation  of  this  theory  of  the  deve- 
lopment of  dentine,  and  we  would  recommend  those  who  have  any  doubt 
upon  the  subject  to  study  the  development  of  the  spines  of  the  Skate, 
or  that  of  the  shell  of  the  Crab  or  Lobster. 

The  mode  of  development  of  the  enamel  appears  to  us  to  be  a  very 
difficult  subject,  and  requires  to  be  most  carefully  studied.  Taking 
into  consideration  the  facts  that  a  distinction  of  a  superficial  and  a  deep 
layer  of  calcified  tissue  is  very  general  in  the  tegumentary  organs — 


APPENDIX.  791 

that  in  a  Molluscan  shell,  for  instance  (e.  g.  Trigonici),  we  may  have  a 
superficial  membranous  layer  corresponding  with  Nasmyth's  membrane, 
a  deeper  prismatic  layer,  whose  prisms  precisely  resemble  those  of 
enamel  on  a  large  scale,  and  an  internal  laminated  tubular  layer,  corre- 
sponding with  dentine ;  and  knowing,  further,  that  these  varieties  of 
structure  thus  arranged  are  (whatever  view  we  take  of  shell-structure) 
nothing  but  the  result  of  the  different  modes  in  which  calcified  deposit 
has  successively  taken  place  in  the  same  organ,  it  is  sufficiently  obvious 
that  there  are  abundant  analogical  grounds  for  considering  the  enamel 
and  the  dentine  as  modifications  of  one  and  the  same  tissue. 

Nor  does  the  structure  of  the  enamel  in  the  Fish  or  the  Batrachian 
present  any  difficulty  in  the  way  of  this  view.  It  is,  at  most,  indistinctly 
fibrous  and  contains  so  large  a  quantity  of  calcareous  matter  in  propor- 
tion to  the  dentine,  that  the  differences  between  the  two  may  well  be 
supposed  to  arise — as  we  believe  they  do — from  this  circumstance 
alone. 

In  the  higher  Vertebrata,  however,  when  the  enamel  in  its  young 
state  consists  of  definite  fibres  composed  of  organic  substance,  which 
are  added  to  the  surface  of  the  tooth  only  after  the  formation  of  a  sub- 
jacent scale  of  dentine,  it  becomes  more  difficult  to  comprehend  the 
development  of  the  former.  There  appears  to  be  three  possibilities. 

1.  What  we  call  the  primary  scale  of  dentine  is  not,  on  the  crown  of 
the  tooth,  dentine  at  all,  but  young  enamel,  becoming  converted  into 
the  latter  structure,  and  not  into  the  former,  as  development  proceeds. 
This  appears,  as  first  sight,  a  startling  hypothesis  enough  ;  but  there 
are,  so  far  as  we  know,  no  means  of  disproving  it.     Young  dentine  can 
only  be  known  to  be  such  by  its  relations ;  in  structure  it  is  neither  like 
perfect  dentine  nor  like  perfect  enamel ;  but  might  readily  be  supposed 
to  be  converted  into  either  by  variation  in  the  quantity  and  mode  of 
deposition  of  its  calcareous  element.     If  this  deposit  be  comparatively 
small,  leaving  much  of  the  organic  basis,  and  not  encroaching  upon  the 
existing  cavities,  we  have  dentine ;  increase  the  quantity  of  calcareous 
salts,  and  break  up   the  organic  basis  at  the  same  time  into  fibres,  and 
enamel  would  be  produced. 

2.  The  enamel  is  the  indirect  product  of  the  prismatic  cells  of  the 
enamel  organ,  whose  inner  extremities  pass  into  successive  layers  of 
membrane,  which  are  applied  upon  and  indistinguishably  unite  with  the 
membrana  preformativa  over  the  whole  surface  of  the  developing  enamel. 
The  laminated  membrane  thus  formed  receives  a  calcareous  deposit, 
and  breaks  up  into  the  prisms  of  the  enamel. 

This  hypothesis  likewise,  at  first  sight,  appears  somewhat  improbable, 
but  it  may  be  strictly  parallel  with  what  occurs  in  the  formation  of 
prismatic  shell  substance,  where  a  laminated  membranous  substance  is 


792  APPENDIX. 

produced  from  the  cellular  epidermis  of  the  mantle,  and  subsequently 
breaks  up  into  the  characteristic,  large,  transversely  striated  prisms. 

3.  The  enamel  is  neither  the  result  of  the  modification  of  the  primary 
"dentine,"  nor  superimposed  on  this  from  the  enamel  organ,  but  a  ter- 
tium  quid,  the  product  of  the  growth  and  metamorphosis  of  that  exces- 
sively thin  layer  of  organic  matter  which  lies  between  the  dentine  and 
the  enamel. 

In  support  of  this  view,  also,  a  very  close  analogy  may  be  found  in 
the  mode  of  development  of  the  shaft  of  the  hair — a  structure  which 
exhibits  the  closest  correspondence  with  the  teeth.  The  fibrous  cortex 
of  the  hair  is,  in  fact,  homologous  with  dentine ;  it  is  a  horny  dentine, 
containing  rudimentary  canals.  External  to  this  substance  we  find  two 
layers ;  the  inner  composed  of  parallel  horny,  structureless  plates, 
closely  united  and  set  obliquely  on  the  shaft,  in  fact,  a  rudimentary 
horny  enamel ;  the  outer  consisting  of  a  tough  areolated  membrane, 
outer  layer  of  the  cuticle,  whose  resemblance  to  Nasmyth's  membrane 
cannot  be  overlooked.  Now,  if  we  trace  the  development  of  these  layers 
in  the  long  hairs  of  the  head,  we  find  that  they  pass  on  the  bulb  into  a 
structureless  limitary  membrane,  beneath  which  lie  the  endoplasts  of 
the  pulp ;  this  is,  in  fact,  a  membrana  preformativa  of  the  hair  pulp. 
Passing  from  the  base  towards  the  apex  of  the  hair,  the  deep  endoplasts 
become  surrounded  by  the  horny  matter  and  the  pigment-granules  of 
the  cortex,  while  the  superficial  layer  remains  free  from  the  latter,  but 
gradually  becomes  horny,  and  loses  its  endoplasts.  Its  outer  portion 
then  becomes  the  areolated  outer  (Nasmyth's  membrane)  cuticular  layer, 
while  its  inner  portion  breaks  up  into  the  parallel  plates  of  the  inner 
(enamel)  cuticular  layer.  So  far  as  we  have  been  able  to  observe  in 
the  long  hair,  however,  the  disappearance  of  the  endoplasts  takes  place 
before  the  areolation  and  lamination  of  the  periplast  which  corresponded 
to  them,  so  that,  as  we  have  already  stated  (note,  page  181),  the 
cuticle  does  here  pass  into  an  apparently  structureless  layer.  This, 
however,  is  not,  as  it  seemed,  a  real  discrepancy  from  Prof.  Kolliker's 
views,  for  in  the  short  thick  hairs,  such  as  those  of  the  nostril,  the  endo- 
plasts persist  longer,  and  we  see  that,  as  he  states,  the  areolations  of 
the  outer  cuticle  are  the  representatives  of  the  cell-cavities  of  the  outer 
layer  of  the  pulp  ;  while  the  laminae  of  the  inner  layer  are  the  result  of 
the  lamination  of  the  next  layer  of  the  pulp,  whose  endoplasts  may  be 
seen  gradually  disappearing,  whilst  its  periplast  breaks  up  into  plates. 

Now  in  the  long  hairs  we  have  a  relation  of  the  outer  cuticle  to  the 
cortex  very  similar  to  that  of  Nasmyth's  membrane  to  the  dentine  before 
the  development  of  the  enamel,  and  the  conclusion  is  obvious,  that  as 
the  development  of  the  inner  layer  of  the  cuticle  takes  place  by  the  dif- 
ferentiation of  the  intermediate  substance  between  the  cuticle  and  cortex, 


APPENDIX.  793 

so  that  of  the  enamel  may  take  place  in  the  same  way  in  relation  to 
Nasmyth's  membrane  and  the  dentine. 

These  would  appear  to  be  the  alternatives  concerning  the  development 
of  the  enamel.  At  present  facts  would  seem  to  be  wanting  to  deter- 
mine definitely  which  should  be  accepted. 

Finally  comes  the  question  of  interpretation  of  the  phenomena  of  de- 
velopment of  the  dental  tissues,  and  the  determination  of  the  homolo- 
gies  of  the  latter  with  the  pre-existing  elements  of  the  mucous  mem- 
brane. Professor  Kolliker's  views  are  stated  in  the  text.  He  consi- 
ders the  dentine  and  the  cement  to  be  the  calcified  corium  of  the  mucous 
membrane,  while  the  enamel  is  the  calcified  epithelium. 

The  view  we  have  ourselves  taken  is  that  cement,  dentine,  and  enamel, 
are  calcifications  in  the  same  constituent  of  the  mucous  membrane,  and, 
in  fact,  that  they  entirely  belong  to  its  corium  or  dermal  element.  Tak- 
ing for  granted  that  the  membrana  preformativa  was  a  basement  mem- 
brane, and  furthermore,  the  received  doctrine  that  a  basement  mem- 
brane marks  the  boundary  between  the  dermal  and  epidermal  elements 
of  integument  or  mucous  membrane,  it  was,  in  fact,  impossible  to  come 
to  any  other  conclusion.  An  extensive  study  of  the  integumentary 
organs,  however,  has  ]ed  us  to  reflect  more  closely  upon  this  matter,  and 
to  inquire  what  is  a  basement  membrane,  and  what  is  the  real  distinc- 
tion between  the  epidermic  and  the  dermic  elements  of  a  membrane  ? 
We  cannot  here  enter  into  the  grounds  for  our  conclusions  (which  will 
be  stated  in  full  in  a  forthcoming  article  on  the  "  Tegumentary  Sys- 
tem," in  Todd's  "Cyclopaedia  of  Anatomy  and  Physiology"),  but  must 
be  content  merely  to  state  our  conclusions  that  the  existence  of  a  base- 
ment membrane,  i.  e.,  of  a  structureless  membrane,  internal  or  external 
to  it,  proves  nothing  with  regard  to  the  dermic  or  epidermic  nature  of 
an  organ,  but  that  we  must  be  guided  entirely  by  the  direction  of  its 
growth  and  metamorphosis.  Every  integument  and  every  mucous 
membrane  may,  in  fact,  be  distinguished  into  three  portions  ;  a  central 
plane  of  indiiferent  tissue,  from  which  growth  and  metamorphosis  take 
place  externally,  to  constitute  the  representative  of  epidermis  or  epithe- 
lium, to  which  we  propose  to  give  the  name  of  ecderon  ;  while  internally, 
growth  and  metamorphosis  take  place  from  the  central  plane,  so  as  to 
constitute  the  representative  of  the  derm  or  umucosa,".  which  we  have 
termed  the  enderon. 

Now  the  dental  pulp  is  a  process  of  the  whole  integument,  and  its 
outer  surface,  although  bounded  by  a  "  basement  membrane,"  truly 
represents  the  deepest  layer  of  the  ecderon  of  ordinary  integument, 
while  its  inner  substance  belongs  to  the  enderon.  Although,  therefore, 
the  dentine  is  not  a  calcified  cellular  epidermis,  it  is  a  calcified  ecderon, 
and  grows  in  the  same  manner  as  an  ecderon  would  do.  The  cement 


794  APPENDIX. 

follows  the  dentine,  and  whatever  the  view  we  take  of  the  development 
of  the  enamel,  it  also  belongs  to  the  ecderon.  Although,  therefore,  the 
teeth  are  not,  in  the  ordinary  sense,  epidermic  structures,  they  are 
homologous  with  the  ecderon,  arid  not  with  the  true  derma  or  enderon 
of  the  mucous  membrane. 


INDEX. 


A. 


Air-cells  of  lungs,  structure  of,  575-575,  579. 

Alimentary  canal,  muscular  tunic  of,  503;  li- 
terature of,  527.  See  Stomach,  Intestine. 

Arachnoid  membrane,  structure  of,  in  spinal 
cord,  393;  of  brain,  395;  vessels  of,  398; 
nerves  of,  ib. 

Areolar  tissue,  94;  subcutaneous  areolar 
tissue,  119;  fat  cells  in,  120,  125. 

Arteries,  structure  of  tunics  of,  678-684  ;  lite- 
rature of,  724. 

Articular  capsules,  295. 

Articular  cartilage,  structure  of,  292,  293, 
note  ;  condition  of  bone  beneath,  293;  vas- 
cularity  of,  294. 

Ascherson,  vesicles  of,  41. 

Axile-corpuscles, nature  of,  130;  terminations 
of  nerves  in,  134. 

Axillary  glands,  202. 

Axmann,  Dr.,  on  ganglion -fibres,  406,  note; 
on  axis-cylinder,  409,  note. 

Ayres,  Dr.,  on  prismatic  crystals  in  coagulated 
blood  of  the  Bitch,  715,  note. 


B. 


Barry,  Dr.,  on  structure  of  muscular  fibre,  227. 

Bernard,  M.,  on  secretion  of  submaxillary, 
465 ;  on  muscular  fibres  in  inferior  vena 
cava,  687. 

Berthold,  Dr.,  on  growth  of  hair,  196. 

Berzelius,  Prof.,  on  medulla  of  bone,  282. 

Bibra,  Von,  his  analysis  of  muscle,  250;  on 
chemical  composition  of  dentine,  471 ;  of 
enamel,  477;  of  the  liver,  536. 

Bichat,  Prof.,  his  influence  on  Histology,  33; 
on  vessels  in  bone,  301. 

Bidder,  Dr.,  on  nerve-cells  in  the  glosso- 
pharyngeal  nerve,  417. 

Bile,  constituents  of,  540. 

BischofF,  Prof.,  on  lenticular  glands  of  sto- 
mach, 509,  note. 

Bladder.     See  Urinary  Bladder. 

Blood,  changes  of,  in  spleen,  560;  elements 
of,  703;  elementary  granules  of,  706;  ex- 
traordinary constituents  of,  713  :  occurrence 
of  crystals  in,  714. 

Blood-corpuscles,  red,  form  and  character  of, 
703,  704;  nucleus  of,  704,  722,  note;  me- 
thod of  enumerating,  704,  note  ;  size  of, 
705  ;  diminution  of  number  in  disease,  ib.  ; 
presence  of,  in  chyle,  701  ;  conditions  of,  in 
various  kinds  of  blood,  709;  influence  of 
reagents  upon,  710;  forms  in  blood  of  ani- 
mals, 712,  722,  note  ;  development  of,  717, 
722. 

Blood -corpuscles,  colorless,  form  and  origin 
of,  707  ;  relative  number  of,  compared  with 


red,  708,  709;  development  of,  into  red, 
718-723  ;  literature  of,  724. 

Blood-corpuscle-holding  cells,  occurrence  of 
in  spleen,  558-562 ;  in  congested  lungs, 
559,  note;  in  black  vomit,  ib.  ;  import  of, 
560. 

Blood-crystals,  714. 

Blood-vascular  glands,  tissue  of,  116-118. 

Bloodvessels,  varieties  of,  674;  tissues  enter- 

•  ing  into  their  composition.  674-678;  de- 
velopment of,  715;  literature  of,  724.  See 
Arteries,  Veins,  and  Capillaries. 

Bb'hm,  Dr.,  on  detachment  of  epithelium  in 
cholera,  520. 

Bone,  intimate  structure  of,. 266-281 ;  Haver- 
sian  canals  of,  267-270  ;  lamell®  of,  270- 
275  ;  lacunas  and  cells  of,  275,  279 ;  canaliculi 
of,  276;  contents  of  lacunae  of,  280;  peri- 
osteum, 281;  marrow  of,  282;  cells  of 
medulla  of,  283,  284,  note  ;  connections  of, 
284-291 ;  physical  and  chemical  properties 
of,  299  ;  vessels  of,  301  ;  lymphatics  of,  302  ; 
nerves  of,  303  ;  development  and  formation 
of,  306,  330;  vital  phenomena  of,  336  ;  pa- 
thological changes  of,  340  ;  investigation  of, 
342;  literature  of,  102,344. 

Bowman,  Mr.,  on  structure  of  muscular  fibre, 
225,  228,  note ;  on  rupture  of  muscular 
fibrils  in  tetanus,  258  ;  on  ciliary  motion  in 
Malpighian  corpuscles,  601 ;  on  structure 
of  cornea,  728,  729;  on  nerve-cells  of  retina, 
743 ;  on  constitution  of  vitreous  humor, 
754,  755  ;  on  glands  in  olfactory  mucous 
membrane,  780.  See  Todd  and  Bowman. 

Brain,  ganglia  of,  382.  See  Cerebrum  and 
Cerebellum. 

Brain-sand,  402,  note,  403. 

Bright's  disease,  tubuli  uriniferi  in,  602. 

Bronchia?,  intimate  structure  of,  578;  arteries 
of,  581. 

Briich,  Prof.,  on  the  anatomy  of  the  intestinal 
villi,  518,  note. 

Briicke,  Prof.,  on  cadaveric  rigidity,  253  ;  on 
muscular  fibre  in  villi,  514  ;  on  structure  of 
lacteals  and  absorption  of  chyle,  516,  note  ; 
on  lymphatic  glands,  699;  on  function  of 
bacillar  layer  of  retina,  748;  on  structure  of 
vitreous  body,  754. 

Brulle  and  Hugueny,  MM.,  experiments 
upon  bones  of  growing  animals,  329,  338. 

Brunner's  glands,  structure  of,  519;  vessels 
of,  520  ;  method  of  examining,  527. 

Burnett,  Dr.,  on  development  of  spermatic 
filaments,  625,  note. 

Bursae  mucosas,  structure  of,  123,  239. 

C. 

Capillaries,  structure  of,  689-693;  develop- 
ment of,  716. 


796 


INDEX. 


Carpenter,  Prof.,  on  structure  of  muscular 
fibrUs,  229,  note  ;  on  basement  membrane 
in  corium,  141. 

Cartilage,  its  composition,  79;  varieties  of, 
80;  in  pathological  structure,  322;  lite- 
rature of,  81;  costal  cartilage,  290;  of 
articulations,  291  ;  structure  of,  when  loose 
in  joints,  298;  chemical  composition  of, 
300;  nerves  of,  305;  development  of,  307, 
309,  note;  changes  during  ossification  of, 
313,  316;  vessels  of,  315. 

Cells,  general  anatomy  of,  43-70;  forms  and 
contents  of,  44  ;  size  of,  44,  45  ;  membranes 
of,  45,  47;  chemical  composition  of,  45; 
nuclei  of,  44,  45,  46;  nucleoli  of,  46;  com- 
parison with  primordial  utricle  in  plants, 
47;  development  of,  48,  54  ;  multiplication 
by  division,  54  ;  vital  phenomena  of,  59,  60  ; 
processes  in  the  interior  of,  61 ;  changes, 
and  chemical  composition  of  contents,  165  ; 
elasticity  of  cell-membranes,  67;  excretive 
processes,  ib.  ;  contractility  of,  68;  meta- 
morphoses of,  69,  70. 

Cellular  tissue.     See  Areolar  tissue. 

Cement,  chemical  composiiion  of,  480;  struc- 
ture of,  481  ;  development  of,  492. 

Cerebellum,  elementary  tissues  of,  379  ;  gray 
layer  of,  380;  composition  of  its  crura,  381. 

Cerebral  nerves,  structure  of,  416. 

Cerebro-spinal  fluid,  analysis  of,  401. 

Cerebrum,  ganglia  of,  382;  structure  of  hypo- 
physis, 385:  corpora  striata,  382;  corpora 
quadrigemina,  384;  optic  thalami,  384; 
hemispheres  of,  385 ;  intimate  structure  of 
convolutions,  386  ;  origin  of  nerve-fibres  in, 
390;  membranes  of,  392-399;  ependymaof 
ventricles  of,  397  ;  vessels  of,  400. 

Ceruminous  glands,  structure  of,  209;  secre- 
tion of,  210-212;  literature  of,  212. 

Choroid  coat  of  eye,  layers  of,  733  ;  pigmen- 
tum  nigrum,  735;  vessels  and  nerves  of, 
737-739. 

Chyle,  elements  of,  700. 

Cilia,  structure  of,  in  cells  lining  larynx,  570; 

Ciliary  ligament,  734. 

Ciliary  motion,  agents  for  re-exciting  it,  571, 
note;  in  neck  of  Malpighian  border  of 
kidney,  601. 

Clark,  Prof.,  on  vegetable  growths  on  the 
tongue,  452,  note. 

Clitoris,  655. 

Cochlea,  parts  of,  770-774;  zona  pectinata, 
773;  nerves  of,  774-775,  vessels  of,  775; 
physiology  of,  775,  note;  investigation  of, 
777  ;  literature  of,  778. 

Colostrum,  665,  666. 

Conjunctiva,  structure  of  palpebral,  759;  of 
corneal,  728  ;  vessels  of,  732,  760. 

Con?iective  tissue,  elements  of,  89,  94  ;  chemi- 
cal reactions  of,  90 ;  development  of,  90,  95, 
97,  note  ;  forms  of,  91-94  ;  corpuscles  of,  85. 

Connective- tissue-corpuscles,  85. 

Contractile  tissue,  dependent  on  muscular 
fibre-cells,  104. 

Colloid,  occurrence  of,  in  thyroid  gland,  587; 
in  tubuli  uriniferi  of  kidney,  601. 

Cooper,  Sir  Astley,  on  cavity  of  thymus 
gland,  590. 

Copulation,  motile  phenomena  in  act  of,  637. 

Corium,  structure  of,  123;  development  of, 
134. 

Cornea,  elements  and  structure  of,  727-733; 
vesselsand  lymphaticsof,730;  nervesof,731. 


Corpora  lutea,  formation  of,  643;  structure 
of,  645,  787. 

Corpuscula  amylacea,  of  nervous  system,  41  ; 
in  ventricles  of  the  brain,  401,  402,  note. 

Corpus  striatum,  nerve-fibres  of,  382. 

Corti,  Marquis,  on  connection  of  the  nerve- 
cells  of  the  retina  with  the  nerve-fibres, 
750 ;  on  structure  of  cochlea,  772,  775,  note, 
777. 

Costal  cartilage,  structure  of,  290. 

Cowper,  glands  of,  630,  635. 

Cruveilhier,  Prof.,  on  pathological  changes  in 
articular  cartilage,  295  ;  on  lymphatics  of 
articular  cartilage,  303. 

Czermak,  Prof.,  on  structure  of  dentine,  475, 
note. 


D. 


Dalton,  Dr.,  on  corpus  luteum  of  menstruation 
and  pregnancy,  645,  note. 

Deciduae,  651,  653. 

Deglutition,  organs  of,  499-502.  See  Pharynx, 
(Esophagus. 

Demours,  membrane  of,  729. 

Dentine,  structure  of,  469;  canals  of,  470; 
chemical  composition  of,  471  ;  formation  of, 
491. 

Digestion,  changes  which  the  epithelial  cells 
and  the  villi  undergo  during,  515  ;  organs 
of,  436-568.  See  Intestinal  Canal,  Liver, 
and  Pancreas. 

Donders,  Prof.,  on  development  of  connective 
tissue,  85  ;  on  nature  of  fibres  of  interver- 
tebral  ligaments,  287;  on  composition  of 
cartilage,  300. 

Donne,  M.,  on  spermatozoa,  624;  on  colos- 
trum in  human  milk,  666. 

Ductless  glands,  tissue  of,  116.  See  Spleen, 
Thymus,  Thyroid,  and  Supra-renal  bodies. 

Duhamel,  M.,  his  experiments  upon  grow- 
ing animals,  328. 

Dura  mater,  structure  of,  392,  394  ;  vessels  of, 
397;  nerves  of,  393. 


E. 


Ear.  structure  of  external  canal,  767;  ossicula 
of,  768  ;  membrana  tympani,  768  ;  vesti- 
bule and  osseous  semicircular  canals,  769; 
cochlea,  770-778 ;  development  of,  776 ; 
literature  of,  778. 

Ecker,  Prof.,  on  degenerations  of  thyroid, 
588;  on  structure  and  development  of  thy- 
mus, 592,  595. 

Elastic  ligaments,  284. 

Elastic  Tissue,  elements  of,  81 ;  chemical  re- 
actions of,  82;  development  of,  83  ;  litera- 
ture of,  88  ;  presence  of,  in  ligamentum 
nuchffi,  284. 

Elementary  parts,  simple,  39-70;  higher,  70- 
118;  literature  of,  71. 

Enamel,  structure  of,  476,  478 ;  chemical 
composition  of,  477  ;  Nasmyth's  mem- 
brane, 480  ;  formation  of,  489. 

Endocardium,  structure  of,  669;  nerves  of, 
671. 

Ependyma,  of  ventricles,  396,  401  ;  of  spine, 
397,  note. 

Epidermic  Tissue,  character  of,  74;  forms  of, 
75 ;  prevalence  of,  in  animal  kingdom ;  in 


INDEX. 


'97 


pathological  formations,  78;  literature  of, 
78. 

Epidermis,  139-158;  Malpighian  layer,  140; 
horny  layer,  142 ;  color  of,  144  ;  physical 
and  vital  properties  of,  146 :  action  of  re- 
agents on,  147, 148  ;  on  epidermis  of  Negro, 
149,  note  ;  growth  and  regeneration,  151 ; 
development  of,  154. 

Epididymis,  620,  626. 

Epiglottis,  structure  of,  569 ;  glandules  of, 
572. 

Epithelium,  forms  of,  76  ;  of  stomach,  509; 
of  villi,  514  ;  changes  of,  during  digestion, 
515,  516,  note  ;  ciliated,  of  larynx,  570;  of 
air-cells,  579  ;  of  bronchiae,  578  ;  of  uterus, 
647 ;  varieties  of  lining  vessels,  676 ;  of 
membrane  of  Descemet,  729 ;  of  olfactory 
organ,  779,  781. 

Eulenberg,  Dr.,  his  case  of  black  fur  of  the 
tongue,  453. 

Eye,  tunics  of,  725  ;  sclerotic  coat,  725  ;  vas- 
cular tunic,  733-739  ;  retina,  739-750 ;  lens, 
750-753  ;  vitreous  humor,  753-777  ;  acces- 
sory organs  of,  757-760;  physiological  re- 
marks on,  760 ;  vessels  of  foatus,  761  ; 
histological  development  of,  762  ;  mode  of 
investigating,  763  ;  literature  of,  765. 

Eyelids,  757. 


F. 


Fibro-cartilage,  240 ;  structure  of  interarticu- 

lar,  297  ;  chemical  composition  of,  300. 
Fibrous  tissues,  81,  89.     See  Connective  and 

Elastic  Tissue. 
Filum  terminale,  367;  corpuscula  amylacea 

in,  401. 
Follicles,  solitary,  of  small  intestine,  523;  of 

large  intestine,  525. 
Fremy,  M.,  on  chemical  composition  of  brain, 

359. 
Frerichs,  Prof.,  on  synovia,  298  ;  on  chemical 

composition  of  kidney,  610;  on  semen  of 

the  carp,  624. 

Fuchs,  Prof.,  on  infusoria  in  milk,  666. 
Funke,  Dr.,  on  crystals  in  the  blood.  714. 


G. 

Gall-bladder,  structure  of,  538. 

Ganglia,  fibres  of,  405;  cells  of,  109,  406; 
upon  glosso-pharyngeal  nerve,  454. 

Ganglion-globules.     See  Nerve-cells. 

Ganglionic  nerves,  418.  See  Sympathetic 
nerve. 

Gastric  glands,  structure  of,  506,  507,  note; 
509,  note;  secretions  of,  508. 

Gelatiniform  connective  tissue,  96. 

Genital  organs,  external,  of  male,  630;  of 
female,  655. 

Gerber,  Prof.,  his  method  of  examining  the 
skin,  158. 

Gerlach,  Prof.,  on  Malpighian  bodies,  601, 
note;  on  formation  of  blood-globules,  722. 

Glands,  structure  of,  in  oral  cavity,  456 ;  folli- 
cular,  459;  salivary,  463;  of  stomach,  506  ; 
of  intestine,  518-525;  of  larynx,  572;  of 
trachea,  573;  of  Cowper,  630;  of  Liltre, 
631 ;  of  uterus,  647  ;  of  external  genital 
organs  in  female,  655  ;  Meibomian,  of  eye- 
lid, 758;  "of  Bowman,"  78J, 


Glandular  tissue,  varieties  of,  113-115;  lite- 
rature of,  116. 

Glisson,  capsule  of,  532,  544,  546. 

Gosselin,  M.,  on  composition  of  semen  after 
epididymitis,  625,  note. 

Graafian  vesicles,  640,  643,  645. 

Granules,  general  consideration  of,  41 ;  tre- 
mulous motion  of,  64 ;  formation  of,  in 
nuclei,  64. 

Gums,  composition  of,  484  ;  in  foetus,  488. 


H. 


Hair,  disposition  and  size  of,  171 ;  chemical 
composition  of,  172;  intimate  structure  of, 
173-182;  properties  of,  182;  papilla,  183; 
root  sheath  of,  184;  development  of,  186; 
shedding  of,  191  ;  physiological  observa 
lions  on,  193  ;  abnormal  conditions  of,  197  ; 
method  of  investigating,  ib.;  literature.  198. 

Hancock,  Mr.,  on  organic  muscular  fibres  of 
the  urethra,  631,  note. 

Hannover,  Dr.,  oh  nerve-fibre  in  the  yellow- 
spot  of  the  eye,  750,  note;  on  membranes  in 
fetal  vitreous  humor,  755. 

Harting,  Mr.,  his  measurements  of  blood-cor- 
puscles, .705. 

Hassall,  Mr.,  on  corpuscles  in  Thymus,  593; 
on  peculiar  concentric  bodies  in  fibrinous 
clots  in  the  heart,  713. 

Hasse,  Prof.,  on  medulla-cells  in  cylindrical 
bones,  283. 

Haversian  canals,  origin  of,  318,  327. 

Haversian  glands,  296. 

Heart,  muscular  structure  of,  668,  671-674  ; 
endocardium  of,  669;  bloodvessels  of,  670  ; 
valves  of,  t'6.;  nerves  of,  671  ;  development 
of,  715;  mode  of  examining  its  structure, 
723;  literature  of,  724. 

Henle,  Prof.,  on  smooth  muscles  in  skin,  121; 
on  hair-bulb,  195,  note;  on  cells  of  reticular 
cartilage,  569;  on  composition  of  semen, 
624  ;  on  absence  of  the  "  rods"  in  the  yel- 
low spot  of  the  eye,  746. 

Hepatic  artery,  branches  of,  544-546. 

Hepatic  cells,  532-536. 

Hepatic  ducts,  537-539,  540,  not e;  vasa  aber- 
rantia  of,  538. 

Heyfelder,  Dr.,  on  muscular  layer  in  lympha- 
tic glands,  698. 

Homer,  Prof.,  on  axillary  glands  in  Negro, 
202,  note. 

Hyaloid  membrane,  753,  755. 

Hyrnen,  tissues  of,  654. 

Hypophysis  cerebri,  structure  of,  385. 


I. 


Interlobular  connective  tissue  of  lungs,  580. 

Interosseous  membranes,  structure  of,  238. 

Intervertebral  ligaments,  structure  of,  286. 

Intestinal  canal,  elementary  composition  of, 
436 ;  development  of,  526  ;  literature  of, 
527.  See  Oral  Cavity,  Stomach,  and  In- 
testine. 

Intestine,  small,  mucous  membrane  of,  511 ; 
villi  of,  511-518;  lacteals  of,  513,  5l6,note; 
glands  of,  518-520;  closed  follicles  of,  520- 
524  ;  mode  of  examination  of,  527 ;  litera- 
ture of,  527. 


798 


INDEX. 


Intestine,  large,  mucous  membrane  of,  524  ; 

glands  of,  525  ;  literature  of,  527. 
Iris,  elements  of,  735-738  ;  cause  of  color  of, 

736  ;  vessels  and  nerves  of,  738,  739. 


J. 

Jacob,  membrane  of,  782. 

Jaundice,  teeth  in,  497. 

Jobert  de  Lamballe,  M.,  on  nerves  of  gravid 
uterus,  652. 

Jones,  Dr.  Hanfield,  his  views  on  termination 
of  hepatic  duct,  540,  note;  on  the  develop- 
ment of  the  liver,  547,  note. 

Jones,  Mr.  VVharton,  on  Malpighian  follicles 
of  spleen,  555,  note;  on  blood  of  splenic 
vein,  562,  note;  on  the  blood-corpuscles  in 
animals,  702,  note;  on  nucleus  of  colorless 
blood-corpuscles,  707,  note;  722,  note;  on 
corpora  lutea,  787. 


K. 


Keber,  Dr.,  on  entrance  of  spermatozoon  into 
the  ovum  of  Unio,  637,  note. 

Kidney,  general  composition  of,  596  ;  urinife- 
rous  tubules  of,  597-602;  Malpighian  cor- 
puscles, 598,  600;  pathological  degenera- 
tions of,  601,  606,  611  ;  vessels  and  nerves 
of,  602,  606  ;  stroma  of,  606  ;  calices  and 
'pelvis,  607;  chemical  composition  of,  610; 
mode  of  investigation  of,  611  ;  literature, 
612. 

Kiernan,  Mr.,  on  structure  of  liver,  539,  543. 

Kilian,  Prof.,  on  nerves  of  gravid  uterus,  653. 

Krause,  Prof.,  on  investigation  of  sudoriparous 
glands,  208  ;  on  gastric  villi,  505,  note. 


Lacteal  glands,  structure  of,  661 ;  enlarge- 
ment of,  during  lactation,  662;  physiological 
remarks  on,  663;  secretion  of.  664;  me- 
thod of  examining,  666;  literature  of,  667. 

Langenbeck,  Prof.,  on  muscular  ring  in  zbne 
oi  Zinn,  757. 

Larynx,  cartilages  of,  569  ;  ligaments  of,  ib.  ; 
mucous  membrane  of,  570  ;  glands  of,  572 ; 
vessels  and  nerves  of,  ib. 

Lassaigne,  M.,  his  analysis  of  brain,  359. 

Lee,  Dr.,  on  ganglia  in  the  heart,  671. 

Leeuwenhoek,  on  anastomosis  of  primitive 
fasciculi  of  muscle,  108,  668. 

Lehmann,  Prof.,  on  fluid  of  vesiculae  semi- 
nales,  624 ;  on  presence  of  colostrum-cor- 
puscles in  acute  diseases,  666. 

Leidy,  Prof.,  on  elements  of  articular  car- 
tilage, 293  ;  on  structure  of  liver,  537,  note. 

Lens,  crystalline,  elements  of,  750-754  ;  cap- 
sule of.  750. 

Leydig,  Dr.,  on  nerve-fibres  in  the  skin  of 
Fishes,  415 ;  on  Malpighian  corpuscles  in 
Fishes  and  Reptiles,  555,  556,  note ;  on 
structure  of  supra-renal  capsules  of  mam- 
malia, 617,  note;  on  origin  of  fibres  of  the 
olfactory  nerves  in  the  Plagiostomata,  783. 

Lieberkiihnian  glands,  structure  of,  519,  525  ; 
viscid  secretion  of,  520. 

Ligamenta  flava,  structure  of,  284. 


Ligaments,  connecting  bone,  284;  between 
vertebrae,  285  ;  nerves  of,  305. 

Ligamentum  nuchae,  structure  of,  284;  nerves 
of,  305. 

Listen,  Mr.,  on  vessels  of  articular  cartilage, 
294. 

Liver,  component  parts  of,  528 :  arrangement 
of,  in  animals,  529,  536,  note  ;  in  Man,  531  ; 
secreting  cells  of,  532-536  ;  capsule  of,  532, 
546  ;  chemical  analysis  of,  536  ;  excretory 
ducts  of,  537-540;  secretion  of,  540;  ar- 
rangement of  vessels  in,  541-545;  lym- 
phatics in,  545  ;  nerves  of,  546  ;  develop- 
ment of,  546,  547 ;  mode  of  investigating, 
548  ;  literature  of,  548. 

Loose  cartilages,  in  joints,  structure  of,  298. 

Ludwig,  Prof.,  on  albumen  in  healthy  kid- 
neys, 610;  on  muscular  fibres  of  left 
ventricle,  672. 

Ludwig  and  Nolla,  MM.,  on  structure  of 
lymphatic  glands,  696,  699. 

Lungs,  intricate  structure  of,  574-581 ;  vessels 
and  nerves  of,  581—583;  development  of, 
583  ;  pathological  changes  in  parenchyma, 
584;  mode  of  investigation,  ib.;  literature 
of,  585. 

Luschka,  Prof.,  on  nerves  of  bone,  304;  on 
cellulose  corpuscles  in  the  ganglion  of 
Gasser,  403 ;  on  ligament  of  the  iris  in 
animals,  729. 

Lymph,  elements  of,  700;  formation  of  cor- 
puscles of,  702. 

Lymphatics,  structure  of,  693. 

Lymphatic  glands,  structure  of,  695,  698; 
connection  of,  with  lymphatic  vessels,  696; 
degenerations  of,  699, 


M. 


Malpighi,  Prof.,  on  structure  of  lymphatic 
glands,  696. 

Malpighian  corpuscles,  of  spleen,  552-556, 
557,  note,  786  ;  of  kidney,  597,  600. 

Mammary  Glands.     See  Lacteal  glands. 

Matrix,  of  tissues  in  general,  40;  of  bone,  270. 

Marrow.     See  Medulla. 

Measurements,  those  generally  employed,  43 ; 
table  of,  ib. 

Medulla,  of  bone,  282;  of  cartilage,  291; 
composition  of,  in  fcetus,  322. 

Medulla  oblongata,  structure  of,  372 ;  gray 
substance  of,  374;  origin  of  nerves  from, 
376,  377. 

Meibomian  glands,  758. 

Membrane  of  Descemet,  729,  734. 

Microscopes,  varieties  of,  38. 

Milk,  constituents  of,  664  ;  varieties  of,  666. 

Mohl,  Prof.  Von,  observations  on  cell-division 
in  plants,  56,  note. 

Moleschott,  Dr.,  on  development  of  blood- 
corpuscles,  562,  note  ;  on  relative  number 
of  red  and  white  corpuscles,  708. 

Mouth.     See  Oral  Cavity. 

Mucous  bursae,  239. 

Mucous  corpuscles,  465. 

Mucous  membranes,  general  structure  of, 
436;  of  mouth,  ib. ;  of  tongue,  4^.6;  inti- 
mate structure  of  glands  of,  456 ;  of 
pharynx.  500;  of  intestine,  511,  524;  of 
larynx,  570;  of  bronchia,  578;  olfactory, 
780. 

Mucous  sheaths,  239. 


INDEX. 


799 


Miiller,  Dr.  H.T  on  glands  in  ichthyosis  con- 
genita,  221  ;  on  development  of  bone,  396  ; 
on  radiating  fibre-system  in  retina,  746, 
749,  750,  note. 

Miiller,  Prof.  J.,  on  nerve-fibres  in  orbital 
muscle  of  the  Pike,  249;  on  interarticular 
cartilage,  300 ;  on  Malpighian  corpuscles 
of  spleen,  555  ;  on  helicine  arteries,  633, 
634  ;  on  composition  of  cornea,  727. 

Mulder,  Prof.,  on  chemical  examination  of 
the  nails,  165  ;  on  organic  basis  of  cartilage, 
POO. 

Muscle,  striated,  elements  of,  223;  constitu- 
tion of  fibres  of,  225-230;  nature  of  primi- 
tive fibrils,  227;  connection  of,  with  other 
parts,  231  ;  vessels  in,  243  ;  lymphatics  in, 
245;  nerves  of,  245-250;  chemical  and 
physical  relations  of,  250;  development  of, 
253-257;  pathological  conditions  of,  257- 
259  ;  physiological  remarks  on,  259-264  ; 
method  of  investigating,  264-266  ;  litera- 
ture, 109,  266. 

Muscular  fibre.     See  Muscle. 

Muscular  fibre-cells.  See  Smooth  muscular 
fibres. 

Muscular  system,  constituents  of,  222,266. 

Muscular  tissue,  smooth,  structure  of,  102  ; 
physiological  importance  of,  103;  distribu- 
tion of,  103;  in  contractile  tissues,  104;  in 
vertebrata,  105;  literature  of,  106;  action 
of  reagents  on,  105  ;  presence  of,  in  walls  of 
oesophagus,  501  ;  in  intestine,  511  ;  in  villi, 
514 ;  in  corpora  cavernosa  of  penis,  630  ; 
in  coats  of  vessels,  676  ;  in  arteries,  683 ; 
in  veins,  686,  689. 

Muscular  tissue,  striated,  elements  of,  106, 
225;  chemical  composition  of,  106;  distri- 
bution of,  107,  108 ;  literature  of,  108. 


N. 


Nails,  layers  of,  159;  structure  of,  161  ;  ac- 
tion of  reagents  on,  163;  growth  of,  166; 
pathological  conditions  of,  168;  develop- 
ment of,  169;  method  of  investigating,  170; 
literature,  170. 

Nasmyth,  Mr.,  on  structure  of  enamel,  476, 
note. 

Neill,  Dr.,  on  gastric  villi,  505,  note. 

Neilson,  Dr.,  on  impregnation  of  ovum  in 
Ascaris  mystax,  637,  note. 

Nerve-cells,  structure  of,  357-359 ;  in  me- 
dulla oblongata,  376;  in  cerebellum,  380; 
in  ganglia,  406  ;  pale  processes  of,  408 ;  con- 
nection of,  with  nerve-fibre,  409;  in  the 
sympathetic.  421  ;  development  of,  427. 

Nerve-fibre,  structure  of,  345-356;  medulla 
of,  346,  350;  axis-cylinder  of,  347,  351, 
353-356 ;  sheath  of,  349,  350  ;  in  the  skin 
of  animals,  414  ;  terminations  of,  415 ;  by 
loops,  415,  418;  development  of,  in  Tad- 
pole, 428. 

Nervous  system,  elements  of,  345-359;  di- 
visions of,  345;  central  nervous  system, 
359 ;  peripheral  nervous  system,  404  ;  de- 
velopment of  elements  of,  427-431 ;  func- 
tions of,  431;  literature  of,  112,434.  See 
Cerebrum,  Spinal  Cord,  Cerebellum,  Me- 
dulla oblongata,  Nerve-fibre,  Nerve-cells, 
and  Nervous  Tissue. 

Nervous  tissue,  elements  of,  109,  345  ;  varie- 
ties of,  110;  physiological  importance  of, 


111 ;  distribution  of,  112;  literature  of,  112, 
434;  chemical  composition  of,  111,  359; 
pathological  changes  of,  431 ;  method  to  be 
employed  in  investigations  of,  434. 

Newport,  Mr.,  on  impregnation  of  ovum  of 
Frog,  636,  637,  note. 

Nipple,  structure  of,  662. 

Nose.     See  Olfactory  Organ. 

Nuclei,  occurring  free,  42;  multiplication  of 
by  division,  50;  origin  and  development  of, 
58  ;  importance  of,  in  cell  development,  ib. ; 
occurrence  of,  in  blood-corpuscles,  722,note. 

Nucleus-fibres,  81,  84,  85. 


O. 


(Esophagus,  structure  of  walls  of,  501 ;  litera- 
ture of,  502. 

(Esterlein,  Prof.,  on  epithelial  cells  of  intes- 
tine, 517,  note. 

Olfactory  nerve,  fibres  of,  390,  783. 

Olfactory  organ,  structure  of,  778-783  ;  mu- 
cous membrane  of,  780-783 ;  mode  of 
investigating,  783;  literature  of,  784. 

Optic  nerve,  origin  of  fibres  of,  390;  course 
of  fibres  in  the  eye,  744,  745. 

Oral  cavity,  mucous  membrane  of,  436 ;  mi- 
nute structure  of  mucous  membrane  of, 
437 ;  vessels  and  lymphatics  of,  438  ;  epi- 
thelium of,  439-441  ;  mucous  glands  of, 
455;  their  intimate  structure,  456-459; 
mode  of  examining  its  mucous  membrane, 
466  ;  literature  of,  467.  See  Teeth,  Tongue. 

Organs,  classification  of,  73,  74. 

Osseous  system,  266;  nerves  of,  303-306. 
(See  Bone.) 

Osseous  tissue,  elements  of,  99,  267 ;  distri- 
bution of,  in  vertebrata,  101 ;  literature  of, 
102,  344  ;  forms  of,  266.  See  Bone. 

Otolithes,  composition  of,  770. 

Ovary,  structure  of,  640-642;  mode  of  exa- 
mining, 659 ;  literature,  ib. 

Oviducts,  646. 

Ovum,  composition  of,  642  ;  detachment  and 
reformation  of,  643. 

Owen,  Prof.,  on  "  contour  lines"  of  dentine, 
472 ;  on  dentine  containing  Haversian 
tanals,  474 ;  on  structure  of  dentine,  475, 
note. 


P. 


Pacchionian  granulations,  403. 

Pacini,   Prof.,  on   termination  of  nerves  in 

corpuscles,  412. 

Pacinian  bodies,  structure  of,  413,  785. 
Pancreas,  structure  of,  549  ;  literature  of,  550. 
Panum,    Dr.,   experiments  on  formation    of 

membranes,  43. 
Parotid  gland,  463. 
Parovarium,  642. 
Penis,  structure  of,  630,  634  ;  arteries  of,  633  ; 

literature  of,  639. 
Pericardium,  667. 
Periosteum,  structure  of,  281  ;  lymphatics  of, 

303 ;  layers  of  bone  formed  on  inner  aspect 

of,  324,  328;  lining  osseous  semicircular 

canals,  769. 

Periloneum,  structure  of,  502. 
Peyer's  glands,   composition  of,   521,   523  : 

lymphatics  of,  523,  524. 


800 


INDEX. 


Pharynx,  mucous  membrane  of,  500;  glands 
of,  ib. 

Pia  mater,  of  spinal  cord,  394  ;  of  brain,  395  ; 
bloodvessels  and  lymphatics  of,  398  ;  nerves 
of,  399;  Pacchionian  granulations  of,  403. 

Pigment  cells,  144;  in  skin  of  Negro,  144, 
note. 

Pineal  gland,  structure  of,  385. 

Placenta,  653. 

Pleurae,  structure  of,  574. 

Pons  Varolii,  372,  376. 

Prepuce,  632. 

Primordial  cartilaginous  skeleton,  306 ;  meta- 
morphoses of,  310. 

Prostate  gland,  structure  of,  628-630;  con- 
cretions in,  f>29. 

Purkinje,  Prof.,  observations  on  endocar- 
dium of  Ruminants,  108  ;  on  nerves  in  the 
pia  mater  of  the  Ox,  399. 


Q. 

Quekett,  Prof.,  on  elastic  fibres  in  Giraffe,  81. 


R. 


Reichert,  Dr.,  on  crystalline  form  of  histoge- 
netic  substances,  57;  on  fibrous  tissue,  94; 
on  cortical  substance  of  hair,  176,  note;  on 
epithelium  upon  articular  cartilages,  291 ; 
on  cartilage  corpuscles,  311,  note;  on  crys- 
tallized albuminous  matter,  715. 

Reid,  Dr.  John,  observations  on  paralyzed 
muscles,  258. 

Reiney,  Mr.,  on  existence  of  a  choroideal 
muscle,  739. 

Reinhardt,  Dr.,  on  colostrum,  665. 

Remak,  Prof.,  observations  on  cell-division, 
55;  on  cartilage-corpuscles,  311,  note;  on 
"fibres  of  Remak,"  423,  426;  on  ganglia 
upon  glosso-pharyngeal  nerve,  454  ;  on  de- 
velopment of  thyroid,  588  ;  on  development 
of  kidneys,  608. 

Respiration,  organs  of,  568.  See  Larynx, 
Trachea,  and  Lungs. 

Retina,  structure  of  layers  of,  739-746  ;  con- 
dition of  elements  of,  at  yellow  spot,  746  ; 
connection  of  its  various  layers,  746-751 ; 
physiological  importance  of  the  separate 
layers,  748 ;  especially  of  the  radiating 
fibre-system,  748,  749,  750,  note;  mode, of 
investigating,  764  ;  literature,  766. 

Retzius,  Prof.,  on  cells  of  dentine,  475,  note; 
on  Nasmyth's  membrane,  477,  note. 

Robin,  M.,  on  structure  of  cartilage,  311,  note; 
on  formation  of  bone,  322;  on  vegetable 
growth  on  the  tongue,  452,  note;  on  crys- 
tals obtained  from  blood-serum,  715. 

Rokitansky,  Prof.,  on  new  formation  of  mus- 
cular fibre,  257 ;  on  hypertrophy  of  thyroid, 
588. 


S. 

Saliva,  465. 

Salivary  glands,  structure  of,  464 ;  secretion 
of,  465. 

Salter,  Mr.,  on  structure  of  dentine,  475,  note. 

Schwann,  Prof.,  importance  of  his  researches 
on  Histology,  34  ;  theory  of  cell  develop- 
ment, 56,  57  ;  on  development  of  connec- 


tive tissue,  88,  95  ;  on  development  of  car- 
tilage, 310  ;  on  nerves  of  vas  deferens,  628. 

Sclerotic  coat  of  eye,  structure  of,  725-727. 

Sebaceous  glands,  occurrence  of,  212-215  ; 
structure  of,  216;  development  of,  218- 
220  ;  abnormal  conditions  of,  221  ;  method 
of  investigating,  221  ;  literature,  222. 

Semen,  spermatozoids  of,  622-624  ;  chemical 
composition  of,  624  ;  formation  of,  635,  636. 

Seminal  tubes,  621. 

Septum  narium,  nerves  in,  305  ;  structure  of 
cartilage  of,  310,  note. 

Sesamoid  bones,  240. 

Sexual  organs,  male,  618;  physiological  re- 
marks on,  634;  liferature  of,  638.  See 
Testes,  Penis,  Prostate  Gland. 

Sexual  organs,  female,  640  ;  physiological  re- 
marks on,  656 ;  mode  of  investigating,  659  ; 
literature  of,  ib. 

Sharpey,Dr.,  on  formation  of  certain  bones  of 
the  skull,  335,  note. 

Simon,  Dr.,  on  increase  of  sudoriparous  glands 
in  elephantiasis,  207. 

Simon,  Mr.,  on  structure  and  development  of 
thymus  gland,  590,  595. 

Skin,  layers  of,  119-138;  subcutaneous  cel- 
lular tissue,  120  ;  corium,  121-125  ;  fat  cells, 
125;  vessels,  127;  papilla?,  121,  130;  nerves 
of,  129, 132  ;  physiological  remarks  on,  135  ; 
epidermis,  139-158;  literature,  158;  method 
of  investigating,  157  ;  glands  of,  199-222. 

Smooth  muscular  fibres,  102.  See  Muscular 
Tissue,  smooth. 

Spermatozoa,  composition  of,  622 ;  move- 
merits  of,  624  ;  action  of  reagents  on,  ib.; 
formation  of,  623,  625  ;  absence  and  changes 
of,  in  disease,  625,  note;  as  impregnating 
agents,  636. 

Spinal  cord,  division  of,  360;  intimate  struc- 
ture of  white  substance,  361  ;  structure  of 
gray  substance,  362-365  ;  posterior  roots  of 
nerves  in,  366  ;  filum  ter  mmale,  367 ;  agents 
for  investigating  the  course  of  the  fibres, 
368;  course  of  fibres  in,  369;  membranes 
of,  392-399;  vessel  of,  400;  structure  of 
ganglia  of,  405. 

Spinal  nerves,  origin  of,  404 ;  structure  of 
ganglia  on,  405,  406,  note;  course  and  ter- 
mination of,  411  ;  termination  of,  in  Paci- 
nian  bodies,  412;  neurilemma  of,  414;  ves- 
sels of,  ib. 

Spleen,  coats  and  trabecular  tissue  of,  551; 
Malpighian  corpuscles,  552-556;  pulp  or 
parenchyma,  556-559 ;  changes  undergone 
by  blood-corpuscles  in,  559-562  ;  vessels 
and  nerves  of,  562-565 ;  lymphatics  of, 
566;  physiological  remarks  on,  567;  inves- 
tigation of,  ib.;  literature  of,  563. 

Stilling,  Dr.,  on  structure  of  spinal  cord,  377. 

Stomach,  muscular  tunic  of,  503 ;  mucous 
membrane,  505;  villi  of,  505,  note;  glands 
of,  506-509;  epithelium,  509;  bloodvessels 
of,  510;  lymphatics  of,  ib.;  mode  of  ex- 
amining, 527 ;  literature,  527. 

Sudoriparous  glands,  structure  of,  200 ;  secre- 
tion of,  202  ;  ducts  of,  204  ;  development  of, 
205;  pathological  conditions  of,  207;  me- 
thod of  investigation  of,  208  ;  literature  of, 
ib. 

Sublingual  gland,  463. 

Submaxillary  gland,  463. 

Supra  renal  capsules,  intimate  structure  of, 
613-615,  617,  note;  vessels  and  nerves  of, 


INDEX. 


801 


615  ;  physiological  remarks  on,  616  ;  inves- 
tigation of,  618  ;  literature  of,  ib. 

Sympathetic  nerve,  fibres  of,  418,  422;  rami 
communicantes  of,  419,  421  ;  cells  of  gan- 
glia of.  421,  424;  peripheral  distribution  of, 
423  ;  fibres  of  Remak,  423,  425  ;  ultimate 
course  of  branches  of,  425. 

Synapta  digitata,  development  of  cell  in,  52. 

Symphysis  pubis,  cartilaginous  layer  of,  288; 
formation  of  bone  corpuscles  in,ib. 

Synovia,  microscopical  appearance  of,  298 ; 
chemical  composition  of,  298. 

Synovial  membrane,  239;  intimate  structure 
of,  296. 

Sweat-glands.     See  Sudoriparous  Glands. 

Synovial  sacs,  242  ;  structure  of,  in  muscular 
system,  242;  occurrence  of  cartilage  cells 
in,  242. 


Tactile  corpuscles.     See  Axile  Corpuscles. 

Tarsal  cartilages,  757. 

Teeth,  parts  of,  468  ;  dentine,  468  ;  enamel, 
476;  cement,  480;  pulp  of,  483  ;  develop- 
ment of,  484-494,  789;  pathology  of,  495; 
mode  of  examining,  497;  literature,  498. 

Tendons,  structure  of,  232-235;  ligaments  of, 
239;  vessels  of,  244;  nerves  of,  247;  che- 
mical composition,  252 ;  development  of, 
255. 

Testes,  glandular  substance  of,  620;  semini- 
ferous tubes  of,  621-624;  secretion  of,  624; 
membranes,  vessels,  and  nerves  of,  626  ; 
structure  of  vasa  deferentia  and  ejaculatory 
duct,  627,  628;  development  of,  634  ;  me- 
thod of  examining,  638  ;  literature  of,  ib. 

Thoracic  duct,  694. 

Thyroid  gland,  structure  of,  586;  bloodves- 
sels of,  587  ;  development  of,  588  ;  patholo- 
gical changes  in,  ib.;  literature  of,  589. 

Thymus,  structure  of,  589-593 ;  concentric 
corpuscles  of,  593 ;  development  of,  594 ; 
investigation  of,  595;  literature  of,  ib. 

Tissues,  general  anatomy  of,  39-118;  classi- 
fication of,  72. 

Todd  and  Bowman,  Profs.,  on  ligaments  of 
the  lower  jaw,  285  ;  on  vessels  of  bone,  301  ; 
on  epithelium  of  membrana  tympani,  768  ; 
on  epithelium  of  olfactory  mucous  mem- 
brane, 779,  780. 

Tomes,  Mr.,  on  composition  of  teeth,  471 ;  on 
enamel  prisms,  478,  note. 

Tomes  and  De  Morgan,  MM.,  on  structure 
and  development  of  bone,  270,  note;  274, 
note;  280,  note';  323,  note. 

Tongue,  muscles  of,  441-446 ;  division  of 
striated  fibres  in,  446  ;  mucous  membrane 
of,  447;  papilla)  of,  447-451;  mucedinous 
fungi  on,  451  ;  fur  of,  in  diseases,  451,  452, 
note;  physiology  of  papillae  of,  453 ;  nerves 
of,  454  ;  follicular  glands  of,  459  ;  mode  of 
examining  papilla?,  466  ;  literature,  467. 

Tonsils,  structure  of,  461  ;  vessels  and  nerves 
of,  ib.;  secretion  of,  462. 

Toynbee,  Mr.,  on  termination  of  nerves  in 
kidney,  605,  note. 

Trachea,  tissues  of,  572  ;  glands  of,  573  ;  cili- 
ated epithelium  of,  ib.;  bloodvessels  of,  574. 

Tracheae,  termination  of,  71. 

Tunica  media,  of  arteries,  679,  682. 

51 


U. 


Ureters,  structure  of,  607. 

Urethra,  female,  structure  of,  608. 

Urethra,  male,  structure  of,  631. 

Urinary  bladder,  structure  of,  607. 

Urinary  organs,  enumeration  of,  595  ;  deve- 
lopment of,  608  ;  literature,  612.  See  Kid- 
neys. Ureters,  Bladder,  and  Urethra. 

Urine,  secretion  of,  610;  sediments  in,  610; 
presence  of  albumen,  fibrin,  and  fat  in,  610, 
611. 

Uterus,  structure  of,  646-649  ;  distribution  of 
vessels  in,  648  ;  ligaments  of,  ib.;  changes 
in,  at  menstrual  period  and  in  pregnancy, 
649-654 ;  nerves  of,  652 ;  mode  of  investi- 
gating, 659;  literature  of,  660. 


V. 


Vagina,  654. 

Valentin,  Prof.,  on  termination  of  nerve-fibres 
in  muscle,  248;  on  development  of  bone, 
335  ;  on  movements  of  spermatozoa,  625. 

Vascular  system,  667-725  ;  literature  of,  723. 
See  Heart,  Bloodvessels,  and  Blood. 

Vas  deferens,  627. 

Vasa  vasorurn,  677. 

Vascular  tunic  of  eye,  733.  See  Choroid  and 
Iris. 

Vauquelin,  M.,  his  analysis  of  the  brain,  359  ; 
of  human  semen,  624. 

Veins,  structure  of  coats  of,  684-689;  valves 
of,  689. 

Ventricles  of  heart,  fibres  of,  672. 

Vesicles,  of  Ascherson,  41;  in  milk,  41 ;  in 
the  yelk-substance,  42. 

Vesiculae  seminales,  structure  of,  628. 

Vierordt,  Dr.,  on  enumeration  of  blood-cor- 
puscles, 704,  note. 

Villi,  intestinal,  511  ;  structure  of,  512-514; 
epithelium  of,  514,  516,  note;  changes  they 
undergo  during  digestion,  515,  516,  note; 
lacteals  of,  513,  516,  note. 

Vitreous  humor  of  eye,  constitution  of,  754- 
757;  investing  membrane  of,  754  ;  develop- 
ment of,  755. 

Virchow,  Prof.,  on  connective-tissue  cor- 
puscles, 85;  on  gelatinous  tissue  of  Whar- 
ton,  95;  on  mucoils  tissue,  96  ;  on  contents 
of  bursae  mucosae,  239;  on  inierarticular 
fibre-cartilage,  297,  note ;  on  cartilage- 
corpuscles,  311,  note;  on  microscopical 
conditions  of  osseous  growths,  341 ;  on 
spinal  ependyma,  397,  note;  on  cellulose 
nature  of  the  corpora  amylacea,  402,  note; 
on  colloid  spleen,  554,  note;  on  agents  for 
restoring  ciliary  motion,  571,  note;  on  pro- 
static  concretions,  629;  on  cells  resembling 
pus-corpuscles  'in  the  blood,  713 ;  on  the 
composition  of  the  vitreous  body  in  the 
fcetus,  755. 

Volkmann,  Prof.,  on  origin  of  the  fibres  in 
the  spinal  cord,  370 ;  on  structure  of  glosso- 
pharyngeal  nerve,  417. 


W. 


Wagner,  Prof.,  on  axile- corpuscles,  130;  on 


802 


INDEX. 


termination  of  nerves  in  muscle,  248,  249  ; 
on  ganglion-globules  in  the  Ray,  391,  392  ; 
on  bipolar  cells  in  Fishes,  410. 

Weber,  Prof.,  his  experiments  on  touch,  137 ; 
on  smegma  praputii,  215;  on  elasiicity  of 
muscles,  262;  on  branches  of  hepatic  duct, 
539. 

Wedl,  Dr.,  on  hypertrophy  of  muscular  fibre, 
257,  note;  oa  structure  of  diseased  teeth, 
495,  note. 

Welcker,  Dr.,  his  method  of  counting  blood- 
corpuscles,  704,  note. 

Wrisberg,  cartilage  of,  569,  572. 


X. 

Xanthogenus,  presence  of,  in  milk,  666. 
Y. 

Yelk,  cleavage  of,  51. 

Yellow  fibrous  tissue.     See  Elastic  Tissue. 

Z. 

Zinn,  zone  of,  753,  754,  756. 
Zona  denticulata,  771. 


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